include/sys/rwlock.h

   1 /*
   2  *  This file is part of the SPL: Solaris Porting Layer.
   3  *
   4  *  Copyright (c) 2009 Lawrence Livermore National Security, LLC.
   5  *  Produced at Lawrence Livermore National Laboratory
   6  *  Written by:
   7  *          Brian Behlendorf <behlendorf1@llnl.gov>,
   8  *          Herb Wartens <wartens2@llnl.gov>,
   9  *          Jim Garlick <garlick@llnl.gov>
  10  *  UCRL-CODE-235197
  11  *
  12  *  This is free software; you can redistribute it and/or modify it
  13  *  under the terms of the GNU General Public License as published by
  14  *  the Free Software Foundation; either version 2 of the License, or
  15  *  (at your option) any later version.
  16  *
  17  *  This is distributed in the hope that it will be useful, but WITHOUT
  18  *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  19  *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  20  *  for more details.
  21  *
  22  *  You should have received a copy of the GNU General Public License along
  23  *  with this program; if not, write to the Free Software Foundation, Inc.,
  24  *  51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA.
  25  */
  26
  27 #ifndef _SPL_RWLOCK_H
  28 #define _SPL_RWLOCK_H
  29
  30 #include <sys/types.h>
  31 #include <linux/rwsem.h>
  32
  33 typedef enum {
  34         RW_DRIVER  = 2,
  35         RW_DEFAULT = 4
  36 } krw_type_t;
  37
  38 typedef enum {
  39         RW_NONE   = 0,
  40         RW_WRITER = 1,
  41         RW_READER = 2
  42 } krw_t;
  43
  44 typedef struct {
  45         struct rw_semaphore rw_rwlock;
  46         kthread_t *rw_owner;
  47 } krwlock_t;
  48
  49 /*
  50  * For the generic and x86 implementations of rw-semaphores the following
  51  * is true.  If your semaphore implementation internally represents the
  52  * semaphore state differently special case handling will be required.
  53  * - if activity/count is 0 then there are no active readers or writers
  54  * - if activity/count is +ve then that is the number of active readers
  55  * - if activity/count is -1 then there is one active writer
  56  */
  57 #define SEM(rwp)                        ((struct rw_semaphore *)(rwp))
  58
  59 #if defined(CONFIG_RWSEM_GENERIC_SPINLOCK)
  60 # define RW_COUNT(rwp)                  (SEM(rwp)->activity)
  61 # define rw_exit_locked(rwp)            __up_read_locked(rwp)
  62 # define rw_tryenter_locked(rwp)        __down_write_trylock_locked(rwp)
  63 extern void __up_read_locked(struct rw_semaphore *);
  64 extern int __down_write_trylock_locked(struct rw_semaphore *);
  65 #else
  66 # define RW_COUNT(rwp)                  (SEM(rwp)->count & RWSEM_ACTIVE_MASK)
  67 # define rw_exit_locked(rwp)            up_read(rwp)
  68 # define rw_tryenter_locked(rwp)        down_write_trylock(rwp)
  69 #endif
  70
  71 static inline kthread_t *
  72 spl_rw_get_owner(krwlock_t *rwp)
  73 {
  74         return rwp->rw_owner;
  75 }
  76
  77 static inline void
  78 spl_rw_set_owner(krwlock_t *rwp)
  79 {
  80         unsigned long flags;
  81
  82         spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
  83         rwp->rw_owner = current;
  84         spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
  85 }
  86
  87 static inline void
  88 spl_rw_clear_owner(krwlock_t *rwp)
  89 {
  90         unsigned long flags;
  91
  92         spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
  93         rwp->rw_owner = NULL;
  94         spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
  95 }
  96
  97 static inline kthread_t *
  98 rw_owner(krwlock_t *rwp)
  99 {
 100         unsigned long flags;
 101         kthread_t *owner;
 102
 103         spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
 104         owner = spl_rw_get_owner(rwp);
 105         spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
 106
 107         return owner;
 108 }
 109
 110 static inline int
 111 RW_READ_HELD(krwlock_t *rwp)
 112 {
 113         unsigned long flags;
 114         int rc;
 115
 116         spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
 117         rc = ((RW_COUNT(rwp) > 0) && (spl_rw_get_owner(rwp) == NULL));
 118         spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
 119
 120         return rc;
 121 }
 122
 123 static inline int
 124 RW_WRITE_HELD(krwlock_t *rwp)
 125 {
 126         unsigned long flags;
 127         int rc;
 128
 129         spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
 130         rc = ((RW_COUNT(rwp) < 0) && (spl_rw_get_owner(rwp) == current));
 131         spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
 132
 133         return rc;
 134 }
 135
 136 static inline int
 137 RW_LOCK_HELD(krwlock_t *rwp)
 138 {
 139         unsigned long flags;
 140         int rc;
 141
 142         spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
 143         rc = (RW_COUNT(rwp) != 0);
 144         spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
 145
 146         return rc;
 147 }
 148
 149 /*
 150  * The following functions must be a #define and not static inline.
 151  * This ensures that the native linux semaphore functions (down/up)
 152  * will be correctly located in the users code which is important
 153  * for the built in kernel lock analysis tools
 154  */
 155 #define rw_init(rwp, name, type, arg)                                   \
 156 ({                                                                      \
 157         static struct lock_class_key __key;                             \
 158                                                                         \
 159         __init_rwsem(SEM(rwp), #rwp, &__key);                           \
 160         spl_rw_clear_owner(rwp);                                        \
 161 })
 162
 163 #define rw_destroy(rwp)                                                 \
 164 ({                                                                      \
 165         VERIFY(!RW_LOCK_HELD(rwp));                                     \
 166 })
 167
 168 #define rw_tryenter(rwp, rw)                                            \
 169 ({                                                                      \
 170         int _rc_ = 0;                                                   \
 171                                                                         \
 172         switch (rw) {                                                   \
 173         case RW_READER:                                                 \
 174                 _rc_ = down_read_trylock(SEM(rwp));                     \
 175                 break;                                                  \
 176         case RW_WRITER:                                                 \
 177                 if ((_rc_ = down_write_trylock(SEM(rwp))))              \
 178                         spl_rw_set_owner(rwp);                          \
 179                 break;                                                  \
 180         default:                                                        \
 181                 SBUG();                                                 \
 182         }                                                               \
 183         _rc_;                                                           \
 184 })
 185
 186 #define rw_enter(rwp, rw)                                               \
 187 ({                                                                      \
 188         switch (rw) {                                                   \
 189         case RW_READER:                                                 \
 190                 down_read(SEM(rwp));                                    \
 191                 break;                                                  \
 192         case RW_WRITER:                                                 \
 193                 down_write(SEM(rwp));                                   \
 194                 spl_rw_set_owner(rwp);                                  \
 195                 break;                                                  \
 196         default:                                                        \
 197                 SBUG();                                                 \
 198         }                                                               \
 199 })
 200
 201 #define rw_exit(rwp)                                                    \
 202 ({                                                                      \
 203         if (RW_WRITE_HELD(rwp)) {                                       \
 204                 spl_rw_clear_owner(rwp);                                \
 205                 up_write(SEM(rwp));                                     \
 206         } else {                                                        \
 207                 ASSERT(RW_READ_HELD(rwp));                              \
 208                 up_read(SEM(rwp));                                      \
 209         }                                                               \
 210 })
 211
 212 #define rw_downgrade(rwp)                                               \
 213 ({                                                                      \
 214         spl_rw_clear_owner(rwp);                                        \
 215         downgrade_write(SEM(rwp));                                      \
 216 })
 217
 218 #define rw_tryupgrade(rwp)                                              \
 219 ({                                                                      \
 220         unsigned long _flags_;                                          \
 221         int _rc_ = 0;                                                   \
 222                                                                         \
 223         spin_lock_irqsave(&SEM(rwp)->wait_lock, _flags_);               \
 224         if (list_empty(&SEM(rwp)->wait_list) && (RW_COUNT(rwp) == 1)) { \
 225                 rw_exit_locked(SEM(rwp));                               \
 226                 VERIFY(_rc_ = rw_tryenter_locked(SEM(rwp)));            \
 227                 (rwp)->rw_owner = current;                              \
 228         }                                                               \
 229         spin_unlock_irqrestore(&SEM(rwp)->wait_lock, _flags_);          \
 230         _rc_;                                                           \
 231 })
 232
 233 int spl_rw_init(void);
 234 void spl_rw_fini(void);
 235
 236 #endif /* _SPL_RWLOCK_H */