include/linux/srcu.h

   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  *
  20  * Author: Paul McKenney <paulmck@us.ibm.com>
  21  *
  22  * For detailed explanation of Read-Copy Update mechanism see -
  23  *              Documentation/RCU/ *.txt
  24  *
  25  */
  26
  27 #ifndef _LINUX_SRCU_H
  28 #define _LINUX_SRCU_H
  29
  30 struct srcu_struct_array {
  31         int c[2];
  32 };
  33
  34 struct srcu_struct {
  35         int completed;
  36         struct srcu_struct_array __percpu *per_cpu_ref;
  37         struct mutex mutex;
  38 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  39         struct lockdep_map dep_map;
  40 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
  41 };
  42
  43 #ifndef CONFIG_PREEMPT
  44 #define srcu_barrier() barrier()
  45 #else /* #ifndef CONFIG_PREEMPT */
  46 #define srcu_barrier()
  47 #endif /* #else #ifndef CONFIG_PREEMPT */
  48
  49 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  50
  51 int __init_srcu_struct(struct srcu_struct *sp, const char *name,
  52                        struct lock_class_key *key);
  53
  54 #define init_srcu_struct(sp) \
  55 ({ \
  56         static struct lock_class_key __srcu_key; \
  57         \
  58         __init_srcu_struct((sp), #sp, &__srcu_key); \
  59 })
  60
  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_)
  65
  66 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
  67
  68 int init_srcu_struct(struct srcu_struct *sp);
  69
  70 # define srcu_read_acquire(sp)  do { } while (0)
  71 # define srcu_read_release(sp)  do { } while (0)
  72
  73 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
  74
  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);
  81
  82 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  83
  84 /**
  85  * srcu_read_lock_held - might we be in SRCU read-side critical section?
  86  *
  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
  90  * prove otherwise.
  91  */
  92 static inline int srcu_read_lock_held(struct srcu_struct *sp)
  93 {
  94         if (debug_locks)
  95                 return lock_is_held(&sp->dep_map);
  96         return 1;
  97 }
  98
  99 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 100
 101 static inline int srcu_read_lock_held(struct srcu_struct *sp)
 102 {
 103         return 1;
 104 }
 105
 106 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 107
 108 /**
 109  * srcu_dereference - fetch SRCU-protected pointer with checking
 110  *
 111  * Makes rcu_dereference_check() do the dirty work.
 112  */
 113 #define srcu_dereference(p, sp) \
 114                 rcu_dereference_check(p, srcu_read_lock_held(sp))
 115
 116 /**
 117  * srcu_read_lock - register a new reader for an SRCU-protected structure.
 118  * @sp: srcu_struct in which to register the new reader.
 119  *
 120  * Enter an SRCU read-side critical section.  Note that SRCU read-side
 121  * critical sections may be nested.
 122  */
 123 static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
 124 {
 125         int retval = __srcu_read_lock(sp);
 126
 127         srcu_read_acquire(sp);
 128         return retval;
 129 }
 130
 131 /**
 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().
 135  *
 136  * Exit an SRCU read-side critical section.
 137  */
 138 static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
 139         __releases(sp)
 140 {
 141         srcu_read_release(sp);
 142         __srcu_read_unlock(sp, idx);
 143 }
 144
 145 #endif