Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 1 | /* |
| 2 | * RCU expedited grace periods |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or modify |
| 5 | * it under the terms of the GNU General Public License as published by |
| 6 | * the Free Software Foundation; either version 2 of the License, or |
| 7 | * (at your option) any later version. |
| 8 | * |
| 9 | * This program is distributed in the hope that it will be useful, |
| 10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 12 | * GNU General Public License for more details. |
| 13 | * |
| 14 | * You should have received a copy of the GNU General Public License |
| 15 | * along with this program; if not, you can access it online at |
| 16 | * http://www.gnu.org/licenses/gpl-2.0.html. |
| 17 | * |
| 18 | * Copyright IBM Corporation, 2016 |
| 19 | * |
| 20 | * Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
| 21 | */ |
| 22 | |
Boqun Feng | 55ebfce | 2018-03-09 09:14:51 +0800 | [diff] [blame] | 23 | #include <linux/lockdep.h> |
| 24 | |
Paul E. McKenney | 09e2db3 | 2016-12-18 13:31:02 -0800 | [diff] [blame] | 25 | /* |
| 26 | * Record the start of an expedited grace period. |
| 27 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 28 | static void rcu_exp_gp_seq_start(void) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 29 | { |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 30 | rcu_seq_start(&rcu_state.expedited_sequence); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 31 | } |
Paul E. McKenney | 09e2db3 | 2016-12-18 13:31:02 -0800 | [diff] [blame] | 32 | |
| 33 | /* |
Paul E. McKenney | 9a41420 | 2018-01-31 19:23:24 -0800 | [diff] [blame] | 34 | * Return then value that expedited-grace-period counter will have |
| 35 | * at the end of the current grace period. |
| 36 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 37 | static __maybe_unused unsigned long rcu_exp_gp_seq_endval(void) |
Paul E. McKenney | 9a41420 | 2018-01-31 19:23:24 -0800 | [diff] [blame] | 38 | { |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 39 | return rcu_seq_endval(&rcu_state.expedited_sequence); |
Paul E. McKenney | 9a41420 | 2018-01-31 19:23:24 -0800 | [diff] [blame] | 40 | } |
| 41 | |
| 42 | /* |
Paul E. McKenney | 09e2db3 | 2016-12-18 13:31:02 -0800 | [diff] [blame] | 43 | * Record the end of an expedited grace period. |
| 44 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 45 | static void rcu_exp_gp_seq_end(void) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 46 | { |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 47 | rcu_seq_end(&rcu_state.expedited_sequence); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 48 | smp_mb(); /* Ensure that consecutive grace periods serialize. */ |
| 49 | } |
Paul E. McKenney | 09e2db3 | 2016-12-18 13:31:02 -0800 | [diff] [blame] | 50 | |
| 51 | /* |
| 52 | * Take a snapshot of the expedited-grace-period counter. |
| 53 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 54 | static unsigned long rcu_exp_gp_seq_snap(void) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 55 | { |
| 56 | unsigned long s; |
| 57 | |
| 58 | smp_mb(); /* Caller's modifications seen first by other CPUs. */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 59 | s = rcu_seq_snap(&rcu_state.expedited_sequence); |
| 60 | trace_rcu_exp_grace_period(rcu_state.name, s, TPS("snap")); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 61 | return s; |
| 62 | } |
Paul E. McKenney | 09e2db3 | 2016-12-18 13:31:02 -0800 | [diff] [blame] | 63 | |
| 64 | /* |
| 65 | * Given a counter snapshot from rcu_exp_gp_seq_snap(), return true |
| 66 | * if a full expedited grace period has elapsed since that snapshot |
| 67 | * was taken. |
| 68 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 69 | static bool rcu_exp_gp_seq_done(unsigned long s) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 70 | { |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 71 | return rcu_seq_done(&rcu_state.expedited_sequence, s); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 72 | } |
| 73 | |
| 74 | /* |
| 75 | * Reset the ->expmaskinit values in the rcu_node tree to reflect any |
| 76 | * recent CPU-online activity. Note that these masks are not cleared |
| 77 | * when CPUs go offline, so they reflect the union of all CPUs that have |
| 78 | * ever been online. This means that this function normally takes its |
| 79 | * no-work-to-do fastpath. |
| 80 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 81 | static void sync_exp_reset_tree_hotplug(void) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 82 | { |
| 83 | bool done; |
| 84 | unsigned long flags; |
| 85 | unsigned long mask; |
| 86 | unsigned long oldmask; |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 87 | int ncpus = smp_load_acquire(&rcu_state.ncpus); /* Order vs. locking. */ |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 88 | struct rcu_node *rnp; |
| 89 | struct rcu_node *rnp_up; |
| 90 | |
| 91 | /* If no new CPUs onlined since last time, nothing to do. */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 92 | if (likely(ncpus == rcu_state.ncpus_snap)) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 93 | return; |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 94 | rcu_state.ncpus_snap = ncpus; |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 95 | |
| 96 | /* |
| 97 | * Each pass through the following loop propagates newly onlined |
| 98 | * CPUs for the current rcu_node structure up the rcu_node tree. |
| 99 | */ |
Paul E. McKenney | aedf4ba9 | 2018-07-04 14:33:59 -0700 | [diff] [blame] | 100 | rcu_for_each_leaf_node(rnp) { |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 101 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
| 102 | if (rnp->expmaskinit == rnp->expmaskinitnext) { |
| 103 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
| 104 | continue; /* No new CPUs, nothing to do. */ |
| 105 | } |
| 106 | |
| 107 | /* Update this node's mask, track old value for propagation. */ |
| 108 | oldmask = rnp->expmaskinit; |
| 109 | rnp->expmaskinit = rnp->expmaskinitnext; |
| 110 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
| 111 | |
| 112 | /* If was already nonzero, nothing to propagate. */ |
| 113 | if (oldmask) |
| 114 | continue; |
| 115 | |
| 116 | /* Propagate the new CPU up the tree. */ |
| 117 | mask = rnp->grpmask; |
| 118 | rnp_up = rnp->parent; |
| 119 | done = false; |
| 120 | while (rnp_up) { |
| 121 | raw_spin_lock_irqsave_rcu_node(rnp_up, flags); |
| 122 | if (rnp_up->expmaskinit) |
| 123 | done = true; |
| 124 | rnp_up->expmaskinit |= mask; |
| 125 | raw_spin_unlock_irqrestore_rcu_node(rnp_up, flags); |
| 126 | if (done) |
| 127 | break; |
| 128 | mask = rnp_up->grpmask; |
| 129 | rnp_up = rnp_up->parent; |
| 130 | } |
| 131 | } |
| 132 | } |
| 133 | |
| 134 | /* |
| 135 | * Reset the ->expmask values in the rcu_node tree in preparation for |
| 136 | * a new expedited grace period. |
| 137 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 138 | static void __maybe_unused sync_exp_reset_tree(void) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 139 | { |
| 140 | unsigned long flags; |
| 141 | struct rcu_node *rnp; |
| 142 | |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 143 | sync_exp_reset_tree_hotplug(); |
Paul E. McKenney | aedf4ba9 | 2018-07-04 14:33:59 -0700 | [diff] [blame] | 144 | rcu_for_each_node_breadth_first(rnp) { |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 145 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
| 146 | WARN_ON_ONCE(rnp->expmask); |
| 147 | rnp->expmask = rnp->expmaskinit; |
| 148 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
| 149 | } |
| 150 | } |
| 151 | |
| 152 | /* |
| 153 | * Return non-zero if there is no RCU expedited grace period in progress |
| 154 | * for the specified rcu_node structure, in other words, if all CPUs and |
| 155 | * tasks covered by the specified rcu_node structure have done their bit |
| 156 | * for the current expedited grace period. Works only for preemptible |
| 157 | * RCU -- other RCU implementation use other means. |
| 158 | * |
Boqun Feng | 7be8c56 | 2018-03-07 16:49:39 +0800 | [diff] [blame] | 159 | * Caller must hold the specificed rcu_node structure's ->lock |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 160 | */ |
Paul E. McKenney | dcfc315 | 2017-04-18 09:53:07 -0700 | [diff] [blame] | 161 | static bool sync_rcu_preempt_exp_done(struct rcu_node *rnp) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 162 | { |
Boqun Feng | 55ebfce | 2018-03-09 09:14:51 +0800 | [diff] [blame] | 163 | raw_lockdep_assert_held_rcu_node(rnp); |
| 164 | |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 165 | return rnp->exp_tasks == NULL && |
| 166 | READ_ONCE(rnp->expmask) == 0; |
| 167 | } |
| 168 | |
| 169 | /* |
Boqun Feng | 55ebfce | 2018-03-09 09:14:51 +0800 | [diff] [blame] | 170 | * Like sync_rcu_preempt_exp_done(), but this function assumes the caller |
| 171 | * doesn't hold the rcu_node's ->lock, and will acquire and release the lock |
| 172 | * itself |
| 173 | */ |
| 174 | static bool sync_rcu_preempt_exp_done_unlocked(struct rcu_node *rnp) |
| 175 | { |
| 176 | unsigned long flags; |
| 177 | bool ret; |
| 178 | |
| 179 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
| 180 | ret = sync_rcu_preempt_exp_done(rnp); |
| 181 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
| 182 | |
| 183 | return ret; |
| 184 | } |
| 185 | |
| 186 | |
| 187 | /* |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 188 | * Report the exit from RCU read-side critical section for the last task |
| 189 | * that queued itself during or before the current expedited preemptible-RCU |
| 190 | * grace period. This event is reported either to the rcu_node structure on |
| 191 | * which the task was queued or to one of that rcu_node structure's ancestors, |
| 192 | * recursively up the tree. (Calm down, calm down, we do the recursion |
| 193 | * iteratively!) |
| 194 | * |
Boqun Feng | 7be8c56 | 2018-03-07 16:49:39 +0800 | [diff] [blame] | 195 | * Caller must hold the specified rcu_node structure's ->lock. |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 196 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 197 | static void __rcu_report_exp_rnp(struct rcu_node *rnp, |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 198 | bool wake, unsigned long flags) |
| 199 | __releases(rnp->lock) |
| 200 | { |
| 201 | unsigned long mask; |
| 202 | |
| 203 | for (;;) { |
| 204 | if (!sync_rcu_preempt_exp_done(rnp)) { |
| 205 | if (!rnp->expmask) |
| 206 | rcu_initiate_boost(rnp, flags); |
| 207 | else |
| 208 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
| 209 | break; |
| 210 | } |
| 211 | if (rnp->parent == NULL) { |
| 212 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
| 213 | if (wake) { |
| 214 | smp_mb(); /* EGP done before wake_up(). */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 215 | swake_up_one(&rcu_state.expedited_wq); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 216 | } |
| 217 | break; |
| 218 | } |
| 219 | mask = rnp->grpmask; |
| 220 | raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled */ |
| 221 | rnp = rnp->parent; |
| 222 | raw_spin_lock_rcu_node(rnp); /* irqs already disabled */ |
| 223 | WARN_ON_ONCE(!(rnp->expmask & mask)); |
| 224 | rnp->expmask &= ~mask; |
| 225 | } |
| 226 | } |
| 227 | |
| 228 | /* |
| 229 | * Report expedited quiescent state for specified node. This is a |
| 230 | * lock-acquisition wrapper function for __rcu_report_exp_rnp(). |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 231 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 232 | static void __maybe_unused rcu_report_exp_rnp(struct rcu_node *rnp, bool wake) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 233 | { |
| 234 | unsigned long flags; |
| 235 | |
| 236 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 237 | __rcu_report_exp_rnp(rnp, wake, flags); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 238 | } |
| 239 | |
| 240 | /* |
| 241 | * Report expedited quiescent state for multiple CPUs, all covered by the |
Boqun Feng | 7be8c56 | 2018-03-07 16:49:39 +0800 | [diff] [blame] | 242 | * specified leaf rcu_node structure. |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 243 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 244 | static void rcu_report_exp_cpu_mult(struct rcu_node *rnp, |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 245 | unsigned long mask, bool wake) |
| 246 | { |
| 247 | unsigned long flags; |
| 248 | |
| 249 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
| 250 | if (!(rnp->expmask & mask)) { |
| 251 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
| 252 | return; |
| 253 | } |
| 254 | rnp->expmask &= ~mask; |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 255 | __rcu_report_exp_rnp(rnp, wake, flags); /* Releases rnp->lock. */ |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 256 | } |
| 257 | |
| 258 | /* |
| 259 | * Report expedited quiescent state for specified rcu_data (CPU). |
| 260 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 261 | static void rcu_report_exp_rdp(struct rcu_data *rdp) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 262 | { |
Paul E. McKenney | 3e31009 | 2018-06-21 12:50:01 -0700 | [diff] [blame] | 263 | WRITE_ONCE(rdp->deferred_qs, false); |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 264 | rcu_report_exp_cpu_mult(rdp->mynode, rdp->grpmask, true); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 265 | } |
| 266 | |
Paul E. McKenney | 45975c7 | 2018-07-02 14:30:37 -0700 | [diff] [blame] | 267 | /* Common code for work-done checking. */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 268 | static bool sync_exp_work_done(unsigned long s) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 269 | { |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 270 | if (rcu_exp_gp_seq_done(s)) { |
| 271 | trace_rcu_exp_grace_period(rcu_state.name, s, TPS("done")); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 272 | /* Ensure test happens before caller kfree(). */ |
| 273 | smp_mb__before_atomic(); /* ^^^ */ |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 274 | return true; |
| 275 | } |
| 276 | return false; |
| 277 | } |
| 278 | |
| 279 | /* |
| 280 | * Funnel-lock acquisition for expedited grace periods. Returns true |
| 281 | * if some other task completed an expedited grace period that this task |
| 282 | * can piggy-back on, and with no mutex held. Otherwise, returns false |
| 283 | * with the mutex held, indicating that the caller must actually do the |
| 284 | * expedited grace period. |
| 285 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 286 | static bool exp_funnel_lock(unsigned long s) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 287 | { |
Paul E. McKenney | da1df50 | 2018-07-03 15:37:16 -0700 | [diff] [blame] | 288 | struct rcu_data *rdp = per_cpu_ptr(&rcu_data, raw_smp_processor_id()); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 289 | struct rcu_node *rnp = rdp->mynode; |
Paul E. McKenney | 336a4f6 | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 290 | struct rcu_node *rnp_root = rcu_get_root(); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 291 | |
| 292 | /* Low-contention fastpath. */ |
| 293 | if (ULONG_CMP_LT(READ_ONCE(rnp->exp_seq_rq), s) && |
| 294 | (rnp == rnp_root || |
| 295 | ULONG_CMP_LT(READ_ONCE(rnp_root->exp_seq_rq), s)) && |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 296 | mutex_trylock(&rcu_state.exp_mutex)) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 297 | goto fastpath; |
| 298 | |
| 299 | /* |
| 300 | * Each pass through the following loop works its way up |
| 301 | * the rcu_node tree, returning if others have done the work or |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 302 | * otherwise falls through to acquire ->exp_mutex. The mapping |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 303 | * from CPU to rcu_node structure can be inexact, as it is just |
| 304 | * promoting locality and is not strictly needed for correctness. |
| 305 | */ |
| 306 | for (; rnp != NULL; rnp = rnp->parent) { |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 307 | if (sync_exp_work_done(s)) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 308 | return true; |
| 309 | |
| 310 | /* Work not done, either wait here or go up. */ |
| 311 | spin_lock(&rnp->exp_lock); |
| 312 | if (ULONG_CMP_GE(rnp->exp_seq_rq, s)) { |
| 313 | |
| 314 | /* Someone else doing GP, so wait for them. */ |
| 315 | spin_unlock(&rnp->exp_lock); |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 316 | trace_rcu_exp_funnel_lock(rcu_state.name, rnp->level, |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 317 | rnp->grplo, rnp->grphi, |
| 318 | TPS("wait")); |
Paul E. McKenney | 031aeee | 2017-03-21 07:28:14 -0700 | [diff] [blame] | 319 | wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3], |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 320 | sync_exp_work_done(s)); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 321 | return true; |
| 322 | } |
| 323 | rnp->exp_seq_rq = s; /* Followers can wait on us. */ |
| 324 | spin_unlock(&rnp->exp_lock); |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 325 | trace_rcu_exp_funnel_lock(rcu_state.name, rnp->level, |
| 326 | rnp->grplo, rnp->grphi, TPS("nxtlvl")); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 327 | } |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 328 | mutex_lock(&rcu_state.exp_mutex); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 329 | fastpath: |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 330 | if (sync_exp_work_done(s)) { |
| 331 | mutex_unlock(&rcu_state.exp_mutex); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 332 | return true; |
| 333 | } |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 334 | rcu_exp_gp_seq_start(); |
| 335 | trace_rcu_exp_grace_period(rcu_state.name, s, TPS("start")); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 336 | return false; |
| 337 | } |
| 338 | |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 339 | /* |
Paul E. McKenney | 25f3d7e | 2018-02-01 22:05:38 -0800 | [diff] [blame] | 340 | * Select the CPUs within the specified rcu_node that the upcoming |
| 341 | * expedited grace period needs to wait for. |
| 342 | */ |
| 343 | static void sync_rcu_exp_select_node_cpus(struct work_struct *wp) |
| 344 | { |
| 345 | int cpu; |
| 346 | unsigned long flags; |
| 347 | smp_call_func_t func; |
| 348 | unsigned long mask_ofl_test; |
| 349 | unsigned long mask_ofl_ipi; |
| 350 | int ret; |
| 351 | struct rcu_exp_work *rewp = |
| 352 | container_of(wp, struct rcu_exp_work, rew_work); |
| 353 | struct rcu_node *rnp = container_of(rewp, struct rcu_node, rew); |
Paul E. McKenney | 25f3d7e | 2018-02-01 22:05:38 -0800 | [diff] [blame] | 354 | |
| 355 | func = rewp->rew_func; |
| 356 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
| 357 | |
| 358 | /* Each pass checks a CPU for identity, offline, and idle. */ |
| 359 | mask_ofl_test = 0; |
| 360 | for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) { |
| 361 | unsigned long mask = leaf_node_cpu_bit(rnp, cpu); |
Paul E. McKenney | da1df50 | 2018-07-03 15:37:16 -0700 | [diff] [blame] | 362 | struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); |
Paul E. McKenney | 25f3d7e | 2018-02-01 22:05:38 -0800 | [diff] [blame] | 363 | int snap; |
| 364 | |
| 365 | if (raw_smp_processor_id() == cpu || |
| 366 | !(rnp->qsmaskinitnext & mask)) { |
| 367 | mask_ofl_test |= mask; |
| 368 | } else { |
Paul E. McKenney | dc5a4f2 | 2018-08-03 21:00:38 -0700 | [diff] [blame] | 369 | snap = rcu_dynticks_snap(rdp); |
Paul E. McKenney | 25f3d7e | 2018-02-01 22:05:38 -0800 | [diff] [blame] | 370 | if (rcu_dynticks_in_eqs(snap)) |
| 371 | mask_ofl_test |= mask; |
| 372 | else |
| 373 | rdp->exp_dynticks_snap = snap; |
| 374 | } |
| 375 | } |
| 376 | mask_ofl_ipi = rnp->expmask & ~mask_ofl_test; |
| 377 | |
| 378 | /* |
| 379 | * Need to wait for any blocked tasks as well. Note that |
| 380 | * additional blocking tasks will also block the expedited GP |
| 381 | * until such time as the ->expmask bits are cleared. |
| 382 | */ |
| 383 | if (rcu_preempt_has_tasks(rnp)) |
| 384 | rnp->exp_tasks = rnp->blkd_tasks.next; |
| 385 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
| 386 | |
| 387 | /* IPI the remaining CPUs for expedited quiescent state. */ |
| 388 | for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) { |
| 389 | unsigned long mask = leaf_node_cpu_bit(rnp, cpu); |
Paul E. McKenney | da1df50 | 2018-07-03 15:37:16 -0700 | [diff] [blame] | 390 | struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); |
Paul E. McKenney | 25f3d7e | 2018-02-01 22:05:38 -0800 | [diff] [blame] | 391 | |
| 392 | if (!(mask_ofl_ipi & mask)) |
| 393 | continue; |
| 394 | retry_ipi: |
Paul E. McKenney | dc5a4f2 | 2018-08-03 21:00:38 -0700 | [diff] [blame] | 395 | if (rcu_dynticks_in_eqs_since(rdp, rdp->exp_dynticks_snap)) { |
Paul E. McKenney | 25f3d7e | 2018-02-01 22:05:38 -0800 | [diff] [blame] | 396 | mask_ofl_test |= mask; |
| 397 | continue; |
| 398 | } |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 399 | ret = smp_call_function_single(cpu, func, NULL, 0); |
Paul E. McKenney | 25f3d7e | 2018-02-01 22:05:38 -0800 | [diff] [blame] | 400 | if (!ret) { |
| 401 | mask_ofl_ipi &= ~mask; |
| 402 | continue; |
| 403 | } |
| 404 | /* Failed, raced with CPU hotplug operation. */ |
| 405 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
| 406 | if ((rnp->qsmaskinitnext & mask) && |
| 407 | (rnp->expmask & mask)) { |
| 408 | /* Online, so delay for a bit and try again. */ |
| 409 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 410 | trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("selectofl")); |
Paul E. McKenney | 25f3d7e | 2018-02-01 22:05:38 -0800 | [diff] [blame] | 411 | schedule_timeout_uninterruptible(1); |
| 412 | goto retry_ipi; |
| 413 | } |
| 414 | /* CPU really is offline, so we can ignore it. */ |
| 415 | if (!(rnp->expmask & mask)) |
| 416 | mask_ofl_ipi &= ~mask; |
| 417 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
| 418 | } |
| 419 | /* Report quiescent states for those that went offline. */ |
| 420 | mask_ofl_test |= mask_ofl_ipi; |
| 421 | if (mask_ofl_test) |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 422 | rcu_report_exp_cpu_mult(rnp, mask_ofl_test, false); |
Paul E. McKenney | 25f3d7e | 2018-02-01 22:05:38 -0800 | [diff] [blame] | 423 | } |
| 424 | |
| 425 | /* |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 426 | * Select the nodes that the upcoming expedited grace period needs |
| 427 | * to wait for. |
| 428 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 429 | static void sync_rcu_exp_select_cpus(smp_call_func_t func) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 430 | { |
Boqun Feng | fcc6354 | 2018-06-15 12:06:31 -0700 | [diff] [blame] | 431 | int cpu; |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 432 | struct rcu_node *rnp; |
| 433 | |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 434 | trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("reset")); |
| 435 | sync_exp_reset_tree(); |
| 436 | trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("select")); |
Paul E. McKenney | 25f3d7e | 2018-02-01 22:05:38 -0800 | [diff] [blame] | 437 | |
| 438 | /* Schedule work for each leaf rcu_node structure. */ |
Paul E. McKenney | aedf4ba9 | 2018-07-04 14:33:59 -0700 | [diff] [blame] | 439 | rcu_for_each_leaf_node(rnp) { |
Paul E. McKenney | 25f3d7e | 2018-02-01 22:05:38 -0800 | [diff] [blame] | 440 | rnp->exp_need_flush = false; |
| 441 | if (!READ_ONCE(rnp->expmask)) |
| 442 | continue; /* Avoid early boot non-existent wq. */ |
| 443 | rnp->rew.rew_func = func; |
Paul E. McKenney | 25f3d7e | 2018-02-01 22:05:38 -0800 | [diff] [blame] | 444 | if (!READ_ONCE(rcu_par_gp_wq) || |
Paul E. McKenney | 5257514 | 2018-04-24 11:03:39 -0700 | [diff] [blame] | 445 | rcu_scheduler_active != RCU_SCHEDULER_RUNNING || |
Paul E. McKenney | aedf4ba9 | 2018-07-04 14:33:59 -0700 | [diff] [blame] | 446 | rcu_is_last_leaf_node(rnp)) { |
Paul E. McKenney | 5257514 | 2018-04-24 11:03:39 -0700 | [diff] [blame] | 447 | /* No workqueues yet or last leaf, do direct call. */ |
Paul E. McKenney | 25f3d7e | 2018-02-01 22:05:38 -0800 | [diff] [blame] | 448 | sync_rcu_exp_select_node_cpus(&rnp->rew.rew_work); |
| 449 | continue; |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 450 | } |
Paul E. McKenney | 25f3d7e | 2018-02-01 22:05:38 -0800 | [diff] [blame] | 451 | INIT_WORK(&rnp->rew.rew_work, sync_rcu_exp_select_node_cpus); |
Boqun Feng | fcc6354 | 2018-06-15 12:06:31 -0700 | [diff] [blame] | 452 | preempt_disable(); |
| 453 | cpu = cpumask_next(rnp->grplo - 1, cpu_online_mask); |
| 454 | /* If all offline, queue the work on an unbound CPU. */ |
| 455 | if (unlikely(cpu > rnp->grphi)) |
| 456 | cpu = WORK_CPU_UNBOUND; |
| 457 | queue_work_on(cpu, rcu_par_gp_wq, &rnp->rew.rew_work); |
| 458 | preempt_enable(); |
Paul E. McKenney | 25f3d7e | 2018-02-01 22:05:38 -0800 | [diff] [blame] | 459 | rnp->exp_need_flush = true; |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 460 | } |
Paul E. McKenney | 25f3d7e | 2018-02-01 22:05:38 -0800 | [diff] [blame] | 461 | |
| 462 | /* Wait for workqueue jobs (if any) to complete. */ |
Paul E. McKenney | aedf4ba9 | 2018-07-04 14:33:59 -0700 | [diff] [blame] | 463 | rcu_for_each_leaf_node(rnp) |
Paul E. McKenney | 25f3d7e | 2018-02-01 22:05:38 -0800 | [diff] [blame] | 464 | if (rnp->exp_need_flush) |
| 465 | flush_work(&rnp->rew.rew_work); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 466 | } |
| 467 | |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 468 | static void synchronize_sched_expedited_wait(void) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 469 | { |
| 470 | int cpu; |
| 471 | unsigned long jiffies_stall; |
| 472 | unsigned long jiffies_start; |
| 473 | unsigned long mask; |
| 474 | int ndetected; |
| 475 | struct rcu_node *rnp; |
Paul E. McKenney | 336a4f6 | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 476 | struct rcu_node *rnp_root = rcu_get_root(); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 477 | int ret; |
| 478 | |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 479 | trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("startwait")); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 480 | jiffies_stall = rcu_jiffies_till_stall_check(); |
| 481 | jiffies_start = jiffies; |
| 482 | |
| 483 | for (;;) { |
Peter Zijlstra | b3dae10 | 2018-06-12 10:34:52 +0200 | [diff] [blame] | 484 | ret = swait_event_timeout_exclusive( |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 485 | rcu_state.expedited_wq, |
Boqun Feng | 55ebfce | 2018-03-09 09:14:51 +0800 | [diff] [blame] | 486 | sync_rcu_preempt_exp_done_unlocked(rnp_root), |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 487 | jiffies_stall); |
Boqun Feng | 55ebfce | 2018-03-09 09:14:51 +0800 | [diff] [blame] | 488 | if (ret > 0 || sync_rcu_preempt_exp_done_unlocked(rnp_root)) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 489 | return; |
Paul E. McKenney | 908d2c1 | 2016-06-29 14:34:59 -0700 | [diff] [blame] | 490 | WARN_ON(ret < 0); /* workqueues should not be signaled. */ |
Paul E. McKenney | 24a6cff | 2016-06-29 14:49:29 -0700 | [diff] [blame] | 491 | if (rcu_cpu_stall_suppress) |
| 492 | continue; |
| 493 | panic_on_rcu_stall(); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 494 | pr_err("INFO: %s detected expedited stalls on CPUs/tasks: {", |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 495 | rcu_state.name); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 496 | ndetected = 0; |
Paul E. McKenney | aedf4ba9 | 2018-07-04 14:33:59 -0700 | [diff] [blame] | 497 | rcu_for_each_leaf_node(rnp) { |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 498 | ndetected += rcu_print_task_exp_stall(rnp); |
Mark Rutland | bc75e99 | 2016-06-03 15:20:04 +0100 | [diff] [blame] | 499 | for_each_leaf_node_possible_cpu(rnp, cpu) { |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 500 | struct rcu_data *rdp; |
| 501 | |
Mark Rutland | bc75e99 | 2016-06-03 15:20:04 +0100 | [diff] [blame] | 502 | mask = leaf_node_cpu_bit(rnp, cpu); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 503 | if (!(rnp->expmask & mask)) |
| 504 | continue; |
| 505 | ndetected++; |
Paul E. McKenney | da1df50 | 2018-07-03 15:37:16 -0700 | [diff] [blame] | 506 | rdp = per_cpu_ptr(&rcu_data, cpu); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 507 | pr_cont(" %d-%c%c%c", cpu, |
| 508 | "O."[!!cpu_online(cpu)], |
| 509 | "o."[!!(rdp->grpmask & rnp->expmaskinit)], |
| 510 | "N."[!!(rdp->grpmask & rnp->expmaskinitnext)]); |
| 511 | } |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 512 | } |
| 513 | pr_cont(" } %lu jiffies s: %lu root: %#lx/%c\n", |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 514 | jiffies - jiffies_start, rcu_state.expedited_sequence, |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 515 | rnp_root->expmask, ".T"[!!rnp_root->exp_tasks]); |
| 516 | if (ndetected) { |
| 517 | pr_err("blocking rcu_node structures:"); |
Paul E. McKenney | aedf4ba9 | 2018-07-04 14:33:59 -0700 | [diff] [blame] | 518 | rcu_for_each_node_breadth_first(rnp) { |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 519 | if (rnp == rnp_root) |
| 520 | continue; /* printed unconditionally */ |
Boqun Feng | 55ebfce | 2018-03-09 09:14:51 +0800 | [diff] [blame] | 521 | if (sync_rcu_preempt_exp_done_unlocked(rnp)) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 522 | continue; |
| 523 | pr_cont(" l=%u:%d-%d:%#lx/%c", |
| 524 | rnp->level, rnp->grplo, rnp->grphi, |
| 525 | rnp->expmask, |
| 526 | ".T"[!!rnp->exp_tasks]); |
| 527 | } |
| 528 | pr_cont("\n"); |
| 529 | } |
Paul E. McKenney | aedf4ba9 | 2018-07-04 14:33:59 -0700 | [diff] [blame] | 530 | rcu_for_each_leaf_node(rnp) { |
Mark Rutland | bc75e99 | 2016-06-03 15:20:04 +0100 | [diff] [blame] | 531 | for_each_leaf_node_possible_cpu(rnp, cpu) { |
| 532 | mask = leaf_node_cpu_bit(rnp, cpu); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 533 | if (!(rnp->expmask & mask)) |
| 534 | continue; |
| 535 | dump_cpu_task(cpu); |
| 536 | } |
| 537 | } |
| 538 | jiffies_stall = 3 * rcu_jiffies_till_stall_check() + 3; |
| 539 | } |
| 540 | } |
| 541 | |
| 542 | /* |
| 543 | * Wait for the current expedited grace period to complete, and then |
| 544 | * wake up everyone who piggybacked on the just-completed expedited |
| 545 | * grace period. Also update all the ->exp_seq_rq counters as needed |
| 546 | * in order to avoid counter-wrap problems. |
| 547 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 548 | static void rcu_exp_wait_wake(unsigned long s) |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 549 | { |
| 550 | struct rcu_node *rnp; |
| 551 | |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 552 | synchronize_sched_expedited_wait(); |
| 553 | rcu_exp_gp_seq_end(); |
| 554 | trace_rcu_exp_grace_period(rcu_state.name, s, TPS("end")); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 555 | |
| 556 | /* |
| 557 | * Switch over to wakeup mode, allowing the next GP, but -only- the |
| 558 | * next GP, to proceed. |
| 559 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 560 | mutex_lock(&rcu_state.exp_wake_mutex); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 561 | |
Paul E. McKenney | aedf4ba9 | 2018-07-04 14:33:59 -0700 | [diff] [blame] | 562 | rcu_for_each_node_breadth_first(rnp) { |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 563 | if (ULONG_CMP_LT(READ_ONCE(rnp->exp_seq_rq), s)) { |
| 564 | spin_lock(&rnp->exp_lock); |
| 565 | /* Recheck, avoid hang in case someone just arrived. */ |
| 566 | if (ULONG_CMP_LT(rnp->exp_seq_rq, s)) |
| 567 | rnp->exp_seq_rq = s; |
| 568 | spin_unlock(&rnp->exp_lock); |
| 569 | } |
Paul E. McKenney | 3c345825c8 | 2017-03-04 12:33:53 -0800 | [diff] [blame] | 570 | smp_mb(); /* All above changes before wakeup. */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 571 | wake_up_all(&rnp->exp_wq[rcu_seq_ctr(rcu_state.expedited_sequence) & 0x3]); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 572 | } |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 573 | trace_rcu_exp_grace_period(rcu_state.name, s, TPS("endwake")); |
| 574 | mutex_unlock(&rcu_state.exp_wake_mutex); |
Paul E. McKenney | 3549c2b | 2016-04-15 16:35:29 -0700 | [diff] [blame] | 575 | } |
| 576 | |
Paul E. McKenney | 8b355e3 | 2016-06-29 13:46:25 -0700 | [diff] [blame] | 577 | /* |
Paul E. McKenney | 52d7e48 | 2017-01-10 02:28:26 -0800 | [diff] [blame] | 578 | * Common code to drive an expedited grace period forward, used by |
| 579 | * workqueues and mid-boot-time tasks. |
| 580 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 581 | static void rcu_exp_sel_wait_wake(smp_call_func_t func, unsigned long s) |
Paul E. McKenney | 52d7e48 | 2017-01-10 02:28:26 -0800 | [diff] [blame] | 582 | { |
| 583 | /* Initialize the rcu_node tree in preparation for the wait. */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 584 | sync_rcu_exp_select_cpus(func); |
Paul E. McKenney | 52d7e48 | 2017-01-10 02:28:26 -0800 | [diff] [blame] | 585 | |
| 586 | /* Wait and clean up, including waking everyone. */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 587 | rcu_exp_wait_wake(s); |
Paul E. McKenney | 52d7e48 | 2017-01-10 02:28:26 -0800 | [diff] [blame] | 588 | } |
| 589 | |
| 590 | /* |
Paul E. McKenney | 8b355e3 | 2016-06-29 13:46:25 -0700 | [diff] [blame] | 591 | * Work-queue handler to drive an expedited grace period forward. |
| 592 | */ |
| 593 | static void wait_rcu_exp_gp(struct work_struct *wp) |
| 594 | { |
| 595 | struct rcu_exp_work *rewp; |
| 596 | |
Paul E. McKenney | 8b355e3 | 2016-06-29 13:46:25 -0700 | [diff] [blame] | 597 | rewp = container_of(wp, struct rcu_exp_work, rew_work); |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 598 | rcu_exp_sel_wait_wake(rewp->rew_func, rewp->rew_s); |
Paul E. McKenney | 8b355e3 | 2016-06-29 13:46:25 -0700 | [diff] [blame] | 599 | } |
| 600 | |
Paul E. McKenney | f7b8eb8 | 2016-06-24 11:30:32 -0700 | [diff] [blame] | 601 | /* |
Paul E. McKenney | 8fa946d | 2018-07-07 18:12:26 -0700 | [diff] [blame] | 602 | * Given a smp_call_function() handler, kick off the specified |
| 603 | * implementation of expedited grace period. |
Paul E. McKenney | f7b8eb8 | 2016-06-24 11:30:32 -0700 | [diff] [blame] | 604 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 605 | static void _synchronize_rcu_expedited(smp_call_func_t func) |
Paul E. McKenney | f7b8eb8 | 2016-06-24 11:30:32 -0700 | [diff] [blame] | 606 | { |
Paul E. McKenney | 8b355e3 | 2016-06-29 13:46:25 -0700 | [diff] [blame] | 607 | struct rcu_data *rdp; |
| 608 | struct rcu_exp_work rew; |
| 609 | struct rcu_node *rnp; |
Paul E. McKenney | f7b8eb8 | 2016-06-24 11:30:32 -0700 | [diff] [blame] | 610 | unsigned long s; |
| 611 | |
| 612 | /* If expedited grace periods are prohibited, fall back to normal. */ |
| 613 | if (rcu_gp_is_normal()) { |
Paul E. McKenney | ec5dd44 | 2018-07-03 15:02:28 -0700 | [diff] [blame] | 614 | wait_rcu_gp(call_rcu); |
Paul E. McKenney | f7b8eb8 | 2016-06-24 11:30:32 -0700 | [diff] [blame] | 615 | return; |
| 616 | } |
| 617 | |
| 618 | /* Take a snapshot of the sequence number. */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 619 | s = rcu_exp_gp_seq_snap(); |
| 620 | if (exp_funnel_lock(s)) |
Paul E. McKenney | f7b8eb8 | 2016-06-24 11:30:32 -0700 | [diff] [blame] | 621 | return; /* Someone else did our work for us. */ |
| 622 | |
Paul E. McKenney | 52d7e48 | 2017-01-10 02:28:26 -0800 | [diff] [blame] | 623 | /* Ensure that load happens before action based on it. */ |
| 624 | if (unlikely(rcu_scheduler_active == RCU_SCHEDULER_INIT)) { |
| 625 | /* Direct call during scheduler init and early_initcalls(). */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 626 | rcu_exp_sel_wait_wake(func, s); |
Paul E. McKenney | 52d7e48 | 2017-01-10 02:28:26 -0800 | [diff] [blame] | 627 | } else { |
| 628 | /* Marshall arguments & schedule the expedited grace period. */ |
| 629 | rew.rew_func = func; |
Paul E. McKenney | 52d7e48 | 2017-01-10 02:28:26 -0800 | [diff] [blame] | 630 | rew.rew_s = s; |
| 631 | INIT_WORK_ONSTACK(&rew.rew_work, wait_rcu_exp_gp); |
Paul E. McKenney | ad7c946 | 2018-01-08 14:35:52 -0800 | [diff] [blame] | 632 | queue_work(rcu_gp_wq, &rew.rew_work); |
Paul E. McKenney | 52d7e48 | 2017-01-10 02:28:26 -0800 | [diff] [blame] | 633 | } |
Paul E. McKenney | f7b8eb8 | 2016-06-24 11:30:32 -0700 | [diff] [blame] | 634 | |
Paul E. McKenney | 8b355e3 | 2016-06-29 13:46:25 -0700 | [diff] [blame] | 635 | /* Wait for expedited grace period to complete. */ |
Paul E. McKenney | da1df50 | 2018-07-03 15:37:16 -0700 | [diff] [blame] | 636 | rdp = per_cpu_ptr(&rcu_data, raw_smp_processor_id()); |
Paul E. McKenney | 336a4f6 | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 637 | rnp = rcu_get_root(); |
Paul E. McKenney | 031aeee | 2017-03-21 07:28:14 -0700 | [diff] [blame] | 638 | wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3], |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 639 | sync_exp_work_done(s)); |
Paul E. McKenney | 3c345825c8 | 2017-03-04 12:33:53 -0800 | [diff] [blame] | 640 | smp_mb(); /* Workqueue actions happen before return. */ |
Paul E. McKenney | 8b355e3 | 2016-06-29 13:46:25 -0700 | [diff] [blame] | 641 | |
| 642 | /* Let the next expedited grace period start. */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 643 | mutex_unlock(&rcu_state.exp_mutex); |
Paul E. McKenney | f7b8eb8 | 2016-06-24 11:30:32 -0700 | [diff] [blame] | 644 | } |
| 645 | |
Paul E. McKenney | 40e0a6c | 2016-04-15 16:44:07 -0700 | [diff] [blame] | 646 | #ifdef CONFIG_PREEMPT_RCU |
| 647 | |
| 648 | /* |
| 649 | * Remote handler for smp_call_function_single(). If there is an |
| 650 | * RCU read-side critical section in effect, request that the |
| 651 | * next rcu_read_unlock() record the quiescent state up the |
| 652 | * ->expmask fields in the rcu_node tree. Otherwise, immediately |
| 653 | * report the quiescent state. |
| 654 | */ |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 655 | static void sync_rcu_exp_handler(void *unused) |
Paul E. McKenney | 40e0a6c | 2016-04-15 16:44:07 -0700 | [diff] [blame] | 656 | { |
Paul E. McKenney | 3e31009 | 2018-06-21 12:50:01 -0700 | [diff] [blame] | 657 | unsigned long flags; |
Paul E. McKenney | da1df50 | 2018-07-03 15:37:16 -0700 | [diff] [blame] | 658 | struct rcu_data *rdp = this_cpu_ptr(&rcu_data); |
Paul E. McKenney | 3e31009 | 2018-06-21 12:50:01 -0700 | [diff] [blame] | 659 | struct rcu_node *rnp = rdp->mynode; |
Paul E. McKenney | 40e0a6c | 2016-04-15 16:44:07 -0700 | [diff] [blame] | 660 | struct task_struct *t = current; |
| 661 | |
| 662 | /* |
Paul E. McKenney | 3e31009 | 2018-06-21 12:50:01 -0700 | [diff] [blame] | 663 | * First, the common case of not being in an RCU read-side |
| 664 | * critical section. If also enabled or idle, immediately |
| 665 | * report the quiescent state, otherwise defer. |
Paul E. McKenney | 40e0a6c | 2016-04-15 16:44:07 -0700 | [diff] [blame] | 666 | */ |
Paul E. McKenney | 3e31009 | 2018-06-21 12:50:01 -0700 | [diff] [blame] | 667 | if (!t->rcu_read_lock_nesting) { |
| 668 | if (!(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK)) || |
| 669 | rcu_dynticks_curr_cpu_in_eqs()) { |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 670 | rcu_report_exp_rdp(rdp); |
Paul E. McKenney | 3e31009 | 2018-06-21 12:50:01 -0700 | [diff] [blame] | 671 | } else { |
| 672 | rdp->deferred_qs = true; |
Paul E. McKenney | fced9c8 | 2018-07-26 13:44:00 -0700 | [diff] [blame] | 673 | set_tsk_need_resched(t); |
| 674 | set_preempt_need_resched(); |
Paul E. McKenney | 3e31009 | 2018-06-21 12:50:01 -0700 | [diff] [blame] | 675 | } |
Paul E. McKenney | 40e0a6c | 2016-04-15 16:44:07 -0700 | [diff] [blame] | 676 | return; |
| 677 | } |
| 678 | |
| 679 | /* |
Paul E. McKenney | 3e31009 | 2018-06-21 12:50:01 -0700 | [diff] [blame] | 680 | * Second, the less-common case of being in an RCU read-side |
| 681 | * critical section. In this case we can count on a future |
| 682 | * rcu_read_unlock(). However, this rcu_read_unlock() might |
| 683 | * execute on some other CPU, but in that case there will be |
| 684 | * a future context switch. Either way, if the expedited |
| 685 | * grace period is still waiting on this CPU, set ->deferred_qs |
| 686 | * so that the eventual quiescent state will be reported. |
| 687 | * Note that there is a large group of race conditions that |
| 688 | * can have caused this quiescent state to already have been |
| 689 | * reported, so we really do need to check ->expmask. |
Paul E. McKenney | 40e0a6c | 2016-04-15 16:44:07 -0700 | [diff] [blame] | 690 | */ |
Paul E. McKenney | 3e31009 | 2018-06-21 12:50:01 -0700 | [diff] [blame] | 691 | if (t->rcu_read_lock_nesting > 0) { |
| 692 | raw_spin_lock_irqsave_rcu_node(rnp, flags); |
| 693 | if (rnp->expmask & rdp->grpmask) |
| 694 | rdp->deferred_qs = true; |
| 695 | raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
| 696 | } |
| 697 | |
| 698 | /* |
| 699 | * The final and least likely case is where the interrupted |
| 700 | * code was just about to or just finished exiting the RCU-preempt |
| 701 | * read-side critical section, and no, we can't tell which. |
| 702 | * So either way, set ->deferred_qs to flag later code that |
| 703 | * a quiescent state is required. |
| 704 | * |
| 705 | * If the CPU is fully enabled (or if some buggy RCU-preempt |
| 706 | * read-side critical section is being used from idle), just |
| 707 | * invoke rcu_preempt_defer_qs() to immediately report the |
| 708 | * quiescent state. We cannot use rcu_read_unlock_special() |
| 709 | * because we are in an interrupt handler, which will cause that |
| 710 | * function to take an early exit without doing anything. |
| 711 | * |
Paul E. McKenney | fced9c8 | 2018-07-26 13:44:00 -0700 | [diff] [blame] | 712 | * Otherwise, force a context switch after the CPU enables everything. |
Paul E. McKenney | 3e31009 | 2018-06-21 12:50:01 -0700 | [diff] [blame] | 713 | */ |
| 714 | rdp->deferred_qs = true; |
| 715 | if (!(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK)) || |
Paul E. McKenney | fced9c8 | 2018-07-26 13:44:00 -0700 | [diff] [blame] | 716 | WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs())) { |
Paul E. McKenney | 3e31009 | 2018-06-21 12:50:01 -0700 | [diff] [blame] | 717 | rcu_preempt_deferred_qs(t); |
Paul E. McKenney | fced9c8 | 2018-07-26 13:44:00 -0700 | [diff] [blame] | 718 | } else { |
| 719 | set_tsk_need_resched(t); |
| 720 | set_preempt_need_resched(); |
| 721 | } |
Paul E. McKenney | 40e0a6c | 2016-04-15 16:44:07 -0700 | [diff] [blame] | 722 | } |
| 723 | |
Paul E. McKenney | 8fa946d | 2018-07-07 18:12:26 -0700 | [diff] [blame] | 724 | /* PREEMPT=y, so no PREEMPT=n expedited grace period to clean up after. */ |
Paul E. McKenney | 45975c7 | 2018-07-02 14:30:37 -0700 | [diff] [blame] | 725 | static void sync_sched_exp_online_cleanup(int cpu) |
| 726 | { |
| 727 | } |
| 728 | |
Paul E. McKenney | 40e0a6c | 2016-04-15 16:44:07 -0700 | [diff] [blame] | 729 | /** |
| 730 | * synchronize_rcu_expedited - Brute-force RCU grace period |
| 731 | * |
| 732 | * Wait for an RCU-preempt grace period, but expedite it. The basic |
| 733 | * idea is to IPI all non-idle non-nohz online CPUs. The IPI handler |
| 734 | * checks whether the CPU is in an RCU-preempt critical section, and |
| 735 | * if so, it sets a flag that causes the outermost rcu_read_unlock() |
| 736 | * to report the quiescent state. On the other hand, if the CPU is |
| 737 | * not in an RCU read-side critical section, the IPI handler reports |
| 738 | * the quiescent state immediately. |
| 739 | * |
| 740 | * Although this is a greate improvement over previous expedited |
| 741 | * implementations, it is still unfriendly to real-time workloads, so is |
| 742 | * thus not recommended for any sort of common-case code. In fact, if |
| 743 | * you are using synchronize_rcu_expedited() in a loop, please restructure |
| 744 | * your code to batch your updates, and then Use a single synchronize_rcu() |
| 745 | * instead. |
Paul E. McKenney | 45975c7 | 2018-07-02 14:30:37 -0700 | [diff] [blame] | 746 | * |
| 747 | * This has the same semantics as (but is more brutal than) synchronize_rcu(). |
Paul E. McKenney | 40e0a6c | 2016-04-15 16:44:07 -0700 | [diff] [blame] | 748 | */ |
| 749 | void synchronize_rcu_expedited(void) |
| 750 | { |
Paul E. McKenney | 8dc7988 | 2017-01-09 15:25:55 -0800 | [diff] [blame] | 751 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || |
| 752 | lock_is_held(&rcu_lock_map) || |
| 753 | lock_is_held(&rcu_sched_lock_map), |
| 754 | "Illegal synchronize_rcu_expedited() in RCU read-side critical section"); |
| 755 | |
Paul E. McKenney | 52d7e48 | 2017-01-10 02:28:26 -0800 | [diff] [blame] | 756 | if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) |
| 757 | return; |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 758 | _synchronize_rcu_expedited(sync_rcu_exp_handler); |
Paul E. McKenney | 40e0a6c | 2016-04-15 16:44:07 -0700 | [diff] [blame] | 759 | } |
| 760 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); |
| 761 | |
| 762 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
| 763 | |
Paul E. McKenney | 45975c7 | 2018-07-02 14:30:37 -0700 | [diff] [blame] | 764 | /* Invoked on each online non-idle CPU for expedited quiescent state. */ |
Paul E. McKenney | da1df50 | 2018-07-03 15:37:16 -0700 | [diff] [blame] | 765 | static void sync_sched_exp_handler(void *unused) |
Paul E. McKenney | 45975c7 | 2018-07-02 14:30:37 -0700 | [diff] [blame] | 766 | { |
| 767 | struct rcu_data *rdp; |
| 768 | struct rcu_node *rnp; |
Paul E. McKenney | 45975c7 | 2018-07-02 14:30:37 -0700 | [diff] [blame] | 769 | |
Paul E. McKenney | da1df50 | 2018-07-03 15:37:16 -0700 | [diff] [blame] | 770 | rdp = this_cpu_ptr(&rcu_data); |
Paul E. McKenney | 45975c7 | 2018-07-02 14:30:37 -0700 | [diff] [blame] | 771 | rnp = rdp->mynode; |
| 772 | if (!(READ_ONCE(rnp->expmask) & rdp->grpmask) || |
| 773 | __this_cpu_read(rcu_data.cpu_no_qs.b.exp)) |
| 774 | return; |
| 775 | if (rcu_is_cpu_rrupt_from_idle()) { |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 776 | rcu_report_exp_rdp(this_cpu_ptr(&rcu_data)); |
Paul E. McKenney | 45975c7 | 2018-07-02 14:30:37 -0700 | [diff] [blame] | 777 | return; |
| 778 | } |
| 779 | __this_cpu_write(rcu_data.cpu_no_qs.b.exp, true); |
| 780 | /* Store .exp before .rcu_urgent_qs. */ |
Paul E. McKenney | 2dba13f | 2018-08-03 21:00:38 -0700 | [diff] [blame] | 781 | smp_store_release(this_cpu_ptr(&rcu_data.rcu_urgent_qs), true); |
Paul E. McKenney | fced9c8 | 2018-07-26 13:44:00 -0700 | [diff] [blame] | 782 | set_tsk_need_resched(current); |
| 783 | set_preempt_need_resched(); |
Paul E. McKenney | 45975c7 | 2018-07-02 14:30:37 -0700 | [diff] [blame] | 784 | } |
| 785 | |
| 786 | /* Send IPI for expedited cleanup if needed at end of CPU-hotplug operation. */ |
| 787 | static void sync_sched_exp_online_cleanup(int cpu) |
| 788 | { |
| 789 | struct rcu_data *rdp; |
| 790 | int ret; |
| 791 | struct rcu_node *rnp; |
Paul E. McKenney | 45975c7 | 2018-07-02 14:30:37 -0700 | [diff] [blame] | 792 | |
Paul E. McKenney | da1df50 | 2018-07-03 15:37:16 -0700 | [diff] [blame] | 793 | rdp = per_cpu_ptr(&rcu_data, cpu); |
Paul E. McKenney | 45975c7 | 2018-07-02 14:30:37 -0700 | [diff] [blame] | 794 | rnp = rdp->mynode; |
| 795 | if (!(READ_ONCE(rnp->expmask) & rdp->grpmask)) |
| 796 | return; |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 797 | ret = smp_call_function_single(cpu, sync_sched_exp_handler, NULL, 0); |
Paul E. McKenney | 45975c7 | 2018-07-02 14:30:37 -0700 | [diff] [blame] | 798 | WARN_ON_ONCE(ret); |
| 799 | } |
| 800 | |
Paul E. McKenney | 40e0a6c | 2016-04-15 16:44:07 -0700 | [diff] [blame] | 801 | /* |
Paul E. McKenney | 8fa946d | 2018-07-07 18:12:26 -0700 | [diff] [blame] | 802 | * Because a context switch is a grace period for !PREEMPT, any |
| 803 | * blocking grace-period wait automatically implies a grace period if |
| 804 | * there is only one CPU online at any point time during execution of |
| 805 | * either synchronize_rcu() or synchronize_rcu_expedited(). It is OK to |
| 806 | * occasionally incorrectly indicate that there are multiple CPUs online |
| 807 | * when there was in fact only one the whole time, as this just adds some |
| 808 | * overhead: RCU still operates correctly. |
Paul E. McKenney | 40e0a6c | 2016-04-15 16:44:07 -0700 | [diff] [blame] | 809 | */ |
Paul E. McKenney | 45975c7 | 2018-07-02 14:30:37 -0700 | [diff] [blame] | 810 | static int rcu_blocking_is_gp(void) |
| 811 | { |
| 812 | int ret; |
| 813 | |
| 814 | might_sleep(); /* Check for RCU read-side critical section. */ |
| 815 | preempt_disable(); |
| 816 | ret = num_online_cpus() <= 1; |
| 817 | preempt_enable(); |
| 818 | return ret; |
| 819 | } |
| 820 | |
| 821 | /* PREEMPT=n implementation of synchronize_rcu_expedited(). */ |
Paul E. McKenney | 40e0a6c | 2016-04-15 16:44:07 -0700 | [diff] [blame] | 822 | void synchronize_rcu_expedited(void) |
| 823 | { |
Paul E. McKenney | 45975c7 | 2018-07-02 14:30:37 -0700 | [diff] [blame] | 824 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || |
| 825 | lock_is_held(&rcu_lock_map) || |
| 826 | lock_is_held(&rcu_sched_lock_map), |
Paul E. McKenney | 8fa946d | 2018-07-07 18:12:26 -0700 | [diff] [blame] | 827 | "Illegal synchronize_rcu_expedited() in RCU read-side critical section"); |
Paul E. McKenney | 45975c7 | 2018-07-02 14:30:37 -0700 | [diff] [blame] | 828 | |
| 829 | /* If only one CPU, this is automatically a grace period. */ |
| 830 | if (rcu_blocking_is_gp()) |
| 831 | return; |
| 832 | |
Paul E. McKenney | 63d4c8c | 2018-07-03 17:22:34 -0700 | [diff] [blame] | 833 | _synchronize_rcu_expedited(sync_sched_exp_handler); |
Paul E. McKenney | 40e0a6c | 2016-04-15 16:44:07 -0700 | [diff] [blame] | 834 | } |
| 835 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); |
| 836 | |
| 837 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ |