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   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 typedef struct mutex kmutex_t;
  41
  42 static inline kthread_t *
  43 mutex_owner(kmutex_t *mp)
  44 {
  45         struct thread_info *owner;
  46
  47         owner = ACCESS_ONCE(mp->owner);
  48         if (owner)
  49                 return owner->task;
  50
  51         return NULL;
  52 }
  53
  54 static inline int
  55 mutex_owned(kmutex_t *mp)
  56 {
  57         return (ACCESS_ONCE(mp->owner) == current_thread_info());
  58 }
  59
  60 #define MUTEX_HELD(mp)          mutex_owned(mp)
  61 #define MUTEX_NOT_HELD(mp)      (!MUTEX_HELD(mp))
  62 #undef mutex_init
  63 #define mutex_init(mp, name, type, ibc)                                 \
  64 ({                                                                      \
  65         static struct lock_class_key __key;                             \
  66         ASSERT(type == MUTEX_DEFAULT);                                  \
  67                                                                         \
  68         __mutex_init((mp), #mp, &__key);                                \
  69 })
  70
  71 #undef mutex_destroy
  72 #define mutex_destroy(mp)                                               \
  73 ({                                                                      \
  74         VERIFY3P(mutex_owner(mp), ==, NULL);                            \
  75 })
  76
  77 #define mutex_tryenter(mp)              mutex_trylock(mp)
  78 #define mutex_enter(mp)                 mutex_lock(mp)
  79
  80 /* mutex->owner is not cleared when CONFIG_DEBUG_MUTEXES is set */
  81 #ifdef CONFIG_DEBUG_MUTEXES
  82 # define mutex_exit(mp)                                                 \
  83 ({                                                                      \
  84         mutex_unlock(mp);                                               \
  85         (mp)->owner = NULL;                                             \
  86 })
  87 #else
  88 # define mutex_exit(mp)                 mutex_unlock(mp)
  89 #endif /* CONFIG_DEBUG_MUTEXES */
  90
  91 #ifdef HAVE_GPL_ONLY_SYMBOLS
  92 # define mutex_enter_nested(mp, sc)     mutex_lock_nested(mp, sc)
  93 #else
  94 # define mutex_enter_nested(mp, sc)     mutex_enter(mp)
  95 #endif /* HAVE_GPL_ONLY_SYMBOLS */
  96
  97 #else /* HAVE_MUTEX_OWNER */
  98
  99 typedef struct {
 100         struct mutex m_mutex;
 101         kthread_t *m_owner;
 102 } kmutex_t;
 103
 104 #ifdef HAVE_TASK_CURR
 105 extern int spl_mutex_spin_max(void);
 106 #else /* HAVE_TASK_CURR */
 107 # define task_curr(owner)       0
 108 # define spl_mutex_spin_max()   0
 109 #endif /* HAVE_TASK_CURR */
 110
 111 #define MUTEX(mp)               ((struct mutex *)(mp))
 112
 113 static inline kthread_t *
 114 spl_mutex_get_owner(kmutex_t *mp)
 115 {
 116         return mp->m_owner;
 117 }
 118
 119 static inline void
 120 spl_mutex_set_owner(kmutex_t *mp)
 121 {
 122         unsigned long flags;
 123
 124         spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags);
 125         mp->m_owner = current;
 126         spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags);
 127 }
 128
 129 static inline void
 130 spl_mutex_clear_owner(kmutex_t *mp)
 131 {
 132         unsigned long flags;
 133
 134         spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags);
 135         mp->m_owner = NULL;
 136         spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags);
 137 }
 138
 139 static inline kthread_t *
 140 mutex_owner(kmutex_t *mp)
 141 {
 142         unsigned long flags;
 143         kthread_t *owner;
 144
 145         spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags);
 146         owner = spl_mutex_get_owner(mp);
 147         spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags);
 148
 149         return owner;
 150 }
 151
 152 #define mutex_owned(mp)         (mutex_owner(mp) == current)
 153 #define MUTEX_HELD(mp)          mutex_owned(mp)
 154 #define MUTEX_NOT_HELD(mp)      (!MUTEX_HELD(mp))
 155
 156 /*
 157  * The following functions must be a #define and not static inline.
 158  * This ensures that the native linux mutex functions (lock/unlock)
 159  * will be correctly located in the users code which is important
 160  * for the built in kernel lock analysis tools
 161  */
 162 #undef mutex_init
 163 #define mutex_init(mp, name, type, ibc)                                 \
 164 ({                                                                      \
 165         static struct lock_class_key __key;                             \
 166         ASSERT(type == MUTEX_DEFAULT);                                  \
 167                                                                         \
 168         __mutex_init(MUTEX(mp), #mp, &__key);                           \
 169         spl_mutex_clear_owner(mp);                                      \
 170 })
 171
 172 #undef mutex_destroy
 173 #define mutex_destroy(mp)                                               \
 174 ({                                                                      \
 175         VERIFY3P(mutex_owner(mp), ==, NULL);                            \
 176 })
 177
 178 #define mutex_tryenter(mp)                                              \
 179 ({                                                                      \
 180         int _rc_;                                                       \
 181                                                                         \
 182         if ((_rc_ = mutex_trylock(MUTEX(mp))) == 1)                     \
 183                 spl_mutex_set_owner(mp);                                \
 184                                                                         \
 185         _rc_;                                                           \
 186 })
 187
 188 /*
 189  * Adaptive mutexs assume that the lock may be held by a task running
 190  * on a different cpu.  The expectation is that the task will drop the
 191  * lock before leaving the head of the run queue.  So the ideal thing
 192  * to do is spin until we acquire the lock and avoid a context switch.
 193  * However it is also possible the task holding the lock yields the
 194  * processor with out dropping lock.  In this case, we know it's going
 195  * to be a while so we stop spinning and go to sleep waiting for the
 196  * lock to be available.  This should strike the optimum balance
 197  * between spinning and sleeping waiting for a lock.
 198  */
 199 #define mutex_enter(mp)                                                 \
 200 ({                                                                      \
 201         kthread_t *_owner_;                                             \
 202         int _rc_, _count_;                                              \
 203                                                                         \
 204         _rc_ = 0;                                                       \
 205         _count_ = 0;                                                    \
 206         _owner_ = mutex_owner(mp);                                      \
 207                                                                         \
 208         while (_owner_ && task_curr(_owner_) &&                         \
 209                _count_ <= spl_mutex_spin_max()) {                       \
 210                 if ((_rc_ = mutex_trylock(MUTEX(mp))))                  \
 211                         break;                                          \
 212                                                                         \
 213                 _count_++;                                              \
 214         }                                                               \
 215                                                                         \
 216         if (!_rc_)                                                      \
 217                 mutex_lock(MUTEX(mp));                                  \
 218                                                                         \
 219         spl_mutex_set_owner(mp);                                        \
 220 })
 221
 222 #define mutex_exit(mp)                                                  \
 223 ({                                                                      \
 224         spl_mutex_clear_owner(mp);                                      \
 225         mutex_unlock(MUTEX(mp));                                        \
 226 })
 227
 228 #ifdef HAVE_GPL_ONLY_SYMBOLS
 229 # define mutex_enter_nested(mp, sc)                                     \
 230 ({                                                                      \
 231         mutex_lock_nested(MUTEX(mp, sc));                               \
 232         spl_mutex_set_owner(mp);                                        \
 233 })
 234 #else
 235 # define mutex_enter_nested(mp, sc)                                     \
 236 ({                                                                      \
 237         mutex_enter(mp);                                                \
 238 })
 239 #endif
 240
 241 #endif /* HAVE_MUTEX_OWNER */
 242
 243 int spl_mutex_init(void);
 244 void spl_mutex_fini(void);
 245
 246 #endif /* _SPL_MUTEX_H */