Paul E. McKenney | 621934e | 2006-10-04 02:17:02 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Sleepable Read-Copy Update mechanism for mutual exclusion |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or modify |
| 5 | * it under the terms of the GNU General Public License as published by |
| 6 | * the Free Software Foundation; either version 2 of the License, or |
| 7 | * (at your option) any later version. |
| 8 | * |
| 9 | * This program is distributed in the hope that it will be useful, |
| 10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 12 | * GNU General Public License for more details. |
| 13 | * |
| 14 | * You should have received a copy of the GNU General Public License |
| 15 | * along with this program; if not, write to the Free Software |
| 16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 17 | * |
| 18 | * Copyright (C) IBM Corporation, 2006 |
| 19 | * |
| 20 | * Author: Paul McKenney <paulmck@us.ibm.com> |
| 21 | * |
| 22 | * For detailed explanation of Read-Copy Update mechanism see - |
| 23 | * Documentation/RCU/ *.txt |
| 24 | * |
| 25 | */ |
| 26 | |
Alan Stern | eabc069 | 2006-10-04 02:17:04 -0700 | [diff] [blame] | 27 | #ifndef _LINUX_SRCU_H |
| 28 | #define _LINUX_SRCU_H |
| 29 | |
Paul E. McKenney | d14aada | 2010-04-19 22:24:22 -0700 | [diff] [blame] | 30 | #include <linux/mutex.h> |
Paul E. McKenney | ff195cb | 2011-10-07 18:22:04 +0200 | [diff] [blame] | 31 | #include <linux/rcupdate.h> |
Lai Jiangshan | 931ea9d | 2012-03-19 16:12:13 +0800 | [diff] [blame] | 32 | #include <linux/workqueue.h> |
Paul E. McKenney | d14aada | 2010-04-19 22:24:22 -0700 | [diff] [blame] | 33 | |
Paul E. McKenney | 621934e | 2006-10-04 02:17:02 -0700 | [diff] [blame] | 34 | struct srcu_struct_array { |
Paul E. McKenney | cef5012 | 2012-02-05 07:42:44 -0800 | [diff] [blame] | 35 | unsigned long c[2]; |
Lai Jiangshan | b52ce06 | 2012-02-27 09:29:09 -0800 | [diff] [blame] | 36 | unsigned long seq[2]; |
Paul E. McKenney | 621934e | 2006-10-04 02:17:02 -0700 | [diff] [blame] | 37 | }; |
| 38 | |
Lai Jiangshan | 931ea9d | 2012-03-19 16:12:13 +0800 | [diff] [blame] | 39 | struct rcu_batch { |
| 40 | struct rcu_head *head, **tail; |
| 41 | }; |
| 42 | |
Paul E. McKenney | 621934e | 2006-10-04 02:17:02 -0700 | [diff] [blame] | 43 | struct srcu_struct { |
Paul E. McKenney | cef5012 | 2012-02-05 07:42:44 -0800 | [diff] [blame] | 44 | unsigned completed; |
Tejun Heo | 43cf38e | 2010-02-02 14:38:57 +0900 | [diff] [blame] | 45 | struct srcu_struct_array __percpu *per_cpu_ref; |
Lai Jiangshan | 931ea9d | 2012-03-19 16:12:13 +0800 | [diff] [blame] | 46 | spinlock_t queue_lock; /* protect ->batch_queue, ->running */ |
| 47 | bool running; |
| 48 | /* callbacks just queued */ |
| 49 | struct rcu_batch batch_queue; |
| 50 | /* callbacks try to do the first check_zero */ |
| 51 | struct rcu_batch batch_check0; |
| 52 | /* callbacks done with the first check_zero and the flip */ |
| 53 | struct rcu_batch batch_check1; |
| 54 | struct rcu_batch batch_done; |
| 55 | struct delayed_work work; |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 56 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| 57 | struct lockdep_map dep_map; |
| 58 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
Paul E. McKenney | 621934e | 2006-10-04 02:17:02 -0700 | [diff] [blame] | 59 | }; |
| 60 | |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 61 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| 62 | |
| 63 | int __init_srcu_struct(struct srcu_struct *sp, const char *name, |
| 64 | struct lock_class_key *key); |
| 65 | |
| 66 | #define init_srcu_struct(sp) \ |
| 67 | ({ \ |
| 68 | static struct lock_class_key __srcu_key; \ |
| 69 | \ |
| 70 | __init_srcu_struct((sp), #sp, &__srcu_key); \ |
| 71 | }) |
| 72 | |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 73 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| 74 | |
Alan Stern | e6a9201 | 2006-10-04 02:17:05 -0700 | [diff] [blame] | 75 | int init_srcu_struct(struct srcu_struct *sp); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 76 | |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 77 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| 78 | |
Lai Jiangshan | 931ea9d | 2012-03-19 16:12:13 +0800 | [diff] [blame] | 79 | /** |
| 80 | * call_srcu() - Queue a callback for invocation after an SRCU grace period |
| 81 | * @sp: srcu_struct in queue the callback |
| 82 | * @head: structure to be used for queueing the SRCU callback. |
| 83 | * @func: function to be invoked after the SRCU grace period |
| 84 | * |
| 85 | * The callback function will be invoked some time after a full SRCU |
| 86 | * grace period elapses, in other words after all pre-existing SRCU |
| 87 | * read-side critical sections have completed. However, the callback |
| 88 | * function might well execute concurrently with other SRCU read-side |
| 89 | * critical sections that started after call_srcu() was invoked. SRCU |
| 90 | * read-side critical sections are delimited by srcu_read_lock() and |
| 91 | * srcu_read_unlock(), and may be nested. |
| 92 | * |
| 93 | * The callback will be invoked from process context, but must nevertheless |
| 94 | * be fast and must not block. |
| 95 | */ |
| 96 | void call_srcu(struct srcu_struct *sp, struct rcu_head *head, |
| 97 | void (*func)(struct rcu_head *head)); |
| 98 | |
Paul E. McKenney | 621934e | 2006-10-04 02:17:02 -0700 | [diff] [blame] | 99 | void cleanup_srcu_struct(struct srcu_struct *sp); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 100 | int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp); |
| 101 | void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp); |
Paul E. McKenney | 621934e | 2006-10-04 02:17:02 -0700 | [diff] [blame] | 102 | void synchronize_srcu(struct srcu_struct *sp); |
Paul E. McKenney | 0cd397d | 2009-10-25 19:03:51 -0700 | [diff] [blame] | 103 | void synchronize_srcu_expedited(struct srcu_struct *sp); |
Paul E. McKenney | 621934e | 2006-10-04 02:17:02 -0700 | [diff] [blame] | 104 | long srcu_batches_completed(struct srcu_struct *sp); |
Lai Jiangshan | 931ea9d | 2012-03-19 16:12:13 +0800 | [diff] [blame] | 105 | void srcu_barrier(struct srcu_struct *sp); |
Alan Stern | eabc069 | 2006-10-04 02:17:04 -0700 | [diff] [blame] | 106 | |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 107 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| 108 | |
| 109 | /** |
| 110 | * srcu_read_lock_held - might we be in SRCU read-side critical section? |
| 111 | * |
Paul E. McKenney | d20200b | 2010-03-30 10:52:21 -0700 | [diff] [blame] | 112 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU |
| 113 | * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 114 | * this assumes we are in an SRCU read-side critical section unless it can |
| 115 | * prove otherwise. |
Paul E. McKenney | ff195cb | 2011-10-07 18:22:04 +0200 | [diff] [blame] | 116 | * |
Paul E. McKenney | 867f236 | 2011-10-07 18:22:05 +0200 | [diff] [blame] | 117 | * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot |
| 118 | * and while lockdep is disabled. |
| 119 | * |
Paul E. McKenney | ff195cb | 2011-10-07 18:22:04 +0200 | [diff] [blame] | 120 | * Note that if the CPU is in the idle loop from an RCU point of view |
| 121 | * (ie: that we are in the section between rcu_idle_enter() and |
| 122 | * rcu_idle_exit()) then srcu_read_lock_held() returns false even if |
| 123 | * the CPU did an srcu_read_lock(). The reason for this is that RCU |
| 124 | * ignores CPUs that are in such a section, considering these as in |
| 125 | * extended quiescent state, so such a CPU is effectively never in an |
| 126 | * RCU read-side critical section regardless of what RCU primitives it |
| 127 | * invokes. This state of affairs is required --- we need to keep an |
| 128 | * RCU-free window in idle where the CPU may possibly enter into low |
| 129 | * power mode. This way we can notice an extended quiescent state to |
| 130 | * other CPUs that started a grace period. Otherwise we would delay any |
| 131 | * grace period as long as we run in the idle task. |
Paul E. McKenney | c0d6d01 | 2012-01-23 12:41:26 -0800 | [diff] [blame] | 132 | * |
| 133 | * Similarly, we avoid claiming an SRCU read lock held if the current |
| 134 | * CPU is offline. |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 135 | */ |
| 136 | static inline int srcu_read_lock_held(struct srcu_struct *sp) |
| 137 | { |
Paul E. McKenney | 867f236 | 2011-10-07 18:22:05 +0200 | [diff] [blame] | 138 | if (!debug_lockdep_rcu_enabled()) |
Paul E. McKenney | ff195cb | 2011-10-07 18:22:04 +0200 | [diff] [blame] | 139 | return 1; |
Paul E. McKenney | c0d6d01 | 2012-01-23 12:41:26 -0800 | [diff] [blame] | 140 | if (rcu_is_cpu_idle()) |
| 141 | return 0; |
| 142 | if (!rcu_lockdep_current_cpu_online()) |
| 143 | return 0; |
Paul E. McKenney | ff195cb | 2011-10-07 18:22:04 +0200 | [diff] [blame] | 144 | return lock_is_held(&sp->dep_map); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 145 | } |
| 146 | |
| 147 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| 148 | |
| 149 | static inline int srcu_read_lock_held(struct srcu_struct *sp) |
| 150 | { |
| 151 | return 1; |
| 152 | } |
| 153 | |
| 154 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| 155 | |
| 156 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 157 | * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing |
| 158 | * @p: the pointer to fetch and protect for later dereferencing |
| 159 | * @sp: pointer to the srcu_struct, which is used to check that we |
| 160 | * really are in an SRCU read-side critical section. |
| 161 | * @c: condition to check for update-side use |
Paul E. McKenney | c26d34a | 2010-02-22 17:04:46 -0800 | [diff] [blame] | 162 | * |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 163 | * If PROVE_RCU is enabled, invoking this outside of an RCU read-side |
| 164 | * critical section will result in an RCU-lockdep splat, unless @c evaluates |
| 165 | * to 1. The @c argument will normally be a logical expression containing |
| 166 | * lockdep_is_held() calls. |
Paul E. McKenney | c26d34a | 2010-02-22 17:04:46 -0800 | [diff] [blame] | 167 | */ |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 168 | #define srcu_dereference_check(p, sp, c) \ |
| 169 | __rcu_dereference_check((p), srcu_read_lock_held(sp) || (c), __rcu) |
| 170 | |
| 171 | /** |
| 172 | * srcu_dereference - fetch SRCU-protected pointer for later dereferencing |
| 173 | * @p: the pointer to fetch and protect for later dereferencing |
| 174 | * @sp: pointer to the srcu_struct, which is used to check that we |
| 175 | * really are in an SRCU read-side critical section. |
| 176 | * |
| 177 | * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU |
| 178 | * is enabled, invoking this outside of an RCU read-side critical |
| 179 | * section will result in an RCU-lockdep splat. |
| 180 | */ |
| 181 | #define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0) |
Paul E. McKenney | c26d34a | 2010-02-22 17:04:46 -0800 | [diff] [blame] | 182 | |
| 183 | /** |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 184 | * srcu_read_lock - register a new reader for an SRCU-protected structure. |
| 185 | * @sp: srcu_struct in which to register the new reader. |
| 186 | * |
| 187 | * Enter an SRCU read-side critical section. Note that SRCU read-side |
Paul E. McKenney | 73d4da4 | 2010-08-16 10:50:54 -0700 | [diff] [blame] | 188 | * critical sections may be nested. However, it is illegal to |
| 189 | * call anything that waits on an SRCU grace period for the same |
| 190 | * srcu_struct, whether directly or indirectly. Please note that |
| 191 | * one way to indirectly wait on an SRCU grace period is to acquire |
| 192 | * a mutex that is held elsewhere while calling synchronize_srcu() or |
| 193 | * synchronize_srcu_expedited(). |
Paul E. McKenney | 3842a08 | 2011-11-28 10:42:42 -0800 | [diff] [blame] | 194 | * |
| 195 | * Note that srcu_read_lock() and the matching srcu_read_unlock() must |
| 196 | * occur in the same context, for example, it is illegal to invoke |
| 197 | * srcu_read_unlock() in an irq handler if the matching srcu_read_lock() |
| 198 | * was invoked in process context. |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 199 | */ |
| 200 | static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) |
| 201 | { |
| 202 | int retval = __srcu_read_lock(sp); |
| 203 | |
Paul E. McKenney | ff195cb | 2011-10-07 18:22:04 +0200 | [diff] [blame] | 204 | rcu_lock_acquire(&(sp)->dep_map); |
Heiko Carstens | bde23c6 | 2012-02-01 10:30:46 -0800 | [diff] [blame] | 205 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
| 206 | "srcu_read_lock() used illegally while idle"); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 207 | return retval; |
| 208 | } |
| 209 | |
| 210 | /** |
| 211 | * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. |
| 212 | * @sp: srcu_struct in which to unregister the old reader. |
| 213 | * @idx: return value from corresponding srcu_read_lock(). |
| 214 | * |
| 215 | * Exit an SRCU read-side critical section. |
| 216 | */ |
| 217 | static inline void srcu_read_unlock(struct srcu_struct *sp, int idx) |
| 218 | __releases(sp) |
| 219 | { |
Heiko Carstens | bde23c6 | 2012-02-01 10:30:46 -0800 | [diff] [blame] | 220 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
| 221 | "srcu_read_unlock() used illegally while idle"); |
Paul E. McKenney | ff195cb | 2011-10-07 18:22:04 +0200 | [diff] [blame] | 222 | rcu_lock_release(&(sp)->dep_map); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 223 | __srcu_read_unlock(sp, idx); |
| 224 | } |
| 225 | |
Paul E. McKenney | 0c53dd8 | 2011-10-09 15:13:11 -0700 | [diff] [blame] | 226 | /** |
| 227 | * srcu_read_lock_raw - register a new reader for an SRCU-protected structure. |
| 228 | * @sp: srcu_struct in which to register the new reader. |
| 229 | * |
| 230 | * Enter an SRCU read-side critical section. Similar to srcu_read_lock(), |
| 231 | * but avoids the RCU-lockdep checking. This means that it is legal to |
| 232 | * use srcu_read_lock_raw() in one context, for example, in an exception |
| 233 | * handler, and then have the matching srcu_read_unlock_raw() in another |
| 234 | * context, for example in the task that took the exception. |
| 235 | * |
| 236 | * However, the entire SRCU read-side critical section must reside within a |
| 237 | * single task. For example, beware of using srcu_read_lock_raw() in |
| 238 | * a device interrupt handler and srcu_read_unlock() in the interrupted |
| 239 | * task: This will not work if interrupts are threaded. |
| 240 | */ |
| 241 | static inline int srcu_read_lock_raw(struct srcu_struct *sp) |
| 242 | { |
| 243 | unsigned long flags; |
| 244 | int ret; |
| 245 | |
| 246 | local_irq_save(flags); |
| 247 | ret = __srcu_read_lock(sp); |
| 248 | local_irq_restore(flags); |
| 249 | return ret; |
| 250 | } |
| 251 | |
| 252 | /** |
| 253 | * srcu_read_unlock_raw - unregister reader from an SRCU-protected structure. |
| 254 | * @sp: srcu_struct in which to unregister the old reader. |
| 255 | * @idx: return value from corresponding srcu_read_lock_raw(). |
| 256 | * |
| 257 | * Exit an SRCU read-side critical section without lockdep-RCU checking. |
| 258 | * See srcu_read_lock_raw() for more details. |
| 259 | */ |
| 260 | static inline void srcu_read_unlock_raw(struct srcu_struct *sp, int idx) |
| 261 | { |
| 262 | unsigned long flags; |
| 263 | |
| 264 | local_irq_save(flags); |
| 265 | __srcu_read_unlock(sp, idx); |
| 266 | local_irq_restore(flags); |
| 267 | } |
| 268 | |
Alan Stern | eabc069 | 2006-10-04 02:17:04 -0700 | [diff] [blame] | 269 | #endif |