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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, bool quiesced);
 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 /**
 78  * cleanup_srcu_struct - deconstruct a sleep-RCU structure
 79  * @sp: structure to clean up.
 80  *
 81  * Must invoke this after you are finished using a given srcu_struct that
 82  * was initialized via init_srcu_struct(), else you leak memory.
 83  */
 84 static inline void cleanup_srcu_struct(struct srcu_struct *sp)
 85 {
 86         _cleanup_srcu_struct(sp, false);
 87 }
 88 
 89 /**
 90  * cleanup_srcu_struct_quiesced - deconstruct a quiesced sleep-RCU structure
 91  * @sp: structure to clean up.
 92  *
 93  * Must invoke this after you are finished using a given srcu_struct that
 94  * was initialized via init_srcu_struct(), else you leak memory.  Also,
 95  * all grace-period processing must have completed.
 96  *
 97  * "Completed" means that the last synchronize_srcu() and
 98  * synchronize_srcu_expedited() calls must have returned before the call
 99  * to cleanup_srcu_struct_quiesced().  It also means that the callback
100  * from the last call_srcu() must have been invoked before the call to
101  * cleanup_srcu_struct_quiesced(), but you can use srcu_barrier() to help
102  * with this last.  Violating these rules will get you a WARN_ON() splat
103  * (with high probability, anyway), and will also cause the srcu_struct
104  * to be leaked.
105  */
106 static inline void cleanup_srcu_struct_quiesced(struct srcu_struct *sp)
107 {
108         _cleanup_srcu_struct(sp, true);
109 }
110 
111 #ifdef CONFIG_DEBUG_LOCK_ALLOC
112 
113 /**
114  * srcu_read_lock_held - might we be in SRCU read-side critical section?
115  * @sp: The srcu_struct structure to check
116  *
117  * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU
118  * read-side critical section.  In absence of CONFIG_DEBUG_LOCK_ALLOC,
119  * this assumes we are in an SRCU read-side critical section unless it can
120  * prove otherwise.
121  *
122  * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
123  * and while lockdep is disabled.
124  *
125  * Note that SRCU is based on its own statemachine and it doesn't
126  * relies on normal RCU, it can be called from the CPU which
127  * is in the idle loop from an RCU point of view or offline.
128  */
129 static inline int srcu_read_lock_held(const struct srcu_struct *sp)
130 {
131         if (!debug_lockdep_rcu_enabled())
132                 return 1;
133         return lock_is_held(&sp->dep_map);
134 }
135 
136 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
137 
138 static inline int srcu_read_lock_held(const struct srcu_struct *sp)
139 {
140         return 1;
141 }
142 
143 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
144 
145 /**
146  * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
147  * @p: the pointer to fetch and protect for later dereferencing
148  * @sp: pointer to the srcu_struct, which is used to check that we
149  *      really are in an SRCU read-side critical section.
150  * @c: condition to check for update-side use
151  *
152  * If PROVE_RCU is enabled, invoking this outside of an RCU read-side
153  * critical section will result in an RCU-lockdep splat, unless @c evaluates
154  * to 1.  The @c argument will normally be a logical expression containing
155  * lockdep_is_held() calls.
156  */
157 #define srcu_dereference_check(p, sp, c) \
158         __rcu_dereference_check((p), (c) || srcu_read_lock_held(sp), __rcu)
159 
160 /**
161  * srcu_dereference - fetch SRCU-protected pointer for later dereferencing
162  * @p: the pointer to fetch and protect for later dereferencing
163  * @sp: pointer to the srcu_struct, which is used to check that we
164  *      really are in an SRCU read-side critical section.
165  *
166  * Makes rcu_dereference_check() do the dirty work.  If PROVE_RCU
167  * is enabled, invoking this outside of an RCU read-side critical
168  * section will result in an RCU-lockdep splat.
169  */
170 #define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0)
171 
172 /**
173  * srcu_read_lock - register a new reader for an SRCU-protected structure.
174  * @sp: srcu_struct in which to register the new reader.
175  *
176  * Enter an SRCU read-side critical section.  Note that SRCU read-side
177  * critical sections may be nested.  However, it is illegal to
178  * call anything that waits on an SRCU grace period for the same
179  * srcu_struct, whether directly or indirectly.  Please note that
180  * one way to indirectly wait on an SRCU grace period is to acquire
181  * a mutex that is held elsewhere while calling synchronize_srcu() or
182  * synchronize_srcu_expedited().
183  *
184  * Note that srcu_read_lock() and the matching srcu_read_unlock() must
185  * occur in the same context, for example, it is illegal to invoke
186  * srcu_read_unlock() in an irq handler if the matching srcu_read_lock()
187  * was invoked in process context.
188  */
189 static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
190 {
191         int retval;
192 
193         retval = __srcu_read_lock(sp);
194         rcu_lock_acquire(&(sp)->dep_map);
195         return retval;
196 }
197 
198 /**
199  * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
200  * @sp: srcu_struct in which to unregister the old reader.
201  * @idx: return value from corresponding srcu_read_lock().
202  *
203  * Exit an SRCU read-side critical section.
204  */
205 static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
206         __releases(sp)
207 {
208         rcu_lock_release(&(sp)->dep_map);
209         __srcu_read_unlock(sp, idx);
210 }
211 
212 /**
213  * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
214  *
215  * Converts the preceding srcu_read_unlock into a two-way memory barrier.
216  *
217  * Call this after srcu_read_unlock, to guarantee that all memory operations
218  * that occur after smp_mb__after_srcu_read_unlock will appear to happen after
219  * the preceding srcu_read_unlock.
220  */
221 static inline void smp_mb__after_srcu_read_unlock(void)
222 {
223         /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
224 }
225 
226 #endif
227 

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