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 * Copyright (C) Fujitsu, 2012 20 * 21 * Author: Paul McKenney <paulmck@us.ibm.com> 22 * Lai Jiangshan <laijs@cn.fujitsu.com> 23 * 24 * For detailed explanation of Read-Copy Update mechanism see - 25 * Documentation/RCU/ *.txt 26 * 27 */ 28 29#ifndef _LINUX_SRCU_H 30#define _LINUX_SRCU_H 31 32#include <linux/mutex.h> 33#include <linux/rcupdate.h> 34#include <linux/workqueue.h> 35 36struct srcu_struct_array { 37 unsigned long c[2]; 38 unsigned long seq[2]; 39}; 40 41struct rcu_batch { 42 struct rcu_head *head, **tail; 43}; 44 45#define RCU_BATCH_INIT(name) { NULL, &(name.head) } 46 47struct srcu_struct { 48 unsigned completed; 49 struct srcu_struct_array __percpu *per_cpu_ref; 50 spinlock_t queue_lock; /* protect ->batch_queue, ->running */ 51 bool running; 52 /* callbacks just queued */ 53 struct rcu_batch batch_queue; 54 /* callbacks try to do the first check_zero */ 55 struct rcu_batch batch_check0; 56 /* callbacks done with the first check_zero and the flip */ 57 struct rcu_batch batch_check1; 58 struct rcu_batch batch_done; 59 struct delayed_work work; 60#ifdef CONFIG_DEBUG_LOCK_ALLOC 61 struct lockdep_map dep_map; 62#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 63}; 64 65#ifdef CONFIG_DEBUG_LOCK_ALLOC 66 67int __init_srcu_struct(struct srcu_struct *sp, const char *name, 68 struct lock_class_key *key); 69 70#define init_srcu_struct(sp) \ 71({ \ 72 static struct lock_class_key __srcu_key; \ 73 \ 74 __init_srcu_struct((sp), #sp, &__srcu_key); \ 75}) 76 77#define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name }, 78#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 79 80int init_srcu_struct(struct srcu_struct *sp); 81 82#define __SRCU_DEP_MAP_INIT(srcu_name) 83#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 84 85void process_srcu(struct work_struct *work); 86 87#define __SRCU_STRUCT_INIT(name) \ 88 { \ 89 .completed = -300, \ 90 .per_cpu_ref = &name##_srcu_array, \ 91 .queue_lock = __SPIN_LOCK_UNLOCKED(name.queue_lock), \ 92 .running = false, \ 93 .batch_queue = RCU_BATCH_INIT(name.batch_queue), \ 94 .batch_check0 = RCU_BATCH_INIT(name.batch_check0), \ 95 .batch_check1 = RCU_BATCH_INIT(name.batch_check1), \ 96 .batch_done = RCU_BATCH_INIT(name.batch_done), \ 97 .work = __DELAYED_WORK_INITIALIZER(name.work, process_srcu, 0),\ 98 __SRCU_DEP_MAP_INIT(name) \ 99 } 100 101/* 102 * define and init a srcu struct at build time. 103 * dont't call init_srcu_struct() nor cleanup_srcu_struct() on it. 104 */ 105#define DEFINE_SRCU(name) \ 106 static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\ 107 struct srcu_struct name = __SRCU_STRUCT_INIT(name); 108 109#define DEFINE_STATIC_SRCU(name) \ 110 static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\ 111 static struct srcu_struct name = __SRCU_STRUCT_INIT(name); 112 113/** 114 * call_srcu() - Queue a callback for invocation after an SRCU grace period 115 * @sp: srcu_struct in queue the callback 116 * @head: structure to be used for queueing the SRCU callback. 117 * @func: function to be invoked after the SRCU grace period 118 * 119 * The callback function will be invoked some time after a full SRCU 120 * grace period elapses, in other words after all pre-existing SRCU 121 * read-side critical sections have completed. However, the callback 122 * function might well execute concurrently with other SRCU read-side 123 * critical sections that started after call_srcu() was invoked. SRCU 124 * read-side critical sections are delimited by srcu_read_lock() and 125 * srcu_read_unlock(), and may be nested. 126 * 127 * The callback will be invoked from process context, but must nevertheless 128 * be fast and must not block. 129 */ 130void call_srcu(struct srcu_struct *sp, struct rcu_head *head, 131 void (*func)(struct rcu_head *head)); 132 133void cleanup_srcu_struct(struct srcu_struct *sp); 134int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp); 135void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp); 136void synchronize_srcu(struct srcu_struct *sp); 137void synchronize_srcu_expedited(struct srcu_struct *sp); 138long srcu_batches_completed(struct srcu_struct *sp); 139void srcu_barrier(struct srcu_struct *sp); 140 141#ifdef CONFIG_DEBUG_LOCK_ALLOC 142 143/** 144 * srcu_read_lock_held - might we be in SRCU read-side critical section? 145 * 146 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU 147 * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, 148 * this assumes we are in an SRCU read-side critical section unless it can 149 * prove otherwise. 150 * 151 * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot 152 * and while lockdep is disabled. 153 * 154 * Note that SRCU is based on its own statemachine and it doesn't 155 * relies on normal RCU, it can be called from the CPU which 156 * is in the idle loop from an RCU point of view or offline. 157 */ 158static inline int srcu_read_lock_held(struct srcu_struct *sp) 159{ 160 if (!debug_lockdep_rcu_enabled()) 161 return 1; 162 return lock_is_held(&sp->dep_map); 163} 164 165#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 166 167static inline int srcu_read_lock_held(struct srcu_struct *sp) 168{ 169 return 1; 170} 171 172#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 173 174/** 175 * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing 176 * @p: the pointer to fetch and protect for later dereferencing 177 * @sp: pointer to the srcu_struct, which is used to check that we 178 * really are in an SRCU read-side critical section. 179 * @c: condition to check for update-side use 180 * 181 * If PROVE_RCU is enabled, invoking this outside of an RCU read-side 182 * critical section will result in an RCU-lockdep splat, unless @c evaluates 183 * to 1. The @c argument will normally be a logical expression containing 184 * lockdep_is_held() calls. 185 */ 186#define srcu_dereference_check(p, sp, c) \ 187 __rcu_dereference_check((p), srcu_read_lock_held(sp) || (c), __rcu) 188 189/** 190 * srcu_dereference - fetch SRCU-protected pointer for later dereferencing 191 * @p: the pointer to fetch and protect for later dereferencing 192 * @sp: pointer to the srcu_struct, which is used to check that we 193 * really are in an SRCU read-side critical section. 194 * 195 * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU 196 * is enabled, invoking this outside of an RCU read-side critical 197 * section will result in an RCU-lockdep splat. 198 */ 199#define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0) 200 201/** 202 * srcu_read_lock - register a new reader for an SRCU-protected structure. 203 * @sp: srcu_struct in which to register the new reader. 204 * 205 * Enter an SRCU read-side critical section. Note that SRCU read-side 206 * critical sections may be nested. However, it is illegal to 207 * call anything that waits on an SRCU grace period for the same 208 * srcu_struct, whether directly or indirectly. Please note that 209 * one way to indirectly wait on an SRCU grace period is to acquire 210 * a mutex that is held elsewhere while calling synchronize_srcu() or 211 * synchronize_srcu_expedited(). 212 * 213 * Note that srcu_read_lock() and the matching srcu_read_unlock() must 214 * occur in the same context, for example, it is illegal to invoke 215 * srcu_read_unlock() in an irq handler if the matching srcu_read_lock() 216 * was invoked in process context. 217 */ 218static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) 219{ 220 int retval = __srcu_read_lock(sp); 221 222 rcu_lock_acquire(&(sp)->dep_map); 223 return retval; 224} 225 226/** 227 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. 228 * @sp: srcu_struct in which to unregister the old reader. 229 * @idx: return value from corresponding srcu_read_lock(). 230 * 231 * Exit an SRCU read-side critical section. 232 */ 233static inline void srcu_read_unlock(struct srcu_struct *sp, int idx) 234 __releases(sp) 235{ 236 rcu_lock_release(&(sp)->dep_map); 237 __srcu_read_unlock(sp, idx); 238} 239 240#endif 241