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://github.com/behlendorf/spl/>.
  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
  40 /*
  41  * We define a 1-field struct rather than a straight typedef to enforce type
  42  * safety.
  43  */
  44 typedef struct {
  45         struct mutex m;
  46 } kmutex_t;
  47
  48 static inline kthread_t *
  49 mutex_owner(kmutex_t *mp)
  50 {
  51         struct thread_info *owner;
  52
  53         owner = ACCESS_ONCE(mp->m.owner);
  54         if (owner)
  55                 return owner->task;
  56
  57         return NULL;
  58 }
  59
  60 static inline int
  61 mutex_owned(kmutex_t *mp)
  62 {
  63         return (ACCESS_ONCE(mp->m.owner) == current_thread_info());
  64 }
  65
  66 #define MUTEX_HELD(mp)          mutex_owned(mp)
  67 #define MUTEX_NOT_HELD(mp)      (!MUTEX_HELD(mp))
  68 #undef mutex_init
  69 #define mutex_init(mp, name, type, ibc)                                 \
  70 ({                                                                      \
  71         static struct lock_class_key __key;                             \
  72         ASSERT(type == MUTEX_DEFAULT);                                  \
  73                                                                         \
  74         __mutex_init(&(mp)->m, #mp, &__key);                            \
  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)                 mutex_lock(&(mp)->m)
  85
  86 /* mutex->owner is not cleared when CONFIG_DEBUG_MUTEXES is set */
  87 #ifdef CONFIG_DEBUG_MUTEXES
  88 # define mutex_exit(mp)                                                 \
  89 ({                                                                      \
  90         mutex_unlock(&(mp)->m);                                         \
  91         (mp)->m.owner = NULL;                                           \
  92 })
  93 #else
  94 # define mutex_exit(mp)                 mutex_unlock(&(mp)->m)
  95 #endif /* CONFIG_DEBUG_MUTEXES */
  96
  97 #ifdef HAVE_GPL_ONLY_SYMBOLS
  98 # define mutex_enter_nested(mp, sc)     mutex_lock_nested(&(mp)->m, sc)
  99 #else
 100 # define mutex_enter_nested(mp, sc)     mutex_enter(mp)
 101 #endif /* HAVE_GPL_ONLY_SYMBOLS */
 102
 103 #else /* HAVE_MUTEX_OWNER */
 104
 105 typedef struct {
 106         struct mutex m_mutex;
 107         kthread_t *m_owner;
 108 } kmutex_t;
 109
 110 #ifdef HAVE_TASK_CURR
 111 extern int spl_mutex_spin_max(void);
 112 #else /* HAVE_TASK_CURR */
 113 # define task_curr(owner)       0
 114 # define spl_mutex_spin_max()   0
 115 #endif /* HAVE_TASK_CURR */
 116
 117 #define MUTEX(mp)               ((struct mutex *)(mp))
 118
 119 static inline kthread_t *
 120 spl_mutex_get_owner(kmutex_t *mp)
 121 {
 122         return mp->m_owner;
 123 }
 124
 125 static inline void
 126 spl_mutex_set_owner(kmutex_t *mp)
 127 {
 128         unsigned long flags;
 129
 130         spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags);
 131         mp->m_owner = current;
 132         spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags);
 133 }
 134
 135 static inline void
 136 spl_mutex_clear_owner(kmutex_t *mp)
 137 {
 138         unsigned long flags;
 139
 140         spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags);
 141         mp->m_owner = NULL;
 142         spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags);
 143 }
 144
 145 static inline kthread_t *
 146 mutex_owner(kmutex_t *mp)
 147 {
 148         unsigned long flags;
 149         kthread_t *owner;
 150
 151         spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags);
 152         owner = spl_mutex_get_owner(mp);
 153         spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags);
 154
 155         return owner;
 156 }
 157
 158 #define mutex_owned(mp)         (mutex_owner(mp) == current)
 159 #define MUTEX_HELD(mp)          mutex_owned(mp)
 160 #define MUTEX_NOT_HELD(mp)      (!MUTEX_HELD(mp))
 161
 162 /*
 163  * The following functions must be a #define and not static inline.
 164  * This ensures that the native linux mutex functions (lock/unlock)
 165  * will be correctly located in the users code which is important
 166  * for the built in kernel lock analysis tools
 167  */
 168 #undef mutex_init
 169 #define mutex_init(mp, name, type, ibc)                                 \
 170 ({                                                                      \
 171         static struct lock_class_key __key;                             \
 172         ASSERT(type == MUTEX_DEFAULT);                                  \
 173                                                                         \
 174         __mutex_init(MUTEX(mp), #mp, &__key);                           \
 175         spl_mutex_clear_owner(mp);                                      \
 176 })
 177
 178 #undef mutex_destroy
 179 #define mutex_destroy(mp)                                               \
 180 ({                                                                      \
 181         VERIFY3P(mutex_owner(mp), ==, NULL);                            \
 182 })
 183
 184 #define mutex_tryenter(mp)                                              \
 185 ({                                                                      \
 186         int _rc_;                                                       \
 187                                                                         \
 188         if ((_rc_ = mutex_trylock(MUTEX(mp))) == 1)                     \
 189                 spl_mutex_set_owner(mp);                                \
 190                                                                         \
 191         _rc_;                                                           \
 192 })
 193
 194 /*
 195  * Adaptive mutexs assume that the lock may be held by a task running
 196  * on a different cpu.  The expectation is that the task will drop the
 197  * lock before leaving the head of the run queue.  So the ideal thing
 198  * to do is spin until we acquire the lock and avoid a context switch.
 199  * However it is also possible the task holding the lock yields the
 200  * processor with out dropping lock.  In this case, we know it's going
 201  * to be a while so we stop spinning and go to sleep waiting for the
 202  * lock to be available.  This should strike the optimum balance
 203  * between spinning and sleeping waiting for a lock.
 204  */
 205 #define mutex_enter(mp)                                                 \
 206 ({                                                                      \
 207         kthread_t *_owner_;                                             \
 208         int _rc_, _count_;                                              \
 209                                                                         \
 210         _rc_ = 0;                                                       \
 211         _count_ = 0;                                                    \
 212         _owner_ = mutex_owner(mp);                                      \
 213                                                                         \
 214         while (_owner_ && task_curr(_owner_) &&                         \
 215                _count_ <= spl_mutex_spin_max()) {                       \
 216                 if ((_rc_ = mutex_trylock(MUTEX(mp))))                  \
 217                         break;                                          \
 218                                                                         \
 219                 _count_++;                                              \
 220         }                                                               \
 221                                                                         \
 222         if (!_rc_)                                                      \
 223                 mutex_lock(MUTEX(mp));                                  \
 224                                                                         \
 225         spl_mutex_set_owner(mp);                                        \
 226 })
 227
 228 #define mutex_exit(mp)                                                  \
 229 ({                                                                      \
 230         spl_mutex_clear_owner(mp);                                      \
 231         mutex_unlock(MUTEX(mp));                                        \
 232 })
 233
 234 #ifdef HAVE_GPL_ONLY_SYMBOLS
 235 # define mutex_enter_nested(mp, sc)                                     \
 236 ({                                                                      \
 237         mutex_lock_nested(MUTEX(mp, sc));                               \
 238         spl_mutex_set_owner(mp);                                        \
 239 })
 240 #else
 241 # define mutex_enter_nested(mp, sc)                                     \
 242 ({                                                                      \
 243         mutex_enter(mp);                                                \
 244 })
 245 #endif
 246
 247 #endif /* HAVE_MUTEX_OWNER */
 248
 249 int spl_mutex_init(void);
 250 void spl_mutex_fini(void);
 251
 252 #endif /* _SPL_MUTEX_H */