Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
Paul E. McKenney | a71fca5 | 2009-09-18 10:28:19 -0700 | [diff] [blame] | 2 | * Read-Copy Update mechanism for mutual exclusion |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 | * Author: Dipankar Sarma <dipankar@in.ibm.com> |
Paul E. McKenney | a71fca5 | 2009-09-18 10:28:19 -0700 | [diff] [blame] | 21 | * |
Josh Triplett | 595182b | 2006-10-04 02:17:21 -0700 | [diff] [blame] | 22 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 23 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
| 24 | * Papers: |
| 25 | * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf |
| 26 | * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) |
| 27 | * |
| 28 | * For detailed explanation of Read-Copy Update mechanism see - |
Paul E. McKenney | a71fca5 | 2009-09-18 10:28:19 -0700 | [diff] [blame] | 29 | * http://lse.sourceforge.net/locking/rcupdate.html |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 30 | * |
| 31 | */ |
| 32 | |
| 33 | #ifndef __LINUX_RCUPDATE_H |
| 34 | #define __LINUX_RCUPDATE_H |
| 35 | |
Paul E. McKenney | 9909875 | 2011-05-31 21:03:55 -0700 | [diff] [blame^] | 36 | #include <linux/types.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 37 | #include <linux/cache.h> |
| 38 | #include <linux/spinlock.h> |
| 39 | #include <linux/threads.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 40 | #include <linux/cpumask.h> |
| 41 | #include <linux/seqlock.h> |
Peter Zijlstra | 851a67b | 2007-10-11 22:11:12 +0200 | [diff] [blame] | 42 | #include <linux/lockdep.h> |
Paul E. McKenney | 4446a36 | 2008-05-12 21:21:05 +0200 | [diff] [blame] | 43 | #include <linux/completion.h> |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 44 | #include <linux/debugobjects.h> |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 45 | #include <linux/compiler.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 46 | |
Dave Young | e5ab677 | 2010-03-10 15:24:05 -0800 | [diff] [blame] | 47 | #ifdef CONFIG_RCU_TORTURE_TEST |
| 48 | extern int rcutorture_runnable; /* for sysctl */ |
| 49 | #endif /* #ifdef CONFIG_RCU_TORTURE_TEST */ |
| 50 | |
Paul E. McKenney | 4a29865 | 2011-04-03 21:33:51 -0700 | [diff] [blame] | 51 | #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) |
| 52 | extern void rcutorture_record_test_transition(void); |
| 53 | extern void rcutorture_record_progress(unsigned long vernum); |
| 54 | #else |
| 55 | static inline void rcutorture_record_test_transition(void) |
| 56 | { |
| 57 | } |
| 58 | static inline void rcutorture_record_progress(unsigned long vernum) |
| 59 | { |
| 60 | } |
| 61 | #endif |
| 62 | |
Tejun Heo | e27fc96 | 2010-11-22 21:36:11 -0800 | [diff] [blame] | 63 | #define UINT_CMP_GE(a, b) (UINT_MAX / 2 >= (a) - (b)) |
| 64 | #define UINT_CMP_LT(a, b) (UINT_MAX / 2 < (a) - (b)) |
Paul E. McKenney | a3dc3fb | 2010-08-13 16:16:25 -0700 | [diff] [blame] | 65 | #define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b)) |
| 66 | #define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b)) |
| 67 | |
Paul E. McKenney | 03b042b | 2009-06-25 09:08:16 -0700 | [diff] [blame] | 68 | /* Exported common interfaces */ |
Paul E. McKenney | 7b0b759 | 2010-08-17 14:18:46 -0700 | [diff] [blame] | 69 | extern void call_rcu_sched(struct rcu_head *head, |
| 70 | void (*func)(struct rcu_head *rcu)); |
| 71 | extern void synchronize_sched(void); |
Paul E. McKenney | 03b042b | 2009-06-25 09:08:16 -0700 | [diff] [blame] | 72 | extern void rcu_barrier_bh(void); |
| 73 | extern void rcu_barrier_sched(void); |
Paul E. McKenney | 03b042b | 2009-06-25 09:08:16 -0700 | [diff] [blame] | 74 | |
Paul E. McKenney | 7b0b759 | 2010-08-17 14:18:46 -0700 | [diff] [blame] | 75 | static inline void __rcu_read_lock_bh(void) |
| 76 | { |
| 77 | local_bh_disable(); |
| 78 | } |
| 79 | |
| 80 | static inline void __rcu_read_unlock_bh(void) |
| 81 | { |
| 82 | local_bh_enable(); |
| 83 | } |
Paul E. McKenney | a682604 | 2009-02-25 18:03:42 -0800 | [diff] [blame] | 84 | |
Paul E. McKenney | a3dc3fb | 2010-08-13 16:16:25 -0700 | [diff] [blame] | 85 | #ifdef CONFIG_PREEMPT_RCU |
| 86 | |
Paul E. McKenney | 7b0b759 | 2010-08-17 14:18:46 -0700 | [diff] [blame] | 87 | extern void __rcu_read_lock(void); |
| 88 | extern void __rcu_read_unlock(void); |
| 89 | void synchronize_rcu(void); |
| 90 | |
Paul E. McKenney | a3dc3fb | 2010-08-13 16:16:25 -0700 | [diff] [blame] | 91 | /* |
| 92 | * Defined as a macro as it is a very low level header included from |
| 93 | * areas that don't even know about current. This gives the rcu_read_lock() |
| 94 | * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other |
| 95 | * types of kernel builds, the rcu_read_lock() nesting depth is unknowable. |
| 96 | */ |
| 97 | #define rcu_preempt_depth() (current->rcu_read_lock_nesting) |
| 98 | |
Paul E. McKenney | 7b0b759 | 2010-08-17 14:18:46 -0700 | [diff] [blame] | 99 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
| 100 | |
| 101 | static inline void __rcu_read_lock(void) |
| 102 | { |
| 103 | preempt_disable(); |
| 104 | } |
| 105 | |
| 106 | static inline void __rcu_read_unlock(void) |
| 107 | { |
| 108 | preempt_enable(); |
| 109 | } |
| 110 | |
| 111 | static inline void synchronize_rcu(void) |
| 112 | { |
| 113 | synchronize_sched(); |
| 114 | } |
| 115 | |
| 116 | static inline int rcu_preempt_depth(void) |
| 117 | { |
| 118 | return 0; |
| 119 | } |
| 120 | |
| 121 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ |
| 122 | |
| 123 | /* Internal to kernel */ |
Paul E. McKenney | 7b0b759 | 2010-08-17 14:18:46 -0700 | [diff] [blame] | 124 | extern void rcu_sched_qs(int cpu); |
| 125 | extern void rcu_bh_qs(int cpu); |
| 126 | extern void rcu_check_callbacks(int cpu, int user); |
| 127 | struct notifier_block; |
| 128 | |
| 129 | #ifdef CONFIG_NO_HZ |
| 130 | |
| 131 | extern void rcu_enter_nohz(void); |
| 132 | extern void rcu_exit_nohz(void); |
| 133 | |
| 134 | #else /* #ifdef CONFIG_NO_HZ */ |
| 135 | |
| 136 | static inline void rcu_enter_nohz(void) |
| 137 | { |
| 138 | } |
| 139 | |
| 140 | static inline void rcu_exit_nohz(void) |
| 141 | { |
| 142 | } |
| 143 | |
| 144 | #endif /* #else #ifdef CONFIG_NO_HZ */ |
Paul E. McKenney | a3dc3fb | 2010-08-13 16:16:25 -0700 | [diff] [blame] | 145 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 146 | #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 147 | #include <linux/rcutree.h> |
Paul E. McKenney | a57eb94 | 2010-06-29 16:49:16 -0700 | [diff] [blame] | 148 | #elif defined(CONFIG_TINY_RCU) || defined(CONFIG_TINY_PREEMPT_RCU) |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 149 | #include <linux/rcutiny.h> |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 150 | #else |
| 151 | #error "Unknown RCU implementation specified to kernel configuration" |
Paul E. McKenney | 6b3ef48 | 2009-08-22 13:56:53 -0700 | [diff] [blame] | 152 | #endif |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 153 | |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 154 | /* |
| 155 | * init_rcu_head_on_stack()/destroy_rcu_head_on_stack() are needed for dynamic |
| 156 | * initialization and destruction of rcu_head on the stack. rcu_head structures |
| 157 | * allocated dynamically in the heap or defined statically don't need any |
| 158 | * initialization. |
| 159 | */ |
| 160 | #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD |
| 161 | extern void init_rcu_head_on_stack(struct rcu_head *head); |
| 162 | extern void destroy_rcu_head_on_stack(struct rcu_head *head); |
| 163 | #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
Mathieu Desnoyers | 4376030 | 2010-04-17 08:48:39 -0400 | [diff] [blame] | 164 | static inline void init_rcu_head_on_stack(struct rcu_head *head) |
| 165 | { |
| 166 | } |
| 167 | |
| 168 | static inline void destroy_rcu_head_on_stack(struct rcu_head *head) |
| 169 | { |
| 170 | } |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 171 | #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
Mathieu Desnoyers | 4376030 | 2010-04-17 08:48:39 -0400 | [diff] [blame] | 172 | |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 173 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 174 | |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 175 | extern struct lockdep_map rcu_lock_map; |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 176 | # define rcu_read_acquire() \ |
| 177 | lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_) |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 178 | # define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_) |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 179 | |
| 180 | extern struct lockdep_map rcu_bh_lock_map; |
| 181 | # define rcu_read_acquire_bh() \ |
| 182 | lock_acquire(&rcu_bh_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_) |
| 183 | # define rcu_read_release_bh() lock_release(&rcu_bh_lock_map, 1, _THIS_IP_) |
| 184 | |
| 185 | extern struct lockdep_map rcu_sched_lock_map; |
| 186 | # define rcu_read_acquire_sched() \ |
| 187 | lock_acquire(&rcu_sched_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_) |
| 188 | # define rcu_read_release_sched() \ |
| 189 | lock_release(&rcu_sched_lock_map, 1, _THIS_IP_) |
| 190 | |
Paul E. McKenney | bc293d6 | 2010-04-15 12:50:39 -0700 | [diff] [blame] | 191 | extern int debug_lockdep_rcu_enabled(void); |
Paul E. McKenney | 54dbf96 | 2010-03-03 07:46:57 -0800 | [diff] [blame] | 192 | |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 193 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 194 | * rcu_read_lock_held() - might we be in RCU read-side critical section? |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 195 | * |
Paul E. McKenney | d20200b | 2010-03-30 10:52:21 -0700 | [diff] [blame] | 196 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU |
| 197 | * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 198 | * this assumes we are in an RCU read-side critical section unless it can |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 199 | * prove otherwise. This is useful for debug checks in functions that |
| 200 | * require that they be called within an RCU read-side critical section. |
Paul E. McKenney | 54dbf96 | 2010-03-03 07:46:57 -0800 | [diff] [blame] | 201 | * |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 202 | * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot |
Paul E. McKenney | 32c141a | 2010-03-30 10:59:28 -0700 | [diff] [blame] | 203 | * and while lockdep is disabled. |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 204 | */ |
| 205 | static inline int rcu_read_lock_held(void) |
| 206 | { |
Paul E. McKenney | 54dbf96 | 2010-03-03 07:46:57 -0800 | [diff] [blame] | 207 | if (!debug_lockdep_rcu_enabled()) |
| 208 | return 1; |
| 209 | return lock_is_held(&rcu_lock_map); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 210 | } |
| 211 | |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 212 | /* |
| 213 | * rcu_read_lock_bh_held() is defined out of line to avoid #include-file |
| 214 | * hell. |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 215 | */ |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 216 | extern int rcu_read_lock_bh_held(void); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 217 | |
| 218 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 219 | * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section? |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 220 | * |
Paul E. McKenney | d20200b | 2010-03-30 10:52:21 -0700 | [diff] [blame] | 221 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an |
| 222 | * RCU-sched read-side critical section. In absence of |
| 223 | * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side |
| 224 | * critical section unless it can prove otherwise. Note that disabling |
| 225 | * of preemption (including disabling irqs) counts as an RCU-sched |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 226 | * read-side critical section. This is useful for debug checks in functions |
| 227 | * that required that they be called within an RCU-sched read-side |
| 228 | * critical section. |
Paul E. McKenney | 54dbf96 | 2010-03-03 07:46:57 -0800 | [diff] [blame] | 229 | * |
Paul E. McKenney | 32c141a | 2010-03-30 10:59:28 -0700 | [diff] [blame] | 230 | * Check debug_lockdep_rcu_enabled() to prevent false positives during boot |
| 231 | * and while lockdep is disabled. |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 232 | */ |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 233 | #ifdef CONFIG_PREEMPT_COUNT |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 234 | static inline int rcu_read_lock_sched_held(void) |
| 235 | { |
| 236 | int lockdep_opinion = 0; |
| 237 | |
Paul E. McKenney | 54dbf96 | 2010-03-03 07:46:57 -0800 | [diff] [blame] | 238 | if (!debug_lockdep_rcu_enabled()) |
| 239 | return 1; |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 240 | if (debug_locks) |
| 241 | lockdep_opinion = lock_is_held(&rcu_sched_lock_map); |
Lai Jiangshan | 0cff810 | 2010-03-18 12:25:33 -0700 | [diff] [blame] | 242 | return lockdep_opinion || preempt_count() != 0 || irqs_disabled(); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 243 | } |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 244 | #else /* #ifdef CONFIG_PREEMPT_COUNT */ |
Paul E. McKenney | e6033e3 | 2010-03-03 17:50:16 -0800 | [diff] [blame] | 245 | static inline int rcu_read_lock_sched_held(void) |
| 246 | { |
| 247 | return 1; |
| 248 | } |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 249 | #endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 250 | |
| 251 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| 252 | |
| 253 | # define rcu_read_acquire() do { } while (0) |
| 254 | # define rcu_read_release() do { } while (0) |
| 255 | # define rcu_read_acquire_bh() do { } while (0) |
| 256 | # define rcu_read_release_bh() do { } while (0) |
| 257 | # define rcu_read_acquire_sched() do { } while (0) |
| 258 | # define rcu_read_release_sched() do { } while (0) |
| 259 | |
| 260 | static inline int rcu_read_lock_held(void) |
| 261 | { |
| 262 | return 1; |
| 263 | } |
| 264 | |
| 265 | static inline int rcu_read_lock_bh_held(void) |
| 266 | { |
| 267 | return 1; |
| 268 | } |
| 269 | |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 270 | #ifdef CONFIG_PREEMPT_COUNT |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 271 | static inline int rcu_read_lock_sched_held(void) |
| 272 | { |
Paul E. McKenney | bbad937 | 2010-04-02 16:17:17 -0700 | [diff] [blame] | 273 | return preempt_count() != 0 || irqs_disabled(); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 274 | } |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 275 | #else /* #ifdef CONFIG_PREEMPT_COUNT */ |
Paul E. McKenney | e6033e3 | 2010-03-03 17:50:16 -0800 | [diff] [blame] | 276 | static inline int rcu_read_lock_sched_held(void) |
| 277 | { |
| 278 | return 1; |
| 279 | } |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 280 | #endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 281 | |
| 282 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| 283 | |
| 284 | #ifdef CONFIG_PROVE_RCU |
| 285 | |
Paul E. McKenney | ee84b82 | 2010-05-06 09:28:41 -0700 | [diff] [blame] | 286 | extern int rcu_my_thread_group_empty(void); |
| 287 | |
Tetsuo Handa | 4221a99 | 2010-06-26 01:08:19 +0900 | [diff] [blame] | 288 | /** |
| 289 | * rcu_lockdep_assert - emit lockdep splat if specified condition not met |
| 290 | * @c: condition to check |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 291 | * @s: informative message |
Tetsuo Handa | 4221a99 | 2010-06-26 01:08:19 +0900 | [diff] [blame] | 292 | */ |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 293 | #define rcu_lockdep_assert(c, s) \ |
Lai Jiangshan | 2b3fc35 | 2010-04-20 16:23:07 +0800 | [diff] [blame] | 294 | do { \ |
| 295 | static bool __warned; \ |
| 296 | if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \ |
| 297 | __warned = true; \ |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 298 | lockdep_rcu_suspicious(__FILE__, __LINE__, s); \ |
Lai Jiangshan | 2b3fc35 | 2010-04-20 16:23:07 +0800 | [diff] [blame] | 299 | } \ |
| 300 | } while (0) |
| 301 | |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 302 | #define rcu_sleep_check() \ |
| 303 | do { \ |
| 304 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), \ |
| 305 | "Illegal context switch in RCU-bh" \ |
| 306 | " read-side critical section"); \ |
| 307 | rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), \ |
| 308 | "Illegal context switch in RCU-sched"\ |
| 309 | " read-side critical section"); \ |
| 310 | } while (0) |
| 311 | |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 312 | #else /* #ifdef CONFIG_PROVE_RCU */ |
| 313 | |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 314 | #define rcu_lockdep_assert(c, s) do { } while (0) |
| 315 | #define rcu_sleep_check() do { } while (0) |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 316 | |
| 317 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ |
| 318 | |
| 319 | /* |
| 320 | * Helper functions for rcu_dereference_check(), rcu_dereference_protected() |
| 321 | * and rcu_assign_pointer(). Some of these could be folded into their |
| 322 | * callers, but they are left separate in order to ease introduction of |
| 323 | * multiple flavors of pointers to match the multiple flavors of RCU |
| 324 | * (e.g., __rcu_bh, * __rcu_sched, and __srcu), should this make sense in |
| 325 | * the future. |
| 326 | */ |
Paul E. McKenney | 53ecfba | 2010-09-13 17:24:21 -0700 | [diff] [blame] | 327 | |
| 328 | #ifdef __CHECKER__ |
| 329 | #define rcu_dereference_sparse(p, space) \ |
| 330 | ((void)(((typeof(*p) space *)p) == p)) |
| 331 | #else /* #ifdef __CHECKER__ */ |
| 332 | #define rcu_dereference_sparse(p, space) |
| 333 | #endif /* #else #ifdef __CHECKER__ */ |
| 334 | |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 335 | #define __rcu_access_pointer(p, space) \ |
| 336 | ({ \ |
| 337 | typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \ |
Paul E. McKenney | 53ecfba | 2010-09-13 17:24:21 -0700 | [diff] [blame] | 338 | rcu_dereference_sparse(p, space); \ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 339 | ((typeof(*p) __force __kernel *)(_________p1)); \ |
| 340 | }) |
| 341 | #define __rcu_dereference_check(p, c, space) \ |
| 342 | ({ \ |
| 343 | typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \ |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 344 | rcu_lockdep_assert(c, "suspicious rcu_dereference_check()" \ |
| 345 | " usage"); \ |
Paul E. McKenney | 53ecfba | 2010-09-13 17:24:21 -0700 | [diff] [blame] | 346 | rcu_dereference_sparse(p, space); \ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 347 | smp_read_barrier_depends(); \ |
| 348 | ((typeof(*p) __force __kernel *)(_________p1)); \ |
| 349 | }) |
| 350 | #define __rcu_dereference_protected(p, c, space) \ |
| 351 | ({ \ |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 352 | rcu_lockdep_assert(c, "suspicious rcu_dereference_protected()" \ |
| 353 | " usage"); \ |
Paul E. McKenney | 53ecfba | 2010-09-13 17:24:21 -0700 | [diff] [blame] | 354 | rcu_dereference_sparse(p, space); \ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 355 | ((typeof(*p) __force __kernel *)(p)); \ |
| 356 | }) |
| 357 | |
Paul E. McKenney | a4dd992 | 2011-04-01 07:15:14 -0700 | [diff] [blame] | 358 | #define __rcu_access_index(p, space) \ |
| 359 | ({ \ |
| 360 | typeof(p) _________p1 = ACCESS_ONCE(p); \ |
| 361 | rcu_dereference_sparse(p, space); \ |
| 362 | (_________p1); \ |
| 363 | }) |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 364 | #define __rcu_dereference_index_check(p, c) \ |
| 365 | ({ \ |
| 366 | typeof(p) _________p1 = ACCESS_ONCE(p); \ |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 367 | rcu_lockdep_assert(c, \ |
| 368 | "suspicious rcu_dereference_index_check()" \ |
| 369 | " usage"); \ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 370 | smp_read_barrier_depends(); \ |
| 371 | (_________p1); \ |
| 372 | }) |
| 373 | #define __rcu_assign_pointer(p, v, space) \ |
| 374 | ({ \ |
| 375 | if (!__builtin_constant_p(v) || \ |
| 376 | ((v) != NULL)) \ |
| 377 | smp_wmb(); \ |
| 378 | (p) = (typeof(*v) __force space *)(v); \ |
| 379 | }) |
| 380 | |
| 381 | |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 382 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 383 | * rcu_access_pointer() - fetch RCU pointer with no dereferencing |
| 384 | * @p: The pointer to read |
| 385 | * |
| 386 | * Return the value of the specified RCU-protected pointer, but omit the |
| 387 | * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful |
| 388 | * when the value of this pointer is accessed, but the pointer is not |
| 389 | * dereferenced, for example, when testing an RCU-protected pointer against |
| 390 | * NULL. Although rcu_access_pointer() may also be used in cases where |
| 391 | * update-side locks prevent the value of the pointer from changing, you |
| 392 | * should instead use rcu_dereference_protected() for this use case. |
| 393 | */ |
| 394 | #define rcu_access_pointer(p) __rcu_access_pointer((p), __rcu) |
| 395 | |
| 396 | /** |
| 397 | * rcu_dereference_check() - rcu_dereference with debug checking |
David Howells | c08c68d | 2010-04-09 15:39:11 -0700 | [diff] [blame] | 398 | * @p: The pointer to read, prior to dereferencing |
| 399 | * @c: The conditions under which the dereference will take place |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 400 | * |
David Howells | c08c68d | 2010-04-09 15:39:11 -0700 | [diff] [blame] | 401 | * Do an rcu_dereference(), but check that the conditions under which the |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 402 | * dereference will take place are correct. Typically the conditions |
| 403 | * indicate the various locking conditions that should be held at that |
| 404 | * point. The check should return true if the conditions are satisfied. |
| 405 | * An implicit check for being in an RCU read-side critical section |
| 406 | * (rcu_read_lock()) is included. |
David Howells | c08c68d | 2010-04-09 15:39:11 -0700 | [diff] [blame] | 407 | * |
| 408 | * For example: |
| 409 | * |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 410 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock)); |
David Howells | c08c68d | 2010-04-09 15:39:11 -0700 | [diff] [blame] | 411 | * |
| 412 | * could be used to indicate to lockdep that foo->bar may only be dereferenced |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 413 | * if either rcu_read_lock() is held, or that the lock required to replace |
David Howells | c08c68d | 2010-04-09 15:39:11 -0700 | [diff] [blame] | 414 | * the bar struct at foo->bar is held. |
| 415 | * |
| 416 | * Note that the list of conditions may also include indications of when a lock |
| 417 | * need not be held, for example during initialisation or destruction of the |
| 418 | * target struct: |
| 419 | * |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 420 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock) || |
David Howells | c08c68d | 2010-04-09 15:39:11 -0700 | [diff] [blame] | 421 | * atomic_read(&foo->usage) == 0); |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 422 | * |
| 423 | * Inserts memory barriers on architectures that require them |
| 424 | * (currently only the Alpha), prevents the compiler from refetching |
| 425 | * (and from merging fetches), and, more importantly, documents exactly |
| 426 | * which pointers are protected by RCU and checks that the pointer is |
| 427 | * annotated as __rcu. |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 428 | */ |
| 429 | #define rcu_dereference_check(p, c) \ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 430 | __rcu_dereference_check((p), rcu_read_lock_held() || (c), __rcu) |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 431 | |
Paul E. McKenney | b62730b | 2010-04-09 15:39:10 -0700 | [diff] [blame] | 432 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 433 | * rcu_dereference_bh_check() - rcu_dereference_bh with debug checking |
| 434 | * @p: The pointer to read, prior to dereferencing |
| 435 | * @c: The conditions under which the dereference will take place |
| 436 | * |
| 437 | * This is the RCU-bh counterpart to rcu_dereference_check(). |
| 438 | */ |
| 439 | #define rcu_dereference_bh_check(p, c) \ |
| 440 | __rcu_dereference_check((p), rcu_read_lock_bh_held() || (c), __rcu) |
| 441 | |
| 442 | /** |
| 443 | * rcu_dereference_sched_check() - rcu_dereference_sched with debug checking |
| 444 | * @p: The pointer to read, prior to dereferencing |
| 445 | * @c: The conditions under which the dereference will take place |
| 446 | * |
| 447 | * This is the RCU-sched counterpart to rcu_dereference_check(). |
| 448 | */ |
| 449 | #define rcu_dereference_sched_check(p, c) \ |
| 450 | __rcu_dereference_check((p), rcu_read_lock_sched_held() || (c), \ |
| 451 | __rcu) |
| 452 | |
| 453 | #define rcu_dereference_raw(p) rcu_dereference_check(p, 1) /*@@@ needed? @@@*/ |
| 454 | |
| 455 | /** |
Paul E. McKenney | a4dd992 | 2011-04-01 07:15:14 -0700 | [diff] [blame] | 456 | * rcu_access_index() - fetch RCU index with no dereferencing |
| 457 | * @p: The index to read |
| 458 | * |
| 459 | * Return the value of the specified RCU-protected index, but omit the |
| 460 | * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful |
| 461 | * when the value of this index is accessed, but the index is not |
| 462 | * dereferenced, for example, when testing an RCU-protected index against |
| 463 | * -1. Although rcu_access_index() may also be used in cases where |
| 464 | * update-side locks prevent the value of the index from changing, you |
| 465 | * should instead use rcu_dereference_index_protected() for this use case. |
| 466 | */ |
| 467 | #define rcu_access_index(p) __rcu_access_index((p), __rcu) |
| 468 | |
| 469 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 470 | * rcu_dereference_index_check() - rcu_dereference for indices with debug checking |
| 471 | * @p: The pointer to read, prior to dereferencing |
| 472 | * @c: The conditions under which the dereference will take place |
| 473 | * |
| 474 | * Similar to rcu_dereference_check(), but omits the sparse checking. |
| 475 | * This allows rcu_dereference_index_check() to be used on integers, |
| 476 | * which can then be used as array indices. Attempting to use |
| 477 | * rcu_dereference_check() on an integer will give compiler warnings |
| 478 | * because the sparse address-space mechanism relies on dereferencing |
| 479 | * the RCU-protected pointer. Dereferencing integers is not something |
| 480 | * that even gcc will put up with. |
| 481 | * |
| 482 | * Note that this function does not implicitly check for RCU read-side |
| 483 | * critical sections. If this function gains lots of uses, it might |
| 484 | * make sense to provide versions for each flavor of RCU, but it does |
| 485 | * not make sense as of early 2010. |
| 486 | */ |
| 487 | #define rcu_dereference_index_check(p, c) \ |
| 488 | __rcu_dereference_index_check((p), (c)) |
| 489 | |
| 490 | /** |
| 491 | * rcu_dereference_protected() - fetch RCU pointer when updates prevented |
| 492 | * @p: The pointer to read, prior to dereferencing |
| 493 | * @c: The conditions under which the dereference will take place |
Paul E. McKenney | b62730b | 2010-04-09 15:39:10 -0700 | [diff] [blame] | 494 | * |
| 495 | * Return the value of the specified RCU-protected pointer, but omit |
| 496 | * both the smp_read_barrier_depends() and the ACCESS_ONCE(). This |
| 497 | * is useful in cases where update-side locks prevent the value of the |
| 498 | * pointer from changing. Please note that this primitive does -not- |
| 499 | * prevent the compiler from repeating this reference or combining it |
| 500 | * with other references, so it should not be used without protection |
| 501 | * of appropriate locks. |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 502 | * |
| 503 | * This function is only for update-side use. Using this function |
| 504 | * when protected only by rcu_read_lock() will result in infrequent |
| 505 | * but very ugly failures. |
Paul E. McKenney | b62730b | 2010-04-09 15:39:10 -0700 | [diff] [blame] | 506 | */ |
| 507 | #define rcu_dereference_protected(p, c) \ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 508 | __rcu_dereference_protected((p), (c), __rcu) |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 509 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 510 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 511 | * rcu_dereference_bh_protected() - fetch RCU-bh pointer when updates prevented |
| 512 | * @p: The pointer to read, prior to dereferencing |
| 513 | * @c: The conditions under which the dereference will take place |
Paul E. McKenney | b62730b | 2010-04-09 15:39:10 -0700 | [diff] [blame] | 514 | * |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 515 | * This is the RCU-bh counterpart to rcu_dereference_protected(). |
Paul E. McKenney | b62730b | 2010-04-09 15:39:10 -0700 | [diff] [blame] | 516 | */ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 517 | #define rcu_dereference_bh_protected(p, c) \ |
| 518 | __rcu_dereference_protected((p), (c), __rcu) |
Paul E. McKenney | b62730b | 2010-04-09 15:39:10 -0700 | [diff] [blame] | 519 | |
| 520 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 521 | * rcu_dereference_sched_protected() - fetch RCU-sched pointer when updates prevented |
| 522 | * @p: The pointer to read, prior to dereferencing |
| 523 | * @c: The conditions under which the dereference will take place |
| 524 | * |
| 525 | * This is the RCU-sched counterpart to rcu_dereference_protected(). |
| 526 | */ |
| 527 | #define rcu_dereference_sched_protected(p, c) \ |
| 528 | __rcu_dereference_protected((p), (c), __rcu) |
| 529 | |
| 530 | |
| 531 | /** |
| 532 | * rcu_dereference() - fetch RCU-protected pointer for dereferencing |
| 533 | * @p: The pointer to read, prior to dereferencing |
| 534 | * |
| 535 | * This is a simple wrapper around rcu_dereference_check(). |
| 536 | */ |
| 537 | #define rcu_dereference(p) rcu_dereference_check(p, 0) |
| 538 | |
| 539 | /** |
| 540 | * rcu_dereference_bh() - fetch an RCU-bh-protected pointer for dereferencing |
| 541 | * @p: The pointer to read, prior to dereferencing |
| 542 | * |
| 543 | * Makes rcu_dereference_check() do the dirty work. |
| 544 | */ |
| 545 | #define rcu_dereference_bh(p) rcu_dereference_bh_check(p, 0) |
| 546 | |
| 547 | /** |
| 548 | * rcu_dereference_sched() - fetch RCU-sched-protected pointer for dereferencing |
| 549 | * @p: The pointer to read, prior to dereferencing |
| 550 | * |
| 551 | * Makes rcu_dereference_check() do the dirty work. |
| 552 | */ |
| 553 | #define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0) |
| 554 | |
| 555 | /** |
| 556 | * rcu_read_lock() - mark the beginning of an RCU read-side critical section |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 557 | * |
Paul E. McKenney | 9b06e81 | 2005-05-01 08:59:04 -0700 | [diff] [blame] | 558 | * When synchronize_rcu() is invoked on one CPU while other CPUs |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 559 | * are within RCU read-side critical sections, then the |
Paul E. McKenney | 9b06e81 | 2005-05-01 08:59:04 -0700 | [diff] [blame] | 560 | * synchronize_rcu() is guaranteed to block until after all the other |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 561 | * CPUs exit their critical sections. Similarly, if call_rcu() is invoked |
| 562 | * on one CPU while other CPUs are within RCU read-side critical |
| 563 | * sections, invocation of the corresponding RCU callback is deferred |
| 564 | * until after the all the other CPUs exit their critical sections. |
| 565 | * |
| 566 | * Note, however, that RCU callbacks are permitted to run concurrently |
Paul E. McKenney | 77d8485 | 2010-07-08 17:38:59 -0700 | [diff] [blame] | 567 | * with new RCU read-side critical sections. One way that this can happen |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 568 | * is via the following sequence of events: (1) CPU 0 enters an RCU |
| 569 | * read-side critical section, (2) CPU 1 invokes call_rcu() to register |
| 570 | * an RCU callback, (3) CPU 0 exits the RCU read-side critical section, |
| 571 | * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU |
| 572 | * callback is invoked. This is legal, because the RCU read-side critical |
| 573 | * section that was running concurrently with the call_rcu() (and which |
| 574 | * therefore might be referencing something that the corresponding RCU |
| 575 | * callback would free up) has completed before the corresponding |
| 576 | * RCU callback is invoked. |
| 577 | * |
| 578 | * RCU read-side critical sections may be nested. Any deferred actions |
| 579 | * will be deferred until the outermost RCU read-side critical section |
| 580 | * completes. |
| 581 | * |
Paul E. McKenney | 9079fd7 | 2010-08-07 21:59:54 -0700 | [diff] [blame] | 582 | * You can avoid reading and understanding the next paragraph by |
| 583 | * following this rule: don't put anything in an rcu_read_lock() RCU |
| 584 | * read-side critical section that would block in a !PREEMPT kernel. |
| 585 | * But if you want the full story, read on! |
| 586 | * |
| 587 | * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU), it |
| 588 | * is illegal to block while in an RCU read-side critical section. In |
| 589 | * preemptible RCU implementations (TREE_PREEMPT_RCU and TINY_PREEMPT_RCU) |
| 590 | * in CONFIG_PREEMPT kernel builds, RCU read-side critical sections may |
| 591 | * be preempted, but explicit blocking is illegal. Finally, in preemptible |
| 592 | * RCU implementations in real-time (CONFIG_PREEMPT_RT) kernel builds, |
| 593 | * RCU read-side critical sections may be preempted and they may also |
| 594 | * block, but only when acquiring spinlocks that are subject to priority |
| 595 | * inheritance. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 596 | */ |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 597 | static inline void rcu_read_lock(void) |
| 598 | { |
| 599 | __rcu_read_lock(); |
| 600 | __acquire(RCU); |
| 601 | rcu_read_acquire(); |
| 602 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 603 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 604 | /* |
| 605 | * So where is rcu_write_lock()? It does not exist, as there is no |
| 606 | * way for writers to lock out RCU readers. This is a feature, not |
| 607 | * a bug -- this property is what provides RCU's performance benefits. |
| 608 | * Of course, writers must coordinate with each other. The normal |
| 609 | * spinlock primitives work well for this, but any other technique may be |
| 610 | * used as well. RCU does not care how the writers keep out of each |
| 611 | * others' way, as long as they do so. |
| 612 | */ |
Paul E. McKenney | 3d76c08 | 2009-09-28 07:46:32 -0700 | [diff] [blame] | 613 | |
| 614 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 615 | * rcu_read_unlock() - marks the end of an RCU read-side critical section. |
Paul E. McKenney | 3d76c08 | 2009-09-28 07:46:32 -0700 | [diff] [blame] | 616 | * |
| 617 | * See rcu_read_lock() for more information. |
| 618 | */ |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 619 | static inline void rcu_read_unlock(void) |
| 620 | { |
| 621 | rcu_read_release(); |
| 622 | __release(RCU); |
| 623 | __rcu_read_unlock(); |
| 624 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 625 | |
| 626 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 627 | * rcu_read_lock_bh() - mark the beginning of an RCU-bh critical section |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 628 | * |
| 629 | * This is equivalent of rcu_read_lock(), but to be used when updates |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 630 | * are being done using call_rcu_bh() or synchronize_rcu_bh(). Since |
| 631 | * both call_rcu_bh() and synchronize_rcu_bh() consider completion of a |
| 632 | * softirq handler to be a quiescent state, a process in RCU read-side |
| 633 | * critical section must be protected by disabling softirqs. Read-side |
| 634 | * critical sections in interrupt context can use just rcu_read_lock(), |
| 635 | * though this should at least be commented to avoid confusing people |
| 636 | * reading the code. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 637 | */ |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 638 | static inline void rcu_read_lock_bh(void) |
| 639 | { |
| 640 | __rcu_read_lock_bh(); |
| 641 | __acquire(RCU_BH); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 642 | rcu_read_acquire_bh(); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 643 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 644 | |
| 645 | /* |
| 646 | * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section |
| 647 | * |
| 648 | * See rcu_read_lock_bh() for more information. |
| 649 | */ |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 650 | static inline void rcu_read_unlock_bh(void) |
| 651 | { |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 652 | rcu_read_release_bh(); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 653 | __release(RCU_BH); |
| 654 | __rcu_read_unlock_bh(); |
| 655 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 656 | |
| 657 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 658 | * rcu_read_lock_sched() - mark the beginning of a RCU-sched critical section |
Mathieu Desnoyers | 1c50b72 | 2008-09-29 11:06:46 -0400 | [diff] [blame] | 659 | * |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 660 | * This is equivalent of rcu_read_lock(), but to be used when updates |
| 661 | * are being done using call_rcu_sched() or synchronize_rcu_sched(). |
| 662 | * Read-side critical sections can also be introduced by anything that |
| 663 | * disables preemption, including local_irq_disable() and friends. |
Mathieu Desnoyers | 1c50b72 | 2008-09-29 11:06:46 -0400 | [diff] [blame] | 664 | */ |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 665 | static inline void rcu_read_lock_sched(void) |
| 666 | { |
| 667 | preempt_disable(); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 668 | __acquire(RCU_SCHED); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 669 | rcu_read_acquire_sched(); |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 670 | } |
Paul E. McKenney | 1eba8f8 | 2009-09-23 09:50:42 -0700 | [diff] [blame] | 671 | |
| 672 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ |
Paul E. McKenney | 7c614d6 | 2009-08-24 09:42:00 -0700 | [diff] [blame] | 673 | static inline notrace void rcu_read_lock_sched_notrace(void) |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 674 | { |
| 675 | preempt_disable_notrace(); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 676 | __acquire(RCU_SCHED); |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 677 | } |
Mathieu Desnoyers | 1c50b72 | 2008-09-29 11:06:46 -0400 | [diff] [blame] | 678 | |
| 679 | /* |
| 680 | * rcu_read_unlock_sched - marks the end of a RCU-classic critical section |
| 681 | * |
| 682 | * See rcu_read_lock_sched for more information. |
| 683 | */ |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 684 | static inline void rcu_read_unlock_sched(void) |
| 685 | { |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 686 | rcu_read_release_sched(); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 687 | __release(RCU_SCHED); |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 688 | preempt_enable(); |
| 689 | } |
Paul E. McKenney | 1eba8f8 | 2009-09-23 09:50:42 -0700 | [diff] [blame] | 690 | |
| 691 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ |
Paul E. McKenney | 7c614d6 | 2009-08-24 09:42:00 -0700 | [diff] [blame] | 692 | static inline notrace void rcu_read_unlock_sched_notrace(void) |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 693 | { |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 694 | __release(RCU_SCHED); |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 695 | preempt_enable_notrace(); |
| 696 | } |
Mathieu Desnoyers | 1c50b72 | 2008-09-29 11:06:46 -0400 | [diff] [blame] | 697 | |
Mathieu Desnoyers | 1c50b72 | 2008-09-29 11:06:46 -0400 | [diff] [blame] | 698 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 699 | * rcu_assign_pointer() - assign to RCU-protected pointer |
| 700 | * @p: pointer to assign to |
| 701 | * @v: value to assign (publish) |
Paul E. McKenney | c26d34a | 2010-02-22 17:04:46 -0800 | [diff] [blame] | 702 | * |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 703 | * Assigns the specified value to the specified RCU-protected |
| 704 | * pointer, ensuring that any concurrent RCU readers will see |
| 705 | * any prior initialization. Returns the value assigned. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 706 | * |
| 707 | * Inserts memory barriers on architectures that require them |
| 708 | * (pretty much all of them other than x86), and also prevents |
| 709 | * the compiler from reordering the code that initializes the |
| 710 | * structure after the pointer assignment. More importantly, this |
| 711 | * call documents which pointers will be dereferenced by RCU read-side |
| 712 | * code. |
| 713 | */ |
Paul E. McKenney | d99c4f6 | 2008-02-06 01:37:25 -0800 | [diff] [blame] | 714 | #define rcu_assign_pointer(p, v) \ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 715 | __rcu_assign_pointer((p), (v), __rcu) |
| 716 | |
| 717 | /** |
| 718 | * RCU_INIT_POINTER() - initialize an RCU protected pointer |
| 719 | * |
| 720 | * Initialize an RCU-protected pointer in such a way to avoid RCU-lockdep |
| 721 | * splats. |
| 722 | */ |
| 723 | #define RCU_INIT_POINTER(p, v) \ |
| 724 | p = (typeof(*v) __force __rcu *)(v) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 725 | |
Paul E. McKenney | 4446a36 | 2008-05-12 21:21:05 +0200 | [diff] [blame] | 726 | /* Infrastructure to implement the synchronize_() primitives. */ |
| 727 | |
| 728 | struct rcu_synchronize { |
| 729 | struct rcu_head head; |
| 730 | struct completion completion; |
| 731 | }; |
| 732 | |
| 733 | extern void wakeme_after_rcu(struct rcu_head *head); |
| 734 | |
Paul E. McKenney | 7b0b759 | 2010-08-17 14:18:46 -0700 | [diff] [blame] | 735 | #ifdef CONFIG_PREEMPT_RCU |
| 736 | |
Paul E. McKenney | 9b06e81 | 2005-05-01 08:59:04 -0700 | [diff] [blame] | 737 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 738 | * call_rcu() - Queue an RCU callback for invocation after a grace period. |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 739 | * @head: structure to be used for queueing the RCU updates. |
Paul E. McKenney | 77d8485 | 2010-07-08 17:38:59 -0700 | [diff] [blame] | 740 | * @func: actual callback function to be invoked after the grace period |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 741 | * |
Paul E. McKenney | 77d8485 | 2010-07-08 17:38:59 -0700 | [diff] [blame] | 742 | * The callback function will be invoked some time after a full grace |
| 743 | * period elapses, in other words after all pre-existing RCU read-side |
| 744 | * critical sections have completed. However, the callback function |
| 745 | * might well execute concurrently with RCU read-side critical sections |
| 746 | * that started after call_rcu() was invoked. RCU read-side critical |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 747 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), |
| 748 | * and may be nested. |
| 749 | */ |
| 750 | extern void call_rcu(struct rcu_head *head, |
| 751 | void (*func)(struct rcu_head *head)); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 752 | |
Paul E. McKenney | 7b0b759 | 2010-08-17 14:18:46 -0700 | [diff] [blame] | 753 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
| 754 | |
| 755 | /* In classic RCU, call_rcu() is just call_rcu_sched(). */ |
| 756 | #define call_rcu call_rcu_sched |
| 757 | |
| 758 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ |
| 759 | |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 760 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 761 | * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period. |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 762 | * @head: structure to be used for queueing the RCU updates. |
Paul E. McKenney | 77d8485 | 2010-07-08 17:38:59 -0700 | [diff] [blame] | 763 | * @func: actual callback function to be invoked after the grace period |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 764 | * |
Paul E. McKenney | 77d8485 | 2010-07-08 17:38:59 -0700 | [diff] [blame] | 765 | * The callback function will be invoked some time after a full grace |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 766 | * period elapses, in other words after all currently executing RCU |
| 767 | * read-side critical sections have completed. call_rcu_bh() assumes |
| 768 | * that the read-side critical sections end on completion of a softirq |
| 769 | * handler. This means that read-side critical sections in process |
| 770 | * context must not be interrupted by softirqs. This interface is to be |
| 771 | * used when most of the read-side critical sections are in softirq context. |
| 772 | * RCU read-side critical sections are delimited by : |
| 773 | * - rcu_read_lock() and rcu_read_unlock(), if in interrupt context. |
| 774 | * OR |
| 775 | * - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context. |
| 776 | * These may be nested. |
| 777 | */ |
| 778 | extern void call_rcu_bh(struct rcu_head *head, |
| 779 | void (*func)(struct rcu_head *head)); |
| 780 | |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 781 | /* |
| 782 | * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally |
| 783 | * by call_rcu() and rcu callback execution, and are therefore not part of the |
| 784 | * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors. |
| 785 | */ |
| 786 | |
| 787 | #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD |
| 788 | # define STATE_RCU_HEAD_READY 0 |
| 789 | # define STATE_RCU_HEAD_QUEUED 1 |
| 790 | |
| 791 | extern struct debug_obj_descr rcuhead_debug_descr; |
| 792 | |
| 793 | static inline void debug_rcu_head_queue(struct rcu_head *head) |
| 794 | { |
Paul E. McKenney | b0c9d7f | 2011-03-29 12:56:56 -0700 | [diff] [blame] | 795 | WARN_ON_ONCE((unsigned long)head & 0x3); |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 796 | debug_object_activate(head, &rcuhead_debug_descr); |
| 797 | debug_object_active_state(head, &rcuhead_debug_descr, |
| 798 | STATE_RCU_HEAD_READY, |
| 799 | STATE_RCU_HEAD_QUEUED); |
| 800 | } |
| 801 | |
| 802 | static inline void debug_rcu_head_unqueue(struct rcu_head *head) |
| 803 | { |
| 804 | debug_object_active_state(head, &rcuhead_debug_descr, |
| 805 | STATE_RCU_HEAD_QUEUED, |
| 806 | STATE_RCU_HEAD_READY); |
| 807 | debug_object_deactivate(head, &rcuhead_debug_descr); |
| 808 | } |
| 809 | #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
| 810 | static inline void debug_rcu_head_queue(struct rcu_head *head) |
| 811 | { |
| 812 | } |
| 813 | |
| 814 | static inline void debug_rcu_head_unqueue(struct rcu_head *head) |
| 815 | { |
| 816 | } |
| 817 | #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
| 818 | |
Lai Jiangshan | 9ab1544 | 2011-03-18 11:15:47 +0800 | [diff] [blame] | 819 | static __always_inline bool __is_kfree_rcu_offset(unsigned long offset) |
| 820 | { |
| 821 | return offset < 4096; |
| 822 | } |
| 823 | |
| 824 | static __always_inline |
| 825 | void __kfree_rcu(struct rcu_head *head, unsigned long offset) |
| 826 | { |
| 827 | typedef void (*rcu_callback)(struct rcu_head *); |
| 828 | |
| 829 | BUILD_BUG_ON(!__builtin_constant_p(offset)); |
| 830 | |
| 831 | /* See the kfree_rcu() header comment. */ |
| 832 | BUILD_BUG_ON(!__is_kfree_rcu_offset(offset)); |
| 833 | |
| 834 | call_rcu(head, (rcu_callback)offset); |
| 835 | } |
| 836 | |
| 837 | extern void kfree(const void *); |
| 838 | |
| 839 | static inline void __rcu_reclaim(struct rcu_head *head) |
| 840 | { |
| 841 | unsigned long offset = (unsigned long)head->func; |
| 842 | |
| 843 | if (__is_kfree_rcu_offset(offset)) |
| 844 | kfree((void *)head - offset); |
| 845 | else |
| 846 | head->func(head); |
| 847 | } |
| 848 | |
| 849 | /** |
| 850 | * kfree_rcu() - kfree an object after a grace period. |
| 851 | * @ptr: pointer to kfree |
| 852 | * @rcu_head: the name of the struct rcu_head within the type of @ptr. |
| 853 | * |
| 854 | * Many rcu callbacks functions just call kfree() on the base structure. |
| 855 | * These functions are trivial, but their size adds up, and furthermore |
| 856 | * when they are used in a kernel module, that module must invoke the |
| 857 | * high-latency rcu_barrier() function at module-unload time. |
| 858 | * |
| 859 | * The kfree_rcu() function handles this issue. Rather than encoding a |
| 860 | * function address in the embedded rcu_head structure, kfree_rcu() instead |
| 861 | * encodes the offset of the rcu_head structure within the base structure. |
| 862 | * Because the functions are not allowed in the low-order 4096 bytes of |
| 863 | * kernel virtual memory, offsets up to 4095 bytes can be accommodated. |
| 864 | * If the offset is larger than 4095 bytes, a compile-time error will |
| 865 | * be generated in __kfree_rcu(). If this error is triggered, you can |
| 866 | * either fall back to use of call_rcu() or rearrange the structure to |
| 867 | * position the rcu_head structure into the first 4096 bytes. |
| 868 | * |
| 869 | * Note that the allowable offset might decrease in the future, for example, |
| 870 | * to allow something like kmem_cache_free_rcu(). |
| 871 | */ |
| 872 | #define kfree_rcu(ptr, rcu_head) \ |
| 873 | __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head)) |
| 874 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 875 | #endif /* __LINUX_RCUPDATE_H */ |