2 * Sleepable Read-Copy Update mechanism for mutual exclusion
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.
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.
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.
18 * Copyright (C) IBM Corporation, 2006
20 * Author: Paul McKenney <paulmck@us.ibm.com>
22 * For detailed explanation of Read-Copy Update mechanism see -
23 * Documentation/RCU/ *.txt
30 struct srcu_struct_array
{
36 struct srcu_struct_array
*per_cpu_ref
;
38 #ifdef CONFIG_DEBUG_LOCK_ALLOC
39 struct lockdep_map dep_map
;
40 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
43 #ifndef CONFIG_PREEMPT
44 #define srcu_barrier() barrier()
45 #else /* #ifndef CONFIG_PREEMPT */
46 #define srcu_barrier()
47 #endif /* #else #ifndef CONFIG_PREEMPT */
49 #ifdef CONFIG_DEBUG_LOCK_ALLOC
51 int __init_srcu_struct(struct srcu_struct
*sp
, const char *name
,
52 struct lock_class_key
*key
);
54 #define init_srcu_struct(sp) \
56 static struct lock_class_key __srcu_key; \
58 __init_srcu_struct((sp), #sp, &__srcu_key); \
61 # define srcu_read_acquire(sp) \
62 lock_acquire(&(sp)->dep_map, 0, 0, 2, 1, NULL, _THIS_IP_)
63 # define srcu_read_release(sp) \
64 lock_release(&(sp)->dep_map, 1, _THIS_IP_)
66 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
68 int init_srcu_struct(struct srcu_struct
*sp
);
70 # define srcu_read_acquire(sp) do { } while (0)
71 # define srcu_read_release(sp) do { } while (0)
73 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
75 void cleanup_srcu_struct(struct srcu_struct
*sp
);
76 int __srcu_read_lock(struct srcu_struct
*sp
) __acquires(sp
);
77 void __srcu_read_unlock(struct srcu_struct
*sp
, int idx
) __releases(sp
);
78 void synchronize_srcu(struct srcu_struct
*sp
);
79 void synchronize_srcu_expedited(struct srcu_struct
*sp
);
80 long srcu_batches_completed(struct srcu_struct
*sp
);
82 #ifdef CONFIG_DEBUG_LOCK_ALLOC
85 * srcu_read_lock_held - might we be in SRCU read-side critical section?
87 * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in
88 * an SRCU read-side critical section. In absence of CONFIG_PROVE_LOCKING,
89 * this assumes we are in an SRCU read-side critical section unless it can
92 static inline int srcu_read_lock_held(struct srcu_struct
*sp
)
95 return lock_is_held(&sp
->dep_map
);
99 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
101 static inline int srcu_read_lock_held(struct srcu_struct
*sp
)
106 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
109 * srcu_dereference - fetch SRCU-protected pointer with checking
111 * Makes rcu_dereference_check() do the dirty work.
113 #define srcu_dereference(p, sp) \
114 rcu_dereference_check(p, srcu_read_lock_held(sp))
117 * srcu_read_lock - register a new reader for an SRCU-protected structure.
118 * @sp: srcu_struct in which to register the new reader.
120 * Enter an SRCU read-side critical section. Note that SRCU read-side
121 * critical sections may be nested.
123 static inline int srcu_read_lock(struct srcu_struct
*sp
) __acquires(sp
)
125 int retval
= __srcu_read_lock(sp
);
127 srcu_read_acquire(sp
);
132 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
133 * @sp: srcu_struct in which to unregister the old reader.
134 * @idx: return value from corresponding srcu_read_lock().
136 * Exit an SRCU read-side critical section.
138 static inline void srcu_read_unlock(struct srcu_struct
*sp
, int idx
)
141 srcu_read_release(sp
);
142 __srcu_read_unlock(sp
, idx
);