| 1 | |
| 2 | * Sleepable Read-Copy Update mechanism for mutual exclusion
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| 3 | *
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| 4 | * This program is free software; you can redistribute it and/or modify
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| 5 | * it under the terms of the GNU General Public License as published by
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| 6 | * the Free Software Foundation; either version 2 of the License, or
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| 7 | * (at your option) any later version.
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| 8 | *
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| 9 | * This program is distributed in the hope that it will be useful,
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| 10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 12 | * GNU General Public License for more details.
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| 13 | *
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| 14 | * You should have received a copy of the GNU General Public License
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| 15 | * along with this program; if not, you can access it online at
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| 16 | * http://www.gnu.org/licenses/gpl-2.0.html.
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| 17 | *
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| 18 | * Copyright (C) IBM Corporation, 2006
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| 19 | * Copyright (C) Fujitsu, 2012
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| 20 | *
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| 21 | * Author: Paul McKenney <[email protected]>
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| 22 | * Lai Jiangshan <[email protected]>
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| 23 | *
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| 24 | * For detailed explanation of Read-Copy Update mechanism see -
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| 25 | * Documentation/RCU/ *.txt
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| 26 | *
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| 27 |
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| 28 |
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| 29 | #ifndef _LINUX_SRCU_H
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| 30 | #define _LINUX_SRCU_H
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| 31 |
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| 32 | #include <linux/mutex.h>
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| 33 | #include <linux/rcupdate.h>
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| 34 | #include <linux/workqueue.h>
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| 35 |
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| 36 | struct srcu_struct_array {
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| 37 | unsigned long c[2];
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| 38 | unsigned long seq[2];
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| 39 | };
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| 40 |
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| 41 | struct rcu_batch {
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| 42 | struct rcu_head *head, **tail;
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| 43 | };
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| 44 |
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| 45 | #define RCU_BATCH_INIT(name) { NULL, &(name.head) }
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| 46 |
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| 47 | struct srcu_struct {
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| 48 | unsigned completed;
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| 49 | struct srcu_struct_array __percpu *per_cpu_ref;
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| 50 | spinlock_t queue_lock;
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| 51 | bool running;
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| 52 |
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| 53 | struct rcu_batch batch_queue;
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| 54 |
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| 55 | struct rcu_batch batch_check0;
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| 56 |
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| 57 | struct rcu_batch batch_check1;
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| 58 | struct rcu_batch batch_done;
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| 59 | struct delayed_work work;
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| 60 | #ifdef CONFIG_DEBUG_LOCK_ALLOC
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| 61 | struct lockdep_map dep_map;
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| 62 | #endif
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| 63 | };
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| 64 |
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| 65 | #ifdef CONFIG_DEBUG_LOCK_ALLOC
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| 66 |
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| 67 | int __init_srcu_struct(struct srcu_struct *sp, const char *name,
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| 68 | struct lock_class_key *key);
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| 69 |
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| 70 | #define init_srcu_struct(sp) \
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| 71 | ({ \
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| 72 | static struct lock_class_key __srcu_key; \
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| 73 | \
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| 74 | __init_srcu_struct((sp), #sp, &__srcu_key); \
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| 75 | })
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| 76 |
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| 77 | #define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name },
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| 78 | #else
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| 79 |
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| 80 | int init_srcu_struct(struct srcu_struct *sp);
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| 81 |
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| 82 | #define __SRCU_DEP_MAP_INIT(srcu_name)
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| 83 | #endif
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| 84 |
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| 85 | void process_srcu(struct work_struct *work);
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| 86 |
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| 87 | #define __SRCU_STRUCT_INIT(name) \
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| 88 | { \
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| 89 | .completed = -300, \
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| 90 | .per_cpu_ref = &name##_srcu_array, \
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| 91 | .queue_lock = __SPIN_LOCK_UNLOCKED(name.queue_lock), \
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| 92 | .running = false, \
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| 93 | .batch_queue = RCU_BATCH_INIT(name.batch_queue), \
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| 94 | .batch_check0 = RCU_BATCH_INIT(name.batch_check0), \
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| 95 | .batch_check1 = RCU_BATCH_INIT(name.batch_check1), \
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| 96 | .batch_done = RCU_BATCH_INIT(name.batch_done), \
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| 97 | .work = __DELAYED_WORK_INITIALIZER(name.work, process_srcu, 0),\
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| 98 | __SRCU_DEP_MAP_INIT(name) \
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| 99 | }
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| 100 |
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| 101 | |
| 102 | * define and init a srcu struct at build time.
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| 103 | * dont't call init_srcu_struct() nor cleanup_srcu_struct() on it.
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| 104 |
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| 105 | #define DEFINE_SRCU(name) \
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| 106 | static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\
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| 107 | struct srcu_struct name = __SRCU_STRUCT_INIT(name);
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| 108 |
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| 109 | #define DEFINE_STATIC_SRCU(name) \
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| 110 | static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\
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| 111 | static struct srcu_struct name = __SRCU_STRUCT_INIT(name);
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| 112 |
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| 113 | |
| 114 | * call_srcu() - Queue a callback for invocation after an SRCU grace period
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| 115 | * @sp: srcu_struct in queue the callback
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| 116 | * @head: structure to be used for queueing the SRCU callback.
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| 117 | * @func: function to be invoked after the SRCU grace period
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| 118 | *
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| 119 | * The callback function will be invoked some time after a full SRCU
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| 120 | * grace period elapses, in other words after all pre-existing SRCU
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| 121 | * read-side critical sections have completed. However, the callback
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| 122 | * function might well execute concurrently with other SRCU read-side
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| 123 | * critical sections that started after call_srcu() was invoked. SRCU
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| 124 | * read-side critical sections are delimited by srcu_read_lock() and
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| 125 | * srcu_read_unlock(), and may be nested.
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| 126 | *
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| 127 | * The callback will be invoked from process context, but must nevertheless
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| 128 | * be fast and must not block.
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| 129 |
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| 130 | void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
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| 131 | void (*func)(struct rcu_head *head));
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| 132 |
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| 133 | void cleanup_srcu_struct(struct srcu_struct *sp);
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| 134 | int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
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| 135 | void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
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| 136 | void synchronize_srcu(struct srcu_struct *sp);
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| 137 | void synchronize_srcu_expedited(struct srcu_struct *sp);
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| 138 | long srcu_batches_completed(struct srcu_struct *sp);
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| 139 | void srcu_barrier(struct srcu_struct *sp);
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| 140 |
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| 141 | #ifdef CONFIG_DEBUG_LOCK_ALLOC
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| 142 |
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| 143 | |
| 144 | * srcu_read_lock_held - might we be in SRCU read-side critical section?
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| 145 | *
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| 146 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU
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| 147 | * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
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| 148 | * this assumes we are in an SRCU read-side critical section unless it can
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| 149 | * prove otherwise.
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| 150 | *
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| 151 | * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
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| 152 | * and while lockdep is disabled.
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| 153 | *
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| 154 | * Note that SRCU is based on its own statemachine and it doesn't
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| 155 | * relies on normal RCU, it can be called from the CPU which
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| 156 | * is in the idle loop from an RCU point of view or offline.
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| 157 |
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| 158 | static inline int srcu_read_lock_held(struct srcu_struct *sp)
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| 159 | {
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| 160 | if (!debug_lockdep_rcu_enabled())
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| 161 | return 1;
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| 162 | return lock_is_held(&sp->dep_map);
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| 163 | }
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| 164 |
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| 165 | #else
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| 166 |
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| 167 | static inline int srcu_read_lock_held(struct srcu_struct *sp)
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| 168 | {
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| 169 | return 1;
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| 170 | }
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| 171 |
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| 172 | #endif
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| 173 |
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| 174 | |
| 175 | * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
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| 176 | * @p: the pointer to fetch and protect for later dereferencing
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| 177 | * @sp: pointer to the srcu_struct, which is used to check that we
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| 178 | * really are in an SRCU read-side critical section.
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| 179 | * @c: condition to check for update-side use
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| 180 | *
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| 181 | * If PROVE_RCU is enabled, invoking this outside of an RCU read-side
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| 182 | * critical section will result in an RCU-lockdep splat, unless @c evaluates
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| 183 | * to 1. The @c argument will normally be a logical expression containing
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| 184 | * lockdep_is_held() calls.
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| 185 |
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| 186 | #define srcu_dereference_check(p, sp, c) \
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| 187 | __rcu_dereference_check((p), srcu_read_lock_held(sp) || (c), __rcu)
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| 188 |
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| 189 | |
| 190 | * srcu_dereference - fetch SRCU-protected pointer for later dereferencing
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| 191 | * @p: the pointer to fetch and protect for later dereferencing
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| 192 | * @sp: pointer to the srcu_struct, which is used to check that we
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| 193 | * really are in an SRCU read-side critical section.
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| 194 | *
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| 195 | * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU
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| 196 | * is enabled, invoking this outside of an RCU read-side critical
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| 197 | * section will result in an RCU-lockdep splat.
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| 198 |
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| 199 | #define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0)
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| 200 |
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| 201 | |
| 202 | * srcu_read_lock - register a new reader for an SRCU-protected structure.
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| 203 | * @sp: srcu_struct in which to register the new reader.
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| 204 | *
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| 205 | * Enter an SRCU read-side critical section. Note that SRCU read-side
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| 206 | * critical sections may be nested. However, it is illegal to
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| 207 | * call anything that waits on an SRCU grace period for the same
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| 208 | * srcu_struct, whether directly or indirectly. Please note that
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| 209 | * one way to indirectly wait on an SRCU grace period is to acquire
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| 210 | * a mutex that is held elsewhere while calling synchronize_srcu() or
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| 211 | * synchronize_srcu_expedited().
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| 212 | *
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| 213 | * Note that srcu_read_lock() and the matching srcu_read_unlock() must
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| 214 | * occur in the same context, for example, it is illegal to invoke
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| 215 | * srcu_read_unlock() in an irq handler if the matching srcu_read_lock()
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| 216 | * was invoked in process context.
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| 217 |
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| 218 | static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
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| 219 | {
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| 220 | int retval = __srcu_read_lock(sp);
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| 221 |
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| 222 | rcu_lock_acquire(&(sp)->dep_map);
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| 223 | return retval;
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| 224 | }
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| 225 |
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| 226 | |
| 227 | * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
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| 228 | * @sp: srcu_struct in which to unregister the old reader.
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| 229 | * @idx: return value from corresponding srcu_read_lock().
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| 230 | *
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| 231 | * Exit an SRCU read-side critical section.
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| 232 |
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| 233 | static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
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| 234 | __releases(sp)
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| 235 | {
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| 236 | rcu_lock_release(&(sp)->dep_map);
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| 237 | __srcu_read_unlock(sp, idx);
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| 238 | }
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| 239 |
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| 240 | |
| 241 | * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
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| 242 | *
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| 243 | * Converts the preceding srcu_read_unlock into a two-way memory barrier.
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| 244 | *
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| 245 | * Call this after srcu_read_unlock, to guarantee that all memory operations
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| 246 | * that occur after smp_mb__after_srcu_read_unlock will appear to happen after
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| 247 | * the preceding srcu_read_unlock.
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| 248 |
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| 249 | static inline void smp_mb__after_srcu_read_unlock(void)
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| 250 | {
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| 251 |
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| 252 | }
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| 253 |
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| 254 | #endif
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