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 } kmutex_type_t;
  37
  38 #if defined(HAVE_MUTEX_OWNER) && defined(CONFIG_SMP) && \
  39     !defined(CONFIG_DEBUG_MUTEXES)
  40
  41 /*
  42  * We define a 1-field struct rather than a straight typedef to enforce type
  43  * safety.
  44  */
  45 typedef struct {
  46         struct mutex m;
  47         spinlock_t m_lock;      /* used for serializing mutex_exit */
  48 } kmutex_t;
  49
  50 static inline kthread_t *
  51 mutex_owner(kmutex_t *mp)
  52 {
  53 #if defined(HAVE_MUTEX_OWNER_TASK_STRUCT)
  54         return ACCESS_ONCE(mp->m.owner);
  55 #else
  56         struct thread_info *owner = ACCESS_ONCE(mp->m.owner);
  57         if (owner)
  58                 return owner->task;
  59
  60         return NULL;
  61 #endif
  62 }
  63
  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 #undef mutex_init
  68 #define mutex_init(mp, name, type, ibc)                                 \
  69 ({                                                                      \
  70         static struct lock_class_key __key;                             \
  71         ASSERT(type == MUTEX_DEFAULT);                                  \
  72                                                                         \
  73         __mutex_init(&(mp)->m, #mp, &__key);                            \
  74         spin_lock_init(&(mp)->m_lock);                                  \
  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)              mutex_trylock(&(mp)->m)
  84 #define mutex_enter(mp)                                                 \
  85 ({                                                                      \
  86         ASSERT3P(mutex_owner(mp), !=, current);                         \
  87         mutex_lock(&(mp)->m);                                           \
  88 })
  89 /*
  90  * The reason for the spinlock:
  91  *
  92  * The Linux mutex is designed with a fast-path/slow-path design such that it
  93  * does not guarantee serialization upon itself, allowing a race where latter
  94  * acquirers finish mutex_unlock before former ones.
  95  *
  96  * The race renders it unsafe to be used for serializing the freeing of an
  97  * object in which the mutex is embedded, where the latter acquirer could go
  98  * on to free the object while the former one is still doing mutex_unlock and
  99  * causing memory corruption.
 100  *
 101  * However, there are many places in ZFS where the mutex is used for
 102  * serializing object freeing, and the code is shared among other OSes without
 103  * this issue. Thus, we need the spinlock to force the serialization on
 104  * mutex_exit().
 105  *
 106  * See http://lwn.net/Articles/575477/ for the information about the race.
 107  */
 108 #define mutex_exit(mp)                                                  \
 109 ({                                                                      \
 110         spin_lock(&(mp)->m_lock);                                       \
 111         mutex_unlock(&(mp)->m);                                         \
 112         spin_unlock(&(mp)->m_lock);                                     \
 113 })
 114
 115 #else /* HAVE_MUTEX_OWNER */
 116
 117 typedef struct {
 118         struct mutex m_mutex;
 119         spinlock_t m_lock;
 120         kthread_t *m_owner;
 121 } kmutex_t;
 122
 123 #define MUTEX(mp)               (&((mp)->m_mutex))
 124
 125 static inline void
 126 spl_mutex_set_owner(kmutex_t *mp)
 127 {
 128         mp->m_owner = current;
 129 }
 130
 131 static inline void
 132 spl_mutex_clear_owner(kmutex_t *mp)
 133 {
 134         mp->m_owner = NULL;
 135 }
 136
 137 #define mutex_owner(mp)         (ACCESS_ONCE((mp)->m_owner))
 138 #define mutex_owned(mp)         (mutex_owner(mp) == current)
 139 #define MUTEX_HELD(mp)          mutex_owned(mp)
 140 #define MUTEX_NOT_HELD(mp)      (!MUTEX_HELD(mp))
 141
 142 /*
 143  * The following functions must be a #define and not static inline.
 144  * This ensures that the native linux mutex functions (lock/unlock)
 145  * will be correctly located in the users code which is important
 146  * for the built in kernel lock analysis tools
 147  */
 148 #undef mutex_init
 149 #define mutex_init(mp, name, type, ibc)                                 \
 150 ({                                                                      \
 151         static struct lock_class_key __key;                             \
 152         ASSERT(type == MUTEX_DEFAULT);                                  \
 153                                                                         \
 154         __mutex_init(MUTEX(mp), #mp, &__key);                           \
 155         spin_lock_init(&(mp)->m_lock);                                  \
 156         spl_mutex_clear_owner(mp);                                      \
 157 })
 158
 159 #undef mutex_destroy
 160 #define mutex_destroy(mp)                                               \
 161 ({                                                                      \
 162         VERIFY3P(mutex_owner(mp), ==, NULL);                            \
 163 })
 164
 165 #define mutex_tryenter(mp)                                              \
 166 ({                                                                      \
 167         int _rc_;                                                       \
 168                                                                         \
 169         if ((_rc_ = mutex_trylock(MUTEX(mp))) == 1)                     \
 170                 spl_mutex_set_owner(mp);                                \
 171                                                                         \
 172         _rc_;                                                           \
 173 })
 174
 175 #define mutex_enter(mp)                                                 \
 176 ({                                                                      \
 177         ASSERT3P(mutex_owner(mp), !=, current);                         \
 178         mutex_lock(MUTEX(mp));                                          \
 179         spl_mutex_set_owner(mp);                                        \
 180 })
 181
 182 #define mutex_exit(mp)                                                  \
 183 ({                                                                      \
 184         spin_lock(&(mp)->m_lock);                                       \
 185         spl_mutex_clear_owner(mp);                                      \
 186         mutex_unlock(MUTEX(mp));                                        \
 187         spin_unlock(&(mp)->m_lock);                                     \
 188 })
 189
 190 #endif /* HAVE_MUTEX_OWNER */
 191
 192 int spl_mutex_init(void);
 193 void spl_mutex_fini(void);
 194
 195 #endif /* _SPL_MUTEX_H */