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TOMOYO Linux Cross Reference
Linux/include/linux/srcu.h

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  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, you can access it online at
 16  * http://www.gnu.org/licenses/gpl-2.0.html.
 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 #include <linux/rcu_segcblist.h>
 36 
 37 struct srcu_struct;
 38 
 39 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 40 
 41 int __init_srcu_struct(struct srcu_struct *sp, const char *name,
 42                        struct lock_class_key *key);
 43 
 44 #define init_srcu_struct(sp) \
 45 ({ \
 46         static struct lock_class_key __srcu_key; \
 47         \
 48         __init_srcu_struct((sp), #sp, &__srcu_key); \
 49 })
 50 
 51 #define __SRCU_DEP_MAP_INIT(srcu_name)  .dep_map = { .name = #srcu_name },
 52 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 53 
 54 int init_srcu_struct(struct srcu_struct *sp);
 55 
 56 #define __SRCU_DEP_MAP_INIT(srcu_name)
 57 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 58 
 59 #ifdef CONFIG_TINY_SRCU
 60 #include <linux/srcutiny.h>
 61 #elif defined(CONFIG_TREE_SRCU)
 62 #include <linux/srcutree.h>
 63 #elif defined(CONFIG_SRCU)
 64 #error "Unknown SRCU implementation specified to kernel configuration"
 65 #else
 66 /* Dummy definition for things like notifiers.  Actual use gets link error. */
 67 struct srcu_struct { };
 68 #endif
 69 
 70 void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
 71                 void (*func)(struct rcu_head *head));
 72 void cleanup_srcu_struct(struct srcu_struct *sp);
 73 int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
 74 void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
 75 void synchronize_srcu(struct srcu_struct *sp);
 76 
 77 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 78 
 79 /**
 80  * srcu_read_lock_held - might we be in SRCU read-side critical section?
 81  * @sp: The srcu_struct structure to check
 82  *
 83  * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU
 84  * read-side critical section.  In absence of CONFIG_DEBUG_LOCK_ALLOC,
 85  * this assumes we are in an SRCU read-side critical section unless it can
 86  * prove otherwise.
 87  *
 88  * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
 89  * and while lockdep is disabled.
 90  *
 91  * Note that SRCU is based on its own statemachine and it doesn't
 92  * relies on normal RCU, it can be called from the CPU which
 93  * is in the idle loop from an RCU point of view or offline.
 94  */
 95 static inline int srcu_read_lock_held(struct srcu_struct *sp)
 96 {
 97         if (!debug_lockdep_rcu_enabled())
 98                 return 1;
 99         return lock_is_held(&sp->dep_map);
100 }
101 
102 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
103 
104 static inline int srcu_read_lock_held(struct srcu_struct *sp)
105 {
106         return 1;
107 }
108 
109 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
110 
111 /**
112  * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
113  * @p: the pointer to fetch and protect for later dereferencing
114  * @sp: pointer to the srcu_struct, which is used to check that we
115  *      really are in an SRCU read-side critical section.
116  * @c: condition to check for update-side use
117  *
118  * If PROVE_RCU is enabled, invoking this outside of an RCU read-side
119  * critical section will result in an RCU-lockdep splat, unless @c evaluates
120  * to 1.  The @c argument will normally be a logical expression containing
121  * lockdep_is_held() calls.
122  */
123 #define srcu_dereference_check(p, sp, c) \
124         __rcu_dereference_check((p), (c) || srcu_read_lock_held(sp), __rcu)
125 
126 /**
127  * srcu_dereference - fetch SRCU-protected pointer for later dereferencing
128  * @p: the pointer to fetch and protect for later dereferencing
129  * @sp: pointer to the srcu_struct, which is used to check that we
130  *      really are in an SRCU read-side critical section.
131  *
132  * Makes rcu_dereference_check() do the dirty work.  If PROVE_RCU
133  * is enabled, invoking this outside of an RCU read-side critical
134  * section will result in an RCU-lockdep splat.
135  */
136 #define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0)
137 
138 /**
139  * srcu_read_lock - register a new reader for an SRCU-protected structure.
140  * @sp: srcu_struct in which to register the new reader.
141  *
142  * Enter an SRCU read-side critical section.  Note that SRCU read-side
143  * critical sections may be nested.  However, it is illegal to
144  * call anything that waits on an SRCU grace period for the same
145  * srcu_struct, whether directly or indirectly.  Please note that
146  * one way to indirectly wait on an SRCU grace period is to acquire
147  * a mutex that is held elsewhere while calling synchronize_srcu() or
148  * synchronize_srcu_expedited().
149  *
150  * Note that srcu_read_lock() and the matching srcu_read_unlock() must
151  * occur in the same context, for example, it is illegal to invoke
152  * srcu_read_unlock() in an irq handler if the matching srcu_read_lock()
153  * was invoked in process context.
154  */
155 static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
156 {
157         int retval;
158 
159         retval = __srcu_read_lock(sp);
160         rcu_lock_acquire(&(sp)->dep_map);
161         return retval;
162 }
163 
164 /**
165  * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
166  * @sp: srcu_struct in which to unregister the old reader.
167  * @idx: return value from corresponding srcu_read_lock().
168  *
169  * Exit an SRCU read-side critical section.
170  */
171 static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
172         __releases(sp)
173 {
174         rcu_lock_release(&(sp)->dep_map);
175         __srcu_read_unlock(sp, idx);
176 }
177 
178 /**
179  * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
180  *
181  * Converts the preceding srcu_read_unlock into a two-way memory barrier.
182  *
183  * Call this after srcu_read_unlock, to guarantee that all memory operations
184  * that occur after smp_mb__after_srcu_read_unlock will appear to happen after
185  * the preceding srcu_read_unlock.
186  */
187 static inline void smp_mb__after_srcu_read_unlock(void)
188 {
189         /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
190 }
191 
192 #endif
193 

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