Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition. |
| 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, write to the Free Software |
| 16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 17 | * |
| 18 | * Copyright IBM Corporation, 2008 |
| 19 | * |
| 20 | * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
| 21 | * |
| 22 | * For detailed explanation of Read-Copy Update mechanism see - |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 23 | * Documentation/RCU |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 24 | */ |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 25 | #include <linux/completion.h> |
| 26 | #include <linux/interrupt.h> |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 27 | #include <linux/notifier.h> |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 28 | #include <linux/rcupdate.h> |
| 29 | #include <linux/kernel.h> |
Paul Gortmaker | 9984de1 | 2011-05-23 14:51:41 -0400 | [diff] [blame] | 30 | #include <linux/export.h> |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 31 | #include <linux/mutex.h> |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 32 | #include <linux/sched.h> |
| 33 | #include <linux/types.h> |
| 34 | #include <linux/init.h> |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 35 | #include <linux/time.h> |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 36 | #include <linux/cpu.h> |
Linus Torvalds | 268bb0c | 2011-05-20 12:50:29 -0700 | [diff] [blame] | 37 | #include <linux/prefetch.h> |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 38 | |
Paul E. McKenney | 29c00b4 | 2011-06-17 15:53:19 -0700 | [diff] [blame] | 39 | #ifdef CONFIG_RCU_TRACE |
Paul E. McKenney | 29c00b4 | 2011-06-17 15:53:19 -0700 | [diff] [blame] | 40 | #include <trace/events/rcu.h> |
Paul E. McKenney | 29c00b4 | 2011-06-17 15:53:19 -0700 | [diff] [blame] | 41 | #endif /* #else #ifdef CONFIG_RCU_TRACE */ |
| 42 | |
| 43 | #include "rcu.h" |
| 44 | |
Paul E. McKenney | a57eb94 | 2010-06-29 16:49:16 -0700 | [diff] [blame] | 45 | /* Forward declarations for rcutiny_plugin.h. */ |
Paul E. McKenney | 24278d1 | 2010-09-27 17:25:23 -0700 | [diff] [blame] | 46 | struct rcu_ctrlblk; |
Paul E. McKenney | 965a002 | 2011-06-18 09:55:39 -0700 | [diff] [blame] | 47 | static void invoke_rcu_callbacks(void); |
| 48 | static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp); |
| 49 | static void rcu_process_callbacks(struct softirq_action *unused); |
Paul E. McKenney | a57eb94 | 2010-06-29 16:49:16 -0700 | [diff] [blame] | 50 | static void __call_rcu(struct rcu_head *head, |
| 51 | void (*func)(struct rcu_head *rcu), |
| 52 | struct rcu_ctrlblk *rcp); |
| 53 | |
| 54 | #include "rcutiny_plugin.h" |
| 55 | |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 56 | #ifdef CONFIG_NO_HZ |
| 57 | |
| 58 | static long rcu_dynticks_nesting = 1; |
| 59 | |
| 60 | /* |
| 61 | * Enter dynticks-idle mode, which is an extended quiescent state |
| 62 | * if we have fully entered that mode (i.e., if the new value of |
| 63 | * dynticks_nesting is zero). |
| 64 | */ |
| 65 | void rcu_enter_nohz(void) |
| 66 | { |
| 67 | if (--rcu_dynticks_nesting == 0) |
| 68 | rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */ |
| 69 | } |
| 70 | |
| 71 | /* |
| 72 | * Exit dynticks-idle mode, so that we are no longer in an extended |
| 73 | * quiescent state. |
| 74 | */ |
| 75 | void rcu_exit_nohz(void) |
| 76 | { |
| 77 | rcu_dynticks_nesting++; |
| 78 | } |
| 79 | |
| 80 | #endif /* #ifdef CONFIG_NO_HZ */ |
| 81 | |
| 82 | /* |
Eric Dumazet | b554d7de | 2011-04-28 07:23:45 +0200 | [diff] [blame] | 83 | * Helper function for rcu_sched_qs() and rcu_bh_qs(). |
| 84 | * Also irqs are disabled to avoid confusion due to interrupt handlers |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 85 | * invoking call_rcu(). |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 86 | */ |
| 87 | static int rcu_qsctr_help(struct rcu_ctrlblk *rcp) |
| 88 | { |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 89 | if (rcp->rcucblist != NULL && |
| 90 | rcp->donetail != rcp->curtail) { |
| 91 | rcp->donetail = rcp->curtail; |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 92 | return 1; |
| 93 | } |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 94 | |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 95 | return 0; |
| 96 | } |
| 97 | |
| 98 | /* |
| 99 | * Record an rcu quiescent state. And an rcu_bh quiescent state while we |
| 100 | * are at it, given that any rcu quiescent state is also an rcu_bh |
| 101 | * quiescent state. Use "+" instead of "||" to defeat short circuiting. |
| 102 | */ |
| 103 | void rcu_sched_qs(int cpu) |
| 104 | { |
Eric Dumazet | b554d7de | 2011-04-28 07:23:45 +0200 | [diff] [blame] | 105 | unsigned long flags; |
| 106 | |
| 107 | local_irq_save(flags); |
Paul E. McKenney | 99652b5 | 2010-03-30 15:50:01 -0700 | [diff] [blame] | 108 | if (rcu_qsctr_help(&rcu_sched_ctrlblk) + |
| 109 | rcu_qsctr_help(&rcu_bh_ctrlblk)) |
Paul E. McKenney | 965a002 | 2011-06-18 09:55:39 -0700 | [diff] [blame] | 110 | invoke_rcu_callbacks(); |
Eric Dumazet | b554d7de | 2011-04-28 07:23:45 +0200 | [diff] [blame] | 111 | local_irq_restore(flags); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 112 | } |
| 113 | |
| 114 | /* |
| 115 | * Record an rcu_bh quiescent state. |
| 116 | */ |
| 117 | void rcu_bh_qs(int cpu) |
| 118 | { |
Eric Dumazet | b554d7de | 2011-04-28 07:23:45 +0200 | [diff] [blame] | 119 | unsigned long flags; |
| 120 | |
| 121 | local_irq_save(flags); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 122 | if (rcu_qsctr_help(&rcu_bh_ctrlblk)) |
Paul E. McKenney | 965a002 | 2011-06-18 09:55:39 -0700 | [diff] [blame] | 123 | invoke_rcu_callbacks(); |
Eric Dumazet | b554d7de | 2011-04-28 07:23:45 +0200 | [diff] [blame] | 124 | local_irq_restore(flags); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 125 | } |
| 126 | |
| 127 | /* |
| 128 | * Check to see if the scheduling-clock interrupt came from an extended |
| 129 | * quiescent state, and, if so, tell RCU about it. |
| 130 | */ |
| 131 | void rcu_check_callbacks(int cpu, int user) |
| 132 | { |
| 133 | if (user || |
| 134 | (idle_cpu(cpu) && |
| 135 | !in_softirq() && |
| 136 | hardirq_count() <= (1 << HARDIRQ_SHIFT))) |
| 137 | rcu_sched_qs(cpu); |
| 138 | else if (!in_softirq()) |
| 139 | rcu_bh_qs(cpu); |
Paul E. McKenney | a57eb94 | 2010-06-29 16:49:16 -0700 | [diff] [blame] | 140 | rcu_preempt_check_callbacks(); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 141 | } |
| 142 | |
| 143 | /* |
Paul E. McKenney | b2c0710 | 2010-09-09 13:40:39 -0700 | [diff] [blame] | 144 | * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure |
| 145 | * whose grace period has elapsed. |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 146 | */ |
Paul E. McKenney | 965a002 | 2011-06-18 09:55:39 -0700 | [diff] [blame] | 147 | static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 148 | { |
Paul E. McKenney | d4c08f2 | 2011-06-25 06:36:56 -0700 | [diff] [blame] | 149 | char *rn = NULL; |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 150 | struct rcu_head *next, *list; |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 151 | unsigned long flags; |
Paul E. McKenney | 9e571a8 | 2010-09-30 21:26:52 -0700 | [diff] [blame] | 152 | RCU_TRACE(int cb_count = 0); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 153 | |
| 154 | /* If no RCU callbacks ready to invoke, just return. */ |
Paul E. McKenney | 29c00b4 | 2011-06-17 15:53:19 -0700 | [diff] [blame] | 155 | if (&rcp->rcucblist == rcp->donetail) { |
Paul E. McKenney | 72fe701 | 2011-06-21 01:14:54 -0700 | [diff] [blame] | 156 | RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, -1)); |
| 157 | RCU_TRACE(trace_rcu_batch_end(rcp->name, 0)); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 158 | return; |
Paul E. McKenney | 29c00b4 | 2011-06-17 15:53:19 -0700 | [diff] [blame] | 159 | } |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 160 | |
| 161 | /* Move the ready-to-invoke callbacks to a local list. */ |
| 162 | local_irq_save(flags); |
Paul E. McKenney | 72fe701 | 2011-06-21 01:14:54 -0700 | [diff] [blame] | 163 | RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, -1)); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 164 | list = rcp->rcucblist; |
| 165 | rcp->rcucblist = *rcp->donetail; |
| 166 | *rcp->donetail = NULL; |
| 167 | if (rcp->curtail == rcp->donetail) |
| 168 | rcp->curtail = &rcp->rcucblist; |
Paul E. McKenney | a57eb94 | 2010-06-29 16:49:16 -0700 | [diff] [blame] | 169 | rcu_preempt_remove_callbacks(rcp); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 170 | rcp->donetail = &rcp->rcucblist; |
| 171 | local_irq_restore(flags); |
| 172 | |
| 173 | /* Invoke the callbacks on the local list. */ |
Paul E. McKenney | d4c08f2 | 2011-06-25 06:36:56 -0700 | [diff] [blame] | 174 | RCU_TRACE(rn = rcp->name); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 175 | while (list) { |
| 176 | next = list->next; |
| 177 | prefetch(next); |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 178 | debug_rcu_head_unqueue(list); |
Paul E. McKenney | b2c0710 | 2010-09-09 13:40:39 -0700 | [diff] [blame] | 179 | local_bh_disable(); |
Paul E. McKenney | d4c08f2 | 2011-06-25 06:36:56 -0700 | [diff] [blame] | 180 | __rcu_reclaim(rn, list); |
Paul E. McKenney | b2c0710 | 2010-09-09 13:40:39 -0700 | [diff] [blame] | 181 | local_bh_enable(); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 182 | list = next; |
Paul E. McKenney | 9e571a8 | 2010-09-30 21:26:52 -0700 | [diff] [blame] | 183 | RCU_TRACE(cb_count++); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 184 | } |
Paul E. McKenney | 9e571a8 | 2010-09-30 21:26:52 -0700 | [diff] [blame] | 185 | RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count)); |
Paul E. McKenney | 72fe701 | 2011-06-21 01:14:54 -0700 | [diff] [blame] | 186 | RCU_TRACE(trace_rcu_batch_end(rcp->name, cb_count)); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 187 | } |
| 188 | |
Paul E. McKenney | 965a002 | 2011-06-18 09:55:39 -0700 | [diff] [blame] | 189 | static void rcu_process_callbacks(struct softirq_action *unused) |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 190 | { |
Paul E. McKenney | 965a002 | 2011-06-18 09:55:39 -0700 | [diff] [blame] | 191 | __rcu_process_callbacks(&rcu_sched_ctrlblk); |
| 192 | __rcu_process_callbacks(&rcu_bh_ctrlblk); |
| 193 | rcu_preempt_process_callbacks(); |
Paul E. McKenney | b2c0710 | 2010-09-09 13:40:39 -0700 | [diff] [blame] | 194 | } |
| 195 | |
| 196 | /* |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 197 | * Wait for a grace period to elapse. But it is illegal to invoke |
| 198 | * synchronize_sched() from within an RCU read-side critical section. |
| 199 | * Therefore, any legal call to synchronize_sched() is a quiescent |
| 200 | * state, and so on a UP system, synchronize_sched() need do nothing. |
| 201 | * Ditto for synchronize_rcu_bh(). (But Lai Jiangshan points out the |
| 202 | * benefits of doing might_sleep() to reduce latency.) |
| 203 | * |
| 204 | * Cool, huh? (Due to Josh Triplett.) |
| 205 | * |
Paul E. McKenney | da848c4 | 2010-03-30 15:46:01 -0700 | [diff] [blame] | 206 | * But we want to make this a static inline later. The cond_resched() |
| 207 | * currently makes this problematic. |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 208 | */ |
| 209 | void synchronize_sched(void) |
| 210 | { |
| 211 | cond_resched(); |
| 212 | } |
| 213 | EXPORT_SYMBOL_GPL(synchronize_sched); |
| 214 | |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 215 | /* |
| 216 | * Helper function for call_rcu() and call_rcu_bh(). |
| 217 | */ |
| 218 | static void __call_rcu(struct rcu_head *head, |
| 219 | void (*func)(struct rcu_head *rcu), |
| 220 | struct rcu_ctrlblk *rcp) |
| 221 | { |
| 222 | unsigned long flags; |
| 223 | |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 224 | debug_rcu_head_queue(head); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 225 | head->func = func; |
| 226 | head->next = NULL; |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 227 | |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 228 | local_irq_save(flags); |
| 229 | *rcp->curtail = head; |
| 230 | rcp->curtail = &head->next; |
Paul E. McKenney | 9e571a8 | 2010-09-30 21:26:52 -0700 | [diff] [blame] | 231 | RCU_TRACE(rcp->qlen++); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 232 | local_irq_restore(flags); |
| 233 | } |
| 234 | |
| 235 | /* |
Paul E. McKenney | a57eb94 | 2010-06-29 16:49:16 -0700 | [diff] [blame] | 236 | * Post an RCU callback to be invoked after the end of an RCU-sched grace |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 237 | * period. But since we have but one CPU, that would be after any |
| 238 | * quiescent state. |
| 239 | */ |
Paul E. McKenney | a57eb94 | 2010-06-29 16:49:16 -0700 | [diff] [blame] | 240 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 241 | { |
Paul E. McKenney | 99652b5 | 2010-03-30 15:50:01 -0700 | [diff] [blame] | 242 | __call_rcu(head, func, &rcu_sched_ctrlblk); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 243 | } |
Paul E. McKenney | a57eb94 | 2010-06-29 16:49:16 -0700 | [diff] [blame] | 244 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 245 | |
| 246 | /* |
| 247 | * Post an RCU bottom-half callback to be invoked after any subsequent |
| 248 | * quiescent state. |
| 249 | */ |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 250 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 251 | { |
| 252 | __call_rcu(head, func, &rcu_bh_ctrlblk); |
| 253 | } |
| 254 | EXPORT_SYMBOL_GPL(call_rcu_bh); |