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