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 |
Paul E. McKenney | 87de1cf | 2013-12-03 10:02:52 -0800 | [diff] [blame] | 15 | * along with this program; if not, you can access it online at |
| 16 | * http://www.gnu.org/licenses/gpl-2.0.html. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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> |
Paul E. McKenney | 88c1863 | 2013-12-16 13:24:32 -0800 | [diff] [blame] | 47 | #include <asm/barrier.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 48 | |
Paul Gortmaker | 7a75474 | 2014-02-11 16:10:12 -0500 | [diff] [blame] | 49 | extern int rcu_expedited; /* for sysctl */ |
Dave Young | e5ab677 | 2010-03-10 15:24:05 -0800 | [diff] [blame] | 50 | #ifdef CONFIG_RCU_TORTURE_TEST |
| 51 | extern int rcutorture_runnable; /* for sysctl */ |
| 52 | #endif /* #ifdef CONFIG_RCU_TORTURE_TEST */ |
| 53 | |
Paul E. McKenney | ad0dc7f | 2014-02-19 10:51:42 -0800 | [diff] [blame] | 54 | enum rcutorture_type { |
| 55 | RCU_FLAVOR, |
| 56 | RCU_BH_FLAVOR, |
| 57 | RCU_SCHED_FLAVOR, |
| 58 | SRCU_FLAVOR, |
| 59 | INVALID_RCU_FLAVOR |
| 60 | }; |
| 61 | |
Paul E. McKenney | 4a29865 | 2011-04-03 21:33:51 -0700 | [diff] [blame] | 62 | #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) |
Paul E. McKenney | ad0dc7f | 2014-02-19 10:51:42 -0800 | [diff] [blame] | 63 | void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, |
| 64 | unsigned long *gpnum, unsigned long *completed); |
Teodora Baluta | 584dc4c | 2013-11-11 17:11:23 +0200 | [diff] [blame] | 65 | void rcutorture_record_test_transition(void); |
| 66 | void rcutorture_record_progress(unsigned long vernum); |
| 67 | void do_trace_rcu_torture_read(const char *rcutorturename, |
| 68 | struct rcu_head *rhp, |
| 69 | unsigned long secs, |
| 70 | unsigned long c_old, |
| 71 | unsigned long c); |
Paul E. McKenney | 4a29865 | 2011-04-03 21:33:51 -0700 | [diff] [blame] | 72 | #else |
Paul E. McKenney | ad0dc7f | 2014-02-19 10:51:42 -0800 | [diff] [blame] | 73 | static inline void rcutorture_get_gp_data(enum rcutorture_type test_type, |
| 74 | int *flags, |
| 75 | unsigned long *gpnum, |
| 76 | unsigned long *completed) |
| 77 | { |
| 78 | *flags = 0; |
| 79 | *gpnum = 0; |
| 80 | *completed = 0; |
| 81 | } |
Paul E. McKenney | 4a29865 | 2011-04-03 21:33:51 -0700 | [diff] [blame] | 82 | static inline void rcutorture_record_test_transition(void) |
| 83 | { |
| 84 | } |
| 85 | static inline void rcutorture_record_progress(unsigned long vernum) |
| 86 | { |
| 87 | } |
Paul E. McKenney | 91afaf3 | 2011-10-02 07:44:32 -0700 | [diff] [blame] | 88 | #ifdef CONFIG_RCU_TRACE |
Teodora Baluta | 584dc4c | 2013-11-11 17:11:23 +0200 | [diff] [blame] | 89 | void do_trace_rcu_torture_read(const char *rcutorturename, |
| 90 | struct rcu_head *rhp, |
| 91 | unsigned long secs, |
| 92 | unsigned long c_old, |
| 93 | unsigned long c); |
Paul E. McKenney | 91afaf3 | 2011-10-02 07:44:32 -0700 | [diff] [blame] | 94 | #else |
Paul E. McKenney | 5249453 | 2012-11-14 16:26:40 -0800 | [diff] [blame] | 95 | #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ |
| 96 | do { } while (0) |
Paul E. McKenney | 91afaf3 | 2011-10-02 07:44:32 -0700 | [diff] [blame] | 97 | #endif |
Paul E. McKenney | 4a29865 | 2011-04-03 21:33:51 -0700 | [diff] [blame] | 98 | #endif |
| 99 | |
Tejun Heo | e27fc96 | 2010-11-22 21:36:11 -0800 | [diff] [blame] | 100 | #define UINT_CMP_GE(a, b) (UINT_MAX / 2 >= (a) - (b)) |
| 101 | #define UINT_CMP_LT(a, b) (UINT_MAX / 2 < (a) - (b)) |
Paul E. McKenney | a3dc3fb | 2010-08-13 16:16:25 -0700 | [diff] [blame] | 102 | #define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b)) |
| 103 | #define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b)) |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 104 | #define ulong2long(a) (*(long *)(&(a))) |
Paul E. McKenney | a3dc3fb | 2010-08-13 16:16:25 -0700 | [diff] [blame] | 105 | |
Paul E. McKenney | 03b042b | 2009-06-25 09:08:16 -0700 | [diff] [blame] | 106 | /* Exported common interfaces */ |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 107 | |
| 108 | #ifdef CONFIG_PREEMPT_RCU |
| 109 | |
| 110 | /** |
| 111 | * call_rcu() - Queue an RCU callback for invocation after a grace period. |
| 112 | * @head: structure to be used for queueing the RCU updates. |
| 113 | * @func: actual callback function to be invoked after the grace period |
| 114 | * |
| 115 | * The callback function will be invoked some time after a full grace |
| 116 | * period elapses, in other words after all pre-existing RCU read-side |
| 117 | * critical sections have completed. However, the callback function |
| 118 | * might well execute concurrently with RCU read-side critical sections |
| 119 | * that started after call_rcu() was invoked. RCU read-side critical |
| 120 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), |
| 121 | * and may be nested. |
Paul E. McKenney | f0a0e6f | 2012-10-23 13:47:01 -0700 | [diff] [blame] | 122 | * |
| 123 | * Note that all CPUs must agree that the grace period extended beyond |
| 124 | * all pre-existing RCU read-side critical section. On systems with more |
| 125 | * than one CPU, this means that when "func()" is invoked, each CPU is |
| 126 | * guaranteed to have executed a full memory barrier since the end of its |
| 127 | * last RCU read-side critical section whose beginning preceded the call |
| 128 | * to call_rcu(). It also means that each CPU executing an RCU read-side |
| 129 | * critical section that continues beyond the start of "func()" must have |
| 130 | * executed a memory barrier after the call_rcu() but before the beginning |
| 131 | * of that RCU read-side critical section. Note that these guarantees |
| 132 | * include CPUs that are offline, idle, or executing in user mode, as |
| 133 | * well as CPUs that are executing in the kernel. |
| 134 | * |
| 135 | * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the |
| 136 | * resulting RCU callback function "func()", then both CPU A and CPU B are |
| 137 | * guaranteed to execute a full memory barrier during the time interval |
| 138 | * between the call to call_rcu() and the invocation of "func()" -- even |
| 139 | * if CPU A and CPU B are the same CPU (but again only if the system has |
| 140 | * more than one CPU). |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 141 | */ |
Teodora Baluta | 584dc4c | 2013-11-11 17:11:23 +0200 | [diff] [blame] | 142 | void call_rcu(struct rcu_head *head, |
| 143 | void (*func)(struct rcu_head *head)); |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 144 | |
| 145 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
| 146 | |
| 147 | /* In classic RCU, call_rcu() is just call_rcu_sched(). */ |
| 148 | #define call_rcu call_rcu_sched |
| 149 | |
| 150 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ |
| 151 | |
| 152 | /** |
| 153 | * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period. |
| 154 | * @head: structure to be used for queueing the RCU updates. |
| 155 | * @func: actual callback function to be invoked after the grace period |
| 156 | * |
| 157 | * The callback function will be invoked some time after a full grace |
| 158 | * period elapses, in other words after all currently executing RCU |
| 159 | * read-side critical sections have completed. call_rcu_bh() assumes |
| 160 | * that the read-side critical sections end on completion of a softirq |
| 161 | * handler. This means that read-side critical sections in process |
| 162 | * context must not be interrupted by softirqs. This interface is to be |
| 163 | * used when most of the read-side critical sections are in softirq context. |
| 164 | * RCU read-side critical sections are delimited by : |
| 165 | * - rcu_read_lock() and rcu_read_unlock(), if in interrupt context. |
| 166 | * OR |
| 167 | * - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context. |
| 168 | * These may be nested. |
Paul E. McKenney | f0a0e6f | 2012-10-23 13:47:01 -0700 | [diff] [blame] | 169 | * |
| 170 | * See the description of call_rcu() for more detailed information on |
| 171 | * memory ordering guarantees. |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 172 | */ |
Teodora Baluta | 584dc4c | 2013-11-11 17:11:23 +0200 | [diff] [blame] | 173 | void call_rcu_bh(struct rcu_head *head, |
| 174 | void (*func)(struct rcu_head *head)); |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 175 | |
| 176 | /** |
| 177 | * call_rcu_sched() - Queue an RCU for invocation after sched grace period. |
| 178 | * @head: structure to be used for queueing the RCU updates. |
| 179 | * @func: actual callback function to be invoked after the grace period |
| 180 | * |
| 181 | * The callback function will be invoked some time after a full grace |
| 182 | * period elapses, in other words after all currently executing RCU |
| 183 | * read-side critical sections have completed. call_rcu_sched() assumes |
| 184 | * that the read-side critical sections end on enabling of preemption |
| 185 | * or on voluntary preemption. |
| 186 | * RCU read-side critical sections are delimited by : |
| 187 | * - rcu_read_lock_sched() and rcu_read_unlock_sched(), |
| 188 | * OR |
| 189 | * anything that disables preemption. |
| 190 | * These may be nested. |
Paul E. McKenney | f0a0e6f | 2012-10-23 13:47:01 -0700 | [diff] [blame] | 191 | * |
| 192 | * See the description of call_rcu() for more detailed information on |
| 193 | * memory ordering guarantees. |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 194 | */ |
Teodora Baluta | 584dc4c | 2013-11-11 17:11:23 +0200 | [diff] [blame] | 195 | void call_rcu_sched(struct rcu_head *head, |
| 196 | void (*func)(struct rcu_head *rcu)); |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 197 | |
Teodora Baluta | 584dc4c | 2013-11-11 17:11:23 +0200 | [diff] [blame] | 198 | void synchronize_sched(void); |
Paul E. McKenney | 03b042b | 2009-06-25 09:08:16 -0700 | [diff] [blame] | 199 | |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 200 | /** |
| 201 | * call_rcu_tasks() - Queue an RCU for invocation task-based grace period |
| 202 | * @head: structure to be used for queueing the RCU updates. |
| 203 | * @func: actual callback function to be invoked after the grace period |
| 204 | * |
| 205 | * The callback function will be invoked some time after a full grace |
| 206 | * period elapses, in other words after all currently executing RCU |
| 207 | * read-side critical sections have completed. call_rcu_tasks() assumes |
| 208 | * that the read-side critical sections end at a voluntary context |
| 209 | * switch (not a preemption!), entry into idle, or transition to usermode |
| 210 | * execution. As such, there are no read-side primitives analogous to |
| 211 | * rcu_read_lock() and rcu_read_unlock() because this primitive is intended |
| 212 | * to determine that all tasks have passed through a safe state, not so |
| 213 | * much for data-strcuture synchronization. |
| 214 | * |
| 215 | * See the description of call_rcu() for more detailed information on |
| 216 | * memory ordering guarantees. |
| 217 | */ |
| 218 | void call_rcu_tasks(struct rcu_head *head, void (*func)(struct rcu_head *head)); |
Paul E. McKenney | 53c6d4e | 2014-07-01 12:22:23 -0700 | [diff] [blame^] | 219 | void synchronize_rcu_tasks(void); |
| 220 | void rcu_barrier_tasks(void); |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 221 | |
Paul E. McKenney | a3dc3fb | 2010-08-13 16:16:25 -0700 | [diff] [blame] | 222 | #ifdef CONFIG_PREEMPT_RCU |
| 223 | |
Teodora Baluta | 584dc4c | 2013-11-11 17:11:23 +0200 | [diff] [blame] | 224 | void __rcu_read_lock(void); |
| 225 | void __rcu_read_unlock(void); |
| 226 | void rcu_read_unlock_special(struct task_struct *t); |
Paul E. McKenney | 7b0b759 | 2010-08-17 14:18:46 -0700 | [diff] [blame] | 227 | void synchronize_rcu(void); |
| 228 | |
Paul E. McKenney | a3dc3fb | 2010-08-13 16:16:25 -0700 | [diff] [blame] | 229 | /* |
| 230 | * Defined as a macro as it is a very low level header included from |
| 231 | * areas that don't even know about current. This gives the rcu_read_lock() |
| 232 | * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other |
| 233 | * types of kernel builds, the rcu_read_lock() nesting depth is unknowable. |
| 234 | */ |
| 235 | #define rcu_preempt_depth() (current->rcu_read_lock_nesting) |
| 236 | |
Paul E. McKenney | 7b0b759 | 2010-08-17 14:18:46 -0700 | [diff] [blame] | 237 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
| 238 | |
| 239 | static inline void __rcu_read_lock(void) |
| 240 | { |
| 241 | preempt_disable(); |
| 242 | } |
| 243 | |
| 244 | static inline void __rcu_read_unlock(void) |
| 245 | { |
| 246 | preempt_enable(); |
| 247 | } |
| 248 | |
| 249 | static inline void synchronize_rcu(void) |
| 250 | { |
| 251 | synchronize_sched(); |
| 252 | } |
| 253 | |
| 254 | static inline int rcu_preempt_depth(void) |
| 255 | { |
| 256 | return 0; |
| 257 | } |
| 258 | |
| 259 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ |
| 260 | |
| 261 | /* Internal to kernel */ |
Teodora Baluta | 584dc4c | 2013-11-11 17:11:23 +0200 | [diff] [blame] | 262 | void rcu_init(void); |
| 263 | void rcu_sched_qs(int cpu); |
| 264 | void rcu_bh_qs(int cpu); |
| 265 | void rcu_check_callbacks(int cpu, int user); |
Paul E. McKenney | 7b0b759 | 2010-08-17 14:18:46 -0700 | [diff] [blame] | 266 | struct notifier_block; |
Teodora Baluta | 584dc4c | 2013-11-11 17:11:23 +0200 | [diff] [blame] | 267 | void rcu_idle_enter(void); |
| 268 | void rcu_idle_exit(void); |
| 269 | void rcu_irq_enter(void); |
| 270 | void rcu_irq_exit(void); |
Frederic Weisbecker | 2b1d502 | 2012-07-11 20:26:30 +0200 | [diff] [blame] | 271 | |
Rik van Riel | 61f38db | 2014-04-26 23:15:35 -0700 | [diff] [blame] | 272 | #ifdef CONFIG_RCU_STALL_COMMON |
| 273 | void rcu_sysrq_start(void); |
| 274 | void rcu_sysrq_end(void); |
| 275 | #else /* #ifdef CONFIG_RCU_STALL_COMMON */ |
| 276 | static inline void rcu_sysrq_start(void) |
| 277 | { |
| 278 | } |
| 279 | static inline void rcu_sysrq_end(void) |
| 280 | { |
| 281 | } |
| 282 | #endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */ |
| 283 | |
Frederic Weisbecker | 2b1d502 | 2012-07-11 20:26:30 +0200 | [diff] [blame] | 284 | #ifdef CONFIG_RCU_USER_QS |
Teodora Baluta | 584dc4c | 2013-11-11 17:11:23 +0200 | [diff] [blame] | 285 | void rcu_user_enter(void); |
| 286 | void rcu_user_exit(void); |
Frederic Weisbecker | 2b1d502 | 2012-07-11 20:26:30 +0200 | [diff] [blame] | 287 | #else |
| 288 | static inline void rcu_user_enter(void) { } |
| 289 | static inline void rcu_user_exit(void) { } |
Frederic Weisbecker | 4d9a5d4 | 2012-10-11 01:47:16 +0200 | [diff] [blame] | 290 | static inline void rcu_user_hooks_switch(struct task_struct *prev, |
| 291 | struct task_struct *next) { } |
Frederic Weisbecker | 2b1d502 | 2012-07-11 20:26:30 +0200 | [diff] [blame] | 292 | #endif /* CONFIG_RCU_USER_QS */ |
| 293 | |
Paul E. McKenney | 8a2ecf4 | 2012-02-02 15:42:04 -0800 | [diff] [blame] | 294 | /** |
| 295 | * RCU_NONIDLE - Indicate idle-loop code that needs RCU readers |
| 296 | * @a: Code that RCU needs to pay attention to. |
| 297 | * |
| 298 | * RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden |
| 299 | * in the inner idle loop, that is, between the rcu_idle_enter() and |
| 300 | * the rcu_idle_exit() -- RCU will happily ignore any such read-side |
| 301 | * critical sections. However, things like powertop need tracepoints |
| 302 | * in the inner idle loop. |
| 303 | * |
| 304 | * This macro provides the way out: RCU_NONIDLE(do_something_with_RCU()) |
| 305 | * will tell RCU that it needs to pay attending, invoke its argument |
| 306 | * (in this example, a call to the do_something_with_RCU() function), |
| 307 | * and then tell RCU to go back to ignoring this CPU. It is permissible |
| 308 | * to nest RCU_NONIDLE() wrappers, but the nesting level is currently |
| 309 | * quite limited. If deeper nesting is required, it will be necessary |
| 310 | * to adjust DYNTICK_TASK_NESTING_VALUE accordingly. |
Paul E. McKenney | 8a2ecf4 | 2012-02-02 15:42:04 -0800 | [diff] [blame] | 311 | */ |
| 312 | #define RCU_NONIDLE(a) \ |
| 313 | do { \ |
Paul E. McKenney | b4270ee | 2012-07-31 10:12:48 -0700 | [diff] [blame] | 314 | rcu_irq_enter(); \ |
Paul E. McKenney | 8a2ecf4 | 2012-02-02 15:42:04 -0800 | [diff] [blame] | 315 | do { a; } while (0); \ |
Paul E. McKenney | b4270ee | 2012-07-31 10:12:48 -0700 | [diff] [blame] | 316 | rcu_irq_exit(); \ |
Paul E. McKenney | 8a2ecf4 | 2012-02-02 15:42:04 -0800 | [diff] [blame] | 317 | } while (0) |
| 318 | |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 319 | /* |
| 320 | * Note a voluntary context switch for RCU-tasks benefit. This is a |
| 321 | * macro rather than an inline function to avoid #include hell. |
| 322 | */ |
| 323 | #ifdef CONFIG_TASKS_RCU |
| 324 | #define rcu_note_voluntary_context_switch(t) \ |
| 325 | do { \ |
| 326 | preempt_disable(); /* Exclude synchronize_sched(); */ \ |
| 327 | if (ACCESS_ONCE((t)->rcu_tasks_holdout)) \ |
| 328 | ACCESS_ONCE((t)->rcu_tasks_holdout) = false; \ |
| 329 | preempt_enable(); \ |
| 330 | } while (0) |
| 331 | #else /* #ifdef CONFIG_TASKS_RCU */ |
| 332 | #define rcu_note_voluntary_context_switch(t) do { } while (0) |
| 333 | #endif /* #else #ifdef CONFIG_TASKS_RCU */ |
| 334 | |
Paul E. McKenney | bde6c3a | 2014-07-01 11:26:57 -0700 | [diff] [blame] | 335 | /** |
| 336 | * cond_resched_rcu_qs - Report potential quiescent states to RCU |
| 337 | * |
| 338 | * This macro resembles cond_resched(), except that it is defined to |
| 339 | * report potential quiescent states to RCU-tasks even if the cond_resched() |
| 340 | * machinery were to be shut off, as some advocate for PREEMPT kernels. |
| 341 | */ |
| 342 | #define cond_resched_rcu_qs() \ |
| 343 | do { \ |
| 344 | rcu_note_voluntary_context_switch(current); \ |
| 345 | cond_resched(); \ |
| 346 | } while (0) |
| 347 | |
Paul E. McKenney | cc6783f | 2013-09-06 17:39:49 -0700 | [diff] [blame] | 348 | #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) |
Teodora Baluta | 584dc4c | 2013-11-11 17:11:23 +0200 | [diff] [blame] | 349 | bool __rcu_is_watching(void); |
Paul E. McKenney | cc6783f | 2013-09-06 17:39:49 -0700 | [diff] [blame] | 350 | #endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) */ |
| 351 | |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 352 | /* |
| 353 | * Infrastructure to implement the synchronize_() primitives in |
| 354 | * TREE_RCU and rcu_barrier_() primitives in TINY_RCU. |
| 355 | */ |
| 356 | |
| 357 | typedef void call_rcu_func_t(struct rcu_head *head, |
| 358 | void (*func)(struct rcu_head *head)); |
| 359 | void wait_rcu_gp(call_rcu_func_t crf); |
| 360 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 361 | #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 362 | #include <linux/rcutree.h> |
Paul E. McKenney | 127781d | 2013-03-27 08:44:00 -0700 | [diff] [blame] | 363 | #elif defined(CONFIG_TINY_RCU) |
Paul E. McKenney | 9b1d82f | 2009-10-25 19:03:50 -0700 | [diff] [blame] | 364 | #include <linux/rcutiny.h> |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 365 | #else |
| 366 | #error "Unknown RCU implementation specified to kernel configuration" |
Paul E. McKenney | 6b3ef48 | 2009-08-22 13:56:53 -0700 | [diff] [blame] | 367 | #endif |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 368 | |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 369 | /* |
| 370 | * init_rcu_head_on_stack()/destroy_rcu_head_on_stack() are needed for dynamic |
| 371 | * initialization and destruction of rcu_head on the stack. rcu_head structures |
| 372 | * allocated dynamically in the heap or defined statically don't need any |
| 373 | * initialization. |
| 374 | */ |
| 375 | #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD |
Paul E. McKenney | 546a9d8 | 2014-06-19 14:57:10 -0700 | [diff] [blame] | 376 | void init_rcu_head(struct rcu_head *head); |
| 377 | void destroy_rcu_head(struct rcu_head *head); |
Teodora Baluta | 584dc4c | 2013-11-11 17:11:23 +0200 | [diff] [blame] | 378 | void init_rcu_head_on_stack(struct rcu_head *head); |
| 379 | void destroy_rcu_head_on_stack(struct rcu_head *head); |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 380 | #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
Paul E. McKenney | 546a9d8 | 2014-06-19 14:57:10 -0700 | [diff] [blame] | 381 | static inline void init_rcu_head(struct rcu_head *head) |
| 382 | { |
| 383 | } |
| 384 | |
| 385 | static inline void destroy_rcu_head(struct rcu_head *head) |
| 386 | { |
| 387 | } |
| 388 | |
Mathieu Desnoyers | 4376030 | 2010-04-17 08:48:39 -0400 | [diff] [blame] | 389 | static inline void init_rcu_head_on_stack(struct rcu_head *head) |
| 390 | { |
| 391 | } |
| 392 | |
| 393 | static inline void destroy_rcu_head_on_stack(struct rcu_head *head) |
| 394 | { |
| 395 | } |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 396 | #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
Mathieu Desnoyers | 4376030 | 2010-04-17 08:48:39 -0400 | [diff] [blame] | 397 | |
Paul E. McKenney | c0d6d01 | 2012-01-23 12:41:26 -0800 | [diff] [blame] | 398 | #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) |
| 399 | bool rcu_lockdep_current_cpu_online(void); |
| 400 | #else /* #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ |
| 401 | static inline bool rcu_lockdep_current_cpu_online(void) |
| 402 | { |
| 403 | return 1; |
| 404 | } |
| 405 | #endif /* #else #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ |
| 406 | |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 407 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 408 | |
Frederic Weisbecker | 00f49e5 | 2011-10-07 18:22:02 +0200 | [diff] [blame] | 409 | static inline void rcu_lock_acquire(struct lockdep_map *map) |
| 410 | { |
Oleg Nesterov | fb9edbe | 2014-01-20 19:20:06 +0100 | [diff] [blame] | 411 | lock_acquire(map, 0, 0, 2, 0, NULL, _THIS_IP_); |
Frederic Weisbecker | 00f49e5 | 2011-10-07 18:22:02 +0200 | [diff] [blame] | 412 | } |
| 413 | |
| 414 | static inline void rcu_lock_release(struct lockdep_map *map) |
| 415 | { |
Frederic Weisbecker | 00f49e5 | 2011-10-07 18:22:02 +0200 | [diff] [blame] | 416 | lock_release(map, 1, _THIS_IP_); |
| 417 | } |
| 418 | |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 419 | extern struct lockdep_map rcu_lock_map; |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 420 | extern struct lockdep_map rcu_bh_lock_map; |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 421 | extern struct lockdep_map rcu_sched_lock_map; |
Paul E. McKenney | 24ef659 | 2013-10-28 09:22:24 -0700 | [diff] [blame] | 422 | extern struct lockdep_map rcu_callback_map; |
Iulia Manda | a235c09 | 2014-03-12 18:37:24 +0200 | [diff] [blame] | 423 | int debug_lockdep_rcu_enabled(void); |
Paul E. McKenney | 54dbf96 | 2010-03-03 07:46:57 -0800 | [diff] [blame] | 424 | |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 425 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 426 | * 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] | 427 | * |
Paul E. McKenney | d20200b | 2010-03-30 10:52:21 -0700 | [diff] [blame] | 428 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU |
| 429 | * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 430 | * 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] | 431 | * prove otherwise. This is useful for debug checks in functions that |
| 432 | * 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] | 433 | * |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 434 | * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot |
Paul E. McKenney | 32c141a | 2010-03-30 10:59:28 -0700 | [diff] [blame] | 435 | * and while lockdep is disabled. |
Paul E. McKenney | 3842a08 | 2011-11-28 10:42:42 -0800 | [diff] [blame] | 436 | * |
| 437 | * Note that rcu_read_lock() and the matching rcu_read_unlock() must |
| 438 | * occur in the same context, for example, it is illegal to invoke |
| 439 | * rcu_read_unlock() in process context if the matching rcu_read_lock() |
| 440 | * was invoked from within an irq handler. |
Paul E. McKenney | c0d6d01 | 2012-01-23 12:41:26 -0800 | [diff] [blame] | 441 | * |
| 442 | * Note that rcu_read_lock() is disallowed if the CPU is either idle or |
| 443 | * offline from an RCU perspective, so check for those as well. |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 444 | */ |
| 445 | static inline int rcu_read_lock_held(void) |
| 446 | { |
Paul E. McKenney | 54dbf96 | 2010-03-03 07:46:57 -0800 | [diff] [blame] | 447 | if (!debug_lockdep_rcu_enabled()) |
| 448 | return 1; |
Paul E. McKenney | 5c173eb | 2013-09-13 17:20:11 -0700 | [diff] [blame] | 449 | if (!rcu_is_watching()) |
Frederic Weisbecker | e6b80a3 | 2011-10-07 16:25:18 -0700 | [diff] [blame] | 450 | return 0; |
Paul E. McKenney | c0d6d01 | 2012-01-23 12:41:26 -0800 | [diff] [blame] | 451 | if (!rcu_lockdep_current_cpu_online()) |
| 452 | return 0; |
Paul E. McKenney | 54dbf96 | 2010-03-03 07:46:57 -0800 | [diff] [blame] | 453 | return lock_is_held(&rcu_lock_map); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 454 | } |
| 455 | |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 456 | /* |
| 457 | * rcu_read_lock_bh_held() is defined out of line to avoid #include-file |
| 458 | * hell. |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 459 | */ |
Teodora Baluta | 584dc4c | 2013-11-11 17:11:23 +0200 | [diff] [blame] | 460 | int rcu_read_lock_bh_held(void); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 461 | |
| 462 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 463 | * 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] | 464 | * |
Paul E. McKenney | d20200b | 2010-03-30 10:52:21 -0700 | [diff] [blame] | 465 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an |
| 466 | * RCU-sched read-side critical section. In absence of |
| 467 | * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side |
| 468 | * critical section unless it can prove otherwise. Note that disabling |
| 469 | * of preemption (including disabling irqs) counts as an RCU-sched |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 470 | * read-side critical section. This is useful for debug checks in functions |
| 471 | * that required that they be called within an RCU-sched read-side |
| 472 | * critical section. |
Paul E. McKenney | 54dbf96 | 2010-03-03 07:46:57 -0800 | [diff] [blame] | 473 | * |
Paul E. McKenney | 32c141a | 2010-03-30 10:59:28 -0700 | [diff] [blame] | 474 | * Check debug_lockdep_rcu_enabled() to prevent false positives during boot |
| 475 | * and while lockdep is disabled. |
Frederic Weisbecker | e6b80a3 | 2011-10-07 16:25:18 -0700 | [diff] [blame] | 476 | * |
| 477 | * Note that if the CPU is in the idle loop from an RCU point of |
| 478 | * view (ie: that we are in the section between rcu_idle_enter() and |
| 479 | * rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU |
| 480 | * did an rcu_read_lock(). The reason for this is that RCU ignores CPUs |
| 481 | * that are in such a section, considering these as in extended quiescent |
| 482 | * state, so such a CPU is effectively never in an RCU read-side critical |
| 483 | * section regardless of what RCU primitives it invokes. This state of |
| 484 | * affairs is required --- we need to keep an RCU-free window in idle |
| 485 | * where the CPU may possibly enter into low power mode. This way we can |
| 486 | * notice an extended quiescent state to other CPUs that started a grace |
| 487 | * period. Otherwise we would delay any grace period as long as we run in |
| 488 | * the idle task. |
Paul E. McKenney | c0d6d01 | 2012-01-23 12:41:26 -0800 | [diff] [blame] | 489 | * |
| 490 | * Similarly, we avoid claiming an SRCU read lock held if the current |
| 491 | * CPU is offline. |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 492 | */ |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 493 | #ifdef CONFIG_PREEMPT_COUNT |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 494 | static inline int rcu_read_lock_sched_held(void) |
| 495 | { |
| 496 | int lockdep_opinion = 0; |
| 497 | |
Paul E. McKenney | 54dbf96 | 2010-03-03 07:46:57 -0800 | [diff] [blame] | 498 | if (!debug_lockdep_rcu_enabled()) |
| 499 | return 1; |
Paul E. McKenney | 5c173eb | 2013-09-13 17:20:11 -0700 | [diff] [blame] | 500 | if (!rcu_is_watching()) |
Frederic Weisbecker | e6b80a3 | 2011-10-07 16:25:18 -0700 | [diff] [blame] | 501 | return 0; |
Paul E. McKenney | c0d6d01 | 2012-01-23 12:41:26 -0800 | [diff] [blame] | 502 | if (!rcu_lockdep_current_cpu_online()) |
| 503 | return 0; |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 504 | if (debug_locks) |
| 505 | lockdep_opinion = lock_is_held(&rcu_sched_lock_map); |
Lai Jiangshan | 0cff810 | 2010-03-18 12:25:33 -0700 | [diff] [blame] | 506 | return lockdep_opinion || preempt_count() != 0 || irqs_disabled(); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 507 | } |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 508 | #else /* #ifdef CONFIG_PREEMPT_COUNT */ |
Paul E. McKenney | e6033e3 | 2010-03-03 17:50:16 -0800 | [diff] [blame] | 509 | static inline int rcu_read_lock_sched_held(void) |
| 510 | { |
| 511 | return 1; |
| 512 | } |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 513 | #endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 514 | |
| 515 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| 516 | |
Paul E. McKenney | d8ab29f | 2011-10-07 18:22:03 +0200 | [diff] [blame] | 517 | # define rcu_lock_acquire(a) do { } while (0) |
| 518 | # define rcu_lock_release(a) do { } while (0) |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 519 | |
| 520 | static inline int rcu_read_lock_held(void) |
| 521 | { |
| 522 | return 1; |
| 523 | } |
| 524 | |
| 525 | static inline int rcu_read_lock_bh_held(void) |
| 526 | { |
| 527 | return 1; |
| 528 | } |
| 529 | |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 530 | #ifdef CONFIG_PREEMPT_COUNT |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 531 | static inline int rcu_read_lock_sched_held(void) |
| 532 | { |
Paul E. McKenney | bbad937 | 2010-04-02 16:17:17 -0700 | [diff] [blame] | 533 | return preempt_count() != 0 || irqs_disabled(); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 534 | } |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 535 | #else /* #ifdef CONFIG_PREEMPT_COUNT */ |
Paul E. McKenney | e6033e3 | 2010-03-03 17:50:16 -0800 | [diff] [blame] | 536 | static inline int rcu_read_lock_sched_held(void) |
| 537 | { |
| 538 | return 1; |
| 539 | } |
Frederic Weisbecker | bdd4e85 | 2011-06-08 01:13:27 +0200 | [diff] [blame] | 540 | #endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 541 | |
| 542 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| 543 | |
| 544 | #ifdef CONFIG_PROVE_RCU |
| 545 | |
Tetsuo Handa | 4221a99 | 2010-06-26 01:08:19 +0900 | [diff] [blame] | 546 | /** |
| 547 | * rcu_lockdep_assert - emit lockdep splat if specified condition not met |
| 548 | * @c: condition to check |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 549 | * @s: informative message |
Tetsuo Handa | 4221a99 | 2010-06-26 01:08:19 +0900 | [diff] [blame] | 550 | */ |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 551 | #define rcu_lockdep_assert(c, s) \ |
Lai Jiangshan | 2b3fc35 | 2010-04-20 16:23:07 +0800 | [diff] [blame] | 552 | do { \ |
Jan Beulich | 7ccaba5 | 2012-03-23 15:01:52 -0700 | [diff] [blame] | 553 | static bool __section(.data.unlikely) __warned; \ |
Lai Jiangshan | 2b3fc35 | 2010-04-20 16:23:07 +0800 | [diff] [blame] | 554 | if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \ |
| 555 | __warned = true; \ |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 556 | lockdep_rcu_suspicious(__FILE__, __LINE__, s); \ |
Lai Jiangshan | 2b3fc35 | 2010-04-20 16:23:07 +0800 | [diff] [blame] | 557 | } \ |
| 558 | } while (0) |
| 559 | |
Paul E. McKenney | 50406b9 | 2012-01-12 13:49:19 -0800 | [diff] [blame] | 560 | #if defined(CONFIG_PROVE_RCU) && !defined(CONFIG_PREEMPT_RCU) |
| 561 | static inline void rcu_preempt_sleep_check(void) |
| 562 | { |
| 563 | rcu_lockdep_assert(!lock_is_held(&rcu_lock_map), |
Paul E. McKenney | 5cf05ad | 2012-05-17 15:12:45 -0700 | [diff] [blame] | 564 | "Illegal context switch in RCU read-side critical section"); |
Paul E. McKenney | 50406b9 | 2012-01-12 13:49:19 -0800 | [diff] [blame] | 565 | } |
| 566 | #else /* #ifdef CONFIG_PROVE_RCU */ |
| 567 | static inline void rcu_preempt_sleep_check(void) |
| 568 | { |
| 569 | } |
| 570 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ |
| 571 | |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 572 | #define rcu_sleep_check() \ |
| 573 | do { \ |
Paul E. McKenney | 50406b9 | 2012-01-12 13:49:19 -0800 | [diff] [blame] | 574 | rcu_preempt_sleep_check(); \ |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 575 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), \ |
Joe Perches | 41f4abd | 2013-12-05 15:10:23 -0800 | [diff] [blame] | 576 | "Illegal context switch in RCU-bh read-side critical section"); \ |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 577 | rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), \ |
Joe Perches | 41f4abd | 2013-12-05 15:10:23 -0800 | [diff] [blame] | 578 | "Illegal context switch in RCU-sched read-side critical section"); \ |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 579 | } while (0) |
| 580 | |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 581 | #else /* #ifdef CONFIG_PROVE_RCU */ |
| 582 | |
Paul E. McKenney | b3fbab0 | 2011-05-24 08:31:09 -0700 | [diff] [blame] | 583 | #define rcu_lockdep_assert(c, s) do { } while (0) |
| 584 | #define rcu_sleep_check() do { } while (0) |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 585 | |
| 586 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ |
| 587 | |
| 588 | /* |
| 589 | * Helper functions for rcu_dereference_check(), rcu_dereference_protected() |
| 590 | * and rcu_assign_pointer(). Some of these could be folded into their |
| 591 | * callers, but they are left separate in order to ease introduction of |
| 592 | * multiple flavors of pointers to match the multiple flavors of RCU |
| 593 | * (e.g., __rcu_bh, * __rcu_sched, and __srcu), should this make sense in |
| 594 | * the future. |
| 595 | */ |
Paul E. McKenney | 53ecfba | 2010-09-13 17:24:21 -0700 | [diff] [blame] | 596 | |
| 597 | #ifdef __CHECKER__ |
| 598 | #define rcu_dereference_sparse(p, space) \ |
| 599 | ((void)(((typeof(*p) space *)p) == p)) |
| 600 | #else /* #ifdef __CHECKER__ */ |
| 601 | #define rcu_dereference_sparse(p, space) |
| 602 | #endif /* #else #ifdef __CHECKER__ */ |
| 603 | |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 604 | #define __rcu_access_pointer(p, space) \ |
Joe Perches | 0adab9b | 2013-12-05 16:19:15 -0800 | [diff] [blame] | 605 | ({ \ |
| 606 | typeof(*p) *_________p1 = (typeof(*p) *__force)ACCESS_ONCE(p); \ |
| 607 | rcu_dereference_sparse(p, space); \ |
| 608 | ((typeof(*p) __force __kernel *)(_________p1)); \ |
| 609 | }) |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 610 | #define __rcu_dereference_check(p, c, space) \ |
Joe Perches | 0adab9b | 2013-12-05 16:19:15 -0800 | [diff] [blame] | 611 | ({ \ |
| 612 | typeof(*p) *_________p1 = (typeof(*p) *__force)ACCESS_ONCE(p); \ |
| 613 | rcu_lockdep_assert(c, "suspicious rcu_dereference_check() usage"); \ |
| 614 | rcu_dereference_sparse(p, space); \ |
| 615 | smp_read_barrier_depends(); /* Dependency order vs. p above. */ \ |
| 616 | ((typeof(*p) __force __kernel *)(_________p1)); \ |
| 617 | }) |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 618 | #define __rcu_dereference_protected(p, c, space) \ |
Joe Perches | 0adab9b | 2013-12-05 16:19:15 -0800 | [diff] [blame] | 619 | ({ \ |
| 620 | rcu_lockdep_assert(c, "suspicious rcu_dereference_protected() usage"); \ |
| 621 | rcu_dereference_sparse(p, space); \ |
| 622 | ((typeof(*p) __force __kernel *)(p)); \ |
| 623 | }) |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 624 | |
Paul E. McKenney | a4dd992 | 2011-04-01 07:15:14 -0700 | [diff] [blame] | 625 | #define __rcu_access_index(p, space) \ |
Joe Perches | 0adab9b | 2013-12-05 16:19:15 -0800 | [diff] [blame] | 626 | ({ \ |
| 627 | typeof(p) _________p1 = ACCESS_ONCE(p); \ |
| 628 | rcu_dereference_sparse(p, space); \ |
| 629 | (_________p1); \ |
| 630 | }) |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 631 | #define __rcu_dereference_index_check(p, c) \ |
Joe Perches | 0adab9b | 2013-12-05 16:19:15 -0800 | [diff] [blame] | 632 | ({ \ |
| 633 | typeof(p) _________p1 = ACCESS_ONCE(p); \ |
| 634 | rcu_lockdep_assert(c, \ |
| 635 | "suspicious rcu_dereference_index_check() usage"); \ |
| 636 | smp_read_barrier_depends(); /* Dependency order vs. p above. */ \ |
| 637 | (_________p1); \ |
| 638 | }) |
Paul E. McKenney | 462225ae | 2013-11-11 09:59:34 -0800 | [diff] [blame] | 639 | |
| 640 | /** |
| 641 | * RCU_INITIALIZER() - statically initialize an RCU-protected global variable |
| 642 | * @v: The value to statically initialize with. |
| 643 | */ |
| 644 | #define RCU_INITIALIZER(v) (typeof(*(v)) __force __rcu *)(v) |
| 645 | |
| 646 | /** |
| 647 | * rcu_assign_pointer() - assign to RCU-protected pointer |
| 648 | * @p: pointer to assign to |
| 649 | * @v: value to assign (publish) |
| 650 | * |
| 651 | * Assigns the specified value to the specified RCU-protected |
| 652 | * pointer, ensuring that any concurrent RCU readers will see |
| 653 | * any prior initialization. |
| 654 | * |
| 655 | * Inserts memory barriers on architectures that require them |
| 656 | * (which is most of them), and also prevents the compiler from |
| 657 | * reordering the code that initializes the structure after the pointer |
| 658 | * assignment. More importantly, this call documents which pointers |
| 659 | * will be dereferenced by RCU read-side code. |
| 660 | * |
| 661 | * In some special cases, you may use RCU_INIT_POINTER() instead |
| 662 | * of rcu_assign_pointer(). RCU_INIT_POINTER() is a bit faster due |
| 663 | * to the fact that it does not constrain either the CPU or the compiler. |
| 664 | * That said, using RCU_INIT_POINTER() when you should have used |
| 665 | * rcu_assign_pointer() is a very bad thing that results in |
| 666 | * impossible-to-diagnose memory corruption. So please be careful. |
| 667 | * See the RCU_INIT_POINTER() comment header for details. |
| 668 | * |
| 669 | * Note that rcu_assign_pointer() evaluates each of its arguments only |
| 670 | * once, appearances notwithstanding. One of the "extra" evaluations |
| 671 | * is in typeof() and the other visible only to sparse (__CHECKER__), |
| 672 | * neither of which actually execute the argument. As with most cpp |
| 673 | * macros, this execute-arguments-only-once property is important, so |
| 674 | * please be careful when making changes to rcu_assign_pointer() and the |
| 675 | * other macros that it invokes. |
| 676 | */ |
Paul E. McKenney | 88c1863 | 2013-12-16 13:24:32 -0800 | [diff] [blame] | 677 | #define rcu_assign_pointer(p, v) smp_store_release(&p, RCU_INITIALIZER(v)) |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 678 | |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 679 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 680 | * rcu_access_pointer() - fetch RCU pointer with no dereferencing |
| 681 | * @p: The pointer to read |
| 682 | * |
| 683 | * Return the value of the specified RCU-protected pointer, but omit the |
| 684 | * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful |
| 685 | * when the value of this pointer is accessed, but the pointer is not |
| 686 | * dereferenced, for example, when testing an RCU-protected pointer against |
| 687 | * NULL. Although rcu_access_pointer() may also be used in cases where |
| 688 | * update-side locks prevent the value of the pointer from changing, you |
| 689 | * should instead use rcu_dereference_protected() for this use case. |
Paul E. McKenney | 5e1ee6e | 2012-01-12 17:21:20 -0800 | [diff] [blame] | 690 | * |
| 691 | * It is also permissible to use rcu_access_pointer() when read-side |
| 692 | * access to the pointer was removed at least one grace period ago, as |
| 693 | * is the case in the context of the RCU callback that is freeing up |
| 694 | * the data, or after a synchronize_rcu() returns. This can be useful |
| 695 | * when tearing down multi-linked structures after a grace period |
| 696 | * has elapsed. |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 697 | */ |
| 698 | #define rcu_access_pointer(p) __rcu_access_pointer((p), __rcu) |
| 699 | |
| 700 | /** |
| 701 | * rcu_dereference_check() - rcu_dereference with debug checking |
David Howells | c08c68d | 2010-04-09 15:39:11 -0700 | [diff] [blame] | 702 | * @p: The pointer to read, prior to dereferencing |
| 703 | * @c: The conditions under which the dereference will take place |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 704 | * |
David Howells | c08c68d | 2010-04-09 15:39:11 -0700 | [diff] [blame] | 705 | * 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] | 706 | * dereference will take place are correct. Typically the conditions |
| 707 | * indicate the various locking conditions that should be held at that |
| 708 | * point. The check should return true if the conditions are satisfied. |
| 709 | * An implicit check for being in an RCU read-side critical section |
| 710 | * (rcu_read_lock()) is included. |
David Howells | c08c68d | 2010-04-09 15:39:11 -0700 | [diff] [blame] | 711 | * |
| 712 | * For example: |
| 713 | * |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 714 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock)); |
David Howells | c08c68d | 2010-04-09 15:39:11 -0700 | [diff] [blame] | 715 | * |
| 716 | * 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] | 717 | * 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] | 718 | * the bar struct at foo->bar is held. |
| 719 | * |
| 720 | * Note that the list of conditions may also include indications of when a lock |
| 721 | * need not be held, for example during initialisation or destruction of the |
| 722 | * target struct: |
| 723 | * |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 724 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock) || |
David Howells | c08c68d | 2010-04-09 15:39:11 -0700 | [diff] [blame] | 725 | * atomic_read(&foo->usage) == 0); |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 726 | * |
| 727 | * Inserts memory barriers on architectures that require them |
| 728 | * (currently only the Alpha), prevents the compiler from refetching |
| 729 | * (and from merging fetches), and, more importantly, documents exactly |
| 730 | * which pointers are protected by RCU and checks that the pointer is |
| 731 | * annotated as __rcu. |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 732 | */ |
| 733 | #define rcu_dereference_check(p, c) \ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 734 | __rcu_dereference_check((p), rcu_read_lock_held() || (c), __rcu) |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 735 | |
Paul E. McKenney | b62730b | 2010-04-09 15:39:10 -0700 | [diff] [blame] | 736 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 737 | * rcu_dereference_bh_check() - rcu_dereference_bh with debug checking |
| 738 | * @p: The pointer to read, prior to dereferencing |
| 739 | * @c: The conditions under which the dereference will take place |
| 740 | * |
| 741 | * This is the RCU-bh counterpart to rcu_dereference_check(). |
| 742 | */ |
| 743 | #define rcu_dereference_bh_check(p, c) \ |
| 744 | __rcu_dereference_check((p), rcu_read_lock_bh_held() || (c), __rcu) |
| 745 | |
| 746 | /** |
| 747 | * rcu_dereference_sched_check() - rcu_dereference_sched with debug checking |
| 748 | * @p: The pointer to read, prior to dereferencing |
| 749 | * @c: The conditions under which the dereference will take place |
| 750 | * |
| 751 | * This is the RCU-sched counterpart to rcu_dereference_check(). |
| 752 | */ |
| 753 | #define rcu_dereference_sched_check(p, c) \ |
| 754 | __rcu_dereference_check((p), rcu_read_lock_sched_held() || (c), \ |
| 755 | __rcu) |
| 756 | |
| 757 | #define rcu_dereference_raw(p) rcu_dereference_check(p, 1) /*@@@ needed? @@@*/ |
| 758 | |
Steven Rostedt | 12bcbe6 | 2013-05-28 14:38:42 -0400 | [diff] [blame] | 759 | /* |
| 760 | * The tracing infrastructure traces RCU (we want that), but unfortunately |
| 761 | * some of the RCU checks causes tracing to lock up the system. |
| 762 | * |
| 763 | * The tracing version of rcu_dereference_raw() must not call |
| 764 | * rcu_read_lock_held(). |
| 765 | */ |
| 766 | #define rcu_dereference_raw_notrace(p) __rcu_dereference_check((p), 1, __rcu) |
| 767 | |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 768 | /** |
Paul E. McKenney | a4dd992 | 2011-04-01 07:15:14 -0700 | [diff] [blame] | 769 | * rcu_access_index() - fetch RCU index with no dereferencing |
| 770 | * @p: The index to read |
| 771 | * |
| 772 | * Return the value of the specified RCU-protected index, but omit the |
| 773 | * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful |
| 774 | * when the value of this index is accessed, but the index is not |
| 775 | * dereferenced, for example, when testing an RCU-protected index against |
| 776 | * -1. Although rcu_access_index() may also be used in cases where |
| 777 | * update-side locks prevent the value of the index from changing, you |
| 778 | * should instead use rcu_dereference_index_protected() for this use case. |
| 779 | */ |
| 780 | #define rcu_access_index(p) __rcu_access_index((p), __rcu) |
| 781 | |
| 782 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 783 | * rcu_dereference_index_check() - rcu_dereference for indices with debug checking |
| 784 | * @p: The pointer to read, prior to dereferencing |
| 785 | * @c: The conditions under which the dereference will take place |
| 786 | * |
| 787 | * Similar to rcu_dereference_check(), but omits the sparse checking. |
| 788 | * This allows rcu_dereference_index_check() to be used on integers, |
| 789 | * which can then be used as array indices. Attempting to use |
| 790 | * rcu_dereference_check() on an integer will give compiler warnings |
| 791 | * because the sparse address-space mechanism relies on dereferencing |
| 792 | * the RCU-protected pointer. Dereferencing integers is not something |
| 793 | * that even gcc will put up with. |
| 794 | * |
| 795 | * Note that this function does not implicitly check for RCU read-side |
| 796 | * critical sections. If this function gains lots of uses, it might |
| 797 | * make sense to provide versions for each flavor of RCU, but it does |
| 798 | * not make sense as of early 2010. |
| 799 | */ |
| 800 | #define rcu_dereference_index_check(p, c) \ |
| 801 | __rcu_dereference_index_check((p), (c)) |
| 802 | |
| 803 | /** |
| 804 | * rcu_dereference_protected() - fetch RCU pointer when updates prevented |
| 805 | * @p: The pointer to read, prior to dereferencing |
| 806 | * @c: The conditions under which the dereference will take place |
Paul E. McKenney | b62730b | 2010-04-09 15:39:10 -0700 | [diff] [blame] | 807 | * |
| 808 | * Return the value of the specified RCU-protected pointer, but omit |
| 809 | * both the smp_read_barrier_depends() and the ACCESS_ONCE(). This |
| 810 | * is useful in cases where update-side locks prevent the value of the |
| 811 | * pointer from changing. Please note that this primitive does -not- |
| 812 | * prevent the compiler from repeating this reference or combining it |
| 813 | * with other references, so it should not be used without protection |
| 814 | * of appropriate locks. |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 815 | * |
| 816 | * This function is only for update-side use. Using this function |
| 817 | * when protected only by rcu_read_lock() will result in infrequent |
| 818 | * but very ugly failures. |
Paul E. McKenney | b62730b | 2010-04-09 15:39:10 -0700 | [diff] [blame] | 819 | */ |
| 820 | #define rcu_dereference_protected(p, c) \ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 821 | __rcu_dereference_protected((p), (c), __rcu) |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 822 | |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 823 | |
| 824 | /** |
| 825 | * rcu_dereference() - fetch RCU-protected pointer for dereferencing |
| 826 | * @p: The pointer to read, prior to dereferencing |
| 827 | * |
| 828 | * This is a simple wrapper around rcu_dereference_check(). |
| 829 | */ |
| 830 | #define rcu_dereference(p) rcu_dereference_check(p, 0) |
| 831 | |
| 832 | /** |
| 833 | * rcu_dereference_bh() - fetch an RCU-bh-protected pointer for dereferencing |
| 834 | * @p: The pointer to read, prior to dereferencing |
| 835 | * |
| 836 | * Makes rcu_dereference_check() do the dirty work. |
| 837 | */ |
| 838 | #define rcu_dereference_bh(p) rcu_dereference_bh_check(p, 0) |
| 839 | |
| 840 | /** |
| 841 | * rcu_dereference_sched() - fetch RCU-sched-protected pointer for dereferencing |
| 842 | * @p: The pointer to read, prior to dereferencing |
| 843 | * |
| 844 | * Makes rcu_dereference_check() do the dirty work. |
| 845 | */ |
| 846 | #define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0) |
| 847 | |
| 848 | /** |
| 849 | * 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] | 850 | * |
Paul E. McKenney | 9b06e81 | 2005-05-01 08:59:04 -0700 | [diff] [blame] | 851 | * When synchronize_rcu() is invoked on one CPU while other CPUs |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 852 | * are within RCU read-side critical sections, then the |
Paul E. McKenney | 9b06e81 | 2005-05-01 08:59:04 -0700 | [diff] [blame] | 853 | * synchronize_rcu() is guaranteed to block until after all the other |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 854 | * CPUs exit their critical sections. Similarly, if call_rcu() is invoked |
| 855 | * on one CPU while other CPUs are within RCU read-side critical |
| 856 | * sections, invocation of the corresponding RCU callback is deferred |
| 857 | * until after the all the other CPUs exit their critical sections. |
| 858 | * |
| 859 | * Note, however, that RCU callbacks are permitted to run concurrently |
Paul E. McKenney | 77d8485 | 2010-07-08 17:38:59 -0700 | [diff] [blame] | 860 | * 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] | 861 | * is via the following sequence of events: (1) CPU 0 enters an RCU |
| 862 | * read-side critical section, (2) CPU 1 invokes call_rcu() to register |
| 863 | * an RCU callback, (3) CPU 0 exits the RCU read-side critical section, |
| 864 | * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU |
| 865 | * callback is invoked. This is legal, because the RCU read-side critical |
| 866 | * section that was running concurrently with the call_rcu() (and which |
| 867 | * therefore might be referencing something that the corresponding RCU |
| 868 | * callback would free up) has completed before the corresponding |
| 869 | * RCU callback is invoked. |
| 870 | * |
| 871 | * RCU read-side critical sections may be nested. Any deferred actions |
| 872 | * will be deferred until the outermost RCU read-side critical section |
| 873 | * completes. |
| 874 | * |
Paul E. McKenney | 9079fd7 | 2010-08-07 21:59:54 -0700 | [diff] [blame] | 875 | * You can avoid reading and understanding the next paragraph by |
| 876 | * following this rule: don't put anything in an rcu_read_lock() RCU |
| 877 | * read-side critical section that would block in a !PREEMPT kernel. |
| 878 | * But if you want the full story, read on! |
| 879 | * |
Paul E. McKenney | ab74fdf | 2014-05-04 15:41:21 -0700 | [diff] [blame] | 880 | * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU), |
| 881 | * it is illegal to block while in an RCU read-side critical section. |
| 882 | * In preemptible RCU implementations (TREE_PREEMPT_RCU) in CONFIG_PREEMPT |
| 883 | * kernel builds, RCU read-side critical sections may be preempted, |
| 884 | * but explicit blocking is illegal. Finally, in preemptible RCU |
| 885 | * implementations in real-time (with -rt patchset) kernel builds, RCU |
| 886 | * read-side critical sections may be preempted and they may also block, but |
| 887 | * only when acquiring spinlocks that are subject to priority inheritance. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 888 | */ |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 889 | static inline void rcu_read_lock(void) |
| 890 | { |
| 891 | __rcu_read_lock(); |
| 892 | __acquire(RCU); |
Paul E. McKenney | d8ab29f | 2011-10-07 18:22:03 +0200 | [diff] [blame] | 893 | rcu_lock_acquire(&rcu_lock_map); |
Paul E. McKenney | 5c173eb | 2013-09-13 17:20:11 -0700 | [diff] [blame] | 894 | rcu_lockdep_assert(rcu_is_watching(), |
Heiko Carstens | bde23c6 | 2012-02-01 10:30:46 -0800 | [diff] [blame] | 895 | "rcu_read_lock() used illegally while idle"); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 896 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 897 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 898 | /* |
| 899 | * So where is rcu_write_lock()? It does not exist, as there is no |
| 900 | * way for writers to lock out RCU readers. This is a feature, not |
| 901 | * a bug -- this property is what provides RCU's performance benefits. |
| 902 | * Of course, writers must coordinate with each other. The normal |
| 903 | * spinlock primitives work well for this, but any other technique may be |
| 904 | * used as well. RCU does not care how the writers keep out of each |
| 905 | * others' way, as long as they do so. |
| 906 | */ |
Paul E. McKenney | 3d76c08 | 2009-09-28 07:46:32 -0700 | [diff] [blame] | 907 | |
| 908 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 909 | * 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] | 910 | * |
Paul E. McKenney | f27bc48 | 2014-05-04 15:38:38 -0700 | [diff] [blame] | 911 | * In most situations, rcu_read_unlock() is immune from deadlock. |
| 912 | * However, in kernels built with CONFIG_RCU_BOOST, rcu_read_unlock() |
| 913 | * is responsible for deboosting, which it does via rt_mutex_unlock(). |
| 914 | * Unfortunately, this function acquires the scheduler's runqueue and |
| 915 | * priority-inheritance spinlocks. This means that deadlock could result |
| 916 | * if the caller of rcu_read_unlock() already holds one of these locks or |
| 917 | * any lock that is ever acquired while holding them. |
| 918 | * |
| 919 | * That said, RCU readers are never priority boosted unless they were |
| 920 | * preempted. Therefore, one way to avoid deadlock is to make sure |
| 921 | * that preemption never happens within any RCU read-side critical |
| 922 | * section whose outermost rcu_read_unlock() is called with one of |
| 923 | * rt_mutex_unlock()'s locks held. Such preemption can be avoided in |
| 924 | * a number of ways, for example, by invoking preempt_disable() before |
| 925 | * critical section's outermost rcu_read_lock(). |
| 926 | * |
| 927 | * Given that the set of locks acquired by rt_mutex_unlock() might change |
| 928 | * at any time, a somewhat more future-proofed approach is to make sure |
| 929 | * that that preemption never happens within any RCU read-side critical |
| 930 | * section whose outermost rcu_read_unlock() is called with irqs disabled. |
| 931 | * This approach relies on the fact that rt_mutex_unlock() currently only |
| 932 | * acquires irq-disabled locks. |
| 933 | * |
| 934 | * The second of these two approaches is best in most situations, |
| 935 | * however, the first approach can also be useful, at least to those |
| 936 | * developers willing to keep abreast of the set of locks acquired by |
| 937 | * rt_mutex_unlock(). |
| 938 | * |
Paul E. McKenney | 3d76c08 | 2009-09-28 07:46:32 -0700 | [diff] [blame] | 939 | * See rcu_read_lock() for more information. |
| 940 | */ |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 941 | static inline void rcu_read_unlock(void) |
| 942 | { |
Paul E. McKenney | 5c173eb | 2013-09-13 17:20:11 -0700 | [diff] [blame] | 943 | rcu_lockdep_assert(rcu_is_watching(), |
Heiko Carstens | bde23c6 | 2012-02-01 10:30:46 -0800 | [diff] [blame] | 944 | "rcu_read_unlock() used illegally while idle"); |
Paul E. McKenney | d8ab29f | 2011-10-07 18:22:03 +0200 | [diff] [blame] | 945 | rcu_lock_release(&rcu_lock_map); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 946 | __release(RCU); |
| 947 | __rcu_read_unlock(); |
| 948 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 949 | |
| 950 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 951 | * 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] | 952 | * |
| 953 | * 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] | 954 | * are being done using call_rcu_bh() or synchronize_rcu_bh(). Since |
| 955 | * both call_rcu_bh() and synchronize_rcu_bh() consider completion of a |
| 956 | * softirq handler to be a quiescent state, a process in RCU read-side |
| 957 | * critical section must be protected by disabling softirqs. Read-side |
| 958 | * critical sections in interrupt context can use just rcu_read_lock(), |
| 959 | * though this should at least be commented to avoid confusing people |
| 960 | * reading the code. |
Paul E. McKenney | 3842a08 | 2011-11-28 10:42:42 -0800 | [diff] [blame] | 961 | * |
| 962 | * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh() |
| 963 | * must occur in the same context, for example, it is illegal to invoke |
| 964 | * rcu_read_unlock_bh() from one task if the matching rcu_read_lock_bh() |
| 965 | * was invoked from some other task. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 966 | */ |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 967 | static inline void rcu_read_lock_bh(void) |
| 968 | { |
Paul E. McKenney | 6206ab9 | 2011-08-01 06:22:11 -0700 | [diff] [blame] | 969 | local_bh_disable(); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 970 | __acquire(RCU_BH); |
Paul E. McKenney | d8ab29f | 2011-10-07 18:22:03 +0200 | [diff] [blame] | 971 | rcu_lock_acquire(&rcu_bh_lock_map); |
Paul E. McKenney | 5c173eb | 2013-09-13 17:20:11 -0700 | [diff] [blame] | 972 | rcu_lockdep_assert(rcu_is_watching(), |
Heiko Carstens | bde23c6 | 2012-02-01 10:30:46 -0800 | [diff] [blame] | 973 | "rcu_read_lock_bh() used illegally while idle"); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 974 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 975 | |
| 976 | /* |
| 977 | * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section |
| 978 | * |
| 979 | * See rcu_read_lock_bh() for more information. |
| 980 | */ |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 981 | static inline void rcu_read_unlock_bh(void) |
| 982 | { |
Paul E. McKenney | 5c173eb | 2013-09-13 17:20:11 -0700 | [diff] [blame] | 983 | rcu_lockdep_assert(rcu_is_watching(), |
Heiko Carstens | bde23c6 | 2012-02-01 10:30:46 -0800 | [diff] [blame] | 984 | "rcu_read_unlock_bh() used illegally while idle"); |
Paul E. McKenney | d8ab29f | 2011-10-07 18:22:03 +0200 | [diff] [blame] | 985 | rcu_lock_release(&rcu_bh_lock_map); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 986 | __release(RCU_BH); |
Paul E. McKenney | 6206ab9 | 2011-08-01 06:22:11 -0700 | [diff] [blame] | 987 | local_bh_enable(); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 988 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 989 | |
| 990 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 991 | * 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] | 992 | * |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 993 | * This is equivalent of rcu_read_lock(), but to be used when updates |
| 994 | * are being done using call_rcu_sched() or synchronize_rcu_sched(). |
| 995 | * Read-side critical sections can also be introduced by anything that |
| 996 | * disables preemption, including local_irq_disable() and friends. |
Paul E. McKenney | 3842a08 | 2011-11-28 10:42:42 -0800 | [diff] [blame] | 997 | * |
| 998 | * Note that rcu_read_lock_sched() and the matching rcu_read_unlock_sched() |
| 999 | * must occur in the same context, for example, it is illegal to invoke |
| 1000 | * rcu_read_unlock_sched() from process context if the matching |
| 1001 | * rcu_read_lock_sched() was invoked from an NMI handler. |
Mathieu Desnoyers | 1c50b72 | 2008-09-29 11:06:46 -0400 | [diff] [blame] | 1002 | */ |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 1003 | static inline void rcu_read_lock_sched(void) |
| 1004 | { |
| 1005 | preempt_disable(); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 1006 | __acquire(RCU_SCHED); |
Paul E. McKenney | d8ab29f | 2011-10-07 18:22:03 +0200 | [diff] [blame] | 1007 | rcu_lock_acquire(&rcu_sched_lock_map); |
Paul E. McKenney | 5c173eb | 2013-09-13 17:20:11 -0700 | [diff] [blame] | 1008 | rcu_lockdep_assert(rcu_is_watching(), |
Heiko Carstens | bde23c6 | 2012-02-01 10:30:46 -0800 | [diff] [blame] | 1009 | "rcu_read_lock_sched() used illegally while idle"); |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 1010 | } |
Paul E. McKenney | 1eba8f8 | 2009-09-23 09:50:42 -0700 | [diff] [blame] | 1011 | |
| 1012 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ |
Paul E. McKenney | 7c614d6 | 2009-08-24 09:42:00 -0700 | [diff] [blame] | 1013 | static inline notrace void rcu_read_lock_sched_notrace(void) |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 1014 | { |
| 1015 | preempt_disable_notrace(); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 1016 | __acquire(RCU_SCHED); |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 1017 | } |
Mathieu Desnoyers | 1c50b72 | 2008-09-29 11:06:46 -0400 | [diff] [blame] | 1018 | |
| 1019 | /* |
| 1020 | * rcu_read_unlock_sched - marks the end of a RCU-classic critical section |
| 1021 | * |
| 1022 | * See rcu_read_lock_sched for more information. |
| 1023 | */ |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 1024 | static inline void rcu_read_unlock_sched(void) |
| 1025 | { |
Paul E. McKenney | 5c173eb | 2013-09-13 17:20:11 -0700 | [diff] [blame] | 1026 | rcu_lockdep_assert(rcu_is_watching(), |
Heiko Carstens | bde23c6 | 2012-02-01 10:30:46 -0800 | [diff] [blame] | 1027 | "rcu_read_unlock_sched() used illegally while idle"); |
Paul E. McKenney | d8ab29f | 2011-10-07 18:22:03 +0200 | [diff] [blame] | 1028 | rcu_lock_release(&rcu_sched_lock_map); |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 1029 | __release(RCU_SCHED); |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 1030 | preempt_enable(); |
| 1031 | } |
Paul E. McKenney | 1eba8f8 | 2009-09-23 09:50:42 -0700 | [diff] [blame] | 1032 | |
| 1033 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ |
Paul E. McKenney | 7c614d6 | 2009-08-24 09:42:00 -0700 | [diff] [blame] | 1034 | static inline notrace void rcu_read_unlock_sched_notrace(void) |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 1035 | { |
Paul E. McKenney | bc33f24 | 2009-08-22 13:56:47 -0700 | [diff] [blame] | 1036 | __release(RCU_SCHED); |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 1037 | preempt_enable_notrace(); |
| 1038 | } |
Mathieu Desnoyers | 1c50b72 | 2008-09-29 11:06:46 -0400 | [diff] [blame] | 1039 | |
Mathieu Desnoyers | 1c50b72 | 2008-09-29 11:06:46 -0400 | [diff] [blame] | 1040 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 1041 | * RCU_INIT_POINTER() - initialize an RCU protected pointer |
| 1042 | * |
Paul E. McKenney | 6846c0c | 2011-07-31 22:33:02 -0700 | [diff] [blame] | 1043 | * Initialize an RCU-protected pointer in special cases where readers |
| 1044 | * do not need ordering constraints on the CPU or the compiler. These |
| 1045 | * special cases are: |
| 1046 | * |
| 1047 | * 1. This use of RCU_INIT_POINTER() is NULLing out the pointer -or- |
| 1048 | * 2. The caller has taken whatever steps are required to prevent |
| 1049 | * RCU readers from concurrently accessing this pointer -or- |
| 1050 | * 3. The referenced data structure has already been exposed to |
| 1051 | * readers either at compile time or via rcu_assign_pointer() -and- |
| 1052 | * a. You have not made -any- reader-visible changes to |
| 1053 | * this structure since then -or- |
| 1054 | * b. It is OK for readers accessing this structure from its |
| 1055 | * new location to see the old state of the structure. (For |
| 1056 | * example, the changes were to statistical counters or to |
| 1057 | * other state where exact synchronization is not required.) |
| 1058 | * |
| 1059 | * Failure to follow these rules governing use of RCU_INIT_POINTER() will |
| 1060 | * result in impossible-to-diagnose memory corruption. As in the structures |
| 1061 | * will look OK in crash dumps, but any concurrent RCU readers might |
| 1062 | * see pre-initialized values of the referenced data structure. So |
| 1063 | * please be very careful how you use RCU_INIT_POINTER()!!! |
| 1064 | * |
| 1065 | * If you are creating an RCU-protected linked structure that is accessed |
| 1066 | * by a single external-to-structure RCU-protected pointer, then you may |
| 1067 | * use RCU_INIT_POINTER() to initialize the internal RCU-protected |
| 1068 | * pointers, but you must use rcu_assign_pointer() to initialize the |
| 1069 | * external-to-structure pointer -after- you have completely initialized |
| 1070 | * the reader-accessible portions of the linked structure. |
Paul E. McKenney | 71a9b26 | 2014-03-31 13:13:02 -0700 | [diff] [blame] | 1071 | * |
| 1072 | * Note that unlike rcu_assign_pointer(), RCU_INIT_POINTER() provides no |
| 1073 | * ordering guarantees for either the CPU or the compiler. |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 1074 | */ |
| 1075 | #define RCU_INIT_POINTER(p, v) \ |
Paul E. McKenney | d1b88eb | 2012-05-16 15:42:30 -0700 | [diff] [blame] | 1076 | do { \ |
Paul E. McKenney | 462225ae | 2013-11-11 09:59:34 -0800 | [diff] [blame] | 1077 | p = RCU_INITIALIZER(v); \ |
Paul E. McKenney | d1b88eb | 2012-05-16 15:42:30 -0700 | [diff] [blame] | 1078 | } while (0) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1079 | |
Paul E. McKenney | 172708d | 2012-05-16 15:23:45 -0700 | [diff] [blame] | 1080 | /** |
| 1081 | * RCU_POINTER_INITIALIZER() - statically initialize an RCU protected pointer |
| 1082 | * |
| 1083 | * GCC-style initialization for an RCU-protected pointer in a structure field. |
| 1084 | */ |
| 1085 | #define RCU_POINTER_INITIALIZER(p, v) \ |
Paul E. McKenney | 462225ae | 2013-11-11 09:59:34 -0800 | [diff] [blame] | 1086 | .p = RCU_INITIALIZER(v) |
Lai Jiangshan | 9ab1544 | 2011-03-18 11:15:47 +0800 | [diff] [blame] | 1087 | |
Jan Engelhardt | d8169d4 | 2012-04-19 11:44:39 -0700 | [diff] [blame] | 1088 | /* |
| 1089 | * Does the specified offset indicate that the corresponding rcu_head |
| 1090 | * structure can be handled by kfree_rcu()? |
| 1091 | */ |
| 1092 | #define __is_kfree_rcu_offset(offset) ((offset) < 4096) |
| 1093 | |
| 1094 | /* |
| 1095 | * Helper macro for kfree_rcu() to prevent argument-expansion eyestrain. |
| 1096 | */ |
| 1097 | #define __kfree_rcu(head, offset) \ |
| 1098 | do { \ |
| 1099 | BUILD_BUG_ON(!__is_kfree_rcu_offset(offset)); \ |
Paul E. McKenney | 4fa3b6c | 2012-06-05 15:53:53 -0700 | [diff] [blame] | 1100 | kfree_call_rcu(head, (void (*)(struct rcu_head *))(unsigned long)(offset)); \ |
Jan Engelhardt | d8169d4 | 2012-04-19 11:44:39 -0700 | [diff] [blame] | 1101 | } while (0) |
| 1102 | |
Lai Jiangshan | 9ab1544 | 2011-03-18 11:15:47 +0800 | [diff] [blame] | 1103 | /** |
| 1104 | * kfree_rcu() - kfree an object after a grace period. |
| 1105 | * @ptr: pointer to kfree |
| 1106 | * @rcu_head: the name of the struct rcu_head within the type of @ptr. |
| 1107 | * |
| 1108 | * Many rcu callbacks functions just call kfree() on the base structure. |
| 1109 | * These functions are trivial, but their size adds up, and furthermore |
| 1110 | * when they are used in a kernel module, that module must invoke the |
| 1111 | * high-latency rcu_barrier() function at module-unload time. |
| 1112 | * |
| 1113 | * The kfree_rcu() function handles this issue. Rather than encoding a |
| 1114 | * function address in the embedded rcu_head structure, kfree_rcu() instead |
| 1115 | * encodes the offset of the rcu_head structure within the base structure. |
| 1116 | * Because the functions are not allowed in the low-order 4096 bytes of |
| 1117 | * kernel virtual memory, offsets up to 4095 bytes can be accommodated. |
| 1118 | * If the offset is larger than 4095 bytes, a compile-time error will |
| 1119 | * be generated in __kfree_rcu(). If this error is triggered, you can |
| 1120 | * either fall back to use of call_rcu() or rearrange the structure to |
| 1121 | * position the rcu_head structure into the first 4096 bytes. |
| 1122 | * |
| 1123 | * Note that the allowable offset might decrease in the future, for example, |
| 1124 | * to allow something like kmem_cache_free_rcu(). |
Jan Engelhardt | d8169d4 | 2012-04-19 11:44:39 -0700 | [diff] [blame] | 1125 | * |
| 1126 | * The BUILD_BUG_ON check must not involve any function calls, hence the |
| 1127 | * checks are done in macros here. |
Lai Jiangshan | 9ab1544 | 2011-03-18 11:15:47 +0800 | [diff] [blame] | 1128 | */ |
| 1129 | #define kfree_rcu(ptr, rcu_head) \ |
| 1130 | __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head)) |
| 1131 | |
Paul E. McKenney | ffa83fb | 2013-11-17 19:27:16 -0800 | [diff] [blame] | 1132 | #if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL) |
| 1133 | static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies) |
| 1134 | { |
| 1135 | *delta_jiffies = ULONG_MAX; |
| 1136 | return 0; |
| 1137 | } |
| 1138 | #endif /* #if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL) */ |
| 1139 | |
Paul E. McKenney | 2f33b51 | 2013-11-17 18:25:48 -0800 | [diff] [blame] | 1140 | #if defined(CONFIG_RCU_NOCB_CPU_ALL) |
| 1141 | static inline bool rcu_is_nocb_cpu(int cpu) { return true; } |
| 1142 | #elif defined(CONFIG_RCU_NOCB_CPU) |
Teodora Baluta | 584dc4c | 2013-11-11 17:11:23 +0200 | [diff] [blame] | 1143 | bool rcu_is_nocb_cpu(int cpu); |
Frederic Weisbecker | d1e43fa | 2013-03-26 23:47:24 +0100 | [diff] [blame] | 1144 | #else |
| 1145 | static inline bool rcu_is_nocb_cpu(int cpu) { return false; } |
Paul E. McKenney | 2f33b51 | 2013-11-17 18:25:48 -0800 | [diff] [blame] | 1146 | #endif |
Frederic Weisbecker | d1e43fa | 2013-03-26 23:47:24 +0100 | [diff] [blame] | 1147 | |
| 1148 | |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 1149 | /* Only for use by adaptive-ticks code. */ |
| 1150 | #ifdef CONFIG_NO_HZ_FULL_SYSIDLE |
Teodora Baluta | 584dc4c | 2013-11-11 17:11:23 +0200 | [diff] [blame] | 1151 | bool rcu_sys_is_idle(void); |
| 1152 | void rcu_sysidle_force_exit(void); |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 1153 | #else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ |
| 1154 | |
| 1155 | static inline bool rcu_sys_is_idle(void) |
| 1156 | { |
| 1157 | return false; |
| 1158 | } |
| 1159 | |
| 1160 | static inline void rcu_sysidle_force_exit(void) |
| 1161 | { |
| 1162 | } |
| 1163 | |
| 1164 | #endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ |
| 1165 | |
| 1166 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1167 | #endif /* __LINUX_RCUPDATE_H */ |