include/sys/mutex.h

   1 /*
   2  *  Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
   3  *  Copyright (C) 2007 The Regents of the University of California.
   4  *  Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
   5  *  Written by Brian Behlendorf <behlendorf1@llnl.gov>.
   6  *  UCRL-CODE-235197
   7  *
   8  *  This file is part of the SPL, Solaris Porting Layer.
   9  *  For details, see <http://zfsonlinux.org/>.
  10  *
  11  *  The SPL is free software; you can redistribute it and/or modify it
  12  *  under the terms of the GNU General Public License as published by the
  13  *  Free Software Foundation; either version 2 of the License, or (at your
  14  *  option) any later version.
  15  *
  16  *  The SPL is distributed in the hope that it will be useful, but WITHOUT
  17  *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  18  *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  19  *  for more details.
  20  *
  21  *  You should have received a copy of the GNU General Public License along
  22  *  with the SPL.  If not, see <http://www.gnu.org/licenses/>.
  23  */
  24
  25 #ifndef _SPL_MUTEX_H
  26 #define _SPL_MUTEX_H
  27
  28 #include <sys/types.h>
  29 #include <linux/mutex.h>
  30 #include <linux/compiler_compat.h>
  31 #include <linux/lockdep.h>
  32
  33 typedef enum {
  34         MUTEX_DEFAULT   = 0,
  35         MUTEX_SPIN      = 1,
  36         MUTEX_ADAPTIVE  = 2,
  37         MUTEX_NOLOCKDEP = 3
  38 } kmutex_type_t;
  39
  40 typedef struct {
  41         struct mutex            m_mutex;
  42         spinlock_t              m_lock; /* used for serializing mutex_exit */
  43         kthread_t               *m_owner;
  44 #ifdef CONFIG_LOCKDEP
  45         kmutex_type_t           m_type;
  46 #endif /* CONFIG_LOCKDEP */
  47 } kmutex_t;
  48
  49 #define MUTEX(mp)               (&((mp)->m_mutex))
  50
  51 static inline void
  52 spl_mutex_set_owner(kmutex_t *mp)
  53 {
  54         mp->m_owner = current;
  55 }
  56
  57 static inline void
  58 spl_mutex_clear_owner(kmutex_t *mp)
  59 {
  60         mp->m_owner = NULL;
  61 }
  62
  63 #define mutex_owner(mp)         (ACCESS_ONCE((mp)->m_owner))
  64 #define mutex_owned(mp)         (mutex_owner(mp) == current)
  65 #define MUTEX_HELD(mp)          mutex_owned(mp)
  66 #define MUTEX_NOT_HELD(mp)      (!MUTEX_HELD(mp))
  67
  68 #ifdef CONFIG_LOCKDEP
  69 static inline void
  70 spl_mutex_set_type(kmutex_t *mp, kmutex_type_t type)
  71 {
  72         mp->m_type = type;
  73 }
  74 static inline void
  75 spl_mutex_lockdep_off_maybe(kmutex_t *mp)                       \
  76 {                                                               \
  77         if (mp && mp->m_type == MUTEX_NOLOCKDEP)                \
  78                 lockdep_off();                                  \
  79 }
  80 static inline void
  81 spl_mutex_lockdep_on_maybe(kmutex_t *mp)                        \
  82 {                                                               \
  83         if (mp && mp->m_type == MUTEX_NOLOCKDEP)                \
  84                 lockdep_on();                                   \
  85 }
  86 #else  /* CONFIG_LOCKDEP */
  87 #define spl_mutex_set_type(mp, type)
  88 #define spl_mutex_lockdep_off_maybe(mp)
  89 #define spl_mutex_lockdep_on_maybe(mp)
  90 #endif /* CONFIG_LOCKDEP */
  91
  92 /*
  93  * The following functions must be a #define and not static inline.
  94  * This ensures that the native linux mutex functions (lock/unlock)
  95  * will be correctly located in the users code which is important
  96  * for the built in kernel lock analysis tools
  97  */
  98 #undef mutex_init
  99 #define mutex_init(mp, name, type, ibc)                         \
 100 {                                                               \
 101         static struct lock_class_key __key;                     \
 102         ASSERT(type == MUTEX_DEFAULT || type == MUTEX_NOLOCKDEP); \
 103                                                                 \
 104         __mutex_init(MUTEX(mp), (name) ? (#name) : (#mp), &__key); \
 105         spin_lock_init(&(mp)->m_lock);                          \
 106         spl_mutex_clear_owner(mp);                              \
 107         spl_mutex_set_type(mp, type);                           \
 108 }
 109
 110 #undef mutex_destroy
 111 #define mutex_destroy(mp)                                       \
 112 {                                                               \
 113         VERIFY3P(mutex_owner(mp), ==, NULL);                    \
 114 }
 115
 116 #define mutex_tryenter(mp)                                      \
 117 ({                                                              \
 118         int _rc_;                                               \
 119                                                                 \
 120         spl_mutex_lockdep_off_maybe(mp);                        \
 121         if ((_rc_ = mutex_trylock(MUTEX(mp))) == 1)             \
 122                 spl_mutex_set_owner(mp);                        \
 123         spl_mutex_lockdep_on_maybe(mp);                         \
 124                                                                 \
 125         _rc_;                                                   \
 126 })
 127
 128 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 129 #define mutex_enter_nested(mp, subclass)                        \
 130 {                                                               \
 131         ASSERT3P(mutex_owner(mp), !=, current);                 \
 132         spl_mutex_lockdep_off_maybe(mp);                        \
 133         mutex_lock_nested(MUTEX(mp), (subclass));               \
 134         spl_mutex_lockdep_on_maybe(mp);                         \
 135         spl_mutex_set_owner(mp);                                \
 136 }
 137 #else /* CONFIG_DEBUG_LOCK_ALLOC */
 138 #define mutex_enter_nested(mp, subclass)                        \
 139 {                                                               \
 140         ASSERT3P(mutex_owner(mp), !=, current);                 \
 141         spl_mutex_lockdep_off_maybe(mp);                        \
 142         mutex_lock(MUTEX(mp));                                  \
 143         spl_mutex_lockdep_on_maybe(mp);                         \
 144         spl_mutex_set_owner(mp);                                \
 145 }
 146 #endif /*  CONFIG_DEBUG_LOCK_ALLOC */
 147
 148 #define mutex_enter(mp) mutex_enter_nested((mp), 0)
 149
 150 /*
 151  * The reason for the spinlock:
 152  *
 153  * The Linux mutex is designed with a fast-path/slow-path design such that it
 154  * does not guarantee serialization upon itself, allowing a race where latter
 155  * acquirers finish mutex_unlock before former ones.
 156  *
 157  * The race renders it unsafe to be used for serializing the freeing of an
 158  * object in which the mutex is embedded, where the latter acquirer could go
 159  * on to free the object while the former one is still doing mutex_unlock and
 160  * causing memory corruption.
 161  *
 162  * However, there are many places in ZFS where the mutex is used for
 163  * serializing object freeing, and the code is shared among other OSes without
 164  * this issue. Thus, we need the spinlock to force the serialization on
 165  * mutex_exit().
 166  *
 167  * See http://lwn.net/Articles/575477/ for the information about the race.
 168  */
 169 #define mutex_exit(mp)                                          \
 170 {                                                               \
 171         spl_mutex_clear_owner(mp);                              \
 172         spin_lock(&(mp)->m_lock);                               \
 173         spl_mutex_lockdep_off_maybe(mp);                        \
 174         mutex_unlock(MUTEX(mp));                                \
 175         spl_mutex_lockdep_on_maybe(mp);                         \
 176         spin_unlock(&(mp)->m_lock);                             \
 177         /* NOTE: do not dereference mp after this point */      \
 178 }
 179
 180 int spl_mutex_init(void);
 181 void spl_mutex_fini(void);
 182
 183 #endif /* _SPL_MUTEX_H */