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
  31 typedef enum {
  32         MUTEX_DEFAULT  = 0,
  33         MUTEX_SPIN     = 1,
  34         MUTEX_ADAPTIVE = 2
  35 } kmutex_type_t;
  36
  37 #if defined(HAVE_MUTEX_OWNER) && defined(CONFIG_SMP)
  38
  39 typedef struct mutex kmutex_t;
  40
  41 static inline kthread_t *
  42 mutex_owner(kmutex_t *mp)
  43 {
  44         struct thread_info *owner;
  45
  46         owner = ACCESS_ONCE(mp->owner);
  47         if (owner)
  48                 return owner->task;
  49
  50         return NULL;
  51 }
  52
  53 static inline int
  54 mutex_owned(kmutex_t *mp)
  55 {
  56         return (ACCESS_ONCE(mp->owner) == current_thread_info());
  57 }
  58
  59 #define MUTEX_HELD(mp)                  mutex_owned(mp)
  60 #undef mutex_init
  61 #define mutex_init(mp, name, type, ibc)                                 \
  62 ({                                                                      \
  63         static struct lock_class_key __key;                             \
  64         ASSERT(type == MUTEX_DEFAULT);                                  \
  65                                                                         \
  66         __mutex_init((mp), #mp, &__key);                                \
  67 })
  68
  69 #undef mutex_destroy
  70 #define mutex_destroy(mp)                                               \
  71 ({                                                                      \
  72         VERIFY3P(mutex_owner(mp), ==, NULL);                            \
  73 })
  74
  75 #define mutex_tryenter(mp)              mutex_trylock(mp)
  76 #define mutex_enter(mp)                 mutex_lock(mp)
  77
  78 /* mutex->owner is not cleared when CONFIG_DEBUG_MUTEXES is set */
  79 #ifdef CONFIG_DEBUG_MUTEXES
  80 # define mutex_exit(mp)                                                 \
  81 ({                                                                      \
  82          (mp)->owner = NULL;                                            \
  83          mutex_unlock(mp);                                              \
  84 })
  85 #else
  86 # define mutex_exit(mp)                 mutex_unlock(mp)
  87 #endif /* CONFIG_DEBUG_MUTEXES */
  88
  89 #ifdef HAVE_GPL_ONLY_SYMBOLS
  90 # define mutex_enter_nested(mp, sc)     mutex_lock_nested(mp, sc)
  91 #else
  92 # define mutex_enter_nested(mp, sc)     mutex_enter(mp)
  93 #endif /* HAVE_GPL_ONLY_SYMBOLS */
  94
  95 #else /* HAVE_MUTEX_OWNER */
  96
  97 typedef struct {
  98         struct mutex m_mutex;
  99         kthread_t *m_owner;
 100 } kmutex_t;
 101
 102 #ifdef HAVE_TASK_CURR
 103 extern int spl_mutex_spin_max(void);
 104 #else /* HAVE_TASK_CURR */
 105 # define task_curr(owner)       0
 106 # define spl_mutex_spin_max()   0
 107 #endif /* HAVE_TASK_CURR */
 108
 109 #define MUTEX(mp)               ((struct mutex *)(mp))
 110
 111 static inline kthread_t *
 112 spl_mutex_get_owner(kmutex_t *mp)
 113 {
 114         return mp->m_owner;
 115 }
 116
 117 static inline void
 118 spl_mutex_set_owner(kmutex_t *mp)
 119 {
 120         unsigned long flags;
 121
 122         spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags);
 123         mp->m_owner = current;
 124         spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags);
 125 }
 126
 127 static inline void
 128 spl_mutex_clear_owner(kmutex_t *mp)
 129 {
 130         unsigned long flags;
 131
 132         spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags);
 133         mp->m_owner = NULL;
 134         spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags);
 135 }
 136
 137 static inline kthread_t *
 138 mutex_owner(kmutex_t *mp)
 139 {
 140         unsigned long flags;
 141         kthread_t *owner;
 142
 143         spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags);
 144         owner = spl_mutex_get_owner(mp);
 145         spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags);
 146
 147         return owner;
 148 }
 149
 150 #define mutex_owned(mp)         (mutex_owner(mp) == current)
 151 #define MUTEX_HELD(mp)          mutex_owned(mp)
 152
 153 /*
 154  * The following functions must be a #define and not static inline.
 155  * This ensures that the native linux mutex functions (lock/unlock)
 156  * will be correctly located in the users code which is important
 157  * for the built in kernel lock analysis tools
 158  */
 159 #undef mutex_init
 160 #define mutex_init(mp, name, type, ibc)                                 \
 161 ({                                                                      \
 162         static struct lock_class_key __key;                             \
 163         ASSERT(type == MUTEX_DEFAULT);                                  \
 164                                                                         \
 165         __mutex_init(MUTEX(mp), #mp, &__key);                           \
 166         spl_mutex_clear_owner(mp);                                      \
 167 })
 168
 169 #undef mutex_destroy
 170 #define mutex_destroy(mp)                                               \
 171 ({                                                                      \
 172         VERIFY3P(mutex_owner(mp), ==, NULL);                            \
 173 })
 174
 175 #define mutex_tryenter(mp)                                              \
 176 ({                                                                      \
 177         int _rc_;                                                       \
 178                                                                         \
 179         if ((_rc_ = mutex_trylock(MUTEX(mp))) == 1)                     \
 180                 spl_mutex_set_owner(mp);                                \
 181                                                                         \
 182         _rc_;                                                           \
 183 })
 184
 185 /*
 186  * Adaptive mutexs assume that the lock may be held by a task running
 187  * on a different cpu.  The expectation is that the task will drop the
 188  * lock before leaving the head of the run queue.  So the ideal thing
 189  * to do is spin until we acquire the lock and avoid a context switch.
 190  * However it is also possible the task holding the lock yields the
 191  * processor with out dropping lock.  In this case, we know it's going
 192  * to be a while so we stop spinning and go to sleep waiting for the
 193  * lock to be available.  This should strike the optimum balance
 194  * between spinning and sleeping waiting for a lock.
 195  */
 196 #define mutex_enter(mp)                                                 \
 197 ({                                                                      \
 198         kthread_t *_owner_;                                             \
 199         int _rc_, _count_;                                              \
 200                                                                         \
 201         _rc_ = 0;                                                       \
 202         _count_ = 0;                                                    \
 203         _owner_ = mutex_owner(mp);                                      \
 204                                                                         \
 205         while (_owner_ && task_curr(_owner_) &&                         \
 206                _count_ <= spl_mutex_spin_max()) {                       \
 207                 if ((_rc_ = mutex_trylock(MUTEX(mp))))                  \
 208                         break;                                          \
 209                                                                         \
 210                 _count_++;                                              \
 211         }                                                               \
 212                                                                         \
 213         if (!_rc_)                                                      \
 214                 mutex_lock(MUTEX(mp));                                  \
 215                                                                         \
 216         spl_mutex_set_owner(mp);                                        \
 217 })
 218
 219 #define mutex_exit(mp)                                                  \
 220 ({                                                                      \
 221         spl_mutex_clear_owner(mp);                                      \
 222         mutex_unlock(MUTEX(mp));                                        \
 223 })
 224
 225 #ifdef HAVE_GPL_ONLY_SYMBOLS
 226 # define mutex_enter_nested(mp, sc)                                     \
 227 ({                                                                      \
 228         mutex_lock_nested(MUTEX(mp, sc));                               \
 229         spl_mutex_set_owner(mp);                                        \
 230 })
 231 #else
 232 # define mutex_enter_nested(mp, sc)                                     \
 233 ({                                                                      \
 234         mutex_enter(mp);                                                \
 235 })
 236 #endif
 237
 238 #endif /* HAVE_MUTEX_OWNER */
 239
 240 int spl_mutex_init(void);
 241 void spl_mutex_fini(void);
 242
 243 #endif /* _SPL_MUTEX_H */