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 | */ |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 25 | #include <linux/moduleparam.h> |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 26 | #include <linux/completion.h> |
| 27 | #include <linux/interrupt.h> |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 28 | #include <linux/notifier.h> |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 29 | #include <linux/rcupdate.h> |
| 30 | #include <linux/kernel.h> |
| 31 | #include <linux/module.h> |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 32 | #include <linux/mutex.h> |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 33 | #include <linux/sched.h> |
| 34 | #include <linux/types.h> |
| 35 | #include <linux/init.h> |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 36 | #include <linux/time.h> |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 37 | #include <linux/cpu.h> |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 38 | |
| 39 | /* Global control variables for rcupdate callback mechanism. */ |
| 40 | struct rcu_ctrlblk { |
| 41 | struct rcu_head *rcucblist; /* List of pending callbacks (CBs). */ |
| 42 | struct rcu_head **donetail; /* ->next pointer of last "done" CB. */ |
| 43 | struct rcu_head **curtail; /* ->next pointer of last CB. */ |
| 44 | }; |
| 45 | |
| 46 | /* Definition for rcupdate control block. */ |
Paul E. McKenney | 99652b5 | 2010-03-30 15:50:01 -0700 | [diff] [blame] | 47 | static struct rcu_ctrlblk rcu_sched_ctrlblk = { |
| 48 | .donetail = &rcu_sched_ctrlblk.rcucblist, |
| 49 | .curtail = &rcu_sched_ctrlblk.rcucblist, |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 50 | }; |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 51 | |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 52 | static struct rcu_ctrlblk rcu_bh_ctrlblk = { |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 53 | .donetail = &rcu_bh_ctrlblk.rcucblist, |
| 54 | .curtail = &rcu_bh_ctrlblk.rcucblist, |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 55 | }; |
| 56 | |
Paul E. McKenney | bbad937 | 2010-04-02 16:17:17 -0700 | [diff] [blame] | 57 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| 58 | int rcu_scheduler_active __read_mostly; |
| 59 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); |
| 60 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| 61 | |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 62 | #ifdef CONFIG_NO_HZ |
| 63 | |
| 64 | static long rcu_dynticks_nesting = 1; |
| 65 | |
| 66 | /* |
| 67 | * Enter dynticks-idle mode, which is an extended quiescent state |
| 68 | * if we have fully entered that mode (i.e., if the new value of |
| 69 | * dynticks_nesting is zero). |
| 70 | */ |
| 71 | void rcu_enter_nohz(void) |
| 72 | { |
| 73 | if (--rcu_dynticks_nesting == 0) |
| 74 | rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */ |
| 75 | } |
| 76 | |
| 77 | /* |
| 78 | * Exit dynticks-idle mode, so that we are no longer in an extended |
| 79 | * quiescent state. |
| 80 | */ |
| 81 | void rcu_exit_nohz(void) |
| 82 | { |
| 83 | rcu_dynticks_nesting++; |
| 84 | } |
| 85 | |
| 86 | #endif /* #ifdef CONFIG_NO_HZ */ |
| 87 | |
| 88 | /* |
| 89 | * Helper function for rcu_qsctr_inc() and rcu_bh_qsctr_inc(). |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 90 | * Also disable irqs to avoid confusion due to interrupt handlers |
| 91 | * invoking call_rcu(). |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 92 | */ |
| 93 | static int rcu_qsctr_help(struct rcu_ctrlblk *rcp) |
| 94 | { |
| 95 | unsigned long flags; |
| 96 | |
| 97 | local_irq_save(flags); |
| 98 | if (rcp->rcucblist != NULL && |
| 99 | rcp->donetail != rcp->curtail) { |
| 100 | rcp->donetail = rcp->curtail; |
| 101 | local_irq_restore(flags); |
| 102 | return 1; |
| 103 | } |
| 104 | local_irq_restore(flags); |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 105 | |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 106 | return 0; |
| 107 | } |
| 108 | |
| 109 | /* |
| 110 | * Record an rcu quiescent state. And an rcu_bh quiescent state while we |
| 111 | * are at it, given that any rcu quiescent state is also an rcu_bh |
| 112 | * quiescent state. Use "+" instead of "||" to defeat short circuiting. |
| 113 | */ |
| 114 | void rcu_sched_qs(int cpu) |
| 115 | { |
Paul E. McKenney | 99652b5 | 2010-03-30 15:50:01 -0700 | [diff] [blame] | 116 | if (rcu_qsctr_help(&rcu_sched_ctrlblk) + |
| 117 | rcu_qsctr_help(&rcu_bh_ctrlblk)) |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 118 | raise_softirq(RCU_SOFTIRQ); |
| 119 | } |
| 120 | |
| 121 | /* |
| 122 | * Record an rcu_bh quiescent state. |
| 123 | */ |
| 124 | void rcu_bh_qs(int cpu) |
| 125 | { |
| 126 | if (rcu_qsctr_help(&rcu_bh_ctrlblk)) |
| 127 | raise_softirq(RCU_SOFTIRQ); |
| 128 | } |
| 129 | |
| 130 | /* |
| 131 | * Check to see if the scheduling-clock interrupt came from an extended |
| 132 | * quiescent state, and, if so, tell RCU about it. |
| 133 | */ |
| 134 | void rcu_check_callbacks(int cpu, int user) |
| 135 | { |
| 136 | if (user || |
| 137 | (idle_cpu(cpu) && |
| 138 | !in_softirq() && |
| 139 | hardirq_count() <= (1 << HARDIRQ_SHIFT))) |
| 140 | rcu_sched_qs(cpu); |
| 141 | else if (!in_softirq()) |
| 142 | rcu_bh_qs(cpu); |
| 143 | } |
| 144 | |
| 145 | /* |
| 146 | * Helper function for rcu_process_callbacks() that operates on the |
| 147 | * specified rcu_ctrlkblk structure. |
| 148 | */ |
| 149 | static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) |
| 150 | { |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 151 | struct rcu_head *next, *list; |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 152 | unsigned long flags; |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 153 | |
| 154 | /* If no RCU callbacks ready to invoke, just return. */ |
| 155 | if (&rcp->rcucblist == rcp->donetail) |
| 156 | return; |
| 157 | |
| 158 | /* Move the ready-to-invoke callbacks to a local list. */ |
| 159 | local_irq_save(flags); |
| 160 | list = rcp->rcucblist; |
| 161 | rcp->rcucblist = *rcp->donetail; |
| 162 | *rcp->donetail = NULL; |
| 163 | if (rcp->curtail == rcp->donetail) |
| 164 | rcp->curtail = &rcp->rcucblist; |
| 165 | rcp->donetail = &rcp->rcucblist; |
| 166 | local_irq_restore(flags); |
| 167 | |
| 168 | /* Invoke the callbacks on the local list. */ |
| 169 | while (list) { |
| 170 | next = list->next; |
| 171 | prefetch(next); |
| 172 | list->func(list); |
| 173 | list = next; |
| 174 | } |
| 175 | } |
| 176 | |
| 177 | /* |
| 178 | * Invoke any callbacks whose grace period has completed. |
| 179 | */ |
| 180 | static void rcu_process_callbacks(struct softirq_action *unused) |
| 181 | { |
Paul E. McKenney | 99652b5 | 2010-03-30 15:50:01 -0700 | [diff] [blame] | 182 | __rcu_process_callbacks(&rcu_sched_ctrlblk); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 183 | __rcu_process_callbacks(&rcu_bh_ctrlblk); |
| 184 | } |
| 185 | |
| 186 | /* |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 187 | * Wait for a grace period to elapse. But it is illegal to invoke |
| 188 | * synchronize_sched() from within an RCU read-side critical section. |
| 189 | * Therefore, any legal call to synchronize_sched() is a quiescent |
| 190 | * state, and so on a UP system, synchronize_sched() need do nothing. |
| 191 | * Ditto for synchronize_rcu_bh(). (But Lai Jiangshan points out the |
| 192 | * benefits of doing might_sleep() to reduce latency.) |
| 193 | * |
| 194 | * Cool, huh? (Due to Josh Triplett.) |
| 195 | * |
Paul E. McKenney | da848c4 | 2010-03-30 15:46:01 -0700 | [diff] [blame] | 196 | * But we want to make this a static inline later. The cond_resched() |
| 197 | * currently makes this problematic. |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 198 | */ |
| 199 | void synchronize_sched(void) |
| 200 | { |
| 201 | cond_resched(); |
| 202 | } |
| 203 | EXPORT_SYMBOL_GPL(synchronize_sched); |
| 204 | |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 205 | /* |
| 206 | * Helper function for call_rcu() and call_rcu_bh(). |
| 207 | */ |
| 208 | static void __call_rcu(struct rcu_head *head, |
| 209 | void (*func)(struct rcu_head *rcu), |
| 210 | struct rcu_ctrlblk *rcp) |
| 211 | { |
| 212 | unsigned long flags; |
| 213 | |
| 214 | head->func = func; |
| 215 | head->next = NULL; |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 216 | |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 217 | local_irq_save(flags); |
| 218 | *rcp->curtail = head; |
| 219 | rcp->curtail = &head->next; |
| 220 | local_irq_restore(flags); |
| 221 | } |
| 222 | |
| 223 | /* |
| 224 | * Post an RCU callback to be invoked after the end of an RCU grace |
| 225 | * period. But since we have but one CPU, that would be after any |
| 226 | * quiescent state. |
| 227 | */ |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 228 | void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 229 | { |
Paul E. McKenney | 99652b5 | 2010-03-30 15:50:01 -0700 | [diff] [blame] | 230 | __call_rcu(head, func, &rcu_sched_ctrlblk); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 231 | } |
| 232 | EXPORT_SYMBOL_GPL(call_rcu); |
| 233 | |
| 234 | /* |
| 235 | * Post an RCU bottom-half callback to be invoked after any subsequent |
| 236 | * quiescent state. |
| 237 | */ |
Ingo Molnar | 4ce5b90 | 2009-10-26 07:55:55 +0100 | [diff] [blame] | 238 | 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] | 239 | { |
| 240 | __call_rcu(head, func, &rcu_bh_ctrlblk); |
| 241 | } |
| 242 | EXPORT_SYMBOL_GPL(call_rcu_bh); |
| 243 | |
| 244 | void rcu_barrier(void) |
| 245 | { |
| 246 | struct rcu_synchronize rcu; |
| 247 | |
Paul E. McKenney | 72d5a9f | 2010-05-10 17:12:17 -0700 | [diff] [blame] | 248 | init_rcu_head_on_stack(&rcu.head); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 249 | init_completion(&rcu.completion); |
| 250 | /* Will wake me after RCU finished. */ |
| 251 | call_rcu(&rcu.head, wakeme_after_rcu); |
| 252 | /* Wait for it. */ |
| 253 | wait_for_completion(&rcu.completion); |
Paul E. McKenney | 72d5a9f | 2010-05-10 17:12:17 -0700 | [diff] [blame] | 254 | destroy_rcu_head_on_stack(&rcu.head); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 255 | } |
| 256 | EXPORT_SYMBOL_GPL(rcu_barrier); |
| 257 | |
| 258 | void rcu_barrier_bh(void) |
| 259 | { |
| 260 | struct rcu_synchronize rcu; |
| 261 | |
Paul E. McKenney | 72d5a9f | 2010-05-10 17:12:17 -0700 | [diff] [blame] | 262 | init_rcu_head_on_stack(&rcu.head); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 263 | init_completion(&rcu.completion); |
| 264 | /* Will wake me after RCU finished. */ |
| 265 | call_rcu_bh(&rcu.head, wakeme_after_rcu); |
| 266 | /* Wait for it. */ |
| 267 | wait_for_completion(&rcu.completion); |
Paul E. McKenney | 72d5a9f | 2010-05-10 17:12:17 -0700 | [diff] [blame] | 268 | destroy_rcu_head_on_stack(&rcu.head); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 269 | } |
| 270 | EXPORT_SYMBOL_GPL(rcu_barrier_bh); |
| 271 | |
| 272 | void rcu_barrier_sched(void) |
| 273 | { |
| 274 | struct rcu_synchronize rcu; |
| 275 | |
Paul E. McKenney | 72d5a9f | 2010-05-10 17:12:17 -0700 | [diff] [blame] | 276 | init_rcu_head_on_stack(&rcu.head); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 277 | init_completion(&rcu.completion); |
| 278 | /* Will wake me after RCU finished. */ |
| 279 | call_rcu_sched(&rcu.head, wakeme_after_rcu); |
| 280 | /* Wait for it. */ |
| 281 | wait_for_completion(&rcu.completion); |
Paul E. McKenney | 72d5a9f | 2010-05-10 17:12:17 -0700 | [diff] [blame] | 282 | destroy_rcu_head_on_stack(&rcu.head); |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 283 | } |
| 284 | EXPORT_SYMBOL_GPL(rcu_barrier_sched); |
| 285 | |
Paul E. McKenney | 9f680ab | 2009-11-22 08:53:49 -0800 | [diff] [blame] | 286 | void __init rcu_init(void) |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 287 | { |
| 288 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
| 289 | } |
Paul E. McKenney | bbad937 | 2010-04-02 16:17:17 -0700 | [diff] [blame] | 290 | |
| 291 | #include "rcutiny_plugin.h" |