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
  32 typedef enum {
  33         MUTEX_DEFAULT   = 0,
  34         MUTEX_SPIN      = 1,
  35         MUTEX_ADAPTIVE  = 2,
  36         MUTEX_FSTRANS   = 3,
  37 } kmutex_type_t;
  38
  39 typedef struct {
  40         struct mutex            m_mutex;
  41         kmutex_type_t           m_type;
  42         spinlock_t              m_lock; /* used for serializing mutex_exit */
  43         kthread_t               *m_owner;
  44         unsigned int            m_saved_flags;
  45 } kmutex_t;
  46
  47 #define MUTEX(mp)               (&((mp)->m_mutex))
  48 #define mutex_owner(mp)         (ACCESS_ONCE((mp)->m_owner))
  49 #define mutex_owned(mp)         (mutex_owner(mp) == current)
  50 #define MUTEX_HELD(mp)          mutex_owned(mp)
  51 #define MUTEX_NOT_HELD(mp)      (!MUTEX_HELD(mp))
  52
  53 /*
  54  * The following functions must be a #define and not static inline.
  55  * This ensures that the native linux mutex functions (lock/unlock)
  56  * will be correctly located in the users code which is important
  57  * for the built in kernel lock analysis tools
  58  */
  59 #undef mutex_init
  60 #define mutex_init(mp, name, type, ibc)                         \
  61 {                                                               \
  62         static struct lock_class_key __key;                     \
  63                                                                 \
  64         ASSERT3P(mp, !=, NULL);                                 \
  65         ASSERT3P(ibc, ==, NULL);                                \
  66         ASSERT((type == MUTEX_DEFAULT) ||                       \
  67             (type == MUTEX_ADAPTIVE) ||                         \
  68             (type == MUTEX_FSTRANS));                           \
  69                                                                 \
  70         __mutex_init(MUTEX(mp), (name) ? (#name) : (#mp), &__key); \
  71         spin_lock_init(&(mp)->m_lock);                          \
  72         (mp)->m_type = type;                                    \
  73         (mp)->m_owner = NULL;                                   \
  74         (mp)->m_saved_flags = 0;                                \
  75 }
  76
  77 #undef mutex_destroy
  78 #define mutex_destroy(mp)                                       \
  79 {                                                               \
  80         VERIFY3P(mutex_owner(mp), ==, NULL);                    \
  81 }
  82
  83 #define mutex_tryenter(mp)                                      \
  84 ({                                                              \
  85         int _rc_;                                               \
  86                                                                 \
  87         if ((_rc_ = mutex_trylock(MUTEX(mp))) == 1) {           \
  88                 (mp)->m_owner = current;                        \
  89                 if ((mp)->m_type == MUTEX_FSTRANS) {            \
  90                         (mp)->m_saved_flags = current->flags;   \
  91                         current->flags |= PF_FSTRANS;           \
  92                 }                                               \
  93         }                                                       \
  94                                                                 \
  95         _rc_;                                                   \
  96 })
  97
  98 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  99 #define mutex_enter_nested(mp, subclass)                        \
 100 {                                                               \
 101         ASSERT3P(mutex_owner(mp), !=, current);                 \
 102         mutex_lock_nested(MUTEX(mp), (subclass));               \
 103         (mp)->m_owner = current;                                \
 104         if ((mp)->m_type == MUTEX_FSTRANS) {                    \
 105                 (mp)->m_saved_flags = current->flags;           \
 106                 current->flags |= PF_FSTRANS;                   \
 107         }                                                       \
 108 }
 109 #else /* CONFIG_DEBUG_LOCK_ALLOC */
 110 #define mutex_enter_nested(mp, subclass)                        \
 111 {                                                               \
 112         ASSERT3P(mutex_owner(mp), !=, current);                 \
 113         mutex_lock(MUTEX(mp));                                  \
 114         (mp)->m_owner = current;                                \
 115         if ((mp)->m_type == MUTEX_FSTRANS) {                    \
 116                 (mp)->m_saved_flags = current->flags;           \
 117                 current->flags |= PF_FSTRANS;                   \
 118         }                                                       \
 119 }
 120 #endif /*  CONFIG_DEBUG_LOCK_ALLOC */
 121
 122 #define mutex_enter(mp) mutex_enter_nested((mp), 0)
 123
 124 /*
 125  * The reason for the spinlock:
 126  *
 127  * The Linux mutex is designed with a fast-path/slow-path design such that it
 128  * does not guarantee serialization upon itself, allowing a race where latter
 129  * acquirers finish mutex_unlock before former ones.
 130  *
 131  * The race renders it unsafe to be used for serializing the freeing of an
 132  * object in which the mutex is embedded, where the latter acquirer could go
 133  * on to free the object while the former one is still doing mutex_unlock and
 134  * causing memory corruption.
 135  *
 136  * However, there are many places in ZFS where the mutex is used for
 137  * serializing object freeing, and the code is shared among other OSes without
 138  * this issue. Thus, we need the spinlock to force the serialization on
 139  * mutex_exit().
 140  *
 141  * See http://lwn.net/Articles/575477/ for the information about the race.
 142  */
 143 #define mutex_exit(mp)                                          \
 144 {                                                               \
 145         spin_lock(&(mp)->m_lock);                               \
 146         if ((mp)->m_type == MUTEX_FSTRANS) {                    \
 147                 current->flags &= ~(PF_FSTRANS);                \
 148                 current->flags |= (mp)->m_saved_flags;          \
 149         }                                                       \
 150         (mp)->m_owner = NULL;                                   \
 151         mutex_unlock(MUTEX(mp));                                \
 152         spin_unlock(&(mp)->m_lock);                             \
 153 }
 154
 155 int spl_mutex_init(void);
 156 void spl_mutex_fini(void);
 157
 158 #endif /* _SPL_MUTEX_H */