Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Read-Copy Update mechanism for mutual exclusion |
| 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 | * |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 18 | * Copyright IBM Corporation, 2001 |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 19 | * |
| 20 | * Authors: Dipankar Sarma <dipankar@in.ibm.com> |
| 21 | * Manfred Spraul <manfred@colorfullife.com> |
Paul E. McKenney | a71fca5 | 2009-09-18 10:28:19 -0700 | [diff] [blame] | 22 | * |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 23 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> |
| 24 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
| 25 | * Papers: |
| 26 | * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf |
| 27 | * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) |
| 28 | * |
| 29 | * For detailed explanation of Read-Copy Update mechanism see - |
Paul E. McKenney | a71fca5 | 2009-09-18 10:28:19 -0700 | [diff] [blame] | 30 | * http://lse.sourceforge.net/locking/rcupdate.html |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 31 | * |
| 32 | */ |
| 33 | #include <linux/types.h> |
| 34 | #include <linux/kernel.h> |
| 35 | #include <linux/init.h> |
| 36 | #include <linux/spinlock.h> |
| 37 | #include <linux/smp.h> |
| 38 | #include <linux/interrupt.h> |
| 39 | #include <linux/sched.h> |
Arun Sharma | 60063497 | 2011-07-26 16:09:06 -0700 | [diff] [blame] | 40 | #include <linux/atomic.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 41 | #include <linux/bitops.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 42 | #include <linux/percpu.h> |
| 43 | #include <linux/notifier.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 44 | #include <linux/cpu.h> |
Ingo Molnar | 9331b31 | 2006-03-23 03:00:19 -0800 | [diff] [blame] | 45 | #include <linux/mutex.h> |
Paul Gortmaker | 9984de1 | 2011-05-23 14:51:41 -0400 | [diff] [blame] | 46 | #include <linux/export.h> |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 47 | #include <linux/hardirq.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 48 | |
Paul E. McKenney | 29c00b4 | 2011-06-17 15:53:19 -0700 | [diff] [blame] | 49 | #define CREATE_TRACE_POINTS |
| 50 | #include <trace/events/rcu.h> |
| 51 | |
| 52 | #include "rcu.h" |
| 53 | |
Paul E. McKenney | 162cc27 | 2009-09-23 16:18:13 -0700 | [diff] [blame] | 54 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| 55 | static struct lock_class_key rcu_lock_key; |
| 56 | struct lockdep_map rcu_lock_map = |
| 57 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key); |
| 58 | EXPORT_SYMBOL_GPL(rcu_lock_map); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 59 | |
| 60 | static struct lock_class_key rcu_bh_lock_key; |
| 61 | struct lockdep_map rcu_bh_lock_map = |
| 62 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key); |
| 63 | EXPORT_SYMBOL_GPL(rcu_bh_lock_map); |
| 64 | |
| 65 | static struct lock_class_key rcu_sched_lock_key; |
| 66 | struct lockdep_map rcu_sched_lock_map = |
| 67 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key); |
| 68 | EXPORT_SYMBOL_GPL(rcu_sched_lock_map); |
Paul E. McKenney | 162cc27 | 2009-09-23 16:18:13 -0700 | [diff] [blame] | 69 | #endif |
| 70 | |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 71 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| 72 | |
Paul E. McKenney | bc293d6 | 2010-04-15 12:50:39 -0700 | [diff] [blame] | 73 | int debug_lockdep_rcu_enabled(void) |
| 74 | { |
| 75 | return rcu_scheduler_active && debug_locks && |
| 76 | current->lockdep_recursion == 0; |
| 77 | } |
| 78 | EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled); |
| 79 | |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 80 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 81 | * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section? |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 82 | * |
| 83 | * Check for bottom half being disabled, which covers both the |
| 84 | * CONFIG_PROVE_RCU and not cases. Note that if someone uses |
| 85 | * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled) |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 86 | * will show the situation. This is useful for debug checks in functions |
| 87 | * that require that they be called within an RCU read-side critical |
| 88 | * section. |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 89 | * |
| 90 | * Check debug_lockdep_rcu_enabled() to prevent false positives during boot. |
| 91 | */ |
| 92 | int rcu_read_lock_bh_held(void) |
| 93 | { |
| 94 | if (!debug_lockdep_rcu_enabled()) |
| 95 | return 1; |
Paul E. McKenney | 773e3f9 | 2010-10-05 14:03:02 -0700 | [diff] [blame] | 96 | return in_softirq() || irqs_disabled(); |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 97 | } |
| 98 | EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held); |
| 99 | |
| 100 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| 101 | |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 102 | struct rcu_synchronize { |
| 103 | struct rcu_head head; |
| 104 | struct completion completion; |
| 105 | }; |
| 106 | |
Paul E. McKenney | d9f1bb6 | 2010-02-25 14:06:47 -0800 | [diff] [blame] | 107 | /* |
Paul E. McKenney | fbf6bfc | 2008-02-13 15:03:15 -0800 | [diff] [blame] | 108 | * Awaken the corresponding synchronize_rcu() instance now that a |
| 109 | * grace period has elapsed. |
| 110 | */ |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 111 | static void wakeme_after_rcu(struct rcu_head *head) |
Dipankar Sarma | 21a1ea9 | 2006-03-07 21:55:33 -0800 | [diff] [blame] | 112 | { |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 113 | struct rcu_synchronize *rcu; |
| 114 | |
| 115 | rcu = container_of(head, struct rcu_synchronize, head); |
| 116 | complete(&rcu->completion); |
Dipankar Sarma | 21a1ea9 | 2006-03-07 21:55:33 -0800 | [diff] [blame] | 117 | } |
Paul E. McKenney | ee84b82 | 2010-05-06 09:28:41 -0700 | [diff] [blame] | 118 | |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 119 | void wait_rcu_gp(call_rcu_func_t crf) |
| 120 | { |
| 121 | struct rcu_synchronize rcu; |
| 122 | |
| 123 | init_rcu_head_on_stack(&rcu.head); |
| 124 | init_completion(&rcu.completion); |
| 125 | /* Will wake me after RCU finished. */ |
| 126 | crf(&rcu.head, wakeme_after_rcu); |
| 127 | /* Wait for it. */ |
| 128 | wait_for_completion(&rcu.completion); |
| 129 | destroy_rcu_head_on_stack(&rcu.head); |
| 130 | } |
| 131 | EXPORT_SYMBOL_GPL(wait_rcu_gp); |
| 132 | |
Paul E. McKenney | ee84b82 | 2010-05-06 09:28:41 -0700 | [diff] [blame] | 133 | #ifdef CONFIG_PROVE_RCU |
| 134 | /* |
| 135 | * wrapper function to avoid #include problems. |
| 136 | */ |
| 137 | int rcu_my_thread_group_empty(void) |
| 138 | { |
| 139 | return thread_group_empty(current); |
| 140 | } |
| 141 | EXPORT_SYMBOL_GPL(rcu_my_thread_group_empty); |
| 142 | #endif /* #ifdef CONFIG_PROVE_RCU */ |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 143 | |
| 144 | #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD |
| 145 | static inline void debug_init_rcu_head(struct rcu_head *head) |
| 146 | { |
| 147 | debug_object_init(head, &rcuhead_debug_descr); |
| 148 | } |
| 149 | |
| 150 | static inline void debug_rcu_head_free(struct rcu_head *head) |
| 151 | { |
| 152 | debug_object_free(head, &rcuhead_debug_descr); |
| 153 | } |
| 154 | |
| 155 | /* |
| 156 | * fixup_init is called when: |
| 157 | * - an active object is initialized |
| 158 | */ |
| 159 | static int rcuhead_fixup_init(void *addr, enum debug_obj_state state) |
| 160 | { |
| 161 | struct rcu_head *head = addr; |
| 162 | |
| 163 | switch (state) { |
| 164 | case ODEBUG_STATE_ACTIVE: |
| 165 | /* |
| 166 | * Ensure that queued callbacks are all executed. |
| 167 | * If we detect that we are nested in a RCU read-side critical |
| 168 | * section, we should simply fail, otherwise we would deadlock. |
Mathieu Desnoyers | fc2ecf7 | 2011-02-23 09:42:14 -0800 | [diff] [blame] | 169 | * In !PREEMPT configurations, there is no way to tell if we are |
| 170 | * in a RCU read-side critical section or not, so we never |
| 171 | * attempt any fixup and just print a warning. |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 172 | */ |
Mathieu Desnoyers | fc2ecf7 | 2011-02-23 09:42:14 -0800 | [diff] [blame] | 173 | #ifndef CONFIG_PREEMPT |
Paul E. McKenney | 108aae2 | 2011-02-23 09:56:00 -0800 | [diff] [blame] | 174 | WARN_ON_ONCE(1); |
Mathieu Desnoyers | fc2ecf7 | 2011-02-23 09:42:14 -0800 | [diff] [blame] | 175 | return 0; |
| 176 | #endif |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 177 | if (rcu_preempt_depth() != 0 || preempt_count() != 0 || |
| 178 | irqs_disabled()) { |
Paul E. McKenney | 108aae2 | 2011-02-23 09:56:00 -0800 | [diff] [blame] | 179 | WARN_ON_ONCE(1); |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 180 | return 0; |
| 181 | } |
| 182 | rcu_barrier(); |
| 183 | rcu_barrier_sched(); |
| 184 | rcu_barrier_bh(); |
| 185 | debug_object_init(head, &rcuhead_debug_descr); |
| 186 | return 1; |
| 187 | default: |
| 188 | return 0; |
| 189 | } |
| 190 | } |
| 191 | |
| 192 | /* |
| 193 | * fixup_activate is called when: |
| 194 | * - an active object is activated |
| 195 | * - an unknown object is activated (might be a statically initialized object) |
| 196 | * Activation is performed internally by call_rcu(). |
| 197 | */ |
| 198 | static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state) |
| 199 | { |
| 200 | struct rcu_head *head = addr; |
| 201 | |
| 202 | switch (state) { |
| 203 | |
| 204 | case ODEBUG_STATE_NOTAVAILABLE: |
| 205 | /* |
| 206 | * This is not really a fixup. We just make sure that it is |
| 207 | * tracked in the object tracker. |
| 208 | */ |
| 209 | debug_object_init(head, &rcuhead_debug_descr); |
| 210 | debug_object_activate(head, &rcuhead_debug_descr); |
| 211 | return 0; |
| 212 | |
| 213 | case ODEBUG_STATE_ACTIVE: |
| 214 | /* |
| 215 | * Ensure that queued callbacks are all executed. |
| 216 | * If we detect that we are nested in a RCU read-side critical |
| 217 | * section, we should simply fail, otherwise we would deadlock. |
Mathieu Desnoyers | fc2ecf7 | 2011-02-23 09:42:14 -0800 | [diff] [blame] | 218 | * In !PREEMPT configurations, there is no way to tell if we are |
| 219 | * in a RCU read-side critical section or not, so we never |
| 220 | * attempt any fixup and just print a warning. |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 221 | */ |
Mathieu Desnoyers | fc2ecf7 | 2011-02-23 09:42:14 -0800 | [diff] [blame] | 222 | #ifndef CONFIG_PREEMPT |
Paul E. McKenney | 108aae2 | 2011-02-23 09:56:00 -0800 | [diff] [blame] | 223 | WARN_ON_ONCE(1); |
Mathieu Desnoyers | fc2ecf7 | 2011-02-23 09:42:14 -0800 | [diff] [blame] | 224 | return 0; |
| 225 | #endif |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 226 | if (rcu_preempt_depth() != 0 || preempt_count() != 0 || |
| 227 | irqs_disabled()) { |
Paul E. McKenney | 108aae2 | 2011-02-23 09:56:00 -0800 | [diff] [blame] | 228 | WARN_ON_ONCE(1); |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 229 | return 0; |
| 230 | } |
| 231 | rcu_barrier(); |
| 232 | rcu_barrier_sched(); |
| 233 | rcu_barrier_bh(); |
| 234 | debug_object_activate(head, &rcuhead_debug_descr); |
| 235 | return 1; |
| 236 | default: |
| 237 | return 0; |
| 238 | } |
| 239 | } |
| 240 | |
| 241 | /* |
| 242 | * fixup_free is called when: |
| 243 | * - an active object is freed |
| 244 | */ |
| 245 | static int rcuhead_fixup_free(void *addr, enum debug_obj_state state) |
| 246 | { |
| 247 | struct rcu_head *head = addr; |
| 248 | |
| 249 | switch (state) { |
| 250 | case ODEBUG_STATE_ACTIVE: |
| 251 | /* |
| 252 | * Ensure that queued callbacks are all executed. |
| 253 | * If we detect that we are nested in a RCU read-side critical |
| 254 | * section, we should simply fail, otherwise we would deadlock. |
Mathieu Desnoyers | fc2ecf7 | 2011-02-23 09:42:14 -0800 | [diff] [blame] | 255 | * In !PREEMPT configurations, there is no way to tell if we are |
| 256 | * in a RCU read-side critical section or not, so we never |
| 257 | * attempt any fixup and just print a warning. |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 258 | */ |
Mathieu Desnoyers | fc2ecf7 | 2011-02-23 09:42:14 -0800 | [diff] [blame] | 259 | #ifndef CONFIG_PREEMPT |
Paul E. McKenney | 108aae2 | 2011-02-23 09:56:00 -0800 | [diff] [blame] | 260 | WARN_ON_ONCE(1); |
Mathieu Desnoyers | fc2ecf7 | 2011-02-23 09:42:14 -0800 | [diff] [blame] | 261 | return 0; |
| 262 | #endif |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 263 | if (rcu_preempt_depth() != 0 || preempt_count() != 0 || |
| 264 | irqs_disabled()) { |
Paul E. McKenney | 108aae2 | 2011-02-23 09:56:00 -0800 | [diff] [blame] | 265 | WARN_ON_ONCE(1); |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 266 | return 0; |
| 267 | } |
| 268 | rcu_barrier(); |
| 269 | rcu_barrier_sched(); |
| 270 | rcu_barrier_bh(); |
| 271 | debug_object_free(head, &rcuhead_debug_descr); |
| 272 | return 1; |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 273 | default: |
| 274 | return 0; |
| 275 | } |
| 276 | } |
| 277 | |
| 278 | /** |
| 279 | * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects |
| 280 | * @head: pointer to rcu_head structure to be initialized |
| 281 | * |
| 282 | * This function informs debugobjects of a new rcu_head structure that |
| 283 | * has been allocated as an auto variable on the stack. This function |
| 284 | * is not required for rcu_head structures that are statically defined or |
| 285 | * that are dynamically allocated on the heap. This function has no |
| 286 | * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. |
| 287 | */ |
| 288 | void init_rcu_head_on_stack(struct rcu_head *head) |
| 289 | { |
| 290 | debug_object_init_on_stack(head, &rcuhead_debug_descr); |
| 291 | } |
| 292 | EXPORT_SYMBOL_GPL(init_rcu_head_on_stack); |
| 293 | |
| 294 | /** |
| 295 | * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects |
| 296 | * @head: pointer to rcu_head structure to be initialized |
| 297 | * |
| 298 | * This function informs debugobjects that an on-stack rcu_head structure |
| 299 | * is about to go out of scope. As with init_rcu_head_on_stack(), this |
| 300 | * function is not required for rcu_head structures that are statically |
| 301 | * defined or that are dynamically allocated on the heap. Also as with |
| 302 | * init_rcu_head_on_stack(), this function has no effect for |
| 303 | * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. |
| 304 | */ |
| 305 | void destroy_rcu_head_on_stack(struct rcu_head *head) |
| 306 | { |
| 307 | debug_object_free(head, &rcuhead_debug_descr); |
| 308 | } |
| 309 | EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack); |
| 310 | |
| 311 | struct debug_obj_descr rcuhead_debug_descr = { |
| 312 | .name = "rcu_head", |
| 313 | .fixup_init = rcuhead_fixup_init, |
| 314 | .fixup_activate = rcuhead_fixup_activate, |
| 315 | .fixup_free = rcuhead_fixup_free, |
| 316 | }; |
| 317 | EXPORT_SYMBOL_GPL(rcuhead_debug_descr); |
| 318 | #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |