include/spl/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/lockdep.h>
  31
  32 typedef enum {
  33         MUTEX_DEFAULT   = 0,
  34         MUTEX_SPIN      = 1,
  35         MUTEX_ADAPTIVE  = 2,
  36         MUTEX_NOLOCKDEP = 3
  37 } kmutex_type_t;
  38
  39 typedef struct {
  40         struct mutex            m_mutex;
  41         spinlock_t              m_lock; /* used for serializing mutex_exit */
  42         kthread_t               *m_owner;
  43 #ifdef CONFIG_LOCKDEP
  44         kmutex_type_t           m_type;
  45 #endif /* CONFIG_LOCKDEP */
  46 } kmutex_t;
  47
  48 #define MUTEX(mp)               (&((mp)->m_mutex))
  49
  50 static inline void
  51 spl_mutex_set_owner(kmutex_t *mp)
  52 {
  53         mp->m_owner = current;
  54 }
  55
  56 static inline void
  57 spl_mutex_clear_owner(kmutex_t *mp)
  58 {
  59         mp->m_owner = NULL;
  60 }
  61
  62 #define mutex_owner(mp)         (ACCESS_ONCE((mp)->m_owner))
  63 #define mutex_owned(mp)         (mutex_owner(mp) == current)
  64 #define MUTEX_HELD(mp)          mutex_owned(mp)
  65 #define MUTEX_NOT_HELD(mp)      (!MUTEX_HELD(mp))
  66
  67 #ifdef CONFIG_LOCKDEP
  68 static inline void
  69 spl_mutex_set_type(kmutex_t *mp, kmutex_type_t type)
  70 {
  71         mp->m_type = type;
  72 }
  73 static inline void
  74 spl_mutex_lockdep_off_maybe(kmutex_t *mp)                       \
  75 {                                                               \
  76         if (mp && mp->m_type == MUTEX_NOLOCKDEP)                \
  77                 lockdep_off();                                  \
  78 }
  79 static inline void
  80 spl_mutex_lockdep_on_maybe(kmutex_t *mp)                        \
  81 {                                                               \
  82         if (mp && mp->m_type == MUTEX_NOLOCKDEP)                \
  83                 lockdep_on();                                   \
  84 }
  85 #else  /* CONFIG_LOCKDEP */
  86 #define spl_mutex_set_type(mp, type)
  87 #define spl_mutex_lockdep_off_maybe(mp)
  88 #define spl_mutex_lockdep_on_maybe(mp)
  89 #endif /* CONFIG_LOCKDEP */
  90
  91 /*
  92  * The following functions must be a #define    and not static inline.
  93  * This ensures that the native linux mutex functions (lock/unlock)
  94  * will be correctly located in the users code which is important
  95  * for the built in kernel lock analysis tools
  96  */
  97 #undef mutex_init
  98 #define mutex_init(mp, name, type, ibc)                         \
  99 {                                                               \
 100         static struct lock_class_key __key;                     \
 101         ASSERT(type == MUTEX_DEFAULT || type == MUTEX_NOLOCKDEP); \
 102                                                                 \
 103         __mutex_init(MUTEX(mp), (name) ? (#name) : (#mp), &__key); \
 104         spin_lock_init(&(mp)->m_lock);                          \
 105         spl_mutex_clear_owner(mp);                              \
 106         spl_mutex_set_type(mp, type);                           \
 107 }
 108
 109 #undef mutex_destroy
 110 #define mutex_destroy(mp)                                       \
 111 {                                                               \
 112         VERIFY3P(mutex_owner(mp), ==, NULL);                    \
 113 }
 114
 115 /* BEGIN CSTYLED */
 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 /* END CSTYLED */
 128
 129 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 130 #define mutex_enter_nested(mp, subclass)                        \
 131 {                                                               \
 132         ASSERT3P(mutex_owner(mp), !=, current);                 \
 133         spl_mutex_lockdep_off_maybe(mp);                        \
 134         mutex_lock_nested(MUTEX(mp), (subclass));               \
 135         spl_mutex_lockdep_on_maybe(mp);                         \
 136         spl_mutex_set_owner(mp);                                \
 137 }
 138 #else /* CONFIG_DEBUG_LOCK_ALLOC */
 139 #define mutex_enter_nested(mp, subclass)                        \
 140 {                                                               \
 141         ASSERT3P(mutex_owner(mp), !=, current);                 \
 142         spl_mutex_lockdep_off_maybe(mp);                        \
 143         mutex_lock(MUTEX(mp));                                  \
 144         spl_mutex_lockdep_on_maybe(mp);                         \
 145         spl_mutex_set_owner(mp);                                \
 146 }
 147 #endif /*  CONFIG_DEBUG_LOCK_ALLOC */
 148
 149 #define mutex_enter(mp) mutex_enter_nested((mp), 0)
 150
 151 /*
 152  * The reason for the spinlock:
 153  *
 154  * The Linux mutex is designed with a fast-path/slow-path design such that it
 155  * does not guarantee serialization upon itself, allowing a race where latter
 156  * acquirers finish mutex_unlock before former ones.
 157  *
 158  * The race renders it unsafe to be used for serializing the freeing of an
 159  * object in which the mutex is embedded, where the latter acquirer could go
 160  * on to free the object while the former one is still doing mutex_unlock and
 161  * causing memory corruption.
 162  *
 163  * However, there are many places in ZFS where the mutex is used for
 164  * serializing object freeing, and the code is shared among other OSes without
 165  * this issue. Thus, we need the spinlock to force the serialization on
 166  * mutex_exit().
 167  *
 168  * See http://lwn.net/Articles/575477/ for the information about the race.
 169  */
 170 #define mutex_exit(mp)                                          \
 171 {                                                               \
 172         spl_mutex_clear_owner(mp);                              \
 173         spin_lock(&(mp)->m_lock);                               \
 174         spl_mutex_lockdep_off_maybe(mp);                        \
 175         mutex_unlock(MUTEX(mp));                                \
 176         spl_mutex_lockdep_on_maybe(mp);                         \
 177         spin_unlock(&(mp)->m_lock);                             \
 178         /* NOTE: do not dereference mp after this point */      \
 179 }
 180
 181 int spl_mutex_init(void);
 182 void spl_mutex_fini(void);
 183
 184 #endif /* _SPL_MUTEX_H */