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 Gortmaker | 187f188 | 2011-11-23 20:12:59 -0500 | [diff] [blame] | 45 | #include <linux/bug.h> |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 46 | #include <linux/compiler.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 47 | |
Dave Young | e5ab677 | 2010-03-10 15:24:05 -0800 | [diff] [blame] | 48 | #ifdef CONFIG_RCU_TORTURE_TEST |
| 49 | extern int rcutorture_runnable; /* for sysctl */ |
| 50 | #endif /* #ifdef CONFIG_RCU_TORTURE_TEST */ |
| 51 | |
Paul E. McKenney | 4a29865 | 2011-04-03 21:33:51 -0700 | [diff] [blame] | 52 | #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) |
| 53 | extern void rcutorture_record_test_transition(void); |
| 54 | extern void rcutorture_record_progress(unsigned long vernum); |
Paul E. McKenney | 91afaf3 | 2011-10-02 07:44:32 -0700 | [diff] [blame] | 55 | extern void do_trace_rcu_torture_read(char *rcutorturename, |
| 56 | struct rcu_head *rhp); |
Paul E. McKenney | 4a29865 | 2011-04-03 21:33:51 -0700 | [diff] [blame] | 57 | #else |
| 58 | static inline void rcutorture_record_test_transition(void) |
| 59 | { |
| 60 | } |
| 61 | static inline void rcutorture_record_progress(unsigned long vernum) |
| 62 | { |
| 63 | } |
Paul E. McKenney | 91afaf3 | 2011-10-02 07:44:32 -0700 | [diff] [blame] | 64 | #ifdef CONFIG_RCU_TRACE |
| 65 | extern void do_trace_rcu_torture_read(char *rcutorturename, |
| 66 | struct rcu_head *rhp); |
| 67 | #else |
| 68 | #define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0) |
| 69 | #endif |
Paul E. McKenney | 4a29865 | 2011-04-03 21:33:51 -0700 | [diff] [blame] | 70 | #endif |
| 71 | |
Tejun Heo | e27fc96 | 2010-11-22 21:36:11 -0800 | [diff] [blame] | 72 | #define UINT_CMP_GE(a, b) (UINT_MAX / 2 >= (a) - (b)) |
| 73 | #define UINT_CMP_LT(a, b) (UINT_MAX / 2 < (a) - (b)) |
Paul E. McKenney | a3dc3fb | 2010-08-13 16:16:25 -0700 | [diff] [blame] | 74 | #define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b)) |
| 75 | #define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b)) |
| 76 | |
Paul E. McKenney | 03b042b | 2009-06-25 09:08:16 -0700 | [diff] [blame] | 77 | /* Exported common interfaces */ |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 78 | |
| 79 | #ifdef CONFIG_PREEMPT_RCU |
| 80 | |
| 81 | /** |
| 82 | * call_rcu() - Queue an RCU callback for invocation after a grace period. |
| 83 | * @head: structure to be used for queueing the RCU updates. |
| 84 | * @func: actual callback function to be invoked after the grace period |
| 85 | * |
| 86 | * The callback function will be invoked some time after a full grace |
| 87 | * period elapses, in other words after all pre-existing RCU read-side |
| 88 | * critical sections have completed. However, the callback function |
| 89 | * might well execute concurrently with RCU read-side critical sections |
| 90 | * that started after call_rcu() was invoked. RCU read-side critical |
| 91 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), |
| 92 | * and may be nested. |
Paul E. McKenney | f0a0e6f | 2012-10-23 13:47:01 -0700 | [diff] [blame^] | 93 | * |
| 94 | * Note that all CPUs must agree that the grace period extended beyond |
| 95 | * all pre-existing RCU read-side critical section. On systems with more |
| 96 | * than one CPU, this means that when "func()" is invoked, each CPU is |
| 97 | * guaranteed to have executed a full memory barrier since the end of its |
| 98 | * last RCU read-side critical section whose beginning preceded the call |
| 99 | * to call_rcu(). It also means that each CPU executing an RCU read-side |
| 100 | * critical section that continues beyond the start of "func()" must have |
| 101 | * executed a memory barrier after the call_rcu() but before the beginning |
| 102 | * of that RCU read-side critical section. Note that these guarantees |
| 103 | * include CPUs that are offline, idle, or executing in user mode, as |
| 104 | * well as CPUs that are executing in the kernel. |
| 105 | * |
| 106 | * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the |
| 107 | * resulting RCU callback function "func()", then both CPU A and CPU B are |
| 108 | * guaranteed to execute a full memory barrier during the time interval |
| 109 | * between the call to call_rcu() and the invocation of "func()" -- even |
| 110 | * if CPU A and CPU B are the same CPU (but again only if the system has |
| 111 | * more than one CPU). |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 112 | */ |
| 113 | extern void call_rcu(struct rcu_head *head, |
| 114 | void (*func)(struct rcu_head *head)); |
| 115 | |
| 116 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
| 117 | |
| 118 | /* In classic RCU, call_rcu() is just call_rcu_sched(). */ |
| 119 | #define call_rcu call_rcu_sched |
| 120 | |
| 121 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ |
| 122 | |
| 123 | /** |
| 124 | * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period. |
| 125 | * @head: structure to be used for queueing the RCU updates. |
| 126 | * @func: actual callback function to be invoked after the grace period |
| 127 | * |
| 128 | * The callback function will be invoked some time after a full grace |
| 129 | * period elapses, in other words after all currently executing RCU |
| 130 | * read-side critical sections have completed. call_rcu_bh() assumes |
| 131 | * that the read-side critical sections end on completion of a softirq |
| 132 | * handler. This means that read-side critical sections in process |
| 133 | * context must not be interrupted by softirqs. This interface is to be |
| 134 | * used when most of the read-side critical sections are in softirq context. |
| 135 | * RCU read-side critical sections are delimited by : |
| 136 | * - rcu_read_lock() and rcu_read_unlock(), if in interrupt context. |
| 137 | * OR |
| 138 | * - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context. |
| 139 | * These may be nested. |
Paul E. McKenney | f0a0e6f | 2012-10-23 13:47:01 -0700 | [diff] [blame^] | 140 | * |
| 141 | * See the description of call_rcu() for more detailed information on |
| 142 | * memory ordering guarantees. |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 143 | */ |
| 144 | extern void call_rcu_bh(struct rcu_head *head, |
| 145 | void (*func)(struct rcu_head *head)); |
| 146 | |
| 147 | /** |
| 148 | * call_rcu_sched() - Queue an RCU for invocation after sched grace period. |
| 149 | * @head: structure to be used for queueing the RCU updates. |
| 150 | * @func: actual callback function to be invoked after the grace period |
| 151 | * |
| 152 | * The callback function will be invoked some time after a full grace |
| 153 | * period elapses, in other words after all currently executing RCU |
| 154 | * read-side critical sections have completed. call_rcu_sched() assumes |
| 155 | * that the read-side critical sections end on enabling of preemption |
| 156 | * or on voluntary preemption. |
| 157 | * RCU read-side critical sections are delimited by : |
| 158 | * - rcu_read_lock_sched() and rcu_read_unlock_sched(), |
| 159 | * OR |
| 160 | * anything that disables preemption. |
| 161 | * These may be nested. |
Paul E. McKenney | f0a0e6f | 2012-10-23 13:47:01 -0700 | [diff] [blame^] | 162 | * |
| 163 | * See the description of call_rcu() for more detailed information on |
| 164 | * memory ordering guarantees. |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 165 | */ |
Paul E. McKenney | 7b0b759 | 2010-08-17 14:18:46 -0700 | [diff] [blame] | 166 | extern void call_rcu_sched(struct rcu_head *head, |
| 167 | void (*func)(struct rcu_head *rcu)); |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 168 | |
Paul E. McKenney | 7b0b759 | 2010-08-17 14:18:46 -0700 | [diff] [blame] | 169 | extern void synchronize_sched(void); |
Paul E. McKenney | 03b042b | 2009-06-25 09:08:16 -0700 | [diff] [blame] | 170 | |
Paul E. McKenney | a3dc3fb | 2010-08-13 16:16:25 -0700 | [diff] [blame] | 171 | #ifdef CONFIG_PREEMPT_RCU |
| 172 | |
Paul E. McKenney | 7b0b759 | 2010-08-17 14:18:46 -0700 | [diff] [blame] | 173 | extern void __rcu_read_lock(void); |
| 174 | extern void __rcu_read_unlock(void); |
Paul E. McKenney | 2a3fa84 | 2012-05-21 11:58:36 -0700 | [diff] [blame] | 175 | extern void rcu_read_unlock_special(struct task_struct *t); |
Paul E. McKenney | 7b0b759 | 2010-08-17 14:18:46 -0700 | [diff] [blame] | 176 | void synchronize_rcu(void); |
| 177 | |
Paul E. McKenney | a3dc3fb | 2010-08-13 16:16:25 -0700 | [diff] [blame] | 178 | /* |
| 179 | * Defined as a macro as it is a very low level header included from |
| 180 | * areas that don't even know about current. This gives the rcu_read_lock() |
| 181 | * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other |
| 182 | * types of kernel builds, the rcu_read_lock() nesting depth is unknowable. |
| 183 | */ |
| 184 | #define rcu_preempt_depth() (current->rcu_read_lock_nesting) |
| 185 | |
Paul E. McKenney | 7b0b759 | 2010-08-17 14:18:46 -0700 | [diff] [blame] | 186 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
| 187 | |
| 188 | static inline void __rcu_read_lock(void) |
| 189 | { |
| 190 | preempt_disable(); |
| 191 | } |
| 192 | |
| 193 | static inline void __rcu_read_unlock(void) |
| 194 | { |
| 195 | preempt_enable(); |
| 196 | } |
| 197 | |
| 198 | static inline void synchronize_rcu(void) |
| 199 | { |
| 200 | synchronize_sched(); |
| 201 | } |
| 202 | |
| 203 | static inline int rcu_preempt_depth(void) |
| 204 | { |
| 205 | return 0; |
| 206 | } |
| 207 | |
| 208 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ |
| 209 | |
| 210 | /* Internal to kernel */ |
Paul E. McKenney | 7b0b759 | 2010-08-17 14:18:46 -0700 | [diff] [blame] | 211 | extern void rcu_sched_qs(int cpu); |
| 212 | extern void rcu_bh_qs(int cpu); |
| 213 | extern void rcu_check_callbacks(int cpu, int user); |
| 214 | struct notifier_block; |
Paul E. McKenney | 9b2e4f1 | 2011-09-30 12:10:22 -0700 | [diff] [blame] | 215 | extern void rcu_idle_enter(void); |
| 216 | extern void rcu_idle_exit(void); |
| 217 | extern void rcu_irq_enter(void); |
| 218 | extern void rcu_irq_exit(void); |
Frederic Weisbecker | 2b1d502 | 2012-07-11 20:26:30 +0200 | [diff] [blame] | 219 | |
| 220 | #ifdef CONFIG_RCU_USER_QS |
Frederic Weisbecker | adf5091 | 2012-06-28 11:20:21 -0700 | [diff] [blame] | 221 | extern void rcu_user_enter(void); |
| 222 | extern void rcu_user_exit(void); |
Frederic Weisbecker | 19dd1591 | 2012-06-04 16:42:35 -0700 | [diff] [blame] | 223 | extern void rcu_user_enter_after_irq(void); |
| 224 | extern void rcu_user_exit_after_irq(void); |
Frederic Weisbecker | 04e7e95 | 2012-07-16 15:06:40 -0700 | [diff] [blame] | 225 | extern void rcu_user_hooks_switch(struct task_struct *prev, |
| 226 | struct task_struct *next); |
Frederic Weisbecker | 2b1d502 | 2012-07-11 20:26:30 +0200 | [diff] [blame] | 227 | #else |
| 228 | static inline void rcu_user_enter(void) { } |
| 229 | static inline void rcu_user_exit(void) { } |
| 230 | static inline void rcu_user_enter_after_irq(void) { } |
| 231 | static inline void rcu_user_exit_after_irq(void) { } |
| 232 | #endif /* CONFIG_RCU_USER_QS */ |
| 233 | |
Paul E. McKenney | 9dd8fb1 | 2012-04-13 12:54:22 -0700 | [diff] [blame] | 234 | extern void exit_rcu(void); |
Paul E. McKenney | a3dc3fb | 2010-08-13 16:16:25 -0700 | [diff] [blame] | 235 | |
Paul E. McKenney | 8a2ecf4 | 2012-02-02 15:42:04 -0800 | [diff] [blame] | 236 | /** |
| 237 | * RCU_NONIDLE - Indicate idle-loop code that needs RCU readers |
| 238 | * @a: Code that RCU needs to pay attention to. |
| 239 | * |
| 240 | * RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden |
| 241 | * in the inner idle loop, that is, between the rcu_idle_enter() and |
| 242 | * the rcu_idle_exit() -- RCU will happily ignore any such read-side |
| 243 | * critical sections. However, things like powertop need tracepoints |
| 244 | * in the inner idle loop. |
| 245 | * |
| 246 | * This macro provides the way out: RCU_NONIDLE(do_something_with_RCU()) |
| 247 | * will tell RCU that it needs to pay attending, invoke its argument |
| 248 | * (in this example, a call to the do_something_with_RCU() function), |
| 249 | * and then tell RCU to go back to ignoring this CPU. It is permissible |
| 250 | * to nest RCU_NONIDLE() wrappers, but the nesting level is currently |
| 251 | * quite limited. If deeper nesting is required, it will be necessary |
| 252 | * to adjust DYNTICK_TASK_NESTING_VALUE accordingly. |
Paul E. McKenney | 8a2ecf4 | 2012-02-02 15:42:04 -0800 | [diff] [blame] | 253 | */ |
| 254 | #define RCU_NONIDLE(a) \ |
| 255 | do { \ |
Paul E. McKenney | b4270ee | 2012-07-31 10:12:48 -0700 | [diff] [blame] | 256 | rcu_irq_enter(); \ |
Paul E. McKenney | 8a2ecf4 | 2012-02-02 15:42:04 -0800 | [diff] [blame] | 257 | do { a; } while (0); \ |
Paul E. McKenney | b4270ee | 2012-07-31 10:12:48 -0700 | [diff] [blame] | 258 | rcu_irq_exit(); \ |
Paul E. McKenney | 8a2ecf4 | 2012-02-02 15:42:04 -0800 | [diff] [blame] | 259 | } while (0) |
| 260 | |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 261 | /* |
| 262 | * Infrastructure to implement the synchronize_() primitives in |
| 263 | * TREE_RCU and rcu_barrier_() primitives in TINY_RCU. |
| 264 | */ |
| 265 | |
| 266 | typedef void call_rcu_func_t(struct rcu_head *head, |
| 267 | void (*func)(struct rcu_head *head)); |
| 268 | void wait_rcu_gp(call_rcu_func_t crf); |
| 269 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 270 | #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 271 | #include <linux/rcutree.h> |
Paul E. McKenney | a57eb94 | 2010-06-29 16:49:16 -0700 | [diff] [blame] | 272 | #elif defined(CONFIG_TINY_RCU) || defined(CONFIG_TINY_PREEMPT_RCU) |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 273 | #include <linux/rcutiny.h> |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 274 | #else |
| 275 | #error "Unknown RCU implementation specified to kernel configuration" |
Paul E. McKenney | 6b3ef48 | 2009-08-22 13:56:53 -0700 | [diff] [blame] | 276 | #endif |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 277 | |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 278 | /* |
| 279 | * init_rcu_head_on_stack()/destroy_rcu_head_on_stack() are needed for dynamic |
| 280 | * initialization and destruction of rcu_head on the stack. rcu_head structures |
| 281 | * allocated dynamically in the heap or defined statically don't need any |
| 282 | * initialization. |
| 283 | */ |
| 284 | #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD |
| 285 | extern void init_rcu_head_on_stack(struct rcu_head *head); |
| 286 | extern void destroy_rcu_head_on_stack(struct rcu_head *head); |
| 287 | #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
Mathieu Desnoyers | 4376030 | 2010-04-17 08:48:39 -0400 | [diff] [blame] | 288 | static inline void init_rcu_head_on_stack(struct rcu_head *head) |
| 289 | { |
| 290 | } |
| 291 | |
| 292 | static inline void destroy_rcu_head_on_stack(struct rcu_head *head) |
| 293 | { |
| 294 | } |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 295 | #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
Mathieu Desnoyers | 4376030 | 2010-04-17 08:48:39 -0400 | [diff] [blame] | 296 | |
Paul E. McKenney | 62fde6e | 2012-05-22 22:10:24 -0700 | [diff] [blame] | 297 | #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SMP) |
| 298 | extern int rcu_is_cpu_idle(void); |
| 299 | #endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SMP) */ |
| 300 | |
Paul E. McKenney | c0d6d01 | 2012-01-23 12:41:26 -0800 | [diff] [blame] | 301 | #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) |
| 302 | bool rcu_lockdep_current_cpu_online(void); |
| 303 | #else /* #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ |
| 304 | static inline bool rcu_lockdep_current_cpu_online(void) |
| 305 | { |
| 306 | return 1; |
| 307 | } |
| 308 | #endif /* #else #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ |
| 309 | |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 310 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 311 | |
Frederic Weisbecker | 00f49e5 | 2011-10-07 18:22:02 +0200 | [diff] [blame] | 312 | static inline void rcu_lock_acquire(struct lockdep_map *map) |
| 313 | { |
Frederic Weisbecker | 00f49e5 | 2011-10-07 18:22:02 +0200 | [diff] [blame] | 314 | lock_acquire(map, 0, 0, 2, 1, NULL, _THIS_IP_); |
| 315 | } |
| 316 | |
| 317 | static inline void rcu_lock_release(struct lockdep_map *map) |
| 318 | { |
Frederic Weisbecker | 00f49e5 | 2011-10-07 18:22:02 +0200 | [diff] [blame] | 319 | lock_release(map, 1, _THIS_IP_); |
| 320 | } |
| 321 | |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 322 | extern struct lockdep_map rcu_lock_map; |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 323 | extern struct lockdep_map rcu_bh_lock_map; |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 324 | extern struct lockdep_map rcu_sched_lock_map; |
Paul E. McKenney | bc293d6 | 2010-04-15 12:50:39 -0700 | [diff] [blame] | 325 | extern int debug_lockdep_rcu_enabled(void); |
Paul E. McKenney | 54dbf96 | 2010-03-03 07:46:57 -0800 | [diff] [blame] | 326 | |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 327 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 328 | * 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] | 329 | * |
Paul E. McKenney | d20200b | 2010-03-30 10:52:21 -0700 | [diff] [blame] | 330 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU |
| 331 | * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 332 | * 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] | 333 | * prove otherwise. This is useful for debug checks in functions that |
| 334 | * 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] | 335 | * |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 336 | * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot |
Paul E. McKenney | 32c141a | 2010-03-30 10:59:28 -0700 | [diff] [blame] | 337 | * and while lockdep is disabled. |
Paul E. McKenney | 3842a08 | 2011-11-28 10:42:42 -0800 | [diff] [blame] | 338 | * |
| 339 | * Note that rcu_read_lock() and the matching rcu_read_unlock() must |
| 340 | * occur in the same context, for example, it is illegal to invoke |
| 341 | * rcu_read_unlock() in process context if the matching rcu_read_lock() |
| 342 | * was invoked from within an irq handler. |
Paul E. McKenney | c0d6d01 | 2012-01-23 12:41:26 -0800 | [diff] [blame] | 343 | * |
| 344 | * Note that rcu_read_lock() is disallowed if the CPU is either idle or |
| 345 | * offline from an RCU perspective, so check for those as well. |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 346 | */ |
| 347 | static inline int rcu_read_lock_held(void) |
| 348 | { |
Paul E. McKenney | 54dbf96 | 2010-03-03 07:46:57 -0800 | [diff] [blame] | 349 | if (!debug_lockdep_rcu_enabled()) |
| 350 | return 1; |
Frederic Weisbecker | e6b80a3 | 2011-10-07 16:25:18 -0700 | [diff] [blame] | 351 | if (rcu_is_cpu_idle()) |
| 352 | return 0; |
Paul E. McKenney | c0d6d01 | 2012-01-23 12:41:26 -0800 | [diff] [blame] | 353 | if (!rcu_lockdep_current_cpu_online()) |
| 354 | return 0; |
Paul E. McKenney | 54dbf96 | 2010-03-03 07:46:57 -0800 | [diff] [blame] | 355 | return lock_is_held(&rcu_lock_map); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 356 | } |
| 357 | |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 358 | /* |
| 359 | * rcu_read_lock_bh_held() is defined out of line to avoid #include-file |
| 360 | * hell. |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 361 | */ |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 362 | extern int rcu_read_lock_bh_held(void); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 363 | |
| 364 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 365 | * 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] | 366 | * |
Paul E. McKenney | d20200b | 2010-03-30 10:52:21 -0700 | [diff] [blame] | 367 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an |
| 368 | * RCU-sched read-side critical section. In absence of |
| 369 | * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side |
| 370 | * critical section unless it can prove otherwise. Note that disabling |
| 371 | * of preemption (including disabling irqs) counts as an RCU-sched |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 372 | * read-side critical section. This is useful for debug checks in functions |
| 373 | * that required that they be called within an RCU-sched read-side |
| 374 | * critical section. |
Paul E. McKenney | 54dbf96 | 2010-03-03 07:46:57 -0800 | [diff] [blame] | 375 | * |
Paul E. McKenney | 32c141a | 2010-03-30 10:59:28 -0700 | [diff] [blame] | 376 | * Check debug_lockdep_rcu_enabled() to prevent false positives during boot |
| 377 | * and while lockdep is disabled. |
Frederic Weisbecker | e6b80a3 | 2011-10-07 16:25:18 -0700 | [diff] [blame] | 378 | * |
| 379 | * Note that if the CPU is in the idle loop from an RCU point of |
| 380 | * view (ie: that we are in the section between rcu_idle_enter() and |
| 381 | * rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU |
| 382 | * did an rcu_read_lock(). The reason for this is that RCU ignores CPUs |
| 383 | * that are in such a section, considering these as in extended quiescent |
| 384 | * state, so such a CPU is effectively never in an RCU read-side critical |
| 385 | * section regardless of what RCU primitives it invokes. This state of |
| 386 | * affairs is required --- we need to keep an RCU-free window in idle |
| 387 | * where the CPU may possibly enter into low power mode. This way we can |
| 388 | * notice an extended quiescent state to other CPUs that started a grace |
| 389 | * period. Otherwise we would delay any grace period as long as we run in |
| 390 | * the idle task. |
Paul E. McKenney | c0d6d01 | 2012-01-23 12:41:26 -0800 | [diff] [blame] | 391 | * |
| 392 | * Similarly, we avoid claiming an SRCU read lock held if the current |
| 393 | * CPU is offline. |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 394 | */ |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 395 | #ifdef CONFIG_PREEMPT_COUNT |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 396 | static inline int rcu_read_lock_sched_held(void) |
| 397 | { |
| 398 | int lockdep_opinion = 0; |
| 399 | |
Paul E. McKenney | 54dbf96 | 2010-03-03 07:46:57 -0800 | [diff] [blame] | 400 | if (!debug_lockdep_rcu_enabled()) |
| 401 | return 1; |
Frederic Weisbecker | e6b80a3 | 2011-10-07 16:25:18 -0700 | [diff] [blame] | 402 | if (rcu_is_cpu_idle()) |
| 403 | return 0; |
Paul E. McKenney | c0d6d01 | 2012-01-23 12:41:26 -0800 | [diff] [blame] | 404 | if (!rcu_lockdep_current_cpu_online()) |
| 405 | return 0; |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 406 | if (debug_locks) |
| 407 | lockdep_opinion = lock_is_held(&rcu_sched_lock_map); |
Lai Jiangshan | 0cff810 | 2010-03-18 12:25:33 -0700 | [diff] [blame] | 408 | return lockdep_opinion || preempt_count() != 0 || irqs_disabled(); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 409 | } |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 410 | #else /* #ifdef CONFIG_PREEMPT_COUNT */ |
Paul E. McKenney | e6033e3 | 2010-03-03 17:50:16 -0800 | [diff] [blame] | 411 | static inline int rcu_read_lock_sched_held(void) |
| 412 | { |
| 413 | return 1; |
| 414 | } |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 415 | #endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 416 | |
| 417 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| 418 | |
Paul E. McKenney | d8ab29f | 2011-10-07 18:22:03 +0200 | [diff] [blame] | 419 | # define rcu_lock_acquire(a) do { } while (0) |
| 420 | # define rcu_lock_release(a) do { } while (0) |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 421 | |
| 422 | static inline int rcu_read_lock_held(void) |
| 423 | { |
| 424 | return 1; |
| 425 | } |
| 426 | |
| 427 | static inline int rcu_read_lock_bh_held(void) |
| 428 | { |
| 429 | return 1; |
| 430 | } |
| 431 | |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 432 | #ifdef CONFIG_PREEMPT_COUNT |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 433 | static inline int rcu_read_lock_sched_held(void) |
| 434 | { |
Paul E. McKenney | bbad937 | 2010-04-02 16:17:17 -0700 | [diff] [blame] | 435 | return preempt_count() != 0 || irqs_disabled(); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 436 | } |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 437 | #else /* #ifdef CONFIG_PREEMPT_COUNT */ |
Paul E. McKenney | e6033e3 | 2010-03-03 17:50:16 -0800 | [diff] [blame] | 438 | static inline int rcu_read_lock_sched_held(void) |
| 439 | { |
| 440 | return 1; |
| 441 | } |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 442 | #endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 443 | |
| 444 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| 445 | |
| 446 | #ifdef CONFIG_PROVE_RCU |
| 447 | |
Paul E. McKenney | ee84b82 | 2010-05-06 09:28:41 -0700 | [diff] [blame] | 448 | extern int rcu_my_thread_group_empty(void); |
| 449 | |
Tetsuo Handa | 4221a99 | 2010-06-26 01:08:19 +0900 | [diff] [blame] | 450 | /** |
| 451 | * rcu_lockdep_assert - emit lockdep splat if specified condition not met |
| 452 | * @c: condition to check |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 453 | * @s: informative message |
Tetsuo Handa | 4221a99 | 2010-06-26 01:08:19 +0900 | [diff] [blame] | 454 | */ |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 455 | #define rcu_lockdep_assert(c, s) \ |
Lai Jiangshan | 2b3fc35 | 2010-04-20 16:23:07 +0800 | [diff] [blame] | 456 | do { \ |
Jan Beulich | 7ccaba5 | 2012-03-23 15:01:52 -0700 | [diff] [blame] | 457 | static bool __section(.data.unlikely) __warned; \ |
Lai Jiangshan | 2b3fc35 | 2010-04-20 16:23:07 +0800 | [diff] [blame] | 458 | if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \ |
| 459 | __warned = true; \ |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 460 | lockdep_rcu_suspicious(__FILE__, __LINE__, s); \ |
Lai Jiangshan | 2b3fc35 | 2010-04-20 16:23:07 +0800 | [diff] [blame] | 461 | } \ |
| 462 | } while (0) |
| 463 | |
Paul E. McKenney | 50406b9 | 2012-01-12 13:49:19 -0800 | [diff] [blame] | 464 | #if defined(CONFIG_PROVE_RCU) && !defined(CONFIG_PREEMPT_RCU) |
| 465 | static inline void rcu_preempt_sleep_check(void) |
| 466 | { |
| 467 | rcu_lockdep_assert(!lock_is_held(&rcu_lock_map), |
Paul E. McKenney | 5cf05ad | 2012-05-17 15:12:45 -0700 | [diff] [blame] | 468 | "Illegal context switch in RCU read-side critical section"); |
Paul E. McKenney | 50406b9 | 2012-01-12 13:49:19 -0800 | [diff] [blame] | 469 | } |
| 470 | #else /* #ifdef CONFIG_PROVE_RCU */ |
| 471 | static inline void rcu_preempt_sleep_check(void) |
| 472 | { |
| 473 | } |
| 474 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ |
| 475 | |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 476 | #define rcu_sleep_check() \ |
| 477 | do { \ |
Paul E. McKenney | 50406b9 | 2012-01-12 13:49:19 -0800 | [diff] [blame] | 478 | rcu_preempt_sleep_check(); \ |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 479 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), \ |
| 480 | "Illegal context switch in RCU-bh" \ |
| 481 | " read-side critical section"); \ |
| 482 | rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), \ |
| 483 | "Illegal context switch in RCU-sched"\ |
| 484 | " read-side critical section"); \ |
| 485 | } while (0) |
| 486 | |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 487 | #else /* #ifdef CONFIG_PROVE_RCU */ |
| 488 | |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 489 | #define rcu_lockdep_assert(c, s) do { } while (0) |
| 490 | #define rcu_sleep_check() do { } while (0) |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 491 | |
| 492 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ |
| 493 | |
| 494 | /* |
| 495 | * Helper functions for rcu_dereference_check(), rcu_dereference_protected() |
| 496 | * and rcu_assign_pointer(). Some of these could be folded into their |
| 497 | * callers, but they are left separate in order to ease introduction of |
| 498 | * multiple flavors of pointers to match the multiple flavors of RCU |
| 499 | * (e.g., __rcu_bh, * __rcu_sched, and __srcu), should this make sense in |
| 500 | * the future. |
| 501 | */ |
Paul E. McKenney | 53ecfba | 2010-09-13 17:24:21 -0700 | [diff] [blame] | 502 | |
| 503 | #ifdef __CHECKER__ |
| 504 | #define rcu_dereference_sparse(p, space) \ |
| 505 | ((void)(((typeof(*p) space *)p) == p)) |
| 506 | #else /* #ifdef __CHECKER__ */ |
| 507 | #define rcu_dereference_sparse(p, space) |
| 508 | #endif /* #else #ifdef __CHECKER__ */ |
| 509 | |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 510 | #define __rcu_access_pointer(p, space) \ |
| 511 | ({ \ |
| 512 | typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \ |
Paul E. McKenney | 53ecfba | 2010-09-13 17:24:21 -0700 | [diff] [blame] | 513 | rcu_dereference_sparse(p, space); \ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 514 | ((typeof(*p) __force __kernel *)(_________p1)); \ |
| 515 | }) |
| 516 | #define __rcu_dereference_check(p, c, space) \ |
| 517 | ({ \ |
| 518 | typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \ |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 519 | rcu_lockdep_assert(c, "suspicious rcu_dereference_check()" \ |
| 520 | " usage"); \ |
Paul E. McKenney | 53ecfba | 2010-09-13 17:24:21 -0700 | [diff] [blame] | 521 | rcu_dereference_sparse(p, space); \ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 522 | smp_read_barrier_depends(); \ |
| 523 | ((typeof(*p) __force __kernel *)(_________p1)); \ |
| 524 | }) |
| 525 | #define __rcu_dereference_protected(p, c, space) \ |
| 526 | ({ \ |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 527 | rcu_lockdep_assert(c, "suspicious rcu_dereference_protected()" \ |
| 528 | " usage"); \ |
Paul E. McKenney | 53ecfba | 2010-09-13 17:24:21 -0700 | [diff] [blame] | 529 | rcu_dereference_sparse(p, space); \ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 530 | ((typeof(*p) __force __kernel *)(p)); \ |
| 531 | }) |
| 532 | |
Paul E. McKenney | a4dd992 | 2011-04-01 07:15:14 -0700 | [diff] [blame] | 533 | #define __rcu_access_index(p, space) \ |
| 534 | ({ \ |
| 535 | typeof(p) _________p1 = ACCESS_ONCE(p); \ |
| 536 | rcu_dereference_sparse(p, space); \ |
| 537 | (_________p1); \ |
| 538 | }) |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 539 | #define __rcu_dereference_index_check(p, c) \ |
| 540 | ({ \ |
| 541 | typeof(p) _________p1 = ACCESS_ONCE(p); \ |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 542 | rcu_lockdep_assert(c, \ |
| 543 | "suspicious rcu_dereference_index_check()" \ |
| 544 | " usage"); \ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 545 | smp_read_barrier_depends(); \ |
| 546 | (_________p1); \ |
| 547 | }) |
| 548 | #define __rcu_assign_pointer(p, v, space) \ |
Paul E. McKenney | e9023c4 | 2012-05-16 15:51:08 -0700 | [diff] [blame] | 549 | do { \ |
Eric Dumazet | d322f45 | 2011-07-31 22:09:25 -0700 | [diff] [blame] | 550 | smp_wmb(); \ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 551 | (p) = (typeof(*v) __force space *)(v); \ |
Paul E. McKenney | e9023c4 | 2012-05-16 15:51:08 -0700 | [diff] [blame] | 552 | } while (0) |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 553 | |
| 554 | |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 555 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 556 | * rcu_access_pointer() - fetch RCU pointer with no dereferencing |
| 557 | * @p: The pointer to read |
| 558 | * |
| 559 | * Return the value of the specified RCU-protected pointer, but omit the |
| 560 | * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful |
| 561 | * when the value of this pointer is accessed, but the pointer is not |
| 562 | * dereferenced, for example, when testing an RCU-protected pointer against |
| 563 | * NULL. Although rcu_access_pointer() may also be used in cases where |
| 564 | * update-side locks prevent the value of the pointer from changing, you |
| 565 | * should instead use rcu_dereference_protected() for this use case. |
Paul E. McKenney | 5e1ee6e | 2012-01-12 17:21:20 -0800 | [diff] [blame] | 566 | * |
| 567 | * It is also permissible to use rcu_access_pointer() when read-side |
| 568 | * access to the pointer was removed at least one grace period ago, as |
| 569 | * is the case in the context of the RCU callback that is freeing up |
| 570 | * the data, or after a synchronize_rcu() returns. This can be useful |
| 571 | * when tearing down multi-linked structures after a grace period |
| 572 | * has elapsed. |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 573 | */ |
| 574 | #define rcu_access_pointer(p) __rcu_access_pointer((p), __rcu) |
| 575 | |
| 576 | /** |
| 577 | * rcu_dereference_check() - rcu_dereference with debug checking |
David Howells | c08c68d | 2010-04-09 15:39:11 -0700 | [diff] [blame] | 578 | * @p: The pointer to read, prior to dereferencing |
| 579 | * @c: The conditions under which the dereference will take place |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 580 | * |
David Howells | c08c68d | 2010-04-09 15:39:11 -0700 | [diff] [blame] | 581 | * 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] | 582 | * dereference will take place are correct. Typically the conditions |
| 583 | * indicate the various locking conditions that should be held at that |
| 584 | * point. The check should return true if the conditions are satisfied. |
| 585 | * An implicit check for being in an RCU read-side critical section |
| 586 | * (rcu_read_lock()) is included. |
David Howells | c08c68d | 2010-04-09 15:39:11 -0700 | [diff] [blame] | 587 | * |
| 588 | * For example: |
| 589 | * |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 590 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock)); |
David Howells | c08c68d | 2010-04-09 15:39:11 -0700 | [diff] [blame] | 591 | * |
| 592 | * 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] | 593 | * 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] | 594 | * the bar struct at foo->bar is held. |
| 595 | * |
| 596 | * Note that the list of conditions may also include indications of when a lock |
| 597 | * need not be held, for example during initialisation or destruction of the |
| 598 | * target struct: |
| 599 | * |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 600 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock) || |
David Howells | c08c68d | 2010-04-09 15:39:11 -0700 | [diff] [blame] | 601 | * atomic_read(&foo->usage) == 0); |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 602 | * |
| 603 | * Inserts memory barriers on architectures that require them |
| 604 | * (currently only the Alpha), prevents the compiler from refetching |
| 605 | * (and from merging fetches), and, more importantly, documents exactly |
| 606 | * which pointers are protected by RCU and checks that the pointer is |
| 607 | * annotated as __rcu. |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 608 | */ |
| 609 | #define rcu_dereference_check(p, c) \ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 610 | __rcu_dereference_check((p), rcu_read_lock_held() || (c), __rcu) |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 611 | |
Paul E. McKenney | b62730b | 2010-04-09 15:39:10 -0700 | [diff] [blame] | 612 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 613 | * rcu_dereference_bh_check() - rcu_dereference_bh with debug checking |
| 614 | * @p: The pointer to read, prior to dereferencing |
| 615 | * @c: The conditions under which the dereference will take place |
| 616 | * |
| 617 | * This is the RCU-bh counterpart to rcu_dereference_check(). |
| 618 | */ |
| 619 | #define rcu_dereference_bh_check(p, c) \ |
| 620 | __rcu_dereference_check((p), rcu_read_lock_bh_held() || (c), __rcu) |
| 621 | |
| 622 | /** |
| 623 | * rcu_dereference_sched_check() - rcu_dereference_sched with debug checking |
| 624 | * @p: The pointer to read, prior to dereferencing |
| 625 | * @c: The conditions under which the dereference will take place |
| 626 | * |
| 627 | * This is the RCU-sched counterpart to rcu_dereference_check(). |
| 628 | */ |
| 629 | #define rcu_dereference_sched_check(p, c) \ |
| 630 | __rcu_dereference_check((p), rcu_read_lock_sched_held() || (c), \ |
| 631 | __rcu) |
| 632 | |
| 633 | #define rcu_dereference_raw(p) rcu_dereference_check(p, 1) /*@@@ needed? @@@*/ |
| 634 | |
| 635 | /** |
Paul E. McKenney | a4dd992 | 2011-04-01 07:15:14 -0700 | [diff] [blame] | 636 | * rcu_access_index() - fetch RCU index with no dereferencing |
| 637 | * @p: The index to read |
| 638 | * |
| 639 | * Return the value of the specified RCU-protected index, but omit the |
| 640 | * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful |
| 641 | * when the value of this index is accessed, but the index is not |
| 642 | * dereferenced, for example, when testing an RCU-protected index against |
| 643 | * -1. Although rcu_access_index() may also be used in cases where |
| 644 | * update-side locks prevent the value of the index from changing, you |
| 645 | * should instead use rcu_dereference_index_protected() for this use case. |
| 646 | */ |
| 647 | #define rcu_access_index(p) __rcu_access_index((p), __rcu) |
| 648 | |
| 649 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 650 | * rcu_dereference_index_check() - rcu_dereference for indices with debug checking |
| 651 | * @p: The pointer to read, prior to dereferencing |
| 652 | * @c: The conditions under which the dereference will take place |
| 653 | * |
| 654 | * Similar to rcu_dereference_check(), but omits the sparse checking. |
| 655 | * This allows rcu_dereference_index_check() to be used on integers, |
| 656 | * which can then be used as array indices. Attempting to use |
| 657 | * rcu_dereference_check() on an integer will give compiler warnings |
| 658 | * because the sparse address-space mechanism relies on dereferencing |
| 659 | * the RCU-protected pointer. Dereferencing integers is not something |
| 660 | * that even gcc will put up with. |
| 661 | * |
| 662 | * Note that this function does not implicitly check for RCU read-side |
| 663 | * critical sections. If this function gains lots of uses, it might |
| 664 | * make sense to provide versions for each flavor of RCU, but it does |
| 665 | * not make sense as of early 2010. |
| 666 | */ |
| 667 | #define rcu_dereference_index_check(p, c) \ |
| 668 | __rcu_dereference_index_check((p), (c)) |
| 669 | |
| 670 | /** |
| 671 | * rcu_dereference_protected() - fetch RCU pointer when updates prevented |
| 672 | * @p: The pointer to read, prior to dereferencing |
| 673 | * @c: The conditions under which the dereference will take place |
Paul E. McKenney | b62730b | 2010-04-09 15:39:10 -0700 | [diff] [blame] | 674 | * |
| 675 | * Return the value of the specified RCU-protected pointer, but omit |
| 676 | * both the smp_read_barrier_depends() and the ACCESS_ONCE(). This |
| 677 | * is useful in cases where update-side locks prevent the value of the |
| 678 | * pointer from changing. Please note that this primitive does -not- |
| 679 | * prevent the compiler from repeating this reference or combining it |
| 680 | * with other references, so it should not be used without protection |
| 681 | * of appropriate locks. |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 682 | * |
| 683 | * This function is only for update-side use. Using this function |
| 684 | * when protected only by rcu_read_lock() will result in infrequent |
| 685 | * but very ugly failures. |
Paul E. McKenney | b62730b | 2010-04-09 15:39:10 -0700 | [diff] [blame] | 686 | */ |
| 687 | #define rcu_dereference_protected(p, c) \ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 688 | __rcu_dereference_protected((p), (c), __rcu) |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 689 | |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 690 | |
| 691 | /** |
| 692 | * rcu_dereference() - fetch RCU-protected pointer for dereferencing |
| 693 | * @p: The pointer to read, prior to dereferencing |
| 694 | * |
| 695 | * This is a simple wrapper around rcu_dereference_check(). |
| 696 | */ |
| 697 | #define rcu_dereference(p) rcu_dereference_check(p, 0) |
| 698 | |
| 699 | /** |
| 700 | * rcu_dereference_bh() - fetch an RCU-bh-protected pointer for dereferencing |
| 701 | * @p: The pointer to read, prior to dereferencing |
| 702 | * |
| 703 | * Makes rcu_dereference_check() do the dirty work. |
| 704 | */ |
| 705 | #define rcu_dereference_bh(p) rcu_dereference_bh_check(p, 0) |
| 706 | |
| 707 | /** |
| 708 | * rcu_dereference_sched() - fetch RCU-sched-protected pointer for dereferencing |
| 709 | * @p: The pointer to read, prior to dereferencing |
| 710 | * |
| 711 | * Makes rcu_dereference_check() do the dirty work. |
| 712 | */ |
| 713 | #define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0) |
| 714 | |
| 715 | /** |
| 716 | * 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] | 717 | * |
Paul E. McKenney | 9b06e81 | 2005-05-01 08:59:04 -0700 | [diff] [blame] | 718 | * When synchronize_rcu() is invoked on one CPU while other CPUs |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 719 | * are within RCU read-side critical sections, then the |
Paul E. McKenney | 9b06e81 | 2005-05-01 08:59:04 -0700 | [diff] [blame] | 720 | * synchronize_rcu() is guaranteed to block until after all the other |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 721 | * CPUs exit their critical sections. Similarly, if call_rcu() is invoked |
| 722 | * on one CPU while other CPUs are within RCU read-side critical |
| 723 | * sections, invocation of the corresponding RCU callback is deferred |
| 724 | * until after the all the other CPUs exit their critical sections. |
| 725 | * |
| 726 | * Note, however, that RCU callbacks are permitted to run concurrently |
Paul E. McKenney | 77d8485 | 2010-07-08 17:38:59 -0700 | [diff] [blame] | 727 | * 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] | 728 | * is via the following sequence of events: (1) CPU 0 enters an RCU |
| 729 | * read-side critical section, (2) CPU 1 invokes call_rcu() to register |
| 730 | * an RCU callback, (3) CPU 0 exits the RCU read-side critical section, |
| 731 | * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU |
| 732 | * callback is invoked. This is legal, because the RCU read-side critical |
| 733 | * section that was running concurrently with the call_rcu() (and which |
| 734 | * therefore might be referencing something that the corresponding RCU |
| 735 | * callback would free up) has completed before the corresponding |
| 736 | * RCU callback is invoked. |
| 737 | * |
| 738 | * RCU read-side critical sections may be nested. Any deferred actions |
| 739 | * will be deferred until the outermost RCU read-side critical section |
| 740 | * completes. |
| 741 | * |
Paul E. McKenney | 9079fd7 | 2010-08-07 21:59:54 -0700 | [diff] [blame] | 742 | * You can avoid reading and understanding the next paragraph by |
| 743 | * following this rule: don't put anything in an rcu_read_lock() RCU |
| 744 | * read-side critical section that would block in a !PREEMPT kernel. |
| 745 | * But if you want the full story, read on! |
| 746 | * |
| 747 | * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU), it |
| 748 | * is illegal to block while in an RCU read-side critical section. In |
| 749 | * preemptible RCU implementations (TREE_PREEMPT_RCU and TINY_PREEMPT_RCU) |
| 750 | * in CONFIG_PREEMPT kernel builds, RCU read-side critical sections may |
| 751 | * be preempted, but explicit blocking is illegal. Finally, in preemptible |
| 752 | * RCU implementations in real-time (CONFIG_PREEMPT_RT) kernel builds, |
| 753 | * RCU read-side critical sections may be preempted and they may also |
| 754 | * block, but only when acquiring spinlocks that are subject to priority |
| 755 | * inheritance. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 756 | */ |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 757 | static inline void rcu_read_lock(void) |
| 758 | { |
| 759 | __rcu_read_lock(); |
| 760 | __acquire(RCU); |
Paul E. McKenney | d8ab29f | 2011-10-07 18:22:03 +0200 | [diff] [blame] | 761 | rcu_lock_acquire(&rcu_lock_map); |
Heiko Carstens | bde23c6 | 2012-02-01 10:30:46 -0800 | [diff] [blame] | 762 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
| 763 | "rcu_read_lock() used illegally while idle"); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 764 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 765 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 766 | /* |
| 767 | * So where is rcu_write_lock()? It does not exist, as there is no |
| 768 | * way for writers to lock out RCU readers. This is a feature, not |
| 769 | * a bug -- this property is what provides RCU's performance benefits. |
| 770 | * Of course, writers must coordinate with each other. The normal |
| 771 | * spinlock primitives work well for this, but any other technique may be |
| 772 | * used as well. RCU does not care how the writers keep out of each |
| 773 | * others' way, as long as they do so. |
| 774 | */ |
Paul E. McKenney | 3d76c08 | 2009-09-28 07:46:32 -0700 | [diff] [blame] | 775 | |
| 776 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 777 | * 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] | 778 | * |
| 779 | * See rcu_read_lock() for more information. |
| 780 | */ |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 781 | static inline void rcu_read_unlock(void) |
| 782 | { |
Heiko Carstens | bde23c6 | 2012-02-01 10:30:46 -0800 | [diff] [blame] | 783 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
| 784 | "rcu_read_unlock() used illegally while idle"); |
Paul E. McKenney | d8ab29f | 2011-10-07 18:22:03 +0200 | [diff] [blame] | 785 | rcu_lock_release(&rcu_lock_map); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 786 | __release(RCU); |
| 787 | __rcu_read_unlock(); |
| 788 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 789 | |
| 790 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 791 | * 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] | 792 | * |
| 793 | * 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] | 794 | * are being done using call_rcu_bh() or synchronize_rcu_bh(). Since |
| 795 | * both call_rcu_bh() and synchronize_rcu_bh() consider completion of a |
| 796 | * softirq handler to be a quiescent state, a process in RCU read-side |
| 797 | * critical section must be protected by disabling softirqs. Read-side |
| 798 | * critical sections in interrupt context can use just rcu_read_lock(), |
| 799 | * though this should at least be commented to avoid confusing people |
| 800 | * reading the code. |
Paul E. McKenney | 3842a08 | 2011-11-28 10:42:42 -0800 | [diff] [blame] | 801 | * |
| 802 | * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh() |
| 803 | * must occur in the same context, for example, it is illegal to invoke |
| 804 | * rcu_read_unlock_bh() from one task if the matching rcu_read_lock_bh() |
| 805 | * was invoked from some other task. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 806 | */ |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 807 | static inline void rcu_read_lock_bh(void) |
| 808 | { |
Paul E. McKenney | 6206ab9 | 2011-08-01 06:22:11 -0700 | [diff] [blame] | 809 | local_bh_disable(); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 810 | __acquire(RCU_BH); |
Paul E. McKenney | d8ab29f | 2011-10-07 18:22:03 +0200 | [diff] [blame] | 811 | rcu_lock_acquire(&rcu_bh_lock_map); |
Heiko Carstens | bde23c6 | 2012-02-01 10:30:46 -0800 | [diff] [blame] | 812 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
| 813 | "rcu_read_lock_bh() used illegally while idle"); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 814 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 815 | |
| 816 | /* |
| 817 | * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section |
| 818 | * |
| 819 | * See rcu_read_lock_bh() for more information. |
| 820 | */ |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 821 | static inline void rcu_read_unlock_bh(void) |
| 822 | { |
Heiko Carstens | bde23c6 | 2012-02-01 10:30:46 -0800 | [diff] [blame] | 823 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
| 824 | "rcu_read_unlock_bh() used illegally while idle"); |
Paul E. McKenney | d8ab29f | 2011-10-07 18:22:03 +0200 | [diff] [blame] | 825 | rcu_lock_release(&rcu_bh_lock_map); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 826 | __release(RCU_BH); |
Paul E. McKenney | 6206ab9 | 2011-08-01 06:22:11 -0700 | [diff] [blame] | 827 | local_bh_enable(); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 828 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 829 | |
| 830 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 831 | * 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] | 832 | * |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 833 | * This is equivalent of rcu_read_lock(), but to be used when updates |
| 834 | * are being done using call_rcu_sched() or synchronize_rcu_sched(). |
| 835 | * Read-side critical sections can also be introduced by anything that |
| 836 | * disables preemption, including local_irq_disable() and friends. |
Paul E. McKenney | 3842a08 | 2011-11-28 10:42:42 -0800 | [diff] [blame] | 837 | * |
| 838 | * Note that rcu_read_lock_sched() and the matching rcu_read_unlock_sched() |
| 839 | * must occur in the same context, for example, it is illegal to invoke |
| 840 | * rcu_read_unlock_sched() from process context if the matching |
| 841 | * rcu_read_lock_sched() was invoked from an NMI handler. |
Mathieu Desnoyers | 1c50b72 | 2008-09-29 11:06:46 -0400 | [diff] [blame] | 842 | */ |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 843 | static inline void rcu_read_lock_sched(void) |
| 844 | { |
| 845 | preempt_disable(); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 846 | __acquire(RCU_SCHED); |
Paul E. McKenney | d8ab29f | 2011-10-07 18:22:03 +0200 | [diff] [blame] | 847 | rcu_lock_acquire(&rcu_sched_lock_map); |
Heiko Carstens | bde23c6 | 2012-02-01 10:30:46 -0800 | [diff] [blame] | 848 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
| 849 | "rcu_read_lock_sched() used illegally while idle"); |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 850 | } |
Paul E. McKenney | 1eba8f8 | 2009-09-23 09:50:42 -0700 | [diff] [blame] | 851 | |
| 852 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ |
Paul E. McKenney | 7c614d6 | 2009-08-24 09:42:00 -0700 | [diff] [blame] | 853 | static inline notrace void rcu_read_lock_sched_notrace(void) |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 854 | { |
| 855 | preempt_disable_notrace(); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 856 | __acquire(RCU_SCHED); |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 857 | } |
Mathieu Desnoyers | 1c50b72 | 2008-09-29 11:06:46 -0400 | [diff] [blame] | 858 | |
| 859 | /* |
| 860 | * rcu_read_unlock_sched - marks the end of a RCU-classic critical section |
| 861 | * |
| 862 | * See rcu_read_lock_sched for more information. |
| 863 | */ |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 864 | static inline void rcu_read_unlock_sched(void) |
| 865 | { |
Heiko Carstens | bde23c6 | 2012-02-01 10:30:46 -0800 | [diff] [blame] | 866 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
| 867 | "rcu_read_unlock_sched() used illegally while idle"); |
Paul E. McKenney | d8ab29f | 2011-10-07 18:22:03 +0200 | [diff] [blame] | 868 | rcu_lock_release(&rcu_sched_lock_map); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 869 | __release(RCU_SCHED); |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 870 | preempt_enable(); |
| 871 | } |
Paul E. McKenney | 1eba8f8 | 2009-09-23 09:50:42 -0700 | [diff] [blame] | 872 | |
| 873 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ |
Paul E. McKenney | 7c614d6 | 2009-08-24 09:42:00 -0700 | [diff] [blame] | 874 | static inline notrace void rcu_read_unlock_sched_notrace(void) |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 875 | { |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 876 | __release(RCU_SCHED); |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 877 | preempt_enable_notrace(); |
| 878 | } |
Mathieu Desnoyers | 1c50b72 | 2008-09-29 11:06:46 -0400 | [diff] [blame] | 879 | |
Mathieu Desnoyers | 1c50b72 | 2008-09-29 11:06:46 -0400 | [diff] [blame] | 880 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 881 | * rcu_assign_pointer() - assign to RCU-protected pointer |
| 882 | * @p: pointer to assign to |
| 883 | * @v: value to assign (publish) |
Paul E. McKenney | c26d34a | 2010-02-22 17:04:46 -0800 | [diff] [blame] | 884 | * |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 885 | * Assigns the specified value to the specified RCU-protected |
| 886 | * pointer, ensuring that any concurrent RCU readers will see |
Paul E. McKenney | e9023c4 | 2012-05-16 15:51:08 -0700 | [diff] [blame] | 887 | * any prior initialization. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 888 | * |
| 889 | * Inserts memory barriers on architectures that require them |
Paul E. McKenney | 6846c0c | 2011-07-31 22:33:02 -0700 | [diff] [blame] | 890 | * (which is most of them), and also prevents the compiler from |
| 891 | * reordering the code that initializes the structure after the pointer |
| 892 | * assignment. More importantly, this call documents which pointers |
| 893 | * will be dereferenced by RCU read-side code. |
| 894 | * |
| 895 | * In some special cases, you may use RCU_INIT_POINTER() instead |
| 896 | * of rcu_assign_pointer(). RCU_INIT_POINTER() is a bit faster due |
| 897 | * to the fact that it does not constrain either the CPU or the compiler. |
| 898 | * That said, using RCU_INIT_POINTER() when you should have used |
| 899 | * rcu_assign_pointer() is a very bad thing that results in |
| 900 | * impossible-to-diagnose memory corruption. So please be careful. |
| 901 | * See the RCU_INIT_POINTER() comment header for details. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 902 | */ |
Paul E. McKenney | d99c4f6 | 2008-02-06 01:37:25 -0800 | [diff] [blame] | 903 | #define rcu_assign_pointer(p, v) \ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 904 | __rcu_assign_pointer((p), (v), __rcu) |
| 905 | |
| 906 | /** |
| 907 | * RCU_INIT_POINTER() - initialize an RCU protected pointer |
| 908 | * |
Paul E. McKenney | 6846c0c | 2011-07-31 22:33:02 -0700 | [diff] [blame] | 909 | * Initialize an RCU-protected pointer in special cases where readers |
| 910 | * do not need ordering constraints on the CPU or the compiler. These |
| 911 | * special cases are: |
| 912 | * |
| 913 | * 1. This use of RCU_INIT_POINTER() is NULLing out the pointer -or- |
| 914 | * 2. The caller has taken whatever steps are required to prevent |
| 915 | * RCU readers from concurrently accessing this pointer -or- |
| 916 | * 3. The referenced data structure has already been exposed to |
| 917 | * readers either at compile time or via rcu_assign_pointer() -and- |
| 918 | * a. You have not made -any- reader-visible changes to |
| 919 | * this structure since then -or- |
| 920 | * b. It is OK for readers accessing this structure from its |
| 921 | * new location to see the old state of the structure. (For |
| 922 | * example, the changes were to statistical counters or to |
| 923 | * other state where exact synchronization is not required.) |
| 924 | * |
| 925 | * Failure to follow these rules governing use of RCU_INIT_POINTER() will |
| 926 | * result in impossible-to-diagnose memory corruption. As in the structures |
| 927 | * will look OK in crash dumps, but any concurrent RCU readers might |
| 928 | * see pre-initialized values of the referenced data structure. So |
| 929 | * please be very careful how you use RCU_INIT_POINTER()!!! |
| 930 | * |
| 931 | * If you are creating an RCU-protected linked structure that is accessed |
| 932 | * by a single external-to-structure RCU-protected pointer, then you may |
| 933 | * use RCU_INIT_POINTER() to initialize the internal RCU-protected |
| 934 | * pointers, but you must use rcu_assign_pointer() to initialize the |
| 935 | * external-to-structure pointer -after- you have completely initialized |
| 936 | * the reader-accessible portions of the linked structure. |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 937 | */ |
| 938 | #define RCU_INIT_POINTER(p, v) \ |
Paul E. McKenney | d1b88eb | 2012-05-16 15:42:30 -0700 | [diff] [blame] | 939 | do { \ |
| 940 | p = (typeof(*v) __force __rcu *)(v); \ |
| 941 | } while (0) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 942 | |
Paul E. McKenney | 172708d | 2012-05-16 15:23:45 -0700 | [diff] [blame] | 943 | /** |
| 944 | * RCU_POINTER_INITIALIZER() - statically initialize an RCU protected pointer |
| 945 | * |
| 946 | * GCC-style initialization for an RCU-protected pointer in a structure field. |
| 947 | */ |
| 948 | #define RCU_POINTER_INITIALIZER(p, v) \ |
| 949 | .p = (typeof(*v) __force __rcu *)(v) |
Lai Jiangshan | 9ab1544 | 2011-03-18 11:15:47 +0800 | [diff] [blame] | 950 | |
Jan Engelhardt | d8169d4 | 2012-04-19 11:44:39 -0700 | [diff] [blame] | 951 | /* |
| 952 | * Does the specified offset indicate that the corresponding rcu_head |
| 953 | * structure can be handled by kfree_rcu()? |
| 954 | */ |
| 955 | #define __is_kfree_rcu_offset(offset) ((offset) < 4096) |
| 956 | |
| 957 | /* |
| 958 | * Helper macro for kfree_rcu() to prevent argument-expansion eyestrain. |
| 959 | */ |
| 960 | #define __kfree_rcu(head, offset) \ |
| 961 | do { \ |
| 962 | BUILD_BUG_ON(!__is_kfree_rcu_offset(offset)); \ |
Paul E. McKenney | 4fa3b6c | 2012-06-05 15:53:53 -0700 | [diff] [blame] | 963 | kfree_call_rcu(head, (void (*)(struct rcu_head *))(unsigned long)(offset)); \ |
Jan Engelhardt | d8169d4 | 2012-04-19 11:44:39 -0700 | [diff] [blame] | 964 | } while (0) |
| 965 | |
Lai Jiangshan | 9ab1544 | 2011-03-18 11:15:47 +0800 | [diff] [blame] | 966 | /** |
| 967 | * kfree_rcu() - kfree an object after a grace period. |
| 968 | * @ptr: pointer to kfree |
| 969 | * @rcu_head: the name of the struct rcu_head within the type of @ptr. |
| 970 | * |
| 971 | * Many rcu callbacks functions just call kfree() on the base structure. |
| 972 | * These functions are trivial, but their size adds up, and furthermore |
| 973 | * when they are used in a kernel module, that module must invoke the |
| 974 | * high-latency rcu_barrier() function at module-unload time. |
| 975 | * |
| 976 | * The kfree_rcu() function handles this issue. Rather than encoding a |
| 977 | * function address in the embedded rcu_head structure, kfree_rcu() instead |
| 978 | * encodes the offset of the rcu_head structure within the base structure. |
| 979 | * Because the functions are not allowed in the low-order 4096 bytes of |
| 980 | * kernel virtual memory, offsets up to 4095 bytes can be accommodated. |
| 981 | * If the offset is larger than 4095 bytes, a compile-time error will |
| 982 | * be generated in __kfree_rcu(). If this error is triggered, you can |
| 983 | * either fall back to use of call_rcu() or rearrange the structure to |
| 984 | * position the rcu_head structure into the first 4096 bytes. |
| 985 | * |
| 986 | * Note that the allowable offset might decrease in the future, for example, |
| 987 | * to allow something like kmem_cache_free_rcu(). |
Jan Engelhardt | d8169d4 | 2012-04-19 11:44:39 -0700 | [diff] [blame] | 988 | * |
| 989 | * The BUILD_BUG_ON check must not involve any function calls, hence the |
| 990 | * checks are done in macros here. |
Lai Jiangshan | 9ab1544 | 2011-03-18 11:15:47 +0800 | [diff] [blame] | 991 | */ |
| 992 | #define kfree_rcu(ptr, rcu_head) \ |
| 993 | __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head)) |
| 994 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 995 | #endif /* __LINUX_RCUPDATE_H */ |