Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Read-Copy Update mechanism for mutual exclusion (tree-based version) |
| 3 | * Internal non-public definitions that provide either classic |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 4 | * or preemptible semantics. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 5 | * |
| 6 | * This program is free software; you can redistribute it and/or modify |
| 7 | * it under the terms of the GNU General Public License as published by |
| 8 | * the Free Software Foundation; either version 2 of the License, or |
| 9 | * (at your option) any later version. |
| 10 | * |
| 11 | * This program is distributed in the hope that it will be useful, |
| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | * GNU General Public License for more details. |
| 15 | * |
| 16 | * You should have received a copy of the GNU General Public License |
Paul E. McKenney | 87de1cf | 2013-12-03 10:02:52 -0800 | [diff] [blame] | 17 | * along with this program; if not, you can access it online at |
| 18 | * http://www.gnu.org/licenses/gpl-2.0.html. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 19 | * |
| 20 | * Copyright Red Hat, 2009 |
| 21 | * Copyright IBM Corporation, 2009 |
| 22 | * |
| 23 | * Author: Ingo Molnar <mingo@elte.hu> |
| 24 | * Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
| 25 | */ |
| 26 | |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 27 | #include <linux/delay.h> |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 28 | #include <linux/gfp.h> |
Paul E. McKenney | b626c1b | 2012-06-11 17:39:43 -0700 | [diff] [blame] | 29 | #include <linux/oom.h> |
Ingo Molnar | b17b015 | 2017-02-08 18:51:35 +0100 | [diff] [blame] | 30 | #include <linux/sched/debug.h> |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 31 | #include <linux/smpboot.h> |
Ingo Molnar | ae7e81c | 2017-02-01 18:07:51 +0100 | [diff] [blame] | 32 | #include <uapi/linux/sched/types.h> |
Paul E. McKenney | 4102ada | 2013-10-08 20:23:47 -0700 | [diff] [blame] | 33 | #include "../time/tick-internal.h" |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 34 | |
Mike Galbraith | 5b61b0b | 2011-08-19 11:39:11 -0700 | [diff] [blame] | 35 | #ifdef CONFIG_RCU_BOOST |
Paul E. McKenney | 61cfd09 | 2014-09-02 12:30:58 -0700 | [diff] [blame] | 36 | |
Paul E. McKenney | abaa93d | 2014-06-12 13:30:25 -0700 | [diff] [blame] | 37 | #include "../locking/rtmutex_common.h" |
Clark Williams | 21871d7 | 2014-09-12 21:21:09 -0500 | [diff] [blame] | 38 | |
Paul E. McKenney | 61cfd09 | 2014-09-02 12:30:58 -0700 | [diff] [blame] | 39 | /* |
| 40 | * Control variables for per-CPU and per-rcu_node kthreads. These |
| 41 | * handle all flavors of RCU. |
| 42 | */ |
| 43 | static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); |
| 44 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); |
| 45 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); |
| 46 | DEFINE_PER_CPU(char, rcu_cpu_has_work); |
| 47 | |
Paul E. McKenney | 727b705 | 2015-03-03 14:49:26 -0800 | [diff] [blame] | 48 | #else /* #ifdef CONFIG_RCU_BOOST */ |
| 49 | |
| 50 | /* |
| 51 | * Some architectures do not define rt_mutexes, but if !CONFIG_RCU_BOOST, |
| 52 | * all uses are in dead code. Provide a definition to keep the compiler |
| 53 | * happy, but add WARN_ON_ONCE() to complain if used in the wrong place. |
| 54 | * This probably needs to be excluded from -rt builds. |
| 55 | */ |
| 56 | #define rt_mutex_owner(a) ({ WARN_ON_ONCE(1); NULL; }) |
| 57 | |
| 58 | #endif /* #else #ifdef CONFIG_RCU_BOOST */ |
Mike Galbraith | 5b61b0b | 2011-08-19 11:39:11 -0700 | [diff] [blame] | 59 | |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 60 | #ifdef CONFIG_RCU_NOCB_CPU |
| 61 | static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */ |
| 62 | static bool have_rcu_nocb_mask; /* Was rcu_nocb_mask allocated? */ |
Paul Gortmaker | 1b0048a | 2012-12-20 13:19:22 -0800 | [diff] [blame] | 63 | static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */ |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 64 | #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ |
| 65 | |
Paul E. McKenney | 26845c2 | 2010-04-13 14:19:23 -0700 | [diff] [blame] | 66 | /* |
| 67 | * Check the RCU kernel configuration parameters and print informative |
Paul E. McKenney | 699d403 | 2015-09-29 08:47:49 -0700 | [diff] [blame] | 68 | * messages about anything out of the ordinary. |
Paul E. McKenney | 26845c2 | 2010-04-13 14:19:23 -0700 | [diff] [blame] | 69 | */ |
| 70 | static void __init rcu_bootup_announce_oddness(void) |
| 71 | { |
Paul E. McKenney | ab6f5bd | 2015-01-21 16:58:06 -0800 | [diff] [blame] | 72 | if (IS_ENABLED(CONFIG_RCU_TRACE)) |
Paul E. McKenney | ae91aa0 | 2017-05-15 15:30:32 -0700 | [diff] [blame] | 73 | pr_info("\tRCU event tracing is enabled.\n"); |
Paul E. McKenney | 05c5df3 | 2015-04-20 14:27:43 -0700 | [diff] [blame] | 74 | if ((IS_ENABLED(CONFIG_64BIT) && RCU_FANOUT != 64) || |
| 75 | (!IS_ENABLED(CONFIG_64BIT) && RCU_FANOUT != 32)) |
Paul E. McKenney | ab6f5bd | 2015-01-21 16:58:06 -0800 | [diff] [blame] | 76 | pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d\n", |
Paul E. McKenney | 05c5df3 | 2015-04-20 14:27:43 -0700 | [diff] [blame] | 77 | RCU_FANOUT); |
Paul E. McKenney | 7fa2700 | 2015-04-20 10:27:15 -0700 | [diff] [blame] | 78 | if (rcu_fanout_exact) |
Paul E. McKenney | ab6f5bd | 2015-01-21 16:58:06 -0800 | [diff] [blame] | 79 | pr_info("\tHierarchical RCU autobalancing is disabled.\n"); |
| 80 | if (IS_ENABLED(CONFIG_RCU_FAST_NO_HZ)) |
| 81 | pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n"); |
Paul E. McKenney | c4a09ff | 2017-05-12 14:37:19 -0700 | [diff] [blame] | 82 | if (IS_ENABLED(CONFIG_PROVE_RCU)) |
Paul E. McKenney | ab6f5bd | 2015-01-21 16:58:06 -0800 | [diff] [blame] | 83 | pr_info("\tRCU lockdep checking is enabled.\n"); |
Alexander Gordeev | 4262169 | 2015-06-03 08:18:31 +0200 | [diff] [blame] | 84 | if (RCU_NUM_LVLS >= 4) |
| 85 | pr_info("\tFour(or more)-level hierarchy is enabled.\n"); |
Paul E. McKenney | 47d631a | 2015-04-21 09:12:13 -0700 | [diff] [blame] | 86 | if (RCU_FANOUT_LEAF != 16) |
Paul E. McKenney | a3bd2c09a | 2015-01-21 20:58:57 -0800 | [diff] [blame] | 87 | pr_info("\tBuild-time adjustment of leaf fanout to %d.\n", |
Paul E. McKenney | 47d631a | 2015-04-21 09:12:13 -0700 | [diff] [blame] | 88 | RCU_FANOUT_LEAF); |
| 89 | if (rcu_fanout_leaf != RCU_FANOUT_LEAF) |
Paul E. McKenney | 9a5739d7 | 2013-03-28 20:48:36 -0700 | [diff] [blame] | 90 | pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf); |
Paul E. McKenney | cca6f39 | 2012-05-08 21:00:28 -0700 | [diff] [blame] | 91 | if (nr_cpu_ids != NR_CPUS) |
Alexey Dobriyan | 9b130ad | 2017-09-08 16:14:18 -0700 | [diff] [blame] | 92 | pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%u.\n", NR_CPUS, nr_cpu_ids); |
Paul E. McKenney | 17c7798 | 2017-04-28 11:12:34 -0700 | [diff] [blame] | 93 | #ifdef CONFIG_RCU_BOOST |
| 94 | pr_info("\tRCU priority boosting: priority %d delay %d ms.\n", kthread_prio, CONFIG_RCU_BOOST_DELAY); |
| 95 | #endif |
| 96 | if (blimit != DEFAULT_RCU_BLIMIT) |
| 97 | pr_info("\tBoot-time adjustment of callback invocation limit to %ld.\n", blimit); |
| 98 | if (qhimark != DEFAULT_RCU_QHIMARK) |
| 99 | pr_info("\tBoot-time adjustment of callback high-water mark to %ld.\n", qhimark); |
| 100 | if (qlowmark != DEFAULT_RCU_QLOMARK) |
| 101 | pr_info("\tBoot-time adjustment of callback low-water mark to %ld.\n", qlowmark); |
| 102 | if (jiffies_till_first_fqs != ULONG_MAX) |
| 103 | pr_info("\tBoot-time adjustment of first FQS scan delay to %ld jiffies.\n", jiffies_till_first_fqs); |
| 104 | if (jiffies_till_next_fqs != ULONG_MAX) |
| 105 | pr_info("\tBoot-time adjustment of subsequent FQS scan delay to %ld jiffies.\n", jiffies_till_next_fqs); |
| 106 | if (rcu_kick_kthreads) |
| 107 | pr_info("\tKick kthreads if too-long grace period.\n"); |
| 108 | if (IS_ENABLED(CONFIG_DEBUG_OBJECTS_RCU_HEAD)) |
| 109 | pr_info("\tRCU callback double-/use-after-free debug enabled.\n"); |
Paul E. McKenney | 90040c9 | 2017-05-10 14:36:55 -0700 | [diff] [blame] | 110 | if (gp_preinit_delay) |
Paul E. McKenney | 17c7798 | 2017-04-28 11:12:34 -0700 | [diff] [blame] | 111 | pr_info("\tRCU debug GP pre-init slowdown %d jiffies.\n", gp_preinit_delay); |
Paul E. McKenney | 90040c9 | 2017-05-10 14:36:55 -0700 | [diff] [blame] | 112 | if (gp_init_delay) |
Paul E. McKenney | 17c7798 | 2017-04-28 11:12:34 -0700 | [diff] [blame] | 113 | pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_init_delay); |
Paul E. McKenney | 90040c9 | 2017-05-10 14:36:55 -0700 | [diff] [blame] | 114 | if (gp_cleanup_delay) |
Paul E. McKenney | 17c7798 | 2017-04-28 11:12:34 -0700 | [diff] [blame] | 115 | pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_cleanup_delay); |
| 116 | if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG)) |
| 117 | pr_info("\tRCU debug extended QS entry/exit.\n"); |
Paul E. McKenney | 59d80fd | 2017-04-28 10:20:28 -0700 | [diff] [blame] | 118 | rcupdate_announce_bootup_oddness(); |
Paul E. McKenney | 26845c2 | 2010-04-13 14:19:23 -0700 | [diff] [blame] | 119 | } |
| 120 | |
Pranith Kumar | 28f6569 | 2014-09-22 14:00:48 -0400 | [diff] [blame] | 121 | #ifdef CONFIG_PREEMPT_RCU |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 122 | |
Steven Rostedt (Red Hat) | a41bfeb | 2013-07-12 17:00:28 -0400 | [diff] [blame] | 123 | RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu); |
Paul E. McKenney | b28a7c0 | 2015-03-04 07:39:27 -0800 | [diff] [blame] | 124 | static struct rcu_state *const rcu_state_p = &rcu_preempt_state; |
Paul E. McKenney | 2927a68 | 2015-03-04 07:53:04 -0800 | [diff] [blame] | 125 | static struct rcu_data __percpu *const rcu_data_p = &rcu_preempt_data; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 126 | |
Paul E. McKenney | d19fb8d | 2014-10-31 12:56:16 -0700 | [diff] [blame] | 127 | static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, |
| 128 | bool wake); |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 129 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 130 | /* |
| 131 | * Tell them what RCU they are running. |
| 132 | */ |
Paul E. McKenney | 0e0fc1c | 2009-11-11 11:28:06 -0800 | [diff] [blame] | 133 | static void __init rcu_bootup_announce(void) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 134 | { |
Paul E. McKenney | efc151c | 2013-03-18 16:24:11 -0700 | [diff] [blame] | 135 | pr_info("Preemptible hierarchical RCU implementation.\n"); |
Paul E. McKenney | 26845c2 | 2010-04-13 14:19:23 -0700 | [diff] [blame] | 136 | rcu_bootup_announce_oddness(); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 137 | } |
| 138 | |
Paul E. McKenney | 8203d6d0 | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 139 | /* Flags for rcu_preempt_ctxt_queue() decision table. */ |
| 140 | #define RCU_GP_TASKS 0x8 |
| 141 | #define RCU_EXP_TASKS 0x4 |
| 142 | #define RCU_GP_BLKD 0x2 |
| 143 | #define RCU_EXP_BLKD 0x1 |
| 144 | |
| 145 | /* |
| 146 | * Queues a task preempted within an RCU-preempt read-side critical |
| 147 | * section into the appropriate location within the ->blkd_tasks list, |
| 148 | * depending on the states of any ongoing normal and expedited grace |
| 149 | * periods. The ->gp_tasks pointer indicates which element the normal |
| 150 | * grace period is waiting on (NULL if none), and the ->exp_tasks pointer |
| 151 | * indicates which element the expedited grace period is waiting on (again, |
| 152 | * NULL if none). If a grace period is waiting on a given element in the |
| 153 | * ->blkd_tasks list, it also waits on all subsequent elements. Thus, |
| 154 | * adding a task to the tail of the list blocks any grace period that is |
| 155 | * already waiting on one of the elements. In contrast, adding a task |
| 156 | * to the head of the list won't block any grace period that is already |
| 157 | * waiting on one of the elements. |
| 158 | * |
| 159 | * This queuing is imprecise, and can sometimes make an ongoing grace |
| 160 | * period wait for a task that is not strictly speaking blocking it. |
| 161 | * Given the choice, we needlessly block a normal grace period rather than |
| 162 | * blocking an expedited grace period. |
| 163 | * |
| 164 | * Note that an endless sequence of expedited grace periods still cannot |
| 165 | * indefinitely postpone a normal grace period. Eventually, all of the |
| 166 | * fixed number of preempted tasks blocking the normal grace period that are |
| 167 | * not also blocking the expedited grace period will resume and complete |
| 168 | * their RCU read-side critical sections. At that point, the ->gp_tasks |
| 169 | * pointer will equal the ->exp_tasks pointer, at which point the end of |
| 170 | * the corresponding expedited grace period will also be the end of the |
| 171 | * normal grace period. |
| 172 | */ |
Paul E. McKenney | 46a5d16 | 2015-10-07 09:10:48 -0700 | [diff] [blame] | 173 | static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp) |
| 174 | __releases(rnp->lock) /* But leaves rrupts disabled. */ |
Paul E. McKenney | 8203d6d0 | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 175 | { |
| 176 | int blkd_state = (rnp->gp_tasks ? RCU_GP_TASKS : 0) + |
| 177 | (rnp->exp_tasks ? RCU_EXP_TASKS : 0) + |
| 178 | (rnp->qsmask & rdp->grpmask ? RCU_GP_BLKD : 0) + |
| 179 | (rnp->expmask & rdp->grpmask ? RCU_EXP_BLKD : 0); |
| 180 | struct task_struct *t = current; |
| 181 | |
Paul E. McKenney | ea9b0c8 | 2017-04-28 13:19:28 -0700 | [diff] [blame] | 182 | lockdep_assert_held(&rnp->lock); |
Paul E. McKenney | 2dee940 | 2017-07-11 21:52:31 -0700 | [diff] [blame] | 183 | WARN_ON_ONCE(rdp->mynode != rnp); |
| 184 | WARN_ON_ONCE(rnp->level != rcu_num_lvls - 1); |
Paul E. McKenney | ea9b0c8 | 2017-04-28 13:19:28 -0700 | [diff] [blame] | 185 | |
Paul E. McKenney | 8203d6d0 | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 186 | /* |
| 187 | * Decide where to queue the newly blocked task. In theory, |
| 188 | * this could be an if-statement. In practice, when I tried |
| 189 | * that, it was quite messy. |
| 190 | */ |
| 191 | switch (blkd_state) { |
| 192 | case 0: |
| 193 | case RCU_EXP_TASKS: |
| 194 | case RCU_EXP_TASKS + RCU_GP_BLKD: |
| 195 | case RCU_GP_TASKS: |
| 196 | case RCU_GP_TASKS + RCU_EXP_TASKS: |
| 197 | |
| 198 | /* |
| 199 | * Blocking neither GP, or first task blocking the normal |
| 200 | * GP but not blocking the already-waiting expedited GP. |
| 201 | * Queue at the head of the list to avoid unnecessarily |
| 202 | * blocking the already-waiting GPs. |
| 203 | */ |
| 204 | list_add(&t->rcu_node_entry, &rnp->blkd_tasks); |
| 205 | break; |
| 206 | |
| 207 | case RCU_EXP_BLKD: |
| 208 | case RCU_GP_BLKD: |
| 209 | case RCU_GP_BLKD + RCU_EXP_BLKD: |
| 210 | case RCU_GP_TASKS + RCU_EXP_BLKD: |
| 211 | case RCU_GP_TASKS + RCU_GP_BLKD + RCU_EXP_BLKD: |
| 212 | case RCU_GP_TASKS + RCU_EXP_TASKS + RCU_GP_BLKD + RCU_EXP_BLKD: |
| 213 | |
| 214 | /* |
| 215 | * First task arriving that blocks either GP, or first task |
| 216 | * arriving that blocks the expedited GP (with the normal |
| 217 | * GP already waiting), or a task arriving that blocks |
| 218 | * both GPs with both GPs already waiting. Queue at the |
| 219 | * tail of the list to avoid any GP waiting on any of the |
| 220 | * already queued tasks that are not blocking it. |
| 221 | */ |
| 222 | list_add_tail(&t->rcu_node_entry, &rnp->blkd_tasks); |
| 223 | break; |
| 224 | |
| 225 | case RCU_EXP_TASKS + RCU_EXP_BLKD: |
| 226 | case RCU_EXP_TASKS + RCU_GP_BLKD + RCU_EXP_BLKD: |
| 227 | case RCU_GP_TASKS + RCU_EXP_TASKS + RCU_EXP_BLKD: |
| 228 | |
| 229 | /* |
| 230 | * Second or subsequent task blocking the expedited GP. |
| 231 | * The task either does not block the normal GP, or is the |
| 232 | * first task blocking the normal GP. Queue just after |
| 233 | * the first task blocking the expedited GP. |
| 234 | */ |
| 235 | list_add(&t->rcu_node_entry, rnp->exp_tasks); |
| 236 | break; |
| 237 | |
| 238 | case RCU_GP_TASKS + RCU_GP_BLKD: |
| 239 | case RCU_GP_TASKS + RCU_EXP_TASKS + RCU_GP_BLKD: |
| 240 | |
| 241 | /* |
| 242 | * Second or subsequent task blocking the normal GP. |
| 243 | * The task does not block the expedited GP. Queue just |
| 244 | * after the first task blocking the normal GP. |
| 245 | */ |
| 246 | list_add(&t->rcu_node_entry, rnp->gp_tasks); |
| 247 | break; |
| 248 | |
| 249 | default: |
| 250 | |
| 251 | /* Yet another exercise in excessive paranoia. */ |
| 252 | WARN_ON_ONCE(1); |
| 253 | break; |
| 254 | } |
| 255 | |
| 256 | /* |
| 257 | * We have now queued the task. If it was the first one to |
| 258 | * block either grace period, update the ->gp_tasks and/or |
| 259 | * ->exp_tasks pointers, respectively, to reference the newly |
| 260 | * blocked tasks. |
| 261 | */ |
| 262 | if (!rnp->gp_tasks && (blkd_state & RCU_GP_BLKD)) |
| 263 | rnp->gp_tasks = &t->rcu_node_entry; |
| 264 | if (!rnp->exp_tasks && (blkd_state & RCU_EXP_BLKD)) |
| 265 | rnp->exp_tasks = &t->rcu_node_entry; |
Paul E. McKenney | 2dee940 | 2017-07-11 21:52:31 -0700 | [diff] [blame] | 266 | WARN_ON_ONCE(!(blkd_state & RCU_GP_BLKD) != |
| 267 | !(rnp->qsmask & rdp->grpmask)); |
| 268 | WARN_ON_ONCE(!(blkd_state & RCU_EXP_BLKD) != |
| 269 | !(rnp->expmask & rdp->grpmask)); |
Boqun Feng | 67c583a7 | 2015-12-29 12:18:47 +0800 | [diff] [blame] | 270 | raw_spin_unlock_rcu_node(rnp); /* interrupts remain disabled. */ |
Paul E. McKenney | 8203d6d0 | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 271 | |
| 272 | /* |
| 273 | * Report the quiescent state for the expedited GP. This expedited |
| 274 | * GP should not be able to end until we report, so there should be |
| 275 | * no need to check for a subsequent expedited GP. (Though we are |
| 276 | * still in a quiescent state in any case.) |
| 277 | */ |
| 278 | if (blkd_state & RCU_EXP_BLKD && |
| 279 | t->rcu_read_unlock_special.b.exp_need_qs) { |
| 280 | t->rcu_read_unlock_special.b.exp_need_qs = false; |
| 281 | rcu_report_exp_rdp(rdp->rsp, rdp, true); |
| 282 | } else { |
| 283 | WARN_ON_ONCE(t->rcu_read_unlock_special.b.exp_need_qs); |
| 284 | } |
Paul E. McKenney | 8203d6d0 | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 285 | } |
| 286 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 287 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 288 | * Record a preemptible-RCU quiescent state for the specified CPU. Note |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 289 | * that this just means that the task currently running on the CPU is |
| 290 | * not in a quiescent state. There might be any number of tasks blocked |
| 291 | * while in an RCU read-side critical section. |
Paul E. McKenney | 25502a6 | 2010-04-01 17:37:01 -0700 | [diff] [blame] | 292 | * |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 293 | * As with the other rcu_*_qs() functions, callers to this function |
| 294 | * must disable preemption. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 295 | */ |
Paul E. McKenney | 284a8c9 | 2014-08-14 16:38:46 -0700 | [diff] [blame] | 296 | static void rcu_preempt_qs(void) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 297 | { |
Paul E. McKenney | ea9b0c8 | 2017-04-28 13:19:28 -0700 | [diff] [blame] | 298 | RCU_LOCKDEP_WARN(preemptible(), "rcu_preempt_qs() invoked with preemption enabled!!!\n"); |
Paul E. McKenney | 5b74c45 | 2015-08-06 15:16:57 -0700 | [diff] [blame] | 299 | if (__this_cpu_read(rcu_data_p->cpu_no_qs.s)) { |
Paul E. McKenney | 284a8c9 | 2014-08-14 16:38:46 -0700 | [diff] [blame] | 300 | trace_rcu_grace_period(TPS("rcu_preempt"), |
Paul E. McKenney | 2927a68 | 2015-03-04 07:53:04 -0800 | [diff] [blame] | 301 | __this_cpu_read(rcu_data_p->gpnum), |
Paul E. McKenney | 284a8c9 | 2014-08-14 16:38:46 -0700 | [diff] [blame] | 302 | TPS("cpuqs")); |
Paul E. McKenney | 5b74c45 | 2015-08-06 15:16:57 -0700 | [diff] [blame] | 303 | __this_cpu_write(rcu_data_p->cpu_no_qs.b.norm, false); |
Paul E. McKenney | 284a8c9 | 2014-08-14 16:38:46 -0700 | [diff] [blame] | 304 | barrier(); /* Coordinate with rcu_preempt_check_callbacks(). */ |
| 305 | current->rcu_read_unlock_special.b.need_qs = false; |
| 306 | } |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 307 | } |
| 308 | |
| 309 | /* |
Paul E. McKenney | c3422be | 2009-09-13 09:15:10 -0700 | [diff] [blame] | 310 | * We have entered the scheduler, and the current task might soon be |
| 311 | * context-switched away from. If this task is in an RCU read-side |
| 312 | * critical section, we will no longer be able to rely on the CPU to |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 313 | * record that fact, so we enqueue the task on the blkd_tasks list. |
| 314 | * The task will dequeue itself when it exits the outermost enclosing |
| 315 | * RCU read-side critical section. Therefore, the current grace period |
| 316 | * cannot be permitted to complete until the blkd_tasks list entries |
| 317 | * predating the current grace period drain, in other words, until |
| 318 | * rnp->gp_tasks becomes NULL. |
Paul E. McKenney | c3422be | 2009-09-13 09:15:10 -0700 | [diff] [blame] | 319 | * |
Paul E. McKenney | 46a5d16 | 2015-10-07 09:10:48 -0700 | [diff] [blame] | 320 | * Caller must disable interrupts. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 321 | */ |
Paul E. McKenney | 5b72f96 | 2017-04-12 15:29:14 -0700 | [diff] [blame] | 322 | static void rcu_preempt_note_context_switch(bool preempt) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 323 | { |
| 324 | struct task_struct *t = current; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 325 | struct rcu_data *rdp; |
| 326 | struct rcu_node *rnp; |
| 327 | |
Paul E. McKenney | ea9b0c8 | 2017-04-28 13:19:28 -0700 | [diff] [blame] | 328 | RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_preempt_note_context_switch() invoked with interrupts enabled!!!\n"); |
Paul E. McKenney | 5b72f96 | 2017-04-12 15:29:14 -0700 | [diff] [blame] | 329 | WARN_ON_ONCE(!preempt && t->rcu_read_lock_nesting > 0); |
Paul E. McKenney | 10f39bb | 2011-07-17 21:14:35 -0700 | [diff] [blame] | 330 | if (t->rcu_read_lock_nesting > 0 && |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 331 | !t->rcu_read_unlock_special.b.blocked) { |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 332 | |
| 333 | /* Possibly blocking in an RCU read-side critical section. */ |
Paul E. McKenney | e63c887 | 2015-03-03 12:56:43 -0800 | [diff] [blame] | 334 | rdp = this_cpu_ptr(rcu_state_p->rda); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 335 | rnp = rdp->mynode; |
Paul E. McKenney | 46a5d16 | 2015-10-07 09:10:48 -0700 | [diff] [blame] | 336 | raw_spin_lock_rcu_node(rnp); |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 337 | t->rcu_read_unlock_special.b.blocked = true; |
Paul E. McKenney | 8684896 | 2009-08-27 15:00:12 -0700 | [diff] [blame] | 338 | t->rcu_blocked_node = rnp; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 339 | |
| 340 | /* |
Paul E. McKenney | 8203d6d0 | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 341 | * Verify the CPU's sanity, trace the preemption, and |
| 342 | * then queue the task as required based on the states |
| 343 | * of any ongoing and expedited grace periods. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 344 | */ |
Paul E. McKenney | 0aa04b0 | 2015-01-23 21:52:37 -0800 | [diff] [blame] | 345 | WARN_ON_ONCE((rdp->grpmask & rcu_rnp_online_cpus(rnp)) == 0); |
Paul E. McKenney | e7d8842 | 2009-09-18 09:50:18 -0700 | [diff] [blame] | 346 | WARN_ON_ONCE(!list_empty(&t->rcu_node_entry)); |
Paul E. McKenney | d4c08f2 | 2011-06-25 06:36:56 -0700 | [diff] [blame] | 347 | trace_rcu_preempt_task(rdp->rsp->name, |
| 348 | t->pid, |
| 349 | (rnp->qsmask & rdp->grpmask) |
| 350 | ? rnp->gpnum |
| 351 | : rnp->gpnum + 1); |
Paul E. McKenney | 46a5d16 | 2015-10-07 09:10:48 -0700 | [diff] [blame] | 352 | rcu_preempt_ctxt_queue(rnp, rdp); |
Paul E. McKenney | 10f39bb | 2011-07-17 21:14:35 -0700 | [diff] [blame] | 353 | } else if (t->rcu_read_lock_nesting < 0 && |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 354 | t->rcu_read_unlock_special.s) { |
Paul E. McKenney | 10f39bb | 2011-07-17 21:14:35 -0700 | [diff] [blame] | 355 | |
| 356 | /* |
| 357 | * Complete exit from RCU read-side critical section on |
| 358 | * behalf of preempted instance of __rcu_read_unlock(). |
| 359 | */ |
| 360 | rcu_read_unlock_special(t); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 361 | } |
| 362 | |
| 363 | /* |
| 364 | * Either we were not in an RCU read-side critical section to |
| 365 | * begin with, or we have now recorded that critical section |
| 366 | * globally. Either way, we can now note a quiescent state |
| 367 | * for this CPU. Again, if we were in an RCU read-side critical |
| 368 | * section, and if that critical section was blocking the current |
| 369 | * grace period, then the fact that the task has been enqueued |
| 370 | * means that we continue to block the current grace period. |
| 371 | */ |
Paul E. McKenney | 284a8c9 | 2014-08-14 16:38:46 -0700 | [diff] [blame] | 372 | rcu_preempt_qs(); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 373 | } |
| 374 | |
| 375 | /* |
Paul E. McKenney | fc2219d4 | 2009-09-23 09:50:41 -0700 | [diff] [blame] | 376 | * Check for preempted RCU readers blocking the current grace period |
| 377 | * for the specified rcu_node structure. If the caller needs a reliable |
| 378 | * answer, it must hold the rcu_node's ->lock. |
| 379 | */ |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 380 | static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) |
Paul E. McKenney | fc2219d4 | 2009-09-23 09:50:41 -0700 | [diff] [blame] | 381 | { |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 382 | return rnp->gp_tasks != NULL; |
Paul E. McKenney | fc2219d4 | 2009-09-23 09:50:41 -0700 | [diff] [blame] | 383 | } |
| 384 | |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 385 | /* |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 386 | * Advance a ->blkd_tasks-list pointer to the next entry, instead |
| 387 | * returning NULL if at the end of the list. |
| 388 | */ |
| 389 | static struct list_head *rcu_next_node_entry(struct task_struct *t, |
| 390 | struct rcu_node *rnp) |
| 391 | { |
| 392 | struct list_head *np; |
| 393 | |
| 394 | np = t->rcu_node_entry.next; |
| 395 | if (np == &rnp->blkd_tasks) |
| 396 | np = NULL; |
| 397 | return np; |
| 398 | } |
| 399 | |
| 400 | /* |
Paul E. McKenney | 8af3a5e | 2014-10-31 11:22:37 -0700 | [diff] [blame] | 401 | * Return true if the specified rcu_node structure has tasks that were |
| 402 | * preempted within an RCU read-side critical section. |
| 403 | */ |
| 404 | static bool rcu_preempt_has_tasks(struct rcu_node *rnp) |
| 405 | { |
| 406 | return !list_empty(&rnp->blkd_tasks); |
| 407 | } |
| 408 | |
| 409 | /* |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 410 | * Handle special cases during rcu_read_unlock(), such as needing to |
| 411 | * notify RCU core processing or task having blocked during the RCU |
| 412 | * read-side critical section. |
| 413 | */ |
Paul E. McKenney | 2a3fa84 | 2012-05-21 11:58:36 -0700 | [diff] [blame] | 414 | void rcu_read_unlock_special(struct task_struct *t) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 415 | { |
Paul E. McKenney | b6a932d | 2014-10-31 12:05:04 -0700 | [diff] [blame] | 416 | bool empty_exp; |
| 417 | bool empty_norm; |
| 418 | bool empty_exp_now; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 419 | unsigned long flags; |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 420 | struct list_head *np; |
Paul E. McKenney | abaa93d | 2014-06-12 13:30:25 -0700 | [diff] [blame] | 421 | bool drop_boost_mutex = false; |
Paul E. McKenney | 8203d6d0 | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 422 | struct rcu_data *rdp; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 423 | struct rcu_node *rnp; |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 424 | union rcu_special special; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 425 | |
| 426 | /* NMI handlers cannot block and cannot safely manipulate state. */ |
| 427 | if (in_nmi()) |
| 428 | return; |
| 429 | |
| 430 | local_irq_save(flags); |
| 431 | |
| 432 | /* |
Paul E. McKenney | 8203d6d0 | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 433 | * If RCU core is waiting for this CPU to exit its critical section, |
| 434 | * report the fact that it has exited. Because irqs are disabled, |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 435 | * t->rcu_read_unlock_special cannot change. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 436 | */ |
| 437 | special = t->rcu_read_unlock_special; |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 438 | if (special.b.need_qs) { |
Paul E. McKenney | 284a8c9 | 2014-08-14 16:38:46 -0700 | [diff] [blame] | 439 | rcu_preempt_qs(); |
Paul E. McKenney | c0135d0 | 2015-01-22 22:47:14 -0800 | [diff] [blame] | 440 | t->rcu_read_unlock_special.b.need_qs = false; |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 441 | if (!t->rcu_read_unlock_special.s) { |
Lai Jiangshan | 79a62f9 | 2013-10-30 04:13:22 -0700 | [diff] [blame] | 442 | local_irq_restore(flags); |
| 443 | return; |
| 444 | } |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 445 | } |
| 446 | |
Paul E. McKenney | 8203d6d0 | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 447 | /* |
| 448 | * Respond to a request for an expedited grace period, but only if |
| 449 | * we were not preempted, meaning that we were running on the same |
| 450 | * CPU throughout. If we were preempted, the exp_need_qs flag |
| 451 | * would have been cleared at the time of the first preemption, |
| 452 | * and the quiescent state would be reported when we were dequeued. |
| 453 | */ |
| 454 | if (special.b.exp_need_qs) { |
| 455 | WARN_ON_ONCE(special.b.blocked); |
| 456 | t->rcu_read_unlock_special.b.exp_need_qs = false; |
| 457 | rdp = this_cpu_ptr(rcu_state_p->rda); |
| 458 | rcu_report_exp_rdp(rcu_state_p, rdp, true); |
| 459 | if (!t->rcu_read_unlock_special.s) { |
| 460 | local_irq_restore(flags); |
| 461 | return; |
| 462 | } |
| 463 | } |
| 464 | |
Lai Jiangshan | 79a62f9 | 2013-10-30 04:13:22 -0700 | [diff] [blame] | 465 | /* Hardware IRQ handlers cannot block, complain if they get here. */ |
Paul E. McKenney | d24209bb | 2015-01-21 15:26:03 -0800 | [diff] [blame] | 466 | if (in_irq() || in_serving_softirq()) { |
| 467 | lockdep_rcu_suspicious(__FILE__, __LINE__, |
| 468 | "rcu_read_unlock() from irq or softirq with blocking in critical section!!!\n"); |
Paul E. McKenney | 8203d6d0 | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 469 | pr_alert("->rcu_read_unlock_special: %#x (b: %d, enq: %d nq: %d)\n", |
Paul E. McKenney | d24209bb | 2015-01-21 15:26:03 -0800 | [diff] [blame] | 470 | t->rcu_read_unlock_special.s, |
| 471 | t->rcu_read_unlock_special.b.blocked, |
Paul E. McKenney | 8203d6d0 | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 472 | t->rcu_read_unlock_special.b.exp_need_qs, |
Paul E. McKenney | d24209bb | 2015-01-21 15:26:03 -0800 | [diff] [blame] | 473 | t->rcu_read_unlock_special.b.need_qs); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 474 | local_irq_restore(flags); |
| 475 | return; |
| 476 | } |
| 477 | |
| 478 | /* Clean up if blocked during RCU read-side critical section. */ |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 479 | if (special.b.blocked) { |
| 480 | t->rcu_read_unlock_special.b.blocked = false; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 481 | |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 482 | /* |
Paul E. McKenney | 0a0ba1c | 2015-03-08 14:20:30 -0700 | [diff] [blame] | 483 | * Remove this task from the list it blocked on. The task |
Paul E. McKenney | 8ba9153 | 2015-09-29 07:55:41 -0700 | [diff] [blame] | 484 | * now remains queued on the rcu_node corresponding to the |
| 485 | * CPU it first blocked on, so there is no longer any need |
| 486 | * to loop. Retain a WARN_ON_ONCE() out of sheer paranoia. |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 487 | */ |
Paul E. McKenney | 8ba9153 | 2015-09-29 07:55:41 -0700 | [diff] [blame] | 488 | rnp = t->rcu_blocked_node; |
| 489 | raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ |
| 490 | WARN_ON_ONCE(rnp != t->rcu_blocked_node); |
Paul E. McKenney | 2dee940 | 2017-07-11 21:52:31 -0700 | [diff] [blame] | 491 | WARN_ON_ONCE(rnp->level != rcu_num_lvls - 1); |
Paul E. McKenney | 74e871ac | 2014-10-30 21:08:53 -0700 | [diff] [blame] | 492 | empty_norm = !rcu_preempt_blocked_readers_cgp(rnp); |
Paul E. McKenney | 8203d6d0 | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 493 | empty_exp = sync_rcu_preempt_exp_done(rnp); |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 494 | smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */ |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 495 | np = rcu_next_node_entry(t, rnp); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 496 | list_del_init(&t->rcu_node_entry); |
Paul E. McKenney | 82e78d8 | 2011-08-04 07:55:34 -0700 | [diff] [blame] | 497 | t->rcu_blocked_node = NULL; |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 498 | trace_rcu_unlock_preempted_task(TPS("rcu_preempt"), |
Paul E. McKenney | d4c08f2 | 2011-06-25 06:36:56 -0700 | [diff] [blame] | 499 | rnp->gpnum, t->pid); |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 500 | if (&t->rcu_node_entry == rnp->gp_tasks) |
| 501 | rnp->gp_tasks = np; |
| 502 | if (&t->rcu_node_entry == rnp->exp_tasks) |
| 503 | rnp->exp_tasks = np; |
Paul E. McKenney | 727b705 | 2015-03-03 14:49:26 -0800 | [diff] [blame] | 504 | if (IS_ENABLED(CONFIG_RCU_BOOST)) { |
Paul E. McKenney | 727b705 | 2015-03-03 14:49:26 -0800 | [diff] [blame] | 505 | /* Snapshot ->boost_mtx ownership w/rnp->lock held. */ |
| 506 | drop_boost_mutex = rt_mutex_owner(&rnp->boost_mtx) == t; |
Paul E. McKenney | 2dee940 | 2017-07-11 21:52:31 -0700 | [diff] [blame] | 507 | if (&t->rcu_node_entry == rnp->boost_tasks) |
| 508 | rnp->boost_tasks = np; |
Paul E. McKenney | 727b705 | 2015-03-03 14:49:26 -0800 | [diff] [blame] | 509 | } |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 510 | |
| 511 | /* |
| 512 | * If this was the last task on the current list, and if |
| 513 | * we aren't waiting on any CPUs, report the quiescent state. |
Paul E. McKenney | 389abd4 | 2011-09-21 14:41:37 -0700 | [diff] [blame] | 514 | * Note that rcu_report_unblock_qs_rnp() releases rnp->lock, |
| 515 | * so we must take a snapshot of the expedited state. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 516 | */ |
Paul E. McKenney | 8203d6d0 | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 517 | empty_exp_now = sync_rcu_preempt_exp_done(rnp); |
Paul E. McKenney | 74e871ac | 2014-10-30 21:08:53 -0700 | [diff] [blame] | 518 | if (!empty_norm && !rcu_preempt_blocked_readers_cgp(rnp)) { |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 519 | trace_rcu_quiescent_state_report(TPS("preempt_rcu"), |
Paul E. McKenney | d4c08f2 | 2011-06-25 06:36:56 -0700 | [diff] [blame] | 520 | rnp->gpnum, |
| 521 | 0, rnp->qsmask, |
| 522 | rnp->level, |
| 523 | rnp->grplo, |
| 524 | rnp->grphi, |
| 525 | !!rnp->gp_tasks); |
Paul E. McKenney | e63c887 | 2015-03-03 12:56:43 -0800 | [diff] [blame] | 526 | rcu_report_unblock_qs_rnp(rcu_state_p, rnp, flags); |
Paul E. McKenney | c701d5d | 2012-06-28 08:08:25 -0700 | [diff] [blame] | 527 | } else { |
Boqun Feng | 67c583a7 | 2015-12-29 12:18:47 +0800 | [diff] [blame] | 528 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
Paul E. McKenney | c701d5d | 2012-06-28 08:08:25 -0700 | [diff] [blame] | 529 | } |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 530 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 531 | /* Unboost if we were boosted. */ |
Paul E. McKenney | 727b705 | 2015-03-03 14:49:26 -0800 | [diff] [blame] | 532 | if (IS_ENABLED(CONFIG_RCU_BOOST) && drop_boost_mutex) |
Paul E. McKenney | abaa93d | 2014-06-12 13:30:25 -0700 | [diff] [blame] | 533 | rt_mutex_unlock(&rnp->boost_mtx); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 534 | |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 535 | /* |
| 536 | * If this was the last task on the expedited lists, |
| 537 | * then we need to report up the rcu_node hierarchy. |
| 538 | */ |
Paul E. McKenney | 389abd4 | 2011-09-21 14:41:37 -0700 | [diff] [blame] | 539 | if (!empty_exp && empty_exp_now) |
Paul E. McKenney | e63c887 | 2015-03-03 12:56:43 -0800 | [diff] [blame] | 540 | rcu_report_exp_rnp(rcu_state_p, rnp, true); |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 541 | } else { |
| 542 | local_irq_restore(flags); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 543 | } |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 544 | } |
| 545 | |
Paul E. McKenney | 1ed509a | 2010-02-22 17:05:05 -0800 | [diff] [blame] | 546 | /* |
| 547 | * Dump detailed information for all tasks blocking the current RCU |
| 548 | * grace period on the specified rcu_node structure. |
| 549 | */ |
| 550 | static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp) |
| 551 | { |
| 552 | unsigned long flags; |
Paul E. McKenney | 1ed509a | 2010-02-22 17:05:05 -0800 | [diff] [blame] | 553 | struct task_struct *t; |
| 554 | |
Paul E. McKenney | 6cf1008 | 2015-10-08 15:36:54 -0700 | [diff] [blame] | 555 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
Paul E. McKenney | 5fd4dc0 | 2012-08-10 16:00:11 -0700 | [diff] [blame] | 556 | if (!rcu_preempt_blocked_readers_cgp(rnp)) { |
Boqun Feng | 67c583a7 | 2015-12-29 12:18:47 +0800 | [diff] [blame] | 557 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
Paul E. McKenney | 5fd4dc0 | 2012-08-10 16:00:11 -0700 | [diff] [blame] | 558 | return; |
| 559 | } |
Patrick Daly | 82efed0 | 2015-04-07 15:12:07 -0700 | [diff] [blame] | 560 | t = list_entry(rnp->gp_tasks->prev, |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 561 | struct task_struct, rcu_node_entry); |
| 562 | list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) |
| 563 | sched_show_task(t); |
Boqun Feng | 67c583a7 | 2015-12-29 12:18:47 +0800 | [diff] [blame] | 564 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
Paul E. McKenney | 1ed509a | 2010-02-22 17:05:05 -0800 | [diff] [blame] | 565 | } |
| 566 | |
| 567 | /* |
| 568 | * Dump detailed information for all tasks blocking the current RCU |
| 569 | * grace period. |
| 570 | */ |
| 571 | static void rcu_print_detail_task_stall(struct rcu_state *rsp) |
| 572 | { |
| 573 | struct rcu_node *rnp = rcu_get_root(rsp); |
| 574 | |
| 575 | rcu_print_detail_task_stall_rnp(rnp); |
| 576 | rcu_for_each_leaf_node(rsp, rnp) |
| 577 | rcu_print_detail_task_stall_rnp(rnp); |
| 578 | } |
| 579 | |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 580 | static void rcu_print_task_stall_begin(struct rcu_node *rnp) |
| 581 | { |
Paul E. McKenney | efc151c | 2013-03-18 16:24:11 -0700 | [diff] [blame] | 582 | pr_err("\tTasks blocked on level-%d rcu_node (CPUs %d-%d):", |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 583 | rnp->level, rnp->grplo, rnp->grphi); |
| 584 | } |
| 585 | |
| 586 | static void rcu_print_task_stall_end(void) |
| 587 | { |
Paul E. McKenney | efc151c | 2013-03-18 16:24:11 -0700 | [diff] [blame] | 588 | pr_cont("\n"); |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 589 | } |
| 590 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 591 | /* |
| 592 | * Scan the current list of tasks blocked within RCU read-side critical |
| 593 | * sections, printing out the tid of each. |
| 594 | */ |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 595 | static int rcu_print_task_stall(struct rcu_node *rnp) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 596 | { |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 597 | struct task_struct *t; |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 598 | int ndetected = 0; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 599 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 600 | if (!rcu_preempt_blocked_readers_cgp(rnp)) |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 601 | return 0; |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 602 | rcu_print_task_stall_begin(rnp); |
Patrick Daly | 82efed0 | 2015-04-07 15:12:07 -0700 | [diff] [blame] | 603 | t = list_entry(rnp->gp_tasks->prev, |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 604 | struct task_struct, rcu_node_entry); |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 605 | list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { |
Paul E. McKenney | efc151c | 2013-03-18 16:24:11 -0700 | [diff] [blame] | 606 | pr_cont(" P%d", t->pid); |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 607 | ndetected++; |
| 608 | } |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 609 | rcu_print_task_stall_end(); |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 610 | return ndetected; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 611 | } |
| 612 | |
Paul E. McKenney | 53d84e0 | 2010-08-10 14:28:53 -0700 | [diff] [blame] | 613 | /* |
Paul E. McKenney | 74611ec | 2015-08-18 10:20:43 -0700 | [diff] [blame] | 614 | * Scan the current list of tasks blocked within RCU read-side critical |
| 615 | * sections, printing out the tid of each that is blocking the current |
| 616 | * expedited grace period. |
| 617 | */ |
| 618 | static int rcu_print_task_exp_stall(struct rcu_node *rnp) |
| 619 | { |
| 620 | struct task_struct *t; |
| 621 | int ndetected = 0; |
| 622 | |
| 623 | if (!rnp->exp_tasks) |
| 624 | return 0; |
| 625 | t = list_entry(rnp->exp_tasks->prev, |
| 626 | struct task_struct, rcu_node_entry); |
| 627 | list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { |
| 628 | pr_cont(" P%d", t->pid); |
| 629 | ndetected++; |
| 630 | } |
| 631 | return ndetected; |
| 632 | } |
| 633 | |
| 634 | /* |
Paul E. McKenney | b0e165c0 | 2009-09-13 09:15:09 -0700 | [diff] [blame] | 635 | * Check that the list of blocked tasks for the newly completed grace |
| 636 | * period is in fact empty. It is a serious bug to complete a grace |
| 637 | * period that still has RCU readers blocked! This function must be |
| 638 | * invoked -before- updating this rnp's ->gpnum, and the rnp's ->lock |
| 639 | * must be held by the caller. |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 640 | * |
| 641 | * Also, if there are blocked tasks on the list, they automatically |
| 642 | * block the newly created grace period, so set up ->gp_tasks accordingly. |
Paul E. McKenney | b0e165c0 | 2009-09-13 09:15:09 -0700 | [diff] [blame] | 643 | */ |
| 644 | static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) |
| 645 | { |
Paul E. McKenney | c5ebe66 | 2017-06-19 10:32:23 -0700 | [diff] [blame] | 646 | struct task_struct *t; |
| 647 | |
Paul E. McKenney | ea9b0c8 | 2017-04-28 13:19:28 -0700 | [diff] [blame] | 648 | RCU_LOCKDEP_WARN(preemptible(), "rcu_preempt_check_blocked_tasks() invoked with preemption enabled!!!\n"); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 649 | WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); |
Paul E. McKenney | c5ebe66 | 2017-06-19 10:32:23 -0700 | [diff] [blame] | 650 | if (rcu_preempt_has_tasks(rnp)) { |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 651 | rnp->gp_tasks = rnp->blkd_tasks.next; |
Paul E. McKenney | c5ebe66 | 2017-06-19 10:32:23 -0700 | [diff] [blame] | 652 | t = container_of(rnp->gp_tasks, struct task_struct, |
| 653 | rcu_node_entry); |
| 654 | trace_rcu_unlock_preempted_task(TPS("rcu_preempt-GPS"), |
| 655 | rnp->gpnum, t->pid); |
| 656 | } |
Paul E. McKenney | 28ecd58 | 2009-09-18 09:50:17 -0700 | [diff] [blame] | 657 | WARN_ON_ONCE(rnp->qsmask); |
Paul E. McKenney | b0e165c0 | 2009-09-13 09:15:09 -0700 | [diff] [blame] | 658 | } |
| 659 | |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 660 | /* |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 661 | * Check for a quiescent state from the current CPU. When a task blocks, |
| 662 | * the task is recorded in the corresponding CPU's rcu_node structure, |
| 663 | * which is checked elsewhere. |
| 664 | * |
| 665 | * Caller must disable hard irqs. |
| 666 | */ |
Paul E. McKenney | 86aea0e | 2014-10-21 08:12:00 -0700 | [diff] [blame] | 667 | static void rcu_preempt_check_callbacks(void) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 668 | { |
| 669 | struct task_struct *t = current; |
| 670 | |
| 671 | if (t->rcu_read_lock_nesting == 0) { |
Paul E. McKenney | 284a8c9 | 2014-08-14 16:38:46 -0700 | [diff] [blame] | 672 | rcu_preempt_qs(); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 673 | return; |
| 674 | } |
Paul E. McKenney | 10f39bb | 2011-07-17 21:14:35 -0700 | [diff] [blame] | 675 | if (t->rcu_read_lock_nesting > 0 && |
Paul E. McKenney | 97c668b | 2015-08-06 11:31:51 -0700 | [diff] [blame] | 676 | __this_cpu_read(rcu_data_p->core_needs_qs) && |
Paul E. McKenney | 5b74c45 | 2015-08-06 15:16:57 -0700 | [diff] [blame] | 677 | __this_cpu_read(rcu_data_p->cpu_no_qs.b.norm)) |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 678 | t->rcu_read_unlock_special.b.need_qs = true; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 679 | } |
| 680 | |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 681 | #ifdef CONFIG_RCU_BOOST |
| 682 | |
Shaohua Li | 0922337 | 2011-06-14 13:26:25 +0800 | [diff] [blame] | 683 | static void rcu_preempt_do_callbacks(void) |
| 684 | { |
Paul E. McKenney | 2927a68 | 2015-03-04 07:53:04 -0800 | [diff] [blame] | 685 | rcu_do_batch(rcu_state_p, this_cpu_ptr(rcu_data_p)); |
Shaohua Li | 0922337 | 2011-06-14 13:26:25 +0800 | [diff] [blame] | 686 | } |
| 687 | |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 688 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
| 689 | |
Paul E. McKenney | a68a2bb | 2017-05-03 08:34:57 -0700 | [diff] [blame] | 690 | /** |
| 691 | * call_rcu() - Queue an RCU callback for invocation after a grace period. |
| 692 | * @head: structure to be used for queueing the RCU updates. |
| 693 | * @func: actual callback function to be invoked after the grace period |
| 694 | * |
| 695 | * The callback function will be invoked some time after a full grace |
| 696 | * period elapses, in other words after all pre-existing RCU read-side |
| 697 | * critical sections have completed. However, the callback function |
| 698 | * might well execute concurrently with RCU read-side critical sections |
| 699 | * that started after call_rcu() was invoked. RCU read-side critical |
| 700 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), |
| 701 | * and may be nested. |
| 702 | * |
| 703 | * Note that all CPUs must agree that the grace period extended beyond |
| 704 | * all pre-existing RCU read-side critical section. On systems with more |
| 705 | * than one CPU, this means that when "func()" is invoked, each CPU is |
| 706 | * guaranteed to have executed a full memory barrier since the end of its |
| 707 | * last RCU read-side critical section whose beginning preceded the call |
| 708 | * to call_rcu(). It also means that each CPU executing an RCU read-side |
| 709 | * critical section that continues beyond the start of "func()" must have |
| 710 | * executed a memory barrier after the call_rcu() but before the beginning |
| 711 | * of that RCU read-side critical section. Note that these guarantees |
| 712 | * include CPUs that are offline, idle, or executing in user mode, as |
| 713 | * well as CPUs that are executing in the kernel. |
| 714 | * |
| 715 | * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the |
| 716 | * resulting RCU callback function "func()", then both CPU A and CPU B are |
| 717 | * guaranteed to execute a full memory barrier during the time interval |
| 718 | * between the call to call_rcu() and the invocation of "func()" -- even |
| 719 | * if CPU A and CPU B are the same CPU (but again only if the system has |
| 720 | * more than one CPU). |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 721 | */ |
Boqun Feng | b6a4ae7 | 2015-07-29 13:29:38 +0800 | [diff] [blame] | 722 | void call_rcu(struct rcu_head *head, rcu_callback_t func) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 723 | { |
Paul E. McKenney | e63c887 | 2015-03-03 12:56:43 -0800 | [diff] [blame] | 724 | __call_rcu(head, func, rcu_state_p, -1, 0); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 725 | } |
| 726 | EXPORT_SYMBOL_GPL(call_rcu); |
| 727 | |
Paul E. McKenney | 6ebb237 | 2009-11-22 08:53:50 -0800 | [diff] [blame] | 728 | /** |
| 729 | * synchronize_rcu - wait until a grace period has elapsed. |
| 730 | * |
| 731 | * Control will return to the caller some time after a full grace |
| 732 | * period has elapsed, in other words after all currently executing RCU |
Paul E. McKenney | 77d8485 | 2010-07-08 17:38:59 -0700 | [diff] [blame] | 733 | * read-side critical sections have completed. Note, however, that |
| 734 | * upon return from synchronize_rcu(), the caller might well be executing |
| 735 | * concurrently with new RCU read-side critical sections that began while |
| 736 | * synchronize_rcu() was waiting. RCU read-side critical sections are |
| 737 | * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested. |
Paul E. McKenney | f0a0e6f | 2012-10-23 13:47:01 -0700 | [diff] [blame] | 738 | * |
Paul E. McKenney | e28371c | 2017-04-17 09:59:53 -0700 | [diff] [blame] | 739 | * See the description of synchronize_sched() for more detailed |
| 740 | * information on memory-ordering guarantees. However, please note |
| 741 | * that -only- the memory-ordering guarantees apply. For example, |
| 742 | * synchronize_rcu() is -not- guaranteed to wait on things like code |
| 743 | * protected by preempt_disable(), instead, synchronize_rcu() is -only- |
| 744 | * guaranteed to wait on RCU read-side critical sections, that is, sections |
| 745 | * of code protected by rcu_read_lock(). |
Paul E. McKenney | 6ebb237 | 2009-11-22 08:53:50 -0800 | [diff] [blame] | 746 | */ |
| 747 | void synchronize_rcu(void) |
| 748 | { |
Paul E. McKenney | f78f5b9 | 2015-06-18 15:50:02 -0700 | [diff] [blame] | 749 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || |
| 750 | lock_is_held(&rcu_lock_map) || |
| 751 | lock_is_held(&rcu_sched_lock_map), |
| 752 | "Illegal synchronize_rcu() in RCU read-side critical section"); |
Paul E. McKenney | 52d7e48 | 2017-01-10 02:28:26 -0800 | [diff] [blame] | 753 | if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) |
Paul E. McKenney | 6ebb237 | 2009-11-22 08:53:50 -0800 | [diff] [blame] | 754 | return; |
Paul E. McKenney | 5afff48 | 2015-02-18 16:39:09 -0800 | [diff] [blame] | 755 | if (rcu_gp_is_expedited()) |
Antti P Miettinen | 3705b88 | 2012-10-05 09:59:15 +0300 | [diff] [blame] | 756 | synchronize_rcu_expedited(); |
| 757 | else |
| 758 | wait_rcu_gp(call_rcu); |
Paul E. McKenney | 6ebb237 | 2009-11-22 08:53:50 -0800 | [diff] [blame] | 759 | } |
| 760 | EXPORT_SYMBOL_GPL(synchronize_rcu); |
| 761 | |
Paul E. McKenney | e74f4c4 | 2009-10-06 21:48:17 -0700 | [diff] [blame] | 762 | /** |
| 763 | * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete. |
Paul E. McKenney | f0a0e6f | 2012-10-23 13:47:01 -0700 | [diff] [blame] | 764 | * |
| 765 | * Note that this primitive does not necessarily wait for an RCU grace period |
| 766 | * to complete. For example, if there are no RCU callbacks queued anywhere |
| 767 | * in the system, then rcu_barrier() is within its rights to return |
| 768 | * immediately, without waiting for anything, much less an RCU grace period. |
Paul E. McKenney | e74f4c4 | 2009-10-06 21:48:17 -0700 | [diff] [blame] | 769 | */ |
| 770 | void rcu_barrier(void) |
| 771 | { |
Paul E. McKenney | e63c887 | 2015-03-03 12:56:43 -0800 | [diff] [blame] | 772 | _rcu_barrier(rcu_state_p); |
Paul E. McKenney | e74f4c4 | 2009-10-06 21:48:17 -0700 | [diff] [blame] | 773 | } |
| 774 | EXPORT_SYMBOL_GPL(rcu_barrier); |
| 775 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 776 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 777 | * Initialize preemptible RCU's state structures. |
Paul E. McKenney | 1eba8f8 | 2009-09-23 09:50:42 -0700 | [diff] [blame] | 778 | */ |
| 779 | static void __init __rcu_init_preempt(void) |
| 780 | { |
Paul E. McKenney | a87f203 | 2015-10-20 12:38:49 -0700 | [diff] [blame] | 781 | rcu_init_one(rcu_state_p); |
Paul E. McKenney | 1eba8f8 | 2009-09-23 09:50:42 -0700 | [diff] [blame] | 782 | } |
| 783 | |
Paul E. McKenney | 2439b69 | 2013-04-11 10:15:52 -0700 | [diff] [blame] | 784 | /* |
| 785 | * Check for a task exiting while in a preemptible-RCU read-side |
| 786 | * critical section, clean up if so. No need to issue warnings, |
| 787 | * as debug_check_no_locks_held() already does this if lockdep |
| 788 | * is enabled. |
| 789 | */ |
| 790 | void exit_rcu(void) |
| 791 | { |
| 792 | struct task_struct *t = current; |
| 793 | |
| 794 | if (likely(list_empty(¤t->rcu_node_entry))) |
| 795 | return; |
| 796 | t->rcu_read_lock_nesting = 1; |
| 797 | barrier(); |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 798 | t->rcu_read_unlock_special.b.blocked = true; |
Paul E. McKenney | 2439b69 | 2013-04-11 10:15:52 -0700 | [diff] [blame] | 799 | __rcu_read_unlock(); |
| 800 | } |
| 801 | |
Pranith Kumar | 28f6569 | 2014-09-22 14:00:48 -0400 | [diff] [blame] | 802 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 803 | |
Paul E. McKenney | b28a7c0 | 2015-03-04 07:39:27 -0800 | [diff] [blame] | 804 | static struct rcu_state *const rcu_state_p = &rcu_sched_state; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 805 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 806 | /* |
| 807 | * Tell them what RCU they are running. |
| 808 | */ |
Paul E. McKenney | 0e0fc1c | 2009-11-11 11:28:06 -0800 | [diff] [blame] | 809 | static void __init rcu_bootup_announce(void) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 810 | { |
Paul E. McKenney | efc151c | 2013-03-18 16:24:11 -0700 | [diff] [blame] | 811 | pr_info("Hierarchical RCU implementation.\n"); |
Paul E. McKenney | 26845c2 | 2010-04-13 14:19:23 -0700 | [diff] [blame] | 812 | rcu_bootup_announce_oddness(); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 813 | } |
| 814 | |
| 815 | /* |
Paul E. McKenney | cba6d0d | 2012-07-02 07:08:42 -0700 | [diff] [blame] | 816 | * Because preemptible RCU does not exist, we never have to check for |
| 817 | * CPUs being in quiescent states. |
| 818 | */ |
Paul E. McKenney | 5b72f96 | 2017-04-12 15:29:14 -0700 | [diff] [blame] | 819 | static void rcu_preempt_note_context_switch(bool preempt) |
Paul E. McKenney | cba6d0d | 2012-07-02 07:08:42 -0700 | [diff] [blame] | 820 | { |
| 821 | } |
| 822 | |
| 823 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 824 | * Because preemptible RCU does not exist, there are never any preempted |
Paul E. McKenney | fc2219d4 | 2009-09-23 09:50:41 -0700 | [diff] [blame] | 825 | * RCU readers. |
| 826 | */ |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 827 | static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) |
Paul E. McKenney | fc2219d4 | 2009-09-23 09:50:41 -0700 | [diff] [blame] | 828 | { |
| 829 | return 0; |
| 830 | } |
| 831 | |
Paul E. McKenney | 8af3a5e | 2014-10-31 11:22:37 -0700 | [diff] [blame] | 832 | /* |
| 833 | * Because there is no preemptible RCU, there can be no readers blocked. |
| 834 | */ |
| 835 | static bool rcu_preempt_has_tasks(struct rcu_node *rnp) |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 836 | { |
Paul E. McKenney | 8af3a5e | 2014-10-31 11:22:37 -0700 | [diff] [blame] | 837 | return false; |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 838 | } |
| 839 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 840 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 841 | * Because preemptible RCU does not exist, we never have to check for |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 842 | * tasks blocked within RCU read-side critical sections. |
| 843 | */ |
Paul E. McKenney | 1ed509a | 2010-02-22 17:05:05 -0800 | [diff] [blame] | 844 | static void rcu_print_detail_task_stall(struct rcu_state *rsp) |
| 845 | { |
| 846 | } |
| 847 | |
| 848 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 849 | * Because preemptible RCU does not exist, we never have to check for |
Paul E. McKenney | 1ed509a | 2010-02-22 17:05:05 -0800 | [diff] [blame] | 850 | * tasks blocked within RCU read-side critical sections. |
| 851 | */ |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 852 | static int rcu_print_task_stall(struct rcu_node *rnp) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 853 | { |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 854 | return 0; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 855 | } |
| 856 | |
Paul E. McKenney | 53d84e0 | 2010-08-10 14:28:53 -0700 | [diff] [blame] | 857 | /* |
Paul E. McKenney | 74611ec | 2015-08-18 10:20:43 -0700 | [diff] [blame] | 858 | * Because preemptible RCU does not exist, we never have to check for |
| 859 | * tasks blocked within RCU read-side critical sections that are |
| 860 | * blocking the current expedited grace period. |
| 861 | */ |
| 862 | static int rcu_print_task_exp_stall(struct rcu_node *rnp) |
| 863 | { |
| 864 | return 0; |
| 865 | } |
| 866 | |
| 867 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 868 | * Because there is no preemptible RCU, there can be no readers blocked, |
Paul E. McKenney | 49e2912 | 2009-09-18 09:50:19 -0700 | [diff] [blame] | 869 | * so there is no need to check for blocked tasks. So check only for |
| 870 | * bogus qsmask values. |
Paul E. McKenney | b0e165c0 | 2009-09-13 09:15:09 -0700 | [diff] [blame] | 871 | */ |
| 872 | static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) |
| 873 | { |
Paul E. McKenney | 49e2912 | 2009-09-18 09:50:19 -0700 | [diff] [blame] | 874 | WARN_ON_ONCE(rnp->qsmask); |
Paul E. McKenney | b0e165c0 | 2009-09-13 09:15:09 -0700 | [diff] [blame] | 875 | } |
| 876 | |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 877 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 878 | * Because preemptible RCU does not exist, it never has any callbacks |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 879 | * to check. |
| 880 | */ |
Paul E. McKenney | 86aea0e | 2014-10-21 08:12:00 -0700 | [diff] [blame] | 881 | static void rcu_preempt_check_callbacks(void) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 882 | { |
| 883 | } |
| 884 | |
| 885 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 886 | * Because preemptible RCU does not exist, rcu_barrier() is just |
Paul E. McKenney | e74f4c4 | 2009-10-06 21:48:17 -0700 | [diff] [blame] | 887 | * another name for rcu_barrier_sched(). |
| 888 | */ |
| 889 | void rcu_barrier(void) |
| 890 | { |
| 891 | rcu_barrier_sched(); |
| 892 | } |
| 893 | EXPORT_SYMBOL_GPL(rcu_barrier); |
| 894 | |
| 895 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 896 | * Because preemptible RCU does not exist, it need not be initialized. |
Paul E. McKenney | 1eba8f8 | 2009-09-23 09:50:42 -0700 | [diff] [blame] | 897 | */ |
| 898 | static void __init __rcu_init_preempt(void) |
| 899 | { |
| 900 | } |
| 901 | |
Paul E. McKenney | 2439b69 | 2013-04-11 10:15:52 -0700 | [diff] [blame] | 902 | /* |
| 903 | * Because preemptible RCU does not exist, tasks cannot possibly exit |
| 904 | * while in preemptible RCU read-side critical sections. |
| 905 | */ |
| 906 | void exit_rcu(void) |
| 907 | { |
| 908 | } |
| 909 | |
Pranith Kumar | 28f6569 | 2014-09-22 14:00:48 -0400 | [diff] [blame] | 910 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 911 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 912 | #ifdef CONFIG_RCU_BOOST |
| 913 | |
Peter Zijlstra | 1696a8b | 2013-10-31 18:18:19 +0100 | [diff] [blame] | 914 | #include "../locking/rtmutex_common.h" |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 915 | |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 916 | static void rcu_wake_cond(struct task_struct *t, int status) |
| 917 | { |
| 918 | /* |
| 919 | * If the thread is yielding, only wake it when this |
| 920 | * is invoked from idle |
| 921 | */ |
| 922 | if (status != RCU_KTHREAD_YIELDING || is_idle_task(current)) |
| 923 | wake_up_process(t); |
| 924 | } |
| 925 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 926 | /* |
| 927 | * Carry out RCU priority boosting on the task indicated by ->exp_tasks |
| 928 | * or ->boost_tasks, advancing the pointer to the next task in the |
| 929 | * ->blkd_tasks list. |
| 930 | * |
| 931 | * Note that irqs must be enabled: boosting the task can block. |
| 932 | * Returns 1 if there are more tasks needing to be boosted. |
| 933 | */ |
| 934 | static int rcu_boost(struct rcu_node *rnp) |
| 935 | { |
| 936 | unsigned long flags; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 937 | struct task_struct *t; |
| 938 | struct list_head *tb; |
| 939 | |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 940 | if (READ_ONCE(rnp->exp_tasks) == NULL && |
| 941 | READ_ONCE(rnp->boost_tasks) == NULL) |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 942 | return 0; /* Nothing left to boost. */ |
| 943 | |
Peter Zijlstra | 2a67e74 | 2015-10-08 12:24:23 +0200 | [diff] [blame] | 944 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 945 | |
| 946 | /* |
| 947 | * Recheck under the lock: all tasks in need of boosting |
| 948 | * might exit their RCU read-side critical sections on their own. |
| 949 | */ |
| 950 | if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) { |
Boqun Feng | 67c583a7 | 2015-12-29 12:18:47 +0800 | [diff] [blame] | 951 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 952 | return 0; |
| 953 | } |
| 954 | |
| 955 | /* |
| 956 | * Preferentially boost tasks blocking expedited grace periods. |
| 957 | * This cannot starve the normal grace periods because a second |
| 958 | * expedited grace period must boost all blocked tasks, including |
| 959 | * those blocking the pre-existing normal grace period. |
| 960 | */ |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 961 | if (rnp->exp_tasks != NULL) { |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 962 | tb = rnp->exp_tasks; |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 963 | rnp->n_exp_boosts++; |
| 964 | } else { |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 965 | tb = rnp->boost_tasks; |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 966 | rnp->n_normal_boosts++; |
| 967 | } |
| 968 | rnp->n_tasks_boosted++; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 969 | |
| 970 | /* |
| 971 | * We boost task t by manufacturing an rt_mutex that appears to |
| 972 | * be held by task t. We leave a pointer to that rt_mutex where |
| 973 | * task t can find it, and task t will release the mutex when it |
| 974 | * exits its outermost RCU read-side critical section. Then |
| 975 | * simply acquiring this artificial rt_mutex will boost task |
| 976 | * t's priority. (Thanks to tglx for suggesting this approach!) |
| 977 | * |
| 978 | * Note that task t must acquire rnp->lock to remove itself from |
| 979 | * the ->blkd_tasks list, which it will do from exit() if from |
| 980 | * nowhere else. We therefore are guaranteed that task t will |
| 981 | * stay around at least until we drop rnp->lock. Note that |
| 982 | * rnp->lock also resolves races between our priority boosting |
| 983 | * and task t's exiting its outermost RCU read-side critical |
| 984 | * section. |
| 985 | */ |
| 986 | t = container_of(tb, struct task_struct, rcu_node_entry); |
Paul E. McKenney | abaa93d | 2014-06-12 13:30:25 -0700 | [diff] [blame] | 987 | rt_mutex_init_proxy_locked(&rnp->boost_mtx, t); |
Boqun Feng | 67c583a7 | 2015-12-29 12:18:47 +0800 | [diff] [blame] | 988 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
Paul E. McKenney | abaa93d | 2014-06-12 13:30:25 -0700 | [diff] [blame] | 989 | /* Lock only for side effect: boosts task t's priority. */ |
| 990 | rt_mutex_lock(&rnp->boost_mtx); |
| 991 | rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */ |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 992 | |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 993 | return READ_ONCE(rnp->exp_tasks) != NULL || |
| 994 | READ_ONCE(rnp->boost_tasks) != NULL; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 995 | } |
| 996 | |
| 997 | /* |
Paul E. McKenney | bc17ea1 | 2015-06-06 08:11:43 -0700 | [diff] [blame] | 998 | * Priority-boosting kthread, one per leaf rcu_node. |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 999 | */ |
| 1000 | static int rcu_boost_kthread(void *arg) |
| 1001 | { |
| 1002 | struct rcu_node *rnp = (struct rcu_node *)arg; |
| 1003 | int spincnt = 0; |
| 1004 | int more2boost; |
| 1005 | |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1006 | trace_rcu_utilization(TPS("Start boost kthread@init")); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1007 | for (;;) { |
Paul E. McKenney | d71df90 | 2011-03-29 17:48:28 -0700 | [diff] [blame] | 1008 | rnp->boost_kthread_status = RCU_KTHREAD_WAITING; |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1009 | trace_rcu_utilization(TPS("End boost kthread@rcu_wait")); |
Peter Zijlstra | 08bca60 | 2011-05-20 16:06:29 -0700 | [diff] [blame] | 1010 | rcu_wait(rnp->boost_tasks || rnp->exp_tasks); |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1011 | trace_rcu_utilization(TPS("Start boost kthread@rcu_wait")); |
Paul E. McKenney | d71df90 | 2011-03-29 17:48:28 -0700 | [diff] [blame] | 1012 | rnp->boost_kthread_status = RCU_KTHREAD_RUNNING; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1013 | more2boost = rcu_boost(rnp); |
| 1014 | if (more2boost) |
| 1015 | spincnt++; |
| 1016 | else |
| 1017 | spincnt = 0; |
| 1018 | if (spincnt > 10) { |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1019 | rnp->boost_kthread_status = RCU_KTHREAD_YIELDING; |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1020 | trace_rcu_utilization(TPS("End boost kthread@rcu_yield")); |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1021 | schedule_timeout_interruptible(2); |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1022 | trace_rcu_utilization(TPS("Start boost kthread@rcu_yield")); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1023 | spincnt = 0; |
| 1024 | } |
| 1025 | } |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1026 | /* NOTREACHED */ |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1027 | trace_rcu_utilization(TPS("End boost kthread@notreached")); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1028 | return 0; |
| 1029 | } |
| 1030 | |
| 1031 | /* |
| 1032 | * Check to see if it is time to start boosting RCU readers that are |
| 1033 | * blocking the current grace period, and, if so, tell the per-rcu_node |
| 1034 | * kthread to start boosting them. If there is an expedited grace |
| 1035 | * period in progress, it is always time to boost. |
| 1036 | * |
Paul E. McKenney | b065a85 | 2012-08-01 15:57:54 -0700 | [diff] [blame] | 1037 | * The caller must hold rnp->lock, which this function releases. |
| 1038 | * The ->boost_kthread_task is immortal, so we don't need to worry |
| 1039 | * about it going away. |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1040 | */ |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1041 | static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) |
Pranith Kumar | 615e41c | 2014-06-11 16:39:40 -0400 | [diff] [blame] | 1042 | __releases(rnp->lock) |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1043 | { |
| 1044 | struct task_struct *t; |
| 1045 | |
Paul E. McKenney | ea9b0c8 | 2017-04-28 13:19:28 -0700 | [diff] [blame] | 1046 | lockdep_assert_held(&rnp->lock); |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 1047 | if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) { |
Boqun Feng | 67c583a7 | 2015-12-29 12:18:47 +0800 | [diff] [blame] | 1048 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1049 | return; |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 1050 | } |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1051 | if (rnp->exp_tasks != NULL || |
| 1052 | (rnp->gp_tasks != NULL && |
| 1053 | rnp->boost_tasks == NULL && |
| 1054 | rnp->qsmask == 0 && |
| 1055 | ULONG_CMP_GE(jiffies, rnp->boost_time))) { |
| 1056 | if (rnp->exp_tasks == NULL) |
| 1057 | rnp->boost_tasks = rnp->gp_tasks; |
Boqun Feng | 67c583a7 | 2015-12-29 12:18:47 +0800 | [diff] [blame] | 1058 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1059 | t = rnp->boost_kthread_task; |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1060 | if (t) |
| 1061 | rcu_wake_cond(t, rnp->boost_kthread_status); |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1062 | } else { |
Boqun Feng | 67c583a7 | 2015-12-29 12:18:47 +0800 | [diff] [blame] | 1063 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1064 | } |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1065 | } |
| 1066 | |
Paul E. McKenney | 0f962a5 | 2011-04-14 12:13:53 -0700 | [diff] [blame] | 1067 | /* |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1068 | * Wake up the per-CPU kthread to invoke RCU callbacks. |
| 1069 | */ |
| 1070 | static void invoke_rcu_callbacks_kthread(void) |
| 1071 | { |
| 1072 | unsigned long flags; |
| 1073 | |
| 1074 | local_irq_save(flags); |
| 1075 | __this_cpu_write(rcu_cpu_has_work, 1); |
Shaohua Li | 1eb5212 | 2011-06-16 16:02:54 -0700 | [diff] [blame] | 1076 | if (__this_cpu_read(rcu_cpu_kthread_task) != NULL && |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1077 | current != __this_cpu_read(rcu_cpu_kthread_task)) { |
| 1078 | rcu_wake_cond(__this_cpu_read(rcu_cpu_kthread_task), |
| 1079 | __this_cpu_read(rcu_cpu_kthread_status)); |
| 1080 | } |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1081 | local_irq_restore(flags); |
| 1082 | } |
| 1083 | |
| 1084 | /* |
Paul E. McKenney | dff1672 | 2011-11-29 15:57:13 -0800 | [diff] [blame] | 1085 | * Is the current CPU running the RCU-callbacks kthread? |
| 1086 | * Caller must have preemption disabled. |
| 1087 | */ |
| 1088 | static bool rcu_is_callbacks_kthread(void) |
| 1089 | { |
Christoph Lameter | c9d4b0a | 2013-08-31 13:34:10 -0700 | [diff] [blame] | 1090 | return __this_cpu_read(rcu_cpu_kthread_task) == current; |
Paul E. McKenney | dff1672 | 2011-11-29 15:57:13 -0800 | [diff] [blame] | 1091 | } |
| 1092 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1093 | #define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000) |
| 1094 | |
| 1095 | /* |
| 1096 | * Do priority-boost accounting for the start of a new grace period. |
| 1097 | */ |
| 1098 | static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) |
| 1099 | { |
| 1100 | rnp->boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES; |
| 1101 | } |
| 1102 | |
| 1103 | /* |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1104 | * Create an RCU-boost kthread for the specified node if one does not |
| 1105 | * already exist. We only create this kthread for preemptible RCU. |
| 1106 | * Returns zero if all is well, a negated errno otherwise. |
| 1107 | */ |
Paul Gortmaker | 49fb4c6 | 2013-06-19 14:52:21 -0400 | [diff] [blame] | 1108 | static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp, |
Paul E. McKenney | 0aa04b0 | 2015-01-23 21:52:37 -0800 | [diff] [blame] | 1109 | struct rcu_node *rnp) |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1110 | { |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1111 | int rnp_index = rnp - &rsp->node[0]; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1112 | unsigned long flags; |
| 1113 | struct sched_param sp; |
| 1114 | struct task_struct *t; |
| 1115 | |
Paul E. McKenney | e63c887 | 2015-03-03 12:56:43 -0800 | [diff] [blame] | 1116 | if (rcu_state_p != rsp) |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1117 | return 0; |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1118 | |
Paul E. McKenney | 0aa04b0 | 2015-01-23 21:52:37 -0800 | [diff] [blame] | 1119 | if (!rcu_scheduler_fully_active || rcu_rnp_online_cpus(rnp) == 0) |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1120 | return 0; |
| 1121 | |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1122 | rsp->boost = 1; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1123 | if (rnp->boost_kthread_task != NULL) |
| 1124 | return 0; |
| 1125 | t = kthread_create(rcu_boost_kthread, (void *)rnp, |
Mike Galbraith | 5b61b0b | 2011-08-19 11:39:11 -0700 | [diff] [blame] | 1126 | "rcub/%d", rnp_index); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1127 | if (IS_ERR(t)) |
| 1128 | return PTR_ERR(t); |
Peter Zijlstra | 2a67e74 | 2015-10-08 12:24:23 +0200 | [diff] [blame] | 1129 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1130 | rnp->boost_kthread_task = t; |
Boqun Feng | 67c583a7 | 2015-12-29 12:18:47 +0800 | [diff] [blame] | 1131 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
Clark Williams | 21871d7 | 2014-09-12 21:21:09 -0500 | [diff] [blame] | 1132 | sp.sched_priority = kthread_prio; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1133 | sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); |
Paul E. McKenney | 9a43273 | 2011-05-30 20:38:55 -0700 | [diff] [blame] | 1134 | wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */ |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1135 | return 0; |
| 1136 | } |
| 1137 | |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1138 | static void rcu_kthread_do_work(void) |
| 1139 | { |
Christoph Lameter | c9d4b0a | 2013-08-31 13:34:10 -0700 | [diff] [blame] | 1140 | rcu_do_batch(&rcu_sched_state, this_cpu_ptr(&rcu_sched_data)); |
| 1141 | rcu_do_batch(&rcu_bh_state, this_cpu_ptr(&rcu_bh_data)); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1142 | rcu_preempt_do_callbacks(); |
| 1143 | } |
| 1144 | |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1145 | static void rcu_cpu_kthread_setup(unsigned int cpu) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1146 | { |
| 1147 | struct sched_param sp; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1148 | |
Clark Williams | 21871d7 | 2014-09-12 21:21:09 -0500 | [diff] [blame] | 1149 | sp.sched_priority = kthread_prio; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1150 | sched_setscheduler_nocheck(current, SCHED_FIFO, &sp); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1151 | } |
| 1152 | |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1153 | static void rcu_cpu_kthread_park(unsigned int cpu) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1154 | { |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1155 | per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; |
| 1156 | } |
| 1157 | |
| 1158 | static int rcu_cpu_kthread_should_run(unsigned int cpu) |
| 1159 | { |
Christoph Lameter | c9d4b0a | 2013-08-31 13:34:10 -0700 | [diff] [blame] | 1160 | return __this_cpu_read(rcu_cpu_has_work); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1161 | } |
| 1162 | |
| 1163 | /* |
| 1164 | * Per-CPU kernel thread that invokes RCU callbacks. This replaces the |
Paul E. McKenney | e0f2306 | 2011-06-21 01:29:39 -0700 | [diff] [blame] | 1165 | * RCU softirq used in flavors and configurations of RCU that do not |
| 1166 | * support RCU priority boosting. |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1167 | */ |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1168 | static void rcu_cpu_kthread(unsigned int cpu) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1169 | { |
Christoph Lameter | c9d4b0a | 2013-08-31 13:34:10 -0700 | [diff] [blame] | 1170 | unsigned int *statusp = this_cpu_ptr(&rcu_cpu_kthread_status); |
| 1171 | char work, *workp = this_cpu_ptr(&rcu_cpu_has_work); |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1172 | int spincnt; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1173 | |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1174 | for (spincnt = 0; spincnt < 10; spincnt++) { |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1175 | trace_rcu_utilization(TPS("Start CPU kthread@rcu_wait")); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1176 | local_bh_disable(); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1177 | *statusp = RCU_KTHREAD_RUNNING; |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1178 | this_cpu_inc(rcu_cpu_kthread_loops); |
| 1179 | local_irq_disable(); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1180 | work = *workp; |
| 1181 | *workp = 0; |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1182 | local_irq_enable(); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1183 | if (work) |
| 1184 | rcu_kthread_do_work(); |
| 1185 | local_bh_enable(); |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1186 | if (*workp == 0) { |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1187 | trace_rcu_utilization(TPS("End CPU kthread@rcu_wait")); |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1188 | *statusp = RCU_KTHREAD_WAITING; |
| 1189 | return; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1190 | } |
| 1191 | } |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1192 | *statusp = RCU_KTHREAD_YIELDING; |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1193 | trace_rcu_utilization(TPS("Start CPU kthread@rcu_yield")); |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1194 | schedule_timeout_interruptible(2); |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1195 | trace_rcu_utilization(TPS("End CPU kthread@rcu_yield")); |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1196 | *statusp = RCU_KTHREAD_WAITING; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1197 | } |
| 1198 | |
| 1199 | /* |
| 1200 | * Set the per-rcu_node kthread's affinity to cover all CPUs that are |
| 1201 | * served by the rcu_node in question. The CPU hotplug lock is still |
| 1202 | * held, so the value of rnp->qsmaskinit will be stable. |
| 1203 | * |
| 1204 | * We don't include outgoingcpu in the affinity set, use -1 if there is |
| 1205 | * no outgoing CPU. If there are no CPUs left in the affinity set, |
| 1206 | * this function allows the kthread to execute on any CPU. |
| 1207 | */ |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1208 | static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1209 | { |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1210 | struct task_struct *t = rnp->boost_kthread_task; |
Paul E. McKenney | 0aa04b0 | 2015-01-23 21:52:37 -0800 | [diff] [blame] | 1211 | unsigned long mask = rcu_rnp_online_cpus(rnp); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1212 | cpumask_var_t cm; |
| 1213 | int cpu; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1214 | |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1215 | if (!t) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1216 | return; |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1217 | if (!zalloc_cpumask_var(&cm, GFP_KERNEL)) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1218 | return; |
Mark Rutland | bc75e99 | 2016-06-03 15:20:04 +0100 | [diff] [blame] | 1219 | for_each_leaf_node_possible_cpu(rnp, cpu) |
| 1220 | if ((mask & leaf_node_cpu_bit(rnp, cpu)) && |
| 1221 | cpu != outgoingcpu) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1222 | cpumask_set_cpu(cpu, cm); |
Paul E. McKenney | 5d0b024 | 2014-11-10 08:07:08 -0800 | [diff] [blame] | 1223 | if (cpumask_weight(cm) == 0) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1224 | cpumask_setall(cm); |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1225 | set_cpus_allowed_ptr(t, cm); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1226 | free_cpumask_var(cm); |
| 1227 | } |
| 1228 | |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1229 | static struct smp_hotplug_thread rcu_cpu_thread_spec = { |
| 1230 | .store = &rcu_cpu_kthread_task, |
| 1231 | .thread_should_run = rcu_cpu_kthread_should_run, |
| 1232 | .thread_fn = rcu_cpu_kthread, |
| 1233 | .thread_comm = "rcuc/%u", |
| 1234 | .setup = rcu_cpu_kthread_setup, |
| 1235 | .park = rcu_cpu_kthread_park, |
| 1236 | }; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1237 | |
| 1238 | /* |
Paul E. McKenney | 9386c0b | 2014-07-13 12:00:53 -0700 | [diff] [blame] | 1239 | * Spawn boost kthreads -- called as soon as the scheduler is running. |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1240 | */ |
Paul E. McKenney | 9386c0b | 2014-07-13 12:00:53 -0700 | [diff] [blame] | 1241 | static void __init rcu_spawn_boost_kthreads(void) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1242 | { |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1243 | struct rcu_node *rnp; |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1244 | int cpu; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1245 | |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1246 | for_each_possible_cpu(cpu) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1247 | per_cpu(rcu_cpu_has_work, cpu) = 0; |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1248 | BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec)); |
Paul E. McKenney | 3e9f5c7 | 2014-11-03 18:15:17 -0800 | [diff] [blame] | 1249 | rcu_for_each_leaf_node(rcu_state_p, rnp) |
| 1250 | (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1251 | } |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1252 | |
Paul Gortmaker | 49fb4c6 | 2013-06-19 14:52:21 -0400 | [diff] [blame] | 1253 | static void rcu_prepare_kthreads(int cpu) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1254 | { |
Uma Sharma | e534165 | 2014-03-23 22:32:09 -0700 | [diff] [blame] | 1255 | struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1256 | struct rcu_node *rnp = rdp->mynode; |
| 1257 | |
| 1258 | /* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */ |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1259 | if (rcu_scheduler_fully_active) |
Uma Sharma | e534165 | 2014-03-23 22:32:09 -0700 | [diff] [blame] | 1260 | (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1261 | } |
| 1262 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1263 | #else /* #ifdef CONFIG_RCU_BOOST */ |
| 1264 | |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1265 | static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) |
Pranith Kumar | 615e41c | 2014-06-11 16:39:40 -0400 | [diff] [blame] | 1266 | __releases(rnp->lock) |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1267 | { |
Boqun Feng | 67c583a7 | 2015-12-29 12:18:47 +0800 | [diff] [blame] | 1268 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1269 | } |
| 1270 | |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1271 | static void invoke_rcu_callbacks_kthread(void) |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1272 | { |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1273 | WARN_ON_ONCE(1); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1274 | } |
| 1275 | |
Paul E. McKenney | dff1672 | 2011-11-29 15:57:13 -0800 | [diff] [blame] | 1276 | static bool rcu_is_callbacks_kthread(void) |
| 1277 | { |
| 1278 | return false; |
| 1279 | } |
| 1280 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1281 | static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) |
| 1282 | { |
| 1283 | } |
| 1284 | |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1285 | static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1286 | { |
| 1287 | } |
| 1288 | |
Paul E. McKenney | 9386c0b | 2014-07-13 12:00:53 -0700 | [diff] [blame] | 1289 | static void __init rcu_spawn_boost_kthreads(void) |
Paul E. McKenney | b0d3041 | 2011-07-10 15:57:35 -0700 | [diff] [blame] | 1290 | { |
Paul E. McKenney | b0d3041 | 2011-07-10 15:57:35 -0700 | [diff] [blame] | 1291 | } |
Paul E. McKenney | b0d3041 | 2011-07-10 15:57:35 -0700 | [diff] [blame] | 1292 | |
Paul Gortmaker | 49fb4c6 | 2013-06-19 14:52:21 -0400 | [diff] [blame] | 1293 | static void rcu_prepare_kthreads(int cpu) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1294 | { |
| 1295 | } |
| 1296 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1297 | #endif /* #else #ifdef CONFIG_RCU_BOOST */ |
| 1298 | |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1299 | #if !defined(CONFIG_RCU_FAST_NO_HZ) |
| 1300 | |
| 1301 | /* |
| 1302 | * Check to see if any future RCU-related work will need to be done |
| 1303 | * by the current CPU, even if none need be done immediately, returning |
| 1304 | * 1 if so. This function is part of the RCU implementation; it is -not- |
| 1305 | * an exported member of the RCU API. |
| 1306 | * |
Paul E. McKenney | 7cb9249 | 2011-11-28 12:28:34 -0800 | [diff] [blame] | 1307 | * Because we not have RCU_FAST_NO_HZ, just check whether this CPU needs |
| 1308 | * any flavor of RCU. |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1309 | */ |
Thomas Gleixner | c1ad348 | 2015-04-14 21:08:58 +0000 | [diff] [blame] | 1310 | int rcu_needs_cpu(u64 basemono, u64 *nextevt) |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1311 | { |
Thomas Gleixner | c1ad348 | 2015-04-14 21:08:58 +0000 | [diff] [blame] | 1312 | *nextevt = KTIME_MAX; |
Paul E. McKenney | 44c65ff | 2017-05-15 16:26:34 -0700 | [diff] [blame] | 1313 | return rcu_cpu_has_callbacks(NULL); |
Paul E. McKenney | 7cb9249 | 2011-11-28 12:28:34 -0800 | [diff] [blame] | 1314 | } |
| 1315 | |
| 1316 | /* |
| 1317 | * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up |
| 1318 | * after it. |
| 1319 | */ |
Paul E. McKenney | 8fa7845 | 2014-10-22 15:07:37 -0700 | [diff] [blame] | 1320 | static void rcu_cleanup_after_idle(void) |
Paul E. McKenney | 7cb9249 | 2011-11-28 12:28:34 -0800 | [diff] [blame] | 1321 | { |
| 1322 | } |
| 1323 | |
| 1324 | /* |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1325 | * Do the idle-entry grace-period work, which, because CONFIG_RCU_FAST_NO_HZ=n, |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 1326 | * is nothing. |
| 1327 | */ |
Paul E. McKenney | 198bbf8 | 2014-10-22 15:03:43 -0700 | [diff] [blame] | 1328 | static void rcu_prepare_for_idle(void) |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 1329 | { |
| 1330 | } |
| 1331 | |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 1332 | /* |
| 1333 | * Don't bother keeping a running count of the number of RCU callbacks |
| 1334 | * posted because CONFIG_RCU_FAST_NO_HZ=n. |
| 1335 | */ |
| 1336 | static void rcu_idle_count_callbacks_posted(void) |
| 1337 | { |
| 1338 | } |
| 1339 | |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1340 | #else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */ |
| 1341 | |
Paul E. McKenney | f23f7fa | 2011-11-30 15:41:14 -0800 | [diff] [blame] | 1342 | /* |
| 1343 | * This code is invoked when a CPU goes idle, at which point we want |
| 1344 | * to have the CPU do everything required for RCU so that it can enter |
| 1345 | * the energy-efficient dyntick-idle mode. This is handled by a |
| 1346 | * state machine implemented by rcu_prepare_for_idle() below. |
| 1347 | * |
| 1348 | * The following three proprocessor symbols control this state machine: |
| 1349 | * |
Paul E. McKenney | f23f7fa | 2011-11-30 15:41:14 -0800 | [diff] [blame] | 1350 | * RCU_IDLE_GP_DELAY gives the number of jiffies that a CPU is permitted |
| 1351 | * to sleep in dyntick-idle mode with RCU callbacks pending. This |
| 1352 | * is sized to be roughly one RCU grace period. Those energy-efficiency |
| 1353 | * benchmarkers who might otherwise be tempted to set this to a large |
| 1354 | * number, be warned: Setting RCU_IDLE_GP_DELAY too high can hang your |
| 1355 | * system. And if you are -that- concerned about energy efficiency, |
| 1356 | * just power the system down and be done with it! |
Paul E. McKenney | 778d250 | 2012-01-10 14:13:24 -0800 | [diff] [blame] | 1357 | * RCU_IDLE_LAZY_GP_DELAY gives the number of jiffies that a CPU is |
| 1358 | * permitted to sleep in dyntick-idle mode with only lazy RCU |
| 1359 | * callbacks pending. Setting this too high can OOM your system. |
Paul E. McKenney | f23f7fa | 2011-11-30 15:41:14 -0800 | [diff] [blame] | 1360 | * |
| 1361 | * The values below work well in practice. If future workloads require |
| 1362 | * adjustment, they can be converted into kernel config parameters, though |
| 1363 | * making the state machine smarter might be a better option. |
| 1364 | */ |
Paul E. McKenney | e84c48a | 2012-06-04 20:45:10 -0700 | [diff] [blame] | 1365 | #define RCU_IDLE_GP_DELAY 4 /* Roughly one grace period. */ |
Paul E. McKenney | 778d250 | 2012-01-10 14:13:24 -0800 | [diff] [blame] | 1366 | #define RCU_IDLE_LAZY_GP_DELAY (6 * HZ) /* Roughly six seconds. */ |
Paul E. McKenney | f23f7fa | 2011-11-30 15:41:14 -0800 | [diff] [blame] | 1367 | |
Paul E. McKenney | 5e44ce3 | 2012-12-12 12:35:29 -0800 | [diff] [blame] | 1368 | static int rcu_idle_gp_delay = RCU_IDLE_GP_DELAY; |
| 1369 | module_param(rcu_idle_gp_delay, int, 0644); |
| 1370 | static int rcu_idle_lazy_gp_delay = RCU_IDLE_LAZY_GP_DELAY; |
| 1371 | module_param(rcu_idle_lazy_gp_delay, int, 0644); |
| 1372 | |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1373 | /* |
Paul E. McKenney | c229828 | 2013-08-25 21:20:47 -0700 | [diff] [blame] | 1374 | * Try to advance callbacks for all flavors of RCU on the current CPU, but |
| 1375 | * only if it has been awhile since the last time we did so. Afterwards, |
| 1376 | * if there are any callbacks ready for immediate invocation, return true. |
Paul E. McKenney | 486e259 | 2012-01-06 14:11:30 -0800 | [diff] [blame] | 1377 | */ |
Paul E. McKenney | f1f399d | 2013-11-17 21:08:07 -0800 | [diff] [blame] | 1378 | static bool __maybe_unused rcu_try_advance_all_cbs(void) |
Paul E. McKenney | 486e259 | 2012-01-06 14:11:30 -0800 | [diff] [blame] | 1379 | { |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1380 | bool cbs_ready = false; |
| 1381 | struct rcu_data *rdp; |
Paul E. McKenney | c229828 | 2013-08-25 21:20:47 -0700 | [diff] [blame] | 1382 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1383 | struct rcu_node *rnp; |
| 1384 | struct rcu_state *rsp; |
Paul E. McKenney | 486e259 | 2012-01-06 14:11:30 -0800 | [diff] [blame] | 1385 | |
Paul E. McKenney | c229828 | 2013-08-25 21:20:47 -0700 | [diff] [blame] | 1386 | /* Exit early if we advanced recently. */ |
| 1387 | if (jiffies == rdtp->last_advance_all) |
Pranith Kumar | d0bc90f | 2014-07-08 18:26:13 -0400 | [diff] [blame] | 1388 | return false; |
Paul E. McKenney | c229828 | 2013-08-25 21:20:47 -0700 | [diff] [blame] | 1389 | rdtp->last_advance_all = jiffies; |
| 1390 | |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1391 | for_each_rcu_flavor(rsp) { |
| 1392 | rdp = this_cpu_ptr(rsp->rda); |
| 1393 | rnp = rdp->mynode; |
Paul E. McKenney | 486e259 | 2012-01-06 14:11:30 -0800 | [diff] [blame] | 1394 | |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1395 | /* |
| 1396 | * Don't bother checking unless a grace period has |
| 1397 | * completed since we last checked and there are |
| 1398 | * callbacks not yet ready to invoke. |
| 1399 | */ |
Paul E. McKenney | e3663b1 | 2014-12-08 20:26:55 -0800 | [diff] [blame] | 1400 | if ((rdp->completed != rnp->completed || |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1401 | unlikely(READ_ONCE(rdp->gpwrap))) && |
Paul E. McKenney | 15fecf8 | 2017-02-08 12:36:42 -0800 | [diff] [blame] | 1402 | rcu_segcblist_pend_cbs(&rdp->cblist)) |
Paul E. McKenney | 470716f | 2013-03-19 11:32:11 -0700 | [diff] [blame] | 1403 | note_gp_changes(rsp, rdp); |
Paul E. McKenney | 486e259 | 2012-01-06 14:11:30 -0800 | [diff] [blame] | 1404 | |
Paul E. McKenney | 15fecf8 | 2017-02-08 12:36:42 -0800 | [diff] [blame] | 1405 | if (rcu_segcblist_ready_cbs(&rdp->cblist)) |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1406 | cbs_ready = true; |
| 1407 | } |
| 1408 | return cbs_ready; |
Paul E. McKenney | 486e259 | 2012-01-06 14:11:30 -0800 | [diff] [blame] | 1409 | } |
| 1410 | |
| 1411 | /* |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1412 | * Allow the CPU to enter dyntick-idle mode unless it has callbacks ready |
| 1413 | * to invoke. If the CPU has callbacks, try to advance them. Tell the |
| 1414 | * caller to set the timeout based on whether or not there are non-lazy |
| 1415 | * callbacks. |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1416 | * |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1417 | * The caller must have disabled interrupts. |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1418 | */ |
Thomas Gleixner | c1ad348 | 2015-04-14 21:08:58 +0000 | [diff] [blame] | 1419 | int rcu_needs_cpu(u64 basemono, u64 *nextevt) |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1420 | { |
Paul E. McKenney | aa6da51 | 2014-10-21 13:23:08 -0700 | [diff] [blame] | 1421 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
Thomas Gleixner | c1ad348 | 2015-04-14 21:08:58 +0000 | [diff] [blame] | 1422 | unsigned long dj; |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1423 | |
Paul E. McKenney | ea9b0c8 | 2017-04-28 13:19:28 -0700 | [diff] [blame] | 1424 | RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_needs_cpu() invoked with irqs enabled!!!"); |
Paul E. McKenney | 3382adb | 2015-03-04 15:41:24 -0800 | [diff] [blame] | 1425 | |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1426 | /* Snapshot to detect later posting of non-lazy callback. */ |
| 1427 | rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; |
| 1428 | |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1429 | /* If no callbacks, RCU doesn't need the CPU. */ |
Paul E. McKenney | aa6da51 | 2014-10-21 13:23:08 -0700 | [diff] [blame] | 1430 | if (!rcu_cpu_has_callbacks(&rdtp->all_lazy)) { |
Thomas Gleixner | c1ad348 | 2015-04-14 21:08:58 +0000 | [diff] [blame] | 1431 | *nextevt = KTIME_MAX; |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1432 | return 0; |
| 1433 | } |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1434 | |
| 1435 | /* Attempt to advance callbacks. */ |
| 1436 | if (rcu_try_advance_all_cbs()) { |
| 1437 | /* Some ready to invoke, so initiate later invocation. */ |
| 1438 | invoke_rcu_core(); |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1439 | return 1; |
| 1440 | } |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1441 | rdtp->last_accelerate = jiffies; |
| 1442 | |
| 1443 | /* Request timer delay depending on laziness, and round. */ |
Paul E. McKenney | 6faf728 | 2013-05-13 06:53:37 -0700 | [diff] [blame] | 1444 | if (!rdtp->all_lazy) { |
Thomas Gleixner | c1ad348 | 2015-04-14 21:08:58 +0000 | [diff] [blame] | 1445 | dj = round_up(rcu_idle_gp_delay + jiffies, |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1446 | rcu_idle_gp_delay) - jiffies; |
Paul E. McKenney | e84c48a | 2012-06-04 20:45:10 -0700 | [diff] [blame] | 1447 | } else { |
Thomas Gleixner | c1ad348 | 2015-04-14 21:08:58 +0000 | [diff] [blame] | 1448 | dj = round_jiffies(rcu_idle_lazy_gp_delay + jiffies) - jiffies; |
Paul E. McKenney | e84c48a | 2012-06-04 20:45:10 -0700 | [diff] [blame] | 1449 | } |
Thomas Gleixner | c1ad348 | 2015-04-14 21:08:58 +0000 | [diff] [blame] | 1450 | *nextevt = basemono + dj * TICK_NSEC; |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1451 | return 0; |
| 1452 | } |
| 1453 | |
| 1454 | /* |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1455 | * Prepare a CPU for idle from an RCU perspective. The first major task |
| 1456 | * is to sense whether nohz mode has been enabled or disabled via sysfs. |
| 1457 | * The second major task is to check to see if a non-lazy callback has |
| 1458 | * arrived at a CPU that previously had only lazy callbacks. The third |
| 1459 | * major task is to accelerate (that is, assign grace-period numbers to) |
| 1460 | * any recently arrived callbacks. |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 1461 | * |
| 1462 | * The caller must have disabled interrupts. |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1463 | */ |
Paul E. McKenney | 198bbf8 | 2014-10-22 15:03:43 -0700 | [diff] [blame] | 1464 | static void rcu_prepare_for_idle(void) |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1465 | { |
Paul E. McKenney | 48a7639 | 2014-03-11 13:02:16 -0700 | [diff] [blame] | 1466 | bool needwake; |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1467 | struct rcu_data *rdp; |
Paul E. McKenney | 198bbf8 | 2014-10-22 15:03:43 -0700 | [diff] [blame] | 1468 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1469 | struct rcu_node *rnp; |
| 1470 | struct rcu_state *rsp; |
Paul E. McKenney | 9d2ad24 | 2012-06-24 10:15:02 -0700 | [diff] [blame] | 1471 | int tne; |
| 1472 | |
Paul E. McKenney | ea9b0c8 | 2017-04-28 13:19:28 -0700 | [diff] [blame] | 1473 | RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_prepare_for_idle() invoked with irqs enabled!!!"); |
Paul E. McKenney | 44c65ff | 2017-05-15 16:26:34 -0700 | [diff] [blame] | 1474 | if (rcu_is_nocb_cpu(smp_processor_id())) |
Paul E. McKenney | 3382adb | 2015-03-04 15:41:24 -0800 | [diff] [blame] | 1475 | return; |
| 1476 | |
Paul E. McKenney | 9d2ad24 | 2012-06-24 10:15:02 -0700 | [diff] [blame] | 1477 | /* Handle nohz enablement switches conservatively. */ |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1478 | tne = READ_ONCE(tick_nohz_active); |
Paul E. McKenney | 9d2ad24 | 2012-06-24 10:15:02 -0700 | [diff] [blame] | 1479 | if (tne != rdtp->tick_nohz_enabled_snap) { |
Paul E. McKenney | aa6da51 | 2014-10-21 13:23:08 -0700 | [diff] [blame] | 1480 | if (rcu_cpu_has_callbacks(NULL)) |
Paul E. McKenney | 9d2ad24 | 2012-06-24 10:15:02 -0700 | [diff] [blame] | 1481 | invoke_rcu_core(); /* force nohz to see update. */ |
| 1482 | rdtp->tick_nohz_enabled_snap = tne; |
| 1483 | return; |
| 1484 | } |
| 1485 | if (!tne) |
| 1486 | return; |
Paul E. McKenney | f511fc6 | 2012-03-15 12:16:26 -0700 | [diff] [blame] | 1487 | |
Paul E. McKenney | 3084f2f | 2011-11-22 17:07:11 -0800 | [diff] [blame] | 1488 | /* |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1489 | * If a non-lazy callback arrived at a CPU having only lazy |
| 1490 | * callbacks, invoke RCU core for the side-effect of recalculating |
| 1491 | * idle duration on re-entry to idle. |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 1492 | */ |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1493 | if (rdtp->all_lazy && |
| 1494 | rdtp->nonlazy_posted != rdtp->nonlazy_posted_snap) { |
Paul E. McKenney | c337f8f | 2013-09-05 17:02:11 -0700 | [diff] [blame] | 1495 | rdtp->all_lazy = false; |
| 1496 | rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1497 | invoke_rcu_core(); |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1498 | return; |
| 1499 | } |
| 1500 | |
| 1501 | /* |
| 1502 | * If we have not yet accelerated this jiffy, accelerate all |
| 1503 | * callbacks on this CPU. |
| 1504 | */ |
| 1505 | if (rdtp->last_accelerate == jiffies) |
| 1506 | return; |
| 1507 | rdtp->last_accelerate = jiffies; |
| 1508 | for_each_rcu_flavor(rsp) { |
Paul E. McKenney | 198bbf8 | 2014-10-22 15:03:43 -0700 | [diff] [blame] | 1509 | rdp = this_cpu_ptr(rsp->rda); |
Paul E. McKenney | 15fecf8 | 2017-02-08 12:36:42 -0800 | [diff] [blame] | 1510 | if (rcu_segcblist_pend_cbs(&rdp->cblist)) |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1511 | continue; |
| 1512 | rnp = rdp->mynode; |
Peter Zijlstra | 2a67e74 | 2015-10-08 12:24:23 +0200 | [diff] [blame] | 1513 | raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ |
Paul E. McKenney | 48a7639 | 2014-03-11 13:02:16 -0700 | [diff] [blame] | 1514 | needwake = rcu_accelerate_cbs(rsp, rnp, rdp); |
Boqun Feng | 67c583a7 | 2015-12-29 12:18:47 +0800 | [diff] [blame] | 1515 | raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ |
Paul E. McKenney | 48a7639 | 2014-03-11 13:02:16 -0700 | [diff] [blame] | 1516 | if (needwake) |
| 1517 | rcu_gp_kthread_wake(rsp); |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1518 | } |
| 1519 | } |
| 1520 | |
| 1521 | /* |
| 1522 | * Clean up for exit from idle. Attempt to advance callbacks based on |
| 1523 | * any grace periods that elapsed while the CPU was idle, and if any |
| 1524 | * callbacks are now ready to invoke, initiate invocation. |
| 1525 | */ |
Paul E. McKenney | 8fa7845 | 2014-10-22 15:07:37 -0700 | [diff] [blame] | 1526 | static void rcu_cleanup_after_idle(void) |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1527 | { |
Paul E. McKenney | ea9b0c8 | 2017-04-28 13:19:28 -0700 | [diff] [blame] | 1528 | RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_cleanup_after_idle() invoked with irqs enabled!!!"); |
Paul E. McKenney | 44c65ff | 2017-05-15 16:26:34 -0700 | [diff] [blame] | 1529 | if (rcu_is_nocb_cpu(smp_processor_id())) |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1530 | return; |
Paul E. McKenney | 7a497c9 | 2013-08-22 18:16:16 -0700 | [diff] [blame] | 1531 | if (rcu_try_advance_all_cbs()) |
| 1532 | invoke_rcu_core(); |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1533 | } |
| 1534 | |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 1535 | /* |
Paul E. McKenney | 98248a0 | 2012-05-03 15:38:10 -0700 | [diff] [blame] | 1536 | * Keep a running count of the number of non-lazy callbacks posted |
| 1537 | * on this CPU. This running counter (which is never decremented) allows |
| 1538 | * rcu_prepare_for_idle() to detect when something out of the idle loop |
| 1539 | * posts a callback, even if an equal number of callbacks are invoked. |
| 1540 | * Of course, callbacks should only be posted from within a trace event |
| 1541 | * designed to be called from idle or from within RCU_NONIDLE(). |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 1542 | */ |
| 1543 | static void rcu_idle_count_callbacks_posted(void) |
| 1544 | { |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 1545 | __this_cpu_add(rcu_dynticks.nonlazy_posted, 1); |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 1546 | } |
| 1547 | |
Paul E. McKenney | b626c1b | 2012-06-11 17:39:43 -0700 | [diff] [blame] | 1548 | /* |
| 1549 | * Data for flushing lazy RCU callbacks at OOM time. |
| 1550 | */ |
| 1551 | static atomic_t oom_callback_count; |
| 1552 | static DECLARE_WAIT_QUEUE_HEAD(oom_callback_wq); |
| 1553 | |
| 1554 | /* |
| 1555 | * RCU OOM callback -- decrement the outstanding count and deliver the |
| 1556 | * wake-up if we are the last one. |
| 1557 | */ |
| 1558 | static void rcu_oom_callback(struct rcu_head *rhp) |
| 1559 | { |
| 1560 | if (atomic_dec_and_test(&oom_callback_count)) |
| 1561 | wake_up(&oom_callback_wq); |
| 1562 | } |
| 1563 | |
| 1564 | /* |
| 1565 | * Post an rcu_oom_notify callback on the current CPU if it has at |
| 1566 | * least one lazy callback. This will unnecessarily post callbacks |
| 1567 | * to CPUs that already have a non-lazy callback at the end of their |
| 1568 | * callback list, but this is an infrequent operation, so accept some |
| 1569 | * extra overhead to keep things simple. |
| 1570 | */ |
| 1571 | static void rcu_oom_notify_cpu(void *unused) |
| 1572 | { |
| 1573 | struct rcu_state *rsp; |
| 1574 | struct rcu_data *rdp; |
| 1575 | |
| 1576 | for_each_rcu_flavor(rsp) { |
Christoph Lameter | fa07a58 | 2014-04-15 12:20:12 -0700 | [diff] [blame] | 1577 | rdp = raw_cpu_ptr(rsp->rda); |
Paul E. McKenney | 15fecf8 | 2017-02-08 12:36:42 -0800 | [diff] [blame] | 1578 | if (rcu_segcblist_n_lazy_cbs(&rdp->cblist)) { |
Paul E. McKenney | b626c1b | 2012-06-11 17:39:43 -0700 | [diff] [blame] | 1579 | atomic_inc(&oom_callback_count); |
| 1580 | rsp->call(&rdp->oom_head, rcu_oom_callback); |
| 1581 | } |
| 1582 | } |
| 1583 | } |
| 1584 | |
| 1585 | /* |
| 1586 | * If low on memory, ensure that each CPU has a non-lazy callback. |
| 1587 | * This will wake up CPUs that have only lazy callbacks, in turn |
| 1588 | * ensuring that they free up the corresponding memory in a timely manner. |
| 1589 | * Because an uncertain amount of memory will be freed in some uncertain |
| 1590 | * timeframe, we do not claim to have freed anything. |
| 1591 | */ |
| 1592 | static int rcu_oom_notify(struct notifier_block *self, |
| 1593 | unsigned long notused, void *nfreed) |
| 1594 | { |
| 1595 | int cpu; |
| 1596 | |
| 1597 | /* Wait for callbacks from earlier instance to complete. */ |
| 1598 | wait_event(oom_callback_wq, atomic_read(&oom_callback_count) == 0); |
Paul E. McKenney | 78e4bc3 | 2013-09-24 15:04:06 -0700 | [diff] [blame] | 1599 | smp_mb(); /* Ensure callback reuse happens after callback invocation. */ |
Paul E. McKenney | b626c1b | 2012-06-11 17:39:43 -0700 | [diff] [blame] | 1600 | |
| 1601 | /* |
| 1602 | * Prevent premature wakeup: ensure that all increments happen |
| 1603 | * before there is a chance of the counter reaching zero. |
| 1604 | */ |
| 1605 | atomic_set(&oom_callback_count, 1); |
| 1606 | |
Paul E. McKenney | b626c1b | 2012-06-11 17:39:43 -0700 | [diff] [blame] | 1607 | for_each_online_cpu(cpu) { |
| 1608 | smp_call_function_single(cpu, rcu_oom_notify_cpu, NULL, 1); |
Paul E. McKenney | bde6c3a | 2014-07-01 11:26:57 -0700 | [diff] [blame] | 1609 | cond_resched_rcu_qs(); |
Paul E. McKenney | b626c1b | 2012-06-11 17:39:43 -0700 | [diff] [blame] | 1610 | } |
Paul E. McKenney | b626c1b | 2012-06-11 17:39:43 -0700 | [diff] [blame] | 1611 | |
| 1612 | /* Unconditionally decrement: no need to wake ourselves up. */ |
| 1613 | atomic_dec(&oom_callback_count); |
| 1614 | |
| 1615 | return NOTIFY_OK; |
| 1616 | } |
| 1617 | |
| 1618 | static struct notifier_block rcu_oom_nb = { |
| 1619 | .notifier_call = rcu_oom_notify |
| 1620 | }; |
| 1621 | |
| 1622 | static int __init rcu_register_oom_notifier(void) |
| 1623 | { |
| 1624 | register_oom_notifier(&rcu_oom_nb); |
| 1625 | return 0; |
| 1626 | } |
| 1627 | early_initcall(rcu_register_oom_notifier); |
| 1628 | |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1629 | #endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */ |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1630 | |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1631 | #ifdef CONFIG_RCU_FAST_NO_HZ |
| 1632 | |
| 1633 | static void print_cpu_stall_fast_no_hz(char *cp, int cpu) |
| 1634 | { |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 1635 | struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1636 | unsigned long nlpd = rdtp->nonlazy_posted - rdtp->nonlazy_posted_snap; |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1637 | |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1638 | sprintf(cp, "last_accelerate: %04lx/%04lx, nonlazy_posted: %ld, %c%c", |
| 1639 | rdtp->last_accelerate & 0xffff, jiffies & 0xffff, |
| 1640 | ulong2long(nlpd), |
| 1641 | rdtp->all_lazy ? 'L' : '.', |
| 1642 | rdtp->tick_nohz_enabled_snap ? '.' : 'D'); |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1643 | } |
| 1644 | |
| 1645 | #else /* #ifdef CONFIG_RCU_FAST_NO_HZ */ |
| 1646 | |
| 1647 | static void print_cpu_stall_fast_no_hz(char *cp, int cpu) |
| 1648 | { |
Carsten Emde | 1c17e4d | 2012-06-19 10:43:16 +0200 | [diff] [blame] | 1649 | *cp = '\0'; |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1650 | } |
| 1651 | |
| 1652 | #endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */ |
| 1653 | |
| 1654 | /* Initiate the stall-info list. */ |
| 1655 | static void print_cpu_stall_info_begin(void) |
| 1656 | { |
Paul E. McKenney | efc151c | 2013-03-18 16:24:11 -0700 | [diff] [blame] | 1657 | pr_cont("\n"); |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1658 | } |
| 1659 | |
| 1660 | /* |
| 1661 | * Print out diagnostic information for the specified stalled CPU. |
| 1662 | * |
| 1663 | * If the specified CPU is aware of the current RCU grace period |
| 1664 | * (flavor specified by rsp), then print the number of scheduling |
| 1665 | * clock interrupts the CPU has taken during the time that it has |
| 1666 | * been aware. Otherwise, print the number of RCU grace periods |
| 1667 | * that this CPU is ignorant of, for example, "1" if the CPU was |
| 1668 | * aware of the previous grace period. |
| 1669 | * |
| 1670 | * Also print out idle and (if CONFIG_RCU_FAST_NO_HZ) idle-entry info. |
| 1671 | */ |
| 1672 | static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) |
| 1673 | { |
| 1674 | char fast_no_hz[72]; |
| 1675 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
| 1676 | struct rcu_dynticks *rdtp = rdp->dynticks; |
| 1677 | char *ticks_title; |
| 1678 | unsigned long ticks_value; |
| 1679 | |
| 1680 | if (rsp->gpnum == rdp->gpnum) { |
| 1681 | ticks_title = "ticks this GP"; |
| 1682 | ticks_value = rdp->ticks_this_gp; |
| 1683 | } else { |
| 1684 | ticks_title = "GPs behind"; |
| 1685 | ticks_value = rsp->gpnum - rdp->gpnum; |
| 1686 | } |
| 1687 | print_cpu_stall_fast_no_hz(fast_no_hz, cpu); |
Paul E. McKenney | 7f21aee | 2015-08-15 14:49:50 -0700 | [diff] [blame] | 1688 | pr_err("\t%d-%c%c%c: (%lu %s) idle=%03x/%llx/%d softirq=%u/%u fqs=%ld %s\n", |
| 1689 | cpu, |
| 1690 | "O."[!!cpu_online(cpu)], |
| 1691 | "o."[!!(rdp->grpmask & rdp->mynode->qsmaskinit)], |
| 1692 | "N."[!!(rdp->grpmask & rdp->mynode->qsmaskinitnext)], |
| 1693 | ticks_value, ticks_title, |
Paul E. McKenney | 02a5c550 | 2016-11-02 17:25:06 -0700 | [diff] [blame] | 1694 | rcu_dynticks_snap(rdtp) & 0xfff, |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1695 | rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting, |
Paul E. McKenney | 6231069 | 2013-03-06 13:37:09 -0800 | [diff] [blame] | 1696 | rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu), |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1697 | READ_ONCE(rsp->n_force_qs) - rsp->n_force_qs_gpstart, |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1698 | fast_no_hz); |
| 1699 | } |
| 1700 | |
| 1701 | /* Terminate the stall-info list. */ |
| 1702 | static void print_cpu_stall_info_end(void) |
| 1703 | { |
Paul E. McKenney | efc151c | 2013-03-18 16:24:11 -0700 | [diff] [blame] | 1704 | pr_err("\t"); |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1705 | } |
| 1706 | |
| 1707 | /* Zero ->ticks_this_gp for all flavors of RCU. */ |
| 1708 | static void zero_cpu_stall_ticks(struct rcu_data *rdp) |
| 1709 | { |
| 1710 | rdp->ticks_this_gp = 0; |
Paul E. McKenney | 6231069 | 2013-03-06 13:37:09 -0800 | [diff] [blame] | 1711 | rdp->softirq_snap = kstat_softirqs_cpu(RCU_SOFTIRQ, smp_processor_id()); |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1712 | } |
| 1713 | |
| 1714 | /* Increment ->ticks_this_gp for all flavors of RCU. */ |
| 1715 | static void increment_cpu_stall_ticks(void) |
| 1716 | { |
Paul E. McKenney | 115f7a7 | 2012-08-10 13:55:03 -0700 | [diff] [blame] | 1717 | struct rcu_state *rsp; |
| 1718 | |
| 1719 | for_each_rcu_flavor(rsp) |
Christoph Lameter | fa07a58 | 2014-04-15 12:20:12 -0700 | [diff] [blame] | 1720 | raw_cpu_inc(rsp->rda->ticks_this_gp); |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1721 | } |
| 1722 | |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1723 | #ifdef CONFIG_RCU_NOCB_CPU |
| 1724 | |
| 1725 | /* |
| 1726 | * Offload callback processing from the boot-time-specified set of CPUs |
| 1727 | * specified by rcu_nocb_mask. For each CPU in the set, there is a |
| 1728 | * kthread created that pulls the callbacks from the corresponding CPU, |
| 1729 | * waits for a grace period to elapse, and invokes the callbacks. |
| 1730 | * The no-CBs CPUs do a wake_up() on their kthread when they insert |
| 1731 | * a callback into any empty list, unless the rcu_nocb_poll boot parameter |
| 1732 | * has been specified, in which case each kthread actively polls its |
| 1733 | * CPU. (Which isn't so great for energy efficiency, but which does |
| 1734 | * reduce RCU's overhead on that CPU.) |
| 1735 | * |
| 1736 | * This is intended to be used in conjunction with Frederic Weisbecker's |
| 1737 | * adaptive-idle work, which would seriously reduce OS jitter on CPUs |
| 1738 | * running CPU-bound user-mode computations. |
| 1739 | * |
| 1740 | * Offloading of callback processing could also in theory be used as |
| 1741 | * an energy-efficiency measure because CPUs with no RCU callbacks |
| 1742 | * queued are more aggressive about entering dyntick-idle mode. |
| 1743 | */ |
| 1744 | |
| 1745 | |
| 1746 | /* Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters. */ |
| 1747 | static int __init rcu_nocb_setup(char *str) |
| 1748 | { |
| 1749 | alloc_bootmem_cpumask_var(&rcu_nocb_mask); |
| 1750 | have_rcu_nocb_mask = true; |
| 1751 | cpulist_parse(str, rcu_nocb_mask); |
| 1752 | return 1; |
| 1753 | } |
| 1754 | __setup("rcu_nocbs=", rcu_nocb_setup); |
| 1755 | |
Paul Gortmaker | 1b0048a | 2012-12-20 13:19:22 -0800 | [diff] [blame] | 1756 | static int __init parse_rcu_nocb_poll(char *arg) |
| 1757 | { |
Nicholas Mc Guire | 5455a7f | 2017-03-25 20:46:02 +0100 | [diff] [blame] | 1758 | rcu_nocb_poll = true; |
Paul Gortmaker | 1b0048a | 2012-12-20 13:19:22 -0800 | [diff] [blame] | 1759 | return 0; |
| 1760 | } |
| 1761 | early_param("rcu_nocb_poll", parse_rcu_nocb_poll); |
| 1762 | |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 1763 | /* |
Paul E. McKenney | 0446be4 | 2012-12-30 15:21:01 -0800 | [diff] [blame] | 1764 | * Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended |
| 1765 | * grace period. |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 1766 | */ |
Paul Gortmaker | abedf8e | 2016-02-19 09:46:41 +0100 | [diff] [blame] | 1767 | static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq) |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 1768 | { |
Paul Gortmaker | abedf8e | 2016-02-19 09:46:41 +0100 | [diff] [blame] | 1769 | swake_up_all(sq); |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 1770 | } |
| 1771 | |
| 1772 | /* |
Paul E. McKenney | 8b425aa8 | 2012-12-30 13:06:35 -0800 | [diff] [blame] | 1773 | * Set the root rcu_node structure's ->need_future_gp field |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 1774 | * based on the sum of those of all rcu_node structures. This does |
| 1775 | * double-count the root rcu_node structure's requests, but this |
| 1776 | * is necessary to handle the possibility of a rcu_nocb_kthread() |
| 1777 | * having awakened during the time that the rcu_node structures |
| 1778 | * were being updated for the end of the previous grace period. |
| 1779 | */ |
| 1780 | static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq) |
| 1781 | { |
Paul E. McKenney | 8b425aa8 | 2012-12-30 13:06:35 -0800 | [diff] [blame] | 1782 | rnp->need_future_gp[(rnp->completed + 1) & 0x1] += nrq; |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 1783 | } |
| 1784 | |
Paul Gortmaker | abedf8e | 2016-02-19 09:46:41 +0100 | [diff] [blame] | 1785 | static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp) |
Daniel Wagner | 065bb78 | 2016-02-19 09:46:40 +0100 | [diff] [blame] | 1786 | { |
| 1787 | return &rnp->nocb_gp_wq[rnp->completed & 0x1]; |
| 1788 | } |
| 1789 | |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 1790 | static void rcu_init_one_nocb(struct rcu_node *rnp) |
| 1791 | { |
Paul Gortmaker | abedf8e | 2016-02-19 09:46:41 +0100 | [diff] [blame] | 1792 | init_swait_queue_head(&rnp->nocb_gp_wq[0]); |
| 1793 | init_swait_queue_head(&rnp->nocb_gp_wq[1]); |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 1794 | } |
| 1795 | |
Liu Ping Fan | 24342c9 | 2014-02-24 06:18:09 -0800 | [diff] [blame] | 1796 | /* Is the specified CPU a no-CBs CPU? */ |
Frederic Weisbecker | d1e43fa | 2013-03-26 23:47:24 +0100 | [diff] [blame] | 1797 | bool rcu_is_nocb_cpu(int cpu) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1798 | { |
| 1799 | if (have_rcu_nocb_mask) |
| 1800 | return cpumask_test_cpu(cpu, rcu_nocb_mask); |
| 1801 | return false; |
| 1802 | } |
| 1803 | |
| 1804 | /* |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 1805 | * Kick the leader kthread for this NOCB group. Caller holds ->nocb_lock |
| 1806 | * and this function releases it. |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 1807 | */ |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 1808 | static void __wake_nocb_leader(struct rcu_data *rdp, bool force, |
| 1809 | unsigned long flags) |
| 1810 | __releases(rdp->nocb_lock) |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 1811 | { |
| 1812 | struct rcu_data *rdp_leader = rdp->nocb_leader; |
| 1813 | |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 1814 | lockdep_assert_held(&rdp->nocb_lock); |
| 1815 | if (!READ_ONCE(rdp_leader->nocb_kthread)) { |
| 1816 | raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 1817 | return; |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 1818 | } |
| 1819 | if (rdp_leader->nocb_leader_sleep || force) { |
Paul E. McKenney | 39953df | 2014-08-12 10:47:48 -0700 | [diff] [blame] | 1820 | /* Prior smp_mb__after_atomic() orders against prior enqueue. */ |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1821 | WRITE_ONCE(rdp_leader->nocb_leader_sleep, false); |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 1822 | del_timer(&rdp->nocb_timer); |
| 1823 | raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); |
Paul E. McKenney | 6b5fc3a | 2017-04-28 20:11:09 -0700 | [diff] [blame] | 1824 | smp_mb(); /* ->nocb_leader_sleep before swake_up(). */ |
Paul Gortmaker | abedf8e | 2016-02-19 09:46:41 +0100 | [diff] [blame] | 1825 | swake_up(&rdp_leader->nocb_wq); |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 1826 | } else { |
| 1827 | raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 1828 | } |
| 1829 | } |
| 1830 | |
| 1831 | /* |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 1832 | * Kick the leader kthread for this NOCB group, but caller has not |
| 1833 | * acquired locks. |
| 1834 | */ |
| 1835 | static void wake_nocb_leader(struct rcu_data *rdp, bool force) |
| 1836 | { |
| 1837 | unsigned long flags; |
| 1838 | |
| 1839 | raw_spin_lock_irqsave(&rdp->nocb_lock, flags); |
| 1840 | __wake_nocb_leader(rdp, force, flags); |
| 1841 | } |
| 1842 | |
| 1843 | /* |
| 1844 | * Arrange to wake the leader kthread for this NOCB group at some |
| 1845 | * future time when it is safe to do so. |
| 1846 | */ |
| 1847 | static void wake_nocb_leader_defer(struct rcu_data *rdp, int waketype, |
| 1848 | const char *reason) |
| 1849 | { |
| 1850 | unsigned long flags; |
| 1851 | |
| 1852 | raw_spin_lock_irqsave(&rdp->nocb_lock, flags); |
| 1853 | if (rdp->nocb_defer_wakeup == RCU_NOCB_WAKE_NOT) |
| 1854 | mod_timer(&rdp->nocb_timer, jiffies + 1); |
| 1855 | WRITE_ONCE(rdp->nocb_defer_wakeup, waketype); |
| 1856 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, reason); |
| 1857 | raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); |
| 1858 | } |
| 1859 | |
| 1860 | /* |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1861 | * Does the specified CPU need an RCU callback for the specified flavor |
| 1862 | * of rcu_barrier()? |
| 1863 | */ |
| 1864 | static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu) |
| 1865 | { |
| 1866 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
Paul E. McKenney | 41050a0 | 2014-12-18 12:31:27 -0800 | [diff] [blame] | 1867 | unsigned long ret; |
| 1868 | #ifdef CONFIG_PROVE_RCU |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1869 | struct rcu_head *rhp; |
Paul E. McKenney | 41050a0 | 2014-12-18 12:31:27 -0800 | [diff] [blame] | 1870 | #endif /* #ifdef CONFIG_PROVE_RCU */ |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1871 | |
Paul E. McKenney | 41050a0 | 2014-12-18 12:31:27 -0800 | [diff] [blame] | 1872 | /* |
| 1873 | * Check count of all no-CBs callbacks awaiting invocation. |
| 1874 | * There needs to be a barrier before this function is called, |
| 1875 | * but associated with a prior determination that no more |
| 1876 | * callbacks would be posted. In the worst case, the first |
| 1877 | * barrier in _rcu_barrier() suffices (but the caller cannot |
| 1878 | * necessarily rely on this, not a substitute for the caller |
| 1879 | * getting the concurrency design right!). There must also be |
| 1880 | * a barrier between the following load an posting of a callback |
| 1881 | * (if a callback is in fact needed). This is associated with an |
| 1882 | * atomic_inc() in the caller. |
| 1883 | */ |
| 1884 | ret = atomic_long_read(&rdp->nocb_q_count); |
| 1885 | |
| 1886 | #ifdef CONFIG_PROVE_RCU |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1887 | rhp = READ_ONCE(rdp->nocb_head); |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1888 | if (!rhp) |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1889 | rhp = READ_ONCE(rdp->nocb_gp_head); |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1890 | if (!rhp) |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1891 | rhp = READ_ONCE(rdp->nocb_follower_head); |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1892 | |
| 1893 | /* Having no rcuo kthread but CBs after scheduler starts is bad! */ |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1894 | if (!READ_ONCE(rdp->nocb_kthread) && rhp && |
Paul E. McKenney | 59f792d | 2015-01-19 21:43:40 -0800 | [diff] [blame] | 1895 | rcu_scheduler_fully_active) { |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1896 | /* RCU callback enqueued before CPU first came online??? */ |
| 1897 | pr_err("RCU: Never-onlined no-CBs CPU %d has CB %p\n", |
| 1898 | cpu, rhp->func); |
| 1899 | WARN_ON_ONCE(1); |
| 1900 | } |
Paul E. McKenney | 41050a0 | 2014-12-18 12:31:27 -0800 | [diff] [blame] | 1901 | #endif /* #ifdef CONFIG_PROVE_RCU */ |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1902 | |
Paul E. McKenney | 41050a0 | 2014-12-18 12:31:27 -0800 | [diff] [blame] | 1903 | return !!ret; |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1904 | } |
| 1905 | |
| 1906 | /* |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1907 | * Enqueue the specified string of rcu_head structures onto the specified |
| 1908 | * CPU's no-CBs lists. The CPU is specified by rdp, the head of the |
| 1909 | * string by rhp, and the tail of the string by rhtp. The non-lazy/lazy |
| 1910 | * counts are supplied by rhcount and rhcount_lazy. |
| 1911 | * |
| 1912 | * If warranted, also wake up the kthread servicing this CPUs queues. |
| 1913 | */ |
| 1914 | static void __call_rcu_nocb_enqueue(struct rcu_data *rdp, |
| 1915 | struct rcu_head *rhp, |
| 1916 | struct rcu_head **rhtp, |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 1917 | int rhcount, int rhcount_lazy, |
| 1918 | unsigned long flags) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1919 | { |
| 1920 | int len; |
| 1921 | struct rcu_head **old_rhpp; |
| 1922 | struct task_struct *t; |
| 1923 | |
| 1924 | /* Enqueue the callback on the nocb list and update counts. */ |
Paul E. McKenney | 41050a0 | 2014-12-18 12:31:27 -0800 | [diff] [blame] | 1925 | atomic_long_add(rhcount, &rdp->nocb_q_count); |
| 1926 | /* rcu_barrier() relies on ->nocb_q_count add before xchg. */ |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1927 | old_rhpp = xchg(&rdp->nocb_tail, rhtp); |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1928 | WRITE_ONCE(*old_rhpp, rhp); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1929 | atomic_long_add(rhcount_lazy, &rdp->nocb_q_count_lazy); |
Paul E. McKenney | 39953df | 2014-08-12 10:47:48 -0700 | [diff] [blame] | 1930 | smp_mb__after_atomic(); /* Store *old_rhpp before _wake test. */ |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1931 | |
| 1932 | /* If we are not being polled and there is a kthread, awaken it ... */ |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1933 | t = READ_ONCE(rdp->nocb_kthread); |
Paul E. McKenney | 25e03a7 | 2013-10-15 12:47:04 -0700 | [diff] [blame] | 1934 | if (rcu_nocb_poll || !t) { |
Paul E. McKenney | 9261dd0 | 2013-08-14 16:24:26 -0700 | [diff] [blame] | 1935 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
| 1936 | TPS("WakeNotPoll")); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1937 | return; |
Paul E. McKenney | 9261dd0 | 2013-08-14 16:24:26 -0700 | [diff] [blame] | 1938 | } |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1939 | len = atomic_long_read(&rdp->nocb_q_count); |
| 1940 | if (old_rhpp == &rdp->nocb_head) { |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 1941 | if (!irqs_disabled_flags(flags)) { |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 1942 | /* ... if queue was empty ... */ |
| 1943 | wake_nocb_leader(rdp, false); |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 1944 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
| 1945 | TPS("WakeEmpty")); |
| 1946 | } else { |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 1947 | wake_nocb_leader_defer(rdp, RCU_NOCB_WAKE, |
| 1948 | TPS("WakeEmptyIsDeferred")); |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 1949 | } |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1950 | rdp->qlen_last_fqs_check = 0; |
| 1951 | } else if (len > rdp->qlen_last_fqs_check + qhimark) { |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 1952 | /* ... or if many callbacks queued. */ |
Paul E. McKenney | 9fdd3bc | 2014-07-29 14:50:47 -0700 | [diff] [blame] | 1953 | if (!irqs_disabled_flags(flags)) { |
| 1954 | wake_nocb_leader(rdp, true); |
| 1955 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
| 1956 | TPS("WakeOvf")); |
| 1957 | } else { |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 1958 | wake_nocb_leader_defer(rdp, RCU_NOCB_WAKE, |
| 1959 | TPS("WakeOvfIsDeferred")); |
Paul E. McKenney | 9fdd3bc | 2014-07-29 14:50:47 -0700 | [diff] [blame] | 1960 | } |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1961 | rdp->qlen_last_fqs_check = LONG_MAX / 2; |
Paul E. McKenney | 9261dd0 | 2013-08-14 16:24:26 -0700 | [diff] [blame] | 1962 | } else { |
| 1963 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeNot")); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1964 | } |
| 1965 | return; |
| 1966 | } |
| 1967 | |
| 1968 | /* |
| 1969 | * This is a helper for __call_rcu(), which invokes this when the normal |
| 1970 | * callback queue is inoperable. If this is not a no-CBs CPU, this |
| 1971 | * function returns failure back to __call_rcu(), which can complain |
| 1972 | * appropriately. |
| 1973 | * |
| 1974 | * Otherwise, this function queues the callback where the corresponding |
| 1975 | * "rcuo" kthread can find it. |
| 1976 | */ |
| 1977 | static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 1978 | bool lazy, unsigned long flags) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1979 | { |
| 1980 | |
Frederic Weisbecker | d1e43fa | 2013-03-26 23:47:24 +0100 | [diff] [blame] | 1981 | if (!rcu_is_nocb_cpu(rdp->cpu)) |
Pranith Kumar | c271d3a | 2014-07-08 18:26:14 -0400 | [diff] [blame] | 1982 | return false; |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 1983 | __call_rcu_nocb_enqueue(rdp, rhp, &rhp->next, 1, lazy, flags); |
Paul E. McKenney | 21e7a60 | 2013-02-09 17:42:16 -0800 | [diff] [blame] | 1984 | if (__is_kfree_rcu_offset((unsigned long)rhp->func)) |
| 1985 | trace_rcu_kfree_callback(rdp->rsp->name, rhp, |
| 1986 | (unsigned long)rhp->func, |
Paul E. McKenney | 756cbf6 | 2013-08-15 10:12:12 -0700 | [diff] [blame] | 1987 | -atomic_long_read(&rdp->nocb_q_count_lazy), |
| 1988 | -atomic_long_read(&rdp->nocb_q_count)); |
Paul E. McKenney | 21e7a60 | 2013-02-09 17:42:16 -0800 | [diff] [blame] | 1989 | else |
| 1990 | trace_rcu_callback(rdp->rsp->name, rhp, |
Paul E. McKenney | 756cbf6 | 2013-08-15 10:12:12 -0700 | [diff] [blame] | 1991 | -atomic_long_read(&rdp->nocb_q_count_lazy), |
| 1992 | -atomic_long_read(&rdp->nocb_q_count)); |
Paul E. McKenney | 1772947bd | 2014-08-12 11:27:31 -0700 | [diff] [blame] | 1993 | |
| 1994 | /* |
| 1995 | * If called from an extended quiescent state with interrupts |
| 1996 | * disabled, invoke the RCU core in order to allow the idle-entry |
| 1997 | * deferred-wakeup check to function. |
| 1998 | */ |
| 1999 | if (irqs_disabled_flags(flags) && |
| 2000 | !rcu_is_watching() && |
| 2001 | cpu_online(smp_processor_id())) |
| 2002 | invoke_rcu_core(); |
| 2003 | |
Pranith Kumar | c271d3a | 2014-07-08 18:26:14 -0400 | [diff] [blame] | 2004 | return true; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2005 | } |
| 2006 | |
| 2007 | /* |
| 2008 | * Adopt orphaned callbacks on a no-CBs CPU, or return 0 if this is |
| 2009 | * not a no-CBs CPU. |
| 2010 | */ |
Paul E. McKenney | b1a2d79 | 2017-06-26 12:23:46 -0700 | [diff] [blame] | 2011 | static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_data *my_rdp, |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2012 | struct rcu_data *rdp, |
| 2013 | unsigned long flags) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2014 | { |
Paul E. McKenney | b1a2d79 | 2017-06-26 12:23:46 -0700 | [diff] [blame] | 2015 | RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_nocb_adopt_orphan_cbs() invoked with irqs enabled!!!"); |
Frederic Weisbecker | d1e43fa | 2013-03-26 23:47:24 +0100 | [diff] [blame] | 2016 | if (!rcu_is_nocb_cpu(smp_processor_id())) |
Paul E. McKenney | b1a2d79 | 2017-06-26 12:23:46 -0700 | [diff] [blame] | 2017 | return false; /* Not NOCBs CPU, caller must migrate CBs. */ |
| 2018 | __call_rcu_nocb_enqueue(my_rdp, rcu_segcblist_head(&rdp->cblist), |
| 2019 | rcu_segcblist_tail(&rdp->cblist), |
| 2020 | rcu_segcblist_n_cbs(&rdp->cblist), |
| 2021 | rcu_segcblist_n_lazy_cbs(&rdp->cblist), flags); |
| 2022 | rcu_segcblist_init(&rdp->cblist); |
| 2023 | rcu_segcblist_disable(&rdp->cblist); |
Pranith Kumar | 0a9e1e1 | 2014-07-08 18:26:15 -0400 | [diff] [blame] | 2024 | return true; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2025 | } |
| 2026 | |
| 2027 | /* |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2028 | * If necessary, kick off a new grace period, and either way wait |
| 2029 | * for a subsequent grace period to complete. |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2030 | */ |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2031 | static void rcu_nocb_wait_gp(struct rcu_data *rdp) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2032 | { |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2033 | unsigned long c; |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 2034 | bool d; |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2035 | unsigned long flags; |
Paul E. McKenney | 48a7639 | 2014-03-11 13:02:16 -0700 | [diff] [blame] | 2036 | bool needwake; |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2037 | struct rcu_node *rnp = rdp->mynode; |
| 2038 | |
Peter Zijlstra | 2a67e74 | 2015-10-08 12:24:23 +0200 | [diff] [blame] | 2039 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
Paul E. McKenney | 48a7639 | 2014-03-11 13:02:16 -0700 | [diff] [blame] | 2040 | needwake = rcu_start_future_gp(rnp, rdp, &c); |
Boqun Feng | 67c583a7 | 2015-12-29 12:18:47 +0800 | [diff] [blame] | 2041 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
Paul E. McKenney | 48a7639 | 2014-03-11 13:02:16 -0700 | [diff] [blame] | 2042 | if (needwake) |
| 2043 | rcu_gp_kthread_wake(rdp->rsp); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2044 | |
| 2045 | /* |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2046 | * Wait for the grace period. Do so interruptibly to avoid messing |
| 2047 | * up the load average. |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2048 | */ |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 2049 | trace_rcu_future_gp(rnp, rdp, c, TPS("StartWait")); |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2050 | for (;;) { |
Paul Gortmaker | abedf8e | 2016-02-19 09:46:41 +0100 | [diff] [blame] | 2051 | swait_event_interruptible( |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 2052 | rnp->nocb_gp_wq[c & 0x1], |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2053 | (d = ULONG_CMP_GE(READ_ONCE(rnp->completed), c))); |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 2054 | if (likely(d)) |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2055 | break; |
Paul E. McKenney | 73a860c | 2014-08-14 10:28:23 -0700 | [diff] [blame] | 2056 | WARN_ON(signal_pending(current)); |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 2057 | trace_rcu_future_gp(rnp, rdp, c, TPS("ResumeWait")); |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2058 | } |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 2059 | trace_rcu_future_gp(rnp, rdp, c, TPS("EndWait")); |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2060 | smp_mb(); /* Ensure that CB invocation happens after GP end. */ |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2061 | } |
| 2062 | |
| 2063 | /* |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2064 | * Leaders come here to wait for additional callbacks to show up. |
| 2065 | * This function does not return until callbacks appear. |
| 2066 | */ |
| 2067 | static void nocb_leader_wait(struct rcu_data *my_rdp) |
| 2068 | { |
| 2069 | bool firsttime = true; |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2070 | unsigned long flags; |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2071 | bool gotcbs; |
| 2072 | struct rcu_data *rdp; |
| 2073 | struct rcu_head **tail; |
| 2074 | |
| 2075 | wait_again: |
| 2076 | |
| 2077 | /* Wait for callbacks to appear. */ |
| 2078 | if (!rcu_nocb_poll) { |
Paul E. McKenney | bedbb64 | 2017-06-06 15:49:39 -0700 | [diff] [blame] | 2079 | trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, TPS("Sleep")); |
Paul Gortmaker | abedf8e | 2016-02-19 09:46:41 +0100 | [diff] [blame] | 2080 | swait_event_interruptible(my_rdp->nocb_wq, |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2081 | !READ_ONCE(my_rdp->nocb_leader_sleep)); |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2082 | raw_spin_lock_irqsave(&my_rdp->nocb_lock, flags); |
| 2083 | my_rdp->nocb_leader_sleep = true; |
| 2084 | WRITE_ONCE(my_rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT); |
| 2085 | del_timer(&my_rdp->nocb_timer); |
| 2086 | raw_spin_unlock_irqrestore(&my_rdp->nocb_lock, flags); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2087 | } else if (firsttime) { |
| 2088 | firsttime = false; /* Don't drown trace log with "Poll"! */ |
Paul E. McKenney | bedbb64 | 2017-06-06 15:49:39 -0700 | [diff] [blame] | 2089 | trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, TPS("Poll")); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2090 | } |
| 2091 | |
| 2092 | /* |
| 2093 | * Each pass through the following loop checks a follower for CBs. |
| 2094 | * We are our own first follower. Any CBs found are moved to |
| 2095 | * nocb_gp_head, where they await a grace period. |
| 2096 | */ |
| 2097 | gotcbs = false; |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2098 | smp_mb(); /* wakeup and _sleep before ->nocb_head reads. */ |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2099 | for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) { |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2100 | rdp->nocb_gp_head = READ_ONCE(rdp->nocb_head); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2101 | if (!rdp->nocb_gp_head) |
| 2102 | continue; /* No CBs here, try next follower. */ |
| 2103 | |
| 2104 | /* Move callbacks to wait-for-GP list, which is empty. */ |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2105 | WRITE_ONCE(rdp->nocb_head, NULL); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2106 | rdp->nocb_gp_tail = xchg(&rdp->nocb_tail, &rdp->nocb_head); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2107 | gotcbs = true; |
| 2108 | } |
| 2109 | |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2110 | /* No callbacks? Sleep a bit if polling, and go retry. */ |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2111 | if (unlikely(!gotcbs)) { |
Paul E. McKenney | 73a860c | 2014-08-14 10:28:23 -0700 | [diff] [blame] | 2112 | WARN_ON(signal_pending(current)); |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2113 | if (rcu_nocb_poll) { |
| 2114 | schedule_timeout_interruptible(1); |
| 2115 | } else { |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2116 | trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, |
Paul E. McKenney | bedbb64 | 2017-06-06 15:49:39 -0700 | [diff] [blame] | 2117 | TPS("WokeEmpty")); |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2118 | } |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2119 | goto wait_again; |
| 2120 | } |
| 2121 | |
| 2122 | /* Wait for one grace period. */ |
| 2123 | rcu_nocb_wait_gp(my_rdp); |
| 2124 | |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2125 | /* Each pass through the following loop wakes a follower, if needed. */ |
| 2126 | for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) { |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2127 | if (!rcu_nocb_poll && |
| 2128 | READ_ONCE(rdp->nocb_head) && |
| 2129 | READ_ONCE(my_rdp->nocb_leader_sleep)) { |
| 2130 | raw_spin_lock_irqsave(&my_rdp->nocb_lock, flags); |
Pranith Kumar | 11ed7f9 | 2014-08-27 16:43:40 -0400 | [diff] [blame] | 2131 | my_rdp->nocb_leader_sleep = false;/* No need to sleep.*/ |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2132 | raw_spin_unlock_irqrestore(&my_rdp->nocb_lock, flags); |
| 2133 | } |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2134 | if (!rdp->nocb_gp_head) |
| 2135 | continue; /* No CBs, so no need to wake follower. */ |
| 2136 | |
| 2137 | /* Append callbacks to follower's "done" list. */ |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2138 | raw_spin_lock_irqsave(&rdp->nocb_lock, flags); |
| 2139 | tail = rdp->nocb_follower_tail; |
| 2140 | rdp->nocb_follower_tail = rdp->nocb_gp_tail; |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2141 | *tail = rdp->nocb_gp_head; |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2142 | raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2143 | if (rdp != my_rdp && tail == &rdp->nocb_follower_head) { |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2144 | /* List was empty, so wake up the follower. */ |
Paul Gortmaker | abedf8e | 2016-02-19 09:46:41 +0100 | [diff] [blame] | 2145 | swake_up(&rdp->nocb_wq); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2146 | } |
| 2147 | } |
| 2148 | |
| 2149 | /* If we (the leader) don't have CBs, go wait some more. */ |
| 2150 | if (!my_rdp->nocb_follower_head) |
| 2151 | goto wait_again; |
| 2152 | } |
| 2153 | |
| 2154 | /* |
| 2155 | * Followers come here to wait for additional callbacks to show up. |
| 2156 | * This function does not return until callbacks appear. |
| 2157 | */ |
| 2158 | static void nocb_follower_wait(struct rcu_data *rdp) |
| 2159 | { |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2160 | for (;;) { |
Paul E. McKenney | bedbb64 | 2017-06-06 15:49:39 -0700 | [diff] [blame] | 2161 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("FollowerSleep")); |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2162 | swait_event_interruptible(rdp->nocb_wq, |
| 2163 | READ_ONCE(rdp->nocb_follower_head)); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2164 | if (smp_load_acquire(&rdp->nocb_follower_head)) { |
| 2165 | /* ^^^ Ensure CB invocation follows _head test. */ |
| 2166 | return; |
| 2167 | } |
Paul E. McKenney | 73a860c | 2014-08-14 10:28:23 -0700 | [diff] [blame] | 2168 | WARN_ON(signal_pending(current)); |
Paul E. McKenney | bedbb64 | 2017-06-06 15:49:39 -0700 | [diff] [blame] | 2169 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WokeEmpty")); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2170 | } |
| 2171 | } |
| 2172 | |
| 2173 | /* |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2174 | * Per-rcu_data kthread, but only for no-CBs CPUs. Each kthread invokes |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2175 | * callbacks queued by the corresponding no-CBs CPU, however, there is |
| 2176 | * an optional leader-follower relationship so that the grace-period |
| 2177 | * kthreads don't have to do quite so many wakeups. |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2178 | */ |
| 2179 | static int rcu_nocb_kthread(void *arg) |
| 2180 | { |
| 2181 | int c, cl; |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2182 | unsigned long flags; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2183 | struct rcu_head *list; |
| 2184 | struct rcu_head *next; |
| 2185 | struct rcu_head **tail; |
| 2186 | struct rcu_data *rdp = arg; |
| 2187 | |
| 2188 | /* Each pass through this loop invokes one batch of callbacks */ |
| 2189 | for (;;) { |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2190 | /* Wait for callbacks. */ |
| 2191 | if (rdp->nocb_leader == rdp) |
| 2192 | nocb_leader_wait(rdp); |
| 2193 | else |
| 2194 | nocb_follower_wait(rdp); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2195 | |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2196 | /* Pull the ready-to-invoke callbacks onto local list. */ |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2197 | raw_spin_lock_irqsave(&rdp->nocb_lock, flags); |
| 2198 | list = rdp->nocb_follower_head; |
| 2199 | rdp->nocb_follower_head = NULL; |
| 2200 | tail = rdp->nocb_follower_tail; |
| 2201 | rdp->nocb_follower_tail = &rdp->nocb_follower_head; |
| 2202 | raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2203 | BUG_ON(!list); |
Paul E. McKenney | bedbb64 | 2017-06-06 15:49:39 -0700 | [diff] [blame] | 2204 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WokeNonEmpty")); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2205 | |
| 2206 | /* Each pass through the following loop invokes a callback. */ |
Paul E. McKenney | 41050a0 | 2014-12-18 12:31:27 -0800 | [diff] [blame] | 2207 | trace_rcu_batch_start(rdp->rsp->name, |
| 2208 | atomic_long_read(&rdp->nocb_q_count_lazy), |
| 2209 | atomic_long_read(&rdp->nocb_q_count), -1); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2210 | c = cl = 0; |
| 2211 | while (list) { |
| 2212 | next = list->next; |
| 2213 | /* Wait for enqueuing to complete, if needed. */ |
| 2214 | while (next == NULL && &list->next != tail) { |
Paul E. McKenney | 69a79bb | 2013-08-15 13:23:23 -0700 | [diff] [blame] | 2215 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
| 2216 | TPS("WaitQueue")); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2217 | schedule_timeout_interruptible(1); |
Paul E. McKenney | 69a79bb | 2013-08-15 13:23:23 -0700 | [diff] [blame] | 2218 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
| 2219 | TPS("WokeQueue")); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2220 | next = list->next; |
| 2221 | } |
| 2222 | debug_rcu_head_unqueue(list); |
| 2223 | local_bh_disable(); |
| 2224 | if (__rcu_reclaim(rdp->rsp->name, list)) |
| 2225 | cl++; |
| 2226 | c++; |
| 2227 | local_bh_enable(); |
Ding Tianhong | bedc196 | 2016-06-15 15:27:36 +0800 | [diff] [blame] | 2228 | cond_resched_rcu_qs(); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2229 | list = next; |
| 2230 | } |
| 2231 | trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1); |
Paul E. McKenney | 41050a0 | 2014-12-18 12:31:27 -0800 | [diff] [blame] | 2232 | smp_mb__before_atomic(); /* _add after CB invocation. */ |
| 2233 | atomic_long_add(-c, &rdp->nocb_q_count); |
| 2234 | atomic_long_add(-cl, &rdp->nocb_q_count_lazy); |
Paul E. McKenney | c635a4e1 | 2012-10-29 07:29:20 -0700 | [diff] [blame] | 2235 | rdp->n_nocbs_invoked += c; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2236 | } |
| 2237 | return 0; |
| 2238 | } |
| 2239 | |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2240 | /* Is a deferred wakeup of rcu_nocb_kthread() required? */ |
Paul E. McKenney | 9fdd3bc | 2014-07-29 14:50:47 -0700 | [diff] [blame] | 2241 | static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2242 | { |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2243 | return READ_ONCE(rdp->nocb_defer_wakeup); |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2244 | } |
| 2245 | |
| 2246 | /* Do a deferred wakeup of rcu_nocb_kthread(). */ |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2247 | static void do_nocb_deferred_wakeup_common(struct rcu_data *rdp) |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2248 | { |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2249 | unsigned long flags; |
Paul E. McKenney | 9fdd3bc | 2014-07-29 14:50:47 -0700 | [diff] [blame] | 2250 | int ndw; |
| 2251 | |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2252 | raw_spin_lock_irqsave(&rdp->nocb_lock, flags); |
| 2253 | if (!rcu_nocb_need_deferred_wakeup(rdp)) { |
| 2254 | raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2255 | return; |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2256 | } |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2257 | ndw = READ_ONCE(rdp->nocb_defer_wakeup); |
Paul E. McKenney | 511324e | 2017-04-28 17:04:09 -0700 | [diff] [blame] | 2258 | WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT); |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2259 | __wake_nocb_leader(rdp, ndw == RCU_NOCB_WAKE_FORCE, flags); |
Paul E. McKenney | 9fdd3bc | 2014-07-29 14:50:47 -0700 | [diff] [blame] | 2260 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("DeferredWake")); |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2261 | } |
| 2262 | |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2263 | /* Do a deferred wakeup of rcu_nocb_kthread() from a timer handler. */ |
| 2264 | static void do_nocb_deferred_wakeup_timer(unsigned long x) |
| 2265 | { |
| 2266 | do_nocb_deferred_wakeup_common((struct rcu_data *)x); |
| 2267 | } |
| 2268 | |
| 2269 | /* |
| 2270 | * Do a deferred wakeup of rcu_nocb_kthread() from fastpath. |
| 2271 | * This means we do an inexact common-case check. Note that if |
| 2272 | * we miss, ->nocb_timer will eventually clean things up. |
| 2273 | */ |
| 2274 | static void do_nocb_deferred_wakeup(struct rcu_data *rdp) |
| 2275 | { |
| 2276 | if (rcu_nocb_need_deferred_wakeup(rdp)) |
| 2277 | do_nocb_deferred_wakeup_common(rdp); |
| 2278 | } |
| 2279 | |
Paul E. McKenney | f4579fc | 2014-07-25 11:21:47 -0700 | [diff] [blame] | 2280 | void __init rcu_init_nohz(void) |
| 2281 | { |
| 2282 | int cpu; |
| 2283 | bool need_rcu_nocb_mask = true; |
| 2284 | struct rcu_state *rsp; |
| 2285 | |
Paul E. McKenney | f4579fc | 2014-07-25 11:21:47 -0700 | [diff] [blame] | 2286 | #if defined(CONFIG_NO_HZ_FULL) |
| 2287 | if (tick_nohz_full_running && cpumask_weight(tick_nohz_full_mask)) |
| 2288 | need_rcu_nocb_mask = true; |
| 2289 | #endif /* #if defined(CONFIG_NO_HZ_FULL) */ |
| 2290 | |
| 2291 | if (!have_rcu_nocb_mask && need_rcu_nocb_mask) { |
Pranith Kumar | 949cccd | 2014-07-25 16:02:07 -0700 | [diff] [blame] | 2292 | if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) { |
| 2293 | pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n"); |
| 2294 | return; |
| 2295 | } |
Paul E. McKenney | f4579fc | 2014-07-25 11:21:47 -0700 | [diff] [blame] | 2296 | have_rcu_nocb_mask = true; |
| 2297 | } |
| 2298 | if (!have_rcu_nocb_mask) |
| 2299 | return; |
| 2300 | |
Paul E. McKenney | f4579fc | 2014-07-25 11:21:47 -0700 | [diff] [blame] | 2301 | #if defined(CONFIG_NO_HZ_FULL) |
| 2302 | if (tick_nohz_full_running) |
| 2303 | cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); |
| 2304 | #endif /* #if defined(CONFIG_NO_HZ_FULL) */ |
| 2305 | |
| 2306 | if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { |
| 2307 | pr_info("\tNote: kernel parameter 'rcu_nocbs=' contains nonexistent CPUs.\n"); |
| 2308 | cpumask_and(rcu_nocb_mask, cpu_possible_mask, |
| 2309 | rcu_nocb_mask); |
| 2310 | } |
Tejun Heo | ad853b4 | 2015-02-13 14:37:25 -0800 | [diff] [blame] | 2311 | pr_info("\tOffload RCU callbacks from CPUs: %*pbl.\n", |
| 2312 | cpumask_pr_args(rcu_nocb_mask)); |
Paul E. McKenney | f4579fc | 2014-07-25 11:21:47 -0700 | [diff] [blame] | 2313 | if (rcu_nocb_poll) |
| 2314 | pr_info("\tPoll for callbacks from no-CBs CPUs.\n"); |
| 2315 | |
| 2316 | for_each_rcu_flavor(rsp) { |
Paul E. McKenney | 34404ca | 2015-01-19 20:39:20 -0800 | [diff] [blame] | 2317 | for_each_cpu(cpu, rcu_nocb_mask) |
| 2318 | init_nocb_callback_list(per_cpu_ptr(rsp->rda, cpu)); |
Paul E. McKenney | 35ce7f2 | 2014-07-11 11:30:24 -0700 | [diff] [blame] | 2319 | rcu_organize_nocb_kthreads(rsp); |
Paul E. McKenney | f4579fc | 2014-07-25 11:21:47 -0700 | [diff] [blame] | 2320 | } |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2321 | } |
| 2322 | |
| 2323 | /* Initialize per-rcu_data variables for no-CBs CPUs. */ |
| 2324 | static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) |
| 2325 | { |
| 2326 | rdp->nocb_tail = &rdp->nocb_head; |
Paul Gortmaker | abedf8e | 2016-02-19 09:46:41 +0100 | [diff] [blame] | 2327 | init_swait_queue_head(&rdp->nocb_wq); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2328 | rdp->nocb_follower_tail = &rdp->nocb_follower_head; |
Paul E. McKenney | 8be6e1b | 2017-04-29 20:03:20 -0700 | [diff] [blame] | 2329 | raw_spin_lock_init(&rdp->nocb_lock); |
| 2330 | setup_timer(&rdp->nocb_timer, do_nocb_deferred_wakeup_timer, |
| 2331 | (unsigned long)rdp); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2332 | } |
| 2333 | |
Paul E. McKenney | 35ce7f2 | 2014-07-11 11:30:24 -0700 | [diff] [blame] | 2334 | /* |
| 2335 | * If the specified CPU is a no-CBs CPU that does not already have its |
| 2336 | * rcuo kthread for the specified RCU flavor, spawn it. If the CPUs are |
| 2337 | * brought online out of order, this can require re-organizing the |
| 2338 | * leader-follower relationships. |
| 2339 | */ |
| 2340 | static void rcu_spawn_one_nocb_kthread(struct rcu_state *rsp, int cpu) |
| 2341 | { |
| 2342 | struct rcu_data *rdp; |
| 2343 | struct rcu_data *rdp_last; |
| 2344 | struct rcu_data *rdp_old_leader; |
| 2345 | struct rcu_data *rdp_spawn = per_cpu_ptr(rsp->rda, cpu); |
| 2346 | struct task_struct *t; |
| 2347 | |
| 2348 | /* |
| 2349 | * If this isn't a no-CBs CPU or if it already has an rcuo kthread, |
| 2350 | * then nothing to do. |
| 2351 | */ |
| 2352 | if (!rcu_is_nocb_cpu(cpu) || rdp_spawn->nocb_kthread) |
| 2353 | return; |
| 2354 | |
| 2355 | /* If we didn't spawn the leader first, reorganize! */ |
| 2356 | rdp_old_leader = rdp_spawn->nocb_leader; |
| 2357 | if (rdp_old_leader != rdp_spawn && !rdp_old_leader->nocb_kthread) { |
| 2358 | rdp_last = NULL; |
| 2359 | rdp = rdp_old_leader; |
| 2360 | do { |
| 2361 | rdp->nocb_leader = rdp_spawn; |
| 2362 | if (rdp_last && rdp != rdp_spawn) |
| 2363 | rdp_last->nocb_next_follower = rdp; |
Paul E. McKenney | bbe5d7a | 2014-10-24 11:11:08 -0700 | [diff] [blame] | 2364 | if (rdp == rdp_spawn) { |
| 2365 | rdp = rdp->nocb_next_follower; |
| 2366 | } else { |
| 2367 | rdp_last = rdp; |
| 2368 | rdp = rdp->nocb_next_follower; |
| 2369 | rdp_last->nocb_next_follower = NULL; |
| 2370 | } |
Paul E. McKenney | 35ce7f2 | 2014-07-11 11:30:24 -0700 | [diff] [blame] | 2371 | } while (rdp); |
| 2372 | rdp_spawn->nocb_next_follower = rdp_old_leader; |
| 2373 | } |
| 2374 | |
| 2375 | /* Spawn the kthread for this CPU and RCU flavor. */ |
| 2376 | t = kthread_run(rcu_nocb_kthread, rdp_spawn, |
| 2377 | "rcuo%c/%d", rsp->abbr, cpu); |
| 2378 | BUG_ON(IS_ERR(t)); |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2379 | WRITE_ONCE(rdp_spawn->nocb_kthread, t); |
Paul E. McKenney | 35ce7f2 | 2014-07-11 11:30:24 -0700 | [diff] [blame] | 2380 | } |
| 2381 | |
| 2382 | /* |
| 2383 | * If the specified CPU is a no-CBs CPU that does not already have its |
| 2384 | * rcuo kthreads, spawn them. |
| 2385 | */ |
| 2386 | static void rcu_spawn_all_nocb_kthreads(int cpu) |
| 2387 | { |
| 2388 | struct rcu_state *rsp; |
| 2389 | |
| 2390 | if (rcu_scheduler_fully_active) |
| 2391 | for_each_rcu_flavor(rsp) |
| 2392 | rcu_spawn_one_nocb_kthread(rsp, cpu); |
| 2393 | } |
| 2394 | |
| 2395 | /* |
| 2396 | * Once the scheduler is running, spawn rcuo kthreads for all online |
| 2397 | * no-CBs CPUs. This assumes that the early_initcall()s happen before |
| 2398 | * non-boot CPUs come online -- if this changes, we will need to add |
| 2399 | * some mutual exclusion. |
| 2400 | */ |
| 2401 | static void __init rcu_spawn_nocb_kthreads(void) |
| 2402 | { |
| 2403 | int cpu; |
| 2404 | |
| 2405 | for_each_online_cpu(cpu) |
| 2406 | rcu_spawn_all_nocb_kthreads(cpu); |
| 2407 | } |
| 2408 | |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2409 | /* How many follower CPU IDs per leader? Default of -1 for sqrt(nr_cpu_ids). */ |
| 2410 | static int rcu_nocb_leader_stride = -1; |
| 2411 | module_param(rcu_nocb_leader_stride, int, 0444); |
| 2412 | |
| 2413 | /* |
Paul E. McKenney | 35ce7f2 | 2014-07-11 11:30:24 -0700 | [diff] [blame] | 2414 | * Initialize leader-follower relationships for all no-CBs CPU. |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2415 | */ |
Paul E. McKenney | 35ce7f2 | 2014-07-11 11:30:24 -0700 | [diff] [blame] | 2416 | static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2417 | { |
| 2418 | int cpu; |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2419 | int ls = rcu_nocb_leader_stride; |
| 2420 | int nl = 0; /* Next leader. */ |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2421 | struct rcu_data *rdp; |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2422 | struct rcu_data *rdp_leader = NULL; /* Suppress misguided gcc warn. */ |
| 2423 | struct rcu_data *rdp_prev = NULL; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2424 | |
Pranith Kumar | 22c2f66 | 2014-07-17 20:11:01 -0400 | [diff] [blame] | 2425 | if (!have_rcu_nocb_mask) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2426 | return; |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2427 | if (ls == -1) { |
| 2428 | ls = int_sqrt(nr_cpu_ids); |
| 2429 | rcu_nocb_leader_stride = ls; |
| 2430 | } |
| 2431 | |
| 2432 | /* |
Paul E. McKenney | 9831ce3 | 2017-01-02 14:24:24 -0800 | [diff] [blame] | 2433 | * Each pass through this loop sets up one rcu_data structure. |
| 2434 | * Should the corresponding CPU come online in the future, then |
| 2435 | * we will spawn the needed set of rcu_nocb_kthread() kthreads. |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2436 | */ |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2437 | for_each_cpu(cpu, rcu_nocb_mask) { |
| 2438 | rdp = per_cpu_ptr(rsp->rda, cpu); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2439 | if (rdp->cpu >= nl) { |
| 2440 | /* New leader, set up for followers & next leader. */ |
| 2441 | nl = DIV_ROUND_UP(rdp->cpu + 1, ls) * ls; |
| 2442 | rdp->nocb_leader = rdp; |
| 2443 | rdp_leader = rdp; |
| 2444 | } else { |
| 2445 | /* Another follower, link to previous leader. */ |
| 2446 | rdp->nocb_leader = rdp_leader; |
| 2447 | rdp_prev->nocb_next_follower = rdp; |
| 2448 | } |
| 2449 | rdp_prev = rdp; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2450 | } |
| 2451 | } |
| 2452 | |
| 2453 | /* Prevent __call_rcu() from enqueuing callbacks on no-CBs CPUs */ |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2454 | static bool init_nocb_callback_list(struct rcu_data *rdp) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2455 | { |
Pranith Kumar | 22c2f66 | 2014-07-17 20:11:01 -0400 | [diff] [blame] | 2456 | if (!rcu_is_nocb_cpu(rdp->cpu)) |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2457 | return false; |
Pranith Kumar | 22c2f66 | 2014-07-17 20:11:01 -0400 | [diff] [blame] | 2458 | |
Paul E. McKenney | 34404ca | 2015-01-19 20:39:20 -0800 | [diff] [blame] | 2459 | /* If there are early-boot callbacks, move them to nocb lists. */ |
Paul E. McKenney | 15fecf8 | 2017-02-08 12:36:42 -0800 | [diff] [blame] | 2460 | if (!rcu_segcblist_empty(&rdp->cblist)) { |
| 2461 | rdp->nocb_head = rcu_segcblist_head(&rdp->cblist); |
| 2462 | rdp->nocb_tail = rcu_segcblist_tail(&rdp->cblist); |
| 2463 | atomic_long_set(&rdp->nocb_q_count, |
| 2464 | rcu_segcblist_n_cbs(&rdp->cblist)); |
| 2465 | atomic_long_set(&rdp->nocb_q_count_lazy, |
| 2466 | rcu_segcblist_n_lazy_cbs(&rdp->cblist)); |
| 2467 | rcu_segcblist_init(&rdp->cblist); |
Paul E. McKenney | 34404ca | 2015-01-19 20:39:20 -0800 | [diff] [blame] | 2468 | } |
Paul E. McKenney | 15fecf8 | 2017-02-08 12:36:42 -0800 | [diff] [blame] | 2469 | rcu_segcblist_disable(&rdp->cblist); |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2470 | return true; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2471 | } |
| 2472 | |
| 2473 | #else /* #ifdef CONFIG_RCU_NOCB_CPU */ |
| 2474 | |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 2475 | static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu) |
| 2476 | { |
| 2477 | WARN_ON_ONCE(1); /* Should be dead code. */ |
| 2478 | return false; |
| 2479 | } |
| 2480 | |
Paul Gortmaker | abedf8e | 2016-02-19 09:46:41 +0100 | [diff] [blame] | 2481 | static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq) |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 2482 | { |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 2483 | } |
| 2484 | |
| 2485 | static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq) |
| 2486 | { |
| 2487 | } |
| 2488 | |
Paul Gortmaker | abedf8e | 2016-02-19 09:46:41 +0100 | [diff] [blame] | 2489 | static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp) |
Daniel Wagner | 065bb78 | 2016-02-19 09:46:40 +0100 | [diff] [blame] | 2490 | { |
| 2491 | return NULL; |
| 2492 | } |
| 2493 | |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 2494 | static void rcu_init_one_nocb(struct rcu_node *rnp) |
| 2495 | { |
| 2496 | } |
| 2497 | |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2498 | static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2499 | bool lazy, unsigned long flags) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2500 | { |
Pranith Kumar | 4afc7e2 | 2014-07-08 18:26:16 -0400 | [diff] [blame] | 2501 | return false; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2502 | } |
| 2503 | |
Paul E. McKenney | b1a2d79 | 2017-06-26 12:23:46 -0700 | [diff] [blame] | 2504 | static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_data *my_rdp, |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2505 | struct rcu_data *rdp, |
| 2506 | unsigned long flags) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2507 | { |
Pranith Kumar | f4aa84b | 2014-07-08 18:26:17 -0400 | [diff] [blame] | 2508 | return false; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2509 | } |
| 2510 | |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2511 | static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) |
| 2512 | { |
| 2513 | } |
| 2514 | |
Paul E. McKenney | 9fdd3bc | 2014-07-29 14:50:47 -0700 | [diff] [blame] | 2515 | static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2516 | { |
| 2517 | return false; |
| 2518 | } |
| 2519 | |
| 2520 | static void do_nocb_deferred_wakeup(struct rcu_data *rdp) |
| 2521 | { |
| 2522 | } |
| 2523 | |
Paul E. McKenney | 35ce7f2 | 2014-07-11 11:30:24 -0700 | [diff] [blame] | 2524 | static void rcu_spawn_all_nocb_kthreads(int cpu) |
| 2525 | { |
| 2526 | } |
| 2527 | |
| 2528 | static void __init rcu_spawn_nocb_kthreads(void) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2529 | { |
| 2530 | } |
| 2531 | |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2532 | static bool init_nocb_callback_list(struct rcu_data *rdp) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2533 | { |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2534 | return false; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2535 | } |
| 2536 | |
| 2537 | #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ |
Paul E. McKenney | 65d798f | 2013-04-12 16:19:10 -0700 | [diff] [blame] | 2538 | |
| 2539 | /* |
| 2540 | * An adaptive-ticks CPU can potentially execute in kernel mode for an |
| 2541 | * arbitrarily long period of time with the scheduling-clock tick turned |
| 2542 | * off. RCU will be paying attention to this CPU because it is in the |
| 2543 | * kernel, but the CPU cannot be guaranteed to be executing the RCU state |
| 2544 | * machine because the scheduling-clock tick has been disabled. Therefore, |
| 2545 | * if an adaptive-ticks CPU is failing to respond to the current grace |
| 2546 | * period and has not be idle from an RCU perspective, kick it. |
| 2547 | */ |
Paul E. McKenney | 4a81e83 | 2014-06-20 16:49:01 -0700 | [diff] [blame] | 2548 | static void __maybe_unused rcu_kick_nohz_cpu(int cpu) |
Paul E. McKenney | 65d798f | 2013-04-12 16:19:10 -0700 | [diff] [blame] | 2549 | { |
| 2550 | #ifdef CONFIG_NO_HZ_FULL |
| 2551 | if (tick_nohz_full_cpu(cpu)) |
| 2552 | smp_send_reschedule(cpu); |
| 2553 | #endif /* #ifdef CONFIG_NO_HZ_FULL */ |
| 2554 | } |
Paul E. McKenney | 2333210 | 2013-06-21 12:34:33 -0700 | [diff] [blame] | 2555 | |
Paul E. McKenney | a096932 | 2013-11-08 09:03:10 -0800 | [diff] [blame] | 2556 | /* |
| 2557 | * Is this CPU a NO_HZ_FULL CPU that should ignore RCU so that the |
| 2558 | * grace-period kthread will do force_quiescent_state() processing? |
| 2559 | * The idea is to avoid waking up RCU core processing on such a |
| 2560 | * CPU unless the grace period has extended for too long. |
| 2561 | * |
| 2562 | * This code relies on the fact that all NO_HZ_FULL CPUs are also |
Paul Bolle | 52e2bb9 | 2014-02-09 14:35:11 +0100 | [diff] [blame] | 2563 | * CONFIG_RCU_NOCB_CPU CPUs. |
Paul E. McKenney | a096932 | 2013-11-08 09:03:10 -0800 | [diff] [blame] | 2564 | */ |
| 2565 | static bool rcu_nohz_full_cpu(struct rcu_state *rsp) |
| 2566 | { |
| 2567 | #ifdef CONFIG_NO_HZ_FULL |
| 2568 | if (tick_nohz_full_cpu(smp_processor_id()) && |
| 2569 | (!rcu_gp_in_progress(rsp) || |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2570 | ULONG_CMP_LT(jiffies, READ_ONCE(rsp->gp_start) + HZ))) |
Joe Perches | 5ce035f | 2015-03-30 16:46:16 -0700 | [diff] [blame] | 2571 | return true; |
Paul E. McKenney | a096932 | 2013-11-08 09:03:10 -0800 | [diff] [blame] | 2572 | #endif /* #ifdef CONFIG_NO_HZ_FULL */ |
Joe Perches | 5ce035f | 2015-03-30 16:46:16 -0700 | [diff] [blame] | 2573 | return false; |
Paul E. McKenney | a096932 | 2013-11-08 09:03:10 -0800 | [diff] [blame] | 2574 | } |
Paul E. McKenney | 5057f55e5 | 2014-04-01 11:20:36 -0700 | [diff] [blame] | 2575 | |
| 2576 | /* |
| 2577 | * Bind the grace-period kthread for the sysidle flavor of RCU to the |
| 2578 | * timekeeping CPU. |
| 2579 | */ |
| 2580 | static void rcu_bind_gp_kthread(void) |
| 2581 | { |
Paul E. McKenney | c0f489d | 2014-06-04 13:46:03 -0700 | [diff] [blame] | 2582 | int __maybe_unused cpu; |
Paul E. McKenney | 5057f55e5 | 2014-04-01 11:20:36 -0700 | [diff] [blame] | 2583 | |
Paul E. McKenney | c0f489d | 2014-06-04 13:46:03 -0700 | [diff] [blame] | 2584 | if (!tick_nohz_full_enabled()) |
Paul E. McKenney | 5057f55e5 | 2014-04-01 11:20:36 -0700 | [diff] [blame] | 2585 | return; |
Paul E. McKenney | 5871968 | 2015-02-24 11:05:36 -0800 | [diff] [blame] | 2586 | housekeeping_affine(current); |
Paul E. McKenney | 5057f55e5 | 2014-04-01 11:20:36 -0700 | [diff] [blame] | 2587 | } |
Paul E. McKenney | 176f8f7 | 2014-08-04 17:43:50 -0700 | [diff] [blame] | 2588 | |
| 2589 | /* Record the current task on dyntick-idle entry. */ |
| 2590 | static void rcu_dynticks_task_enter(void) |
| 2591 | { |
| 2592 | #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2593 | WRITE_ONCE(current->rcu_tasks_idle_cpu, smp_processor_id()); |
Paul E. McKenney | 176f8f7 | 2014-08-04 17:43:50 -0700 | [diff] [blame] | 2594 | #endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */ |
| 2595 | } |
| 2596 | |
| 2597 | /* Record no current task on dyntick-idle exit. */ |
| 2598 | static void rcu_dynticks_task_exit(void) |
| 2599 | { |
| 2600 | #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2601 | WRITE_ONCE(current->rcu_tasks_idle_cpu, -1); |
Paul E. McKenney | 176f8f7 | 2014-08-04 17:43:50 -0700 | [diff] [blame] | 2602 | #endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */ |
| 2603 | } |