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 implementations of rw-semaphores the following is
  51  * true.  If your semaphore implementation internally represents the
  52  * semaphore state differently.  Then special case handling will be
  53  * required so RW_COUNT() provides these semantics:
  54  * - if activity/count is 0 then there are no active readers or writers
  55  * - if activity/count is +ve then that is the number of active readers
  56  * - if activity/count is -1 then there is one active writer
  57  */
  58 #define SEM(rwp)                        ((struct rw_semaphore *)(rwp))
  59
  60 #if defined(CONFIG_RWSEM_GENERIC_SPINLOCK)
  61 # define RW_COUNT(rwp)                  (SEM(rwp)->activity)
  62 # define rw_exit_locked(rwp)            __up_read_locked(rwp)
  63 # define rw_tryenter_locked(rwp)        __down_write_trylock_locked(rwp)
  64 extern void __up_read_locked(struct rw_semaphore *);
  65 extern int __down_write_trylock_locked(struct rw_semaphore *);
  66 #else
  67 # ifdef _I386_RWSEM_H
  68 #  define RW_COUNT(rwp)                 ((SEM(rwp)->count < 0) ? (-1) : \
  69                                          (SEM(rwp)->count & RWSEM_ACTIVE_MASK))
  70 # else
  71 #  define RW_COUNT(rwp)                 (SEM(rwp)->count & RWSEM_ACTIVE_MASK)
  72 # endif
  73 # define rw_exit_locked(rwp)           up_read(rwp)
  74 # define rw_tryenter_locked(rwp)       down_write_trylock(rwp)
  75 #endif
  76
  77 static inline kthread_t *
  78 spl_rw_get_owner(krwlock_t *rwp)
  79 {
  80         return rwp->rw_owner;
  81 }
  82
  83 static inline void
  84 spl_rw_set_owner(krwlock_t *rwp)
  85 {
  86         unsigned long flags;
  87
  88         spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
  89         rwp->rw_owner = current;
  90         spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
  91 }
  92
  93 static inline void
  94 spl_rw_clear_owner(krwlock_t *rwp)
  95 {
  96         unsigned long flags;
  97
  98         spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
  99         rwp->rw_owner = NULL;
 100         spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
 101 }
 102
 103 static inline kthread_t *
 104 rw_owner(krwlock_t *rwp)
 105 {
 106         unsigned long flags;
 107         kthread_t *owner;
 108
 109         spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
 110         owner = spl_rw_get_owner(rwp);
 111         spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
 112
 113         return owner;
 114 }
 115
 116 static inline int
 117 RW_READ_HELD(krwlock_t *rwp)
 118 {
 119         unsigned long flags;
 120         int rc;
 121
 122         spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
 123         rc = ((RW_COUNT(rwp) > 0) && (spl_rw_get_owner(rwp) == NULL));
 124         spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
 125
 126         return rc;
 127 }
 128
 129 static inline int
 130 RW_WRITE_HELD(krwlock_t *rwp)
 131 {
 132         unsigned long flags;
 133         int rc;
 134
 135         spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
 136         rc = ((RW_COUNT(rwp) < 0) && (spl_rw_get_owner(rwp) == current));
 137         spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
 138
 139         return rc;
 140 }
 141
 142 static inline int
 143 RW_LOCK_HELD(krwlock_t *rwp)
 144 {
 145         unsigned long flags;
 146         int rc;
 147
 148         spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
 149         rc = (RW_COUNT(rwp) != 0);
 150         spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
 151
 152         return rc;
 153 }
 154
 155 /*
 156  * The following functions must be a #define and not static inline.
 157  * This ensures that the native linux semaphore functions (down/up)
 158  * will be correctly located in the users code which is important
 159  * for the built in kernel lock analysis tools
 160  */
 161 #define rw_init(rwp, name, type, arg)                                   \
 162 ({                                                                      \
 163         static struct lock_class_key __key;                             \
 164                                                                         \
 165         __init_rwsem(SEM(rwp), #rwp, &__key);                           \
 166         spl_rw_clear_owner(rwp);                                        \
 167 })
 168
 169 #define rw_destroy(rwp)                                                 \
 170 ({                                                                      \
 171         VERIFY(!RW_LOCK_HELD(rwp));                                     \
 172 })
 173
 174 #define rw_tryenter(rwp, rw)                                            \
 175 ({                                                                      \
 176         int _rc_ = 0;                                                   \
 177                                                                         \
 178         switch (rw) {                                                   \
 179         case RW_READER:                                                 \
 180                 _rc_ = down_read_trylock(SEM(rwp));                     \
 181                 break;                                                  \
 182         case RW_WRITER:                                                 \
 183                 if ((_rc_ = down_write_trylock(SEM(rwp))))              \
 184                         spl_rw_set_owner(rwp);                          \
 185                 break;                                                  \
 186         default:                                                        \
 187                 SBUG();                                                 \
 188         }                                                               \
 189         _rc_;                                                           \
 190 })
 191
 192 #define rw_enter(rwp, rw)                                               \
 193 ({                                                                      \
 194         switch (rw) {                                                   \
 195         case RW_READER:                                                 \
 196                 down_read(SEM(rwp));                                    \
 197                 break;                                                  \
 198         case RW_WRITER:                                                 \
 199                 down_write(SEM(rwp));                                   \
 200                 spl_rw_set_owner(rwp);                                  \
 201                 break;                                                  \
 202         default:                                                        \
 203                 SBUG();                                                 \
 204         }                                                               \
 205 })
 206
 207 #define rw_exit(rwp)                                                    \
 208 ({                                                                      \
 209         if (RW_WRITE_HELD(rwp)) {                                       \
 210                 spl_rw_clear_owner(rwp);                                \
 211                 up_write(SEM(rwp));                                     \
 212         } else {                                                        \
 213                 ASSERT(RW_READ_HELD(rwp));                              \
 214                 up_read(SEM(rwp));                                      \
 215         }                                                               \
 216 })
 217
 218 #define rw_downgrade(rwp)                                               \
 219 ({                                                                      \
 220         spl_rw_clear_owner(rwp);                                        \
 221         downgrade_write(SEM(rwp));                                      \
 222 })
 223
 224 #define rw_tryupgrade(rwp)                                              \
 225 ({                                                                      \
 226         unsigned long _flags_;                                          \
 227         int _rc_ = 0;                                                   \
 228                                                                         \
 229         spin_lock_irqsave(&SEM(rwp)->wait_lock, _flags_);               \
 230         if (list_empty(&SEM(rwp)->wait_list) && (RW_COUNT(rwp) == 1)) { \
 231                 rw_exit_locked(SEM(rwp));                               \
 232                 VERIFY(_rc_ = rw_tryenter_locked(SEM(rwp)));            \
 233                 (rwp)->rw_owner = current;                              \
 234         }                                                               \
 235         spin_unlock_irqrestore(&SEM(rwp)->wait_lock, _flags_);          \
 236         _rc_;                                                           \
 237 })
 238
 239 int spl_rw_init(void);
 240 void spl_rw_fini(void);
 241
 242 #endif /* _SPL_RWLOCK_H */