sys/sys/rwlock.h

   1 /*-
   2  * Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org>
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24  * SUCH DAMAGE.
  25  *
  26  * $FreeBSD$
  27  */
  28
  29 #ifndef _SYS_RWLOCK_H_
  30 #define _SYS_RWLOCK_H_
  31
  32 #include <sys/_lock.h>
  33 #include <sys/_rwlock.h>
  34 #include <sys/lock_profile.h>
  35 #include <sys/lockstat.h>
  36
  37 #ifdef _KERNEL
  38 #include <sys/pcpu.h>
  39 #include <machine/atomic.h>
  40 #endif
  41
  42 /*
  43  * The rw_lock field consists of several fields.  The low bit indicates
  44  * if the lock is locked with a read (shared) or write (exclusive) lock.
  45  * A value of 0 indicates a write lock, and a value of 1 indicates a read
  46  * lock.  Bit 1 is a boolean indicating if there are any threads waiting
  47  * for a read lock.  Bit 2 is a boolean indicating if there are any threads
  48  * waiting for a write lock.  The rest of the variable's definition is
  49  * dependent on the value of the first bit.  For a write lock, it is a
  50  * pointer to the thread holding the lock, similar to the mtx_lock field of
  51  * mutexes.  For read locks, it is a count of read locks that are held.
  52  *
  53  * When the lock is not locked by any thread, it is encoded as a read lock
  54  * with zero waiters.
  55  */
  56
  57 #define RW_LOCK_READ            0x01
  58 #define RW_LOCK_READ_WAITERS    0x02
  59 #define RW_LOCK_WRITE_WAITERS   0x04
  60 #define RW_LOCK_WRITE_SPINNER   0x08
  61 #define RW_LOCK_FLAGMASK                                                \
  62         (RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS |  \
  63         RW_LOCK_WRITE_SPINNER)
  64 #define RW_LOCK_WAITERS         (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
  65
  66 #define RW_OWNER(x)             ((x) & ~RW_LOCK_FLAGMASK)
  67 #define RW_READERS_SHIFT        4
  68 #define RW_READERS(x)           (RW_OWNER((x)) >> RW_READERS_SHIFT)
  69 #define RW_READERS_LOCK(x)      ((x) << RW_READERS_SHIFT | RW_LOCK_READ)
  70 #define RW_ONE_READER           (1 << RW_READERS_SHIFT)
  71
  72 #define RW_UNLOCKED             RW_READERS_LOCK(0)
  73 #define RW_DESTROYED            (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
  74
  75 #ifdef _KERNEL
  76
  77 #define rw_recurse      lock_object.lo_data
  78
  79 /* Very simple operations on rw_lock. */
  80
  81 /* Try to obtain a write lock once. */
  82 #define _rw_write_lock(rw, tid)                                         \
  83         atomic_cmpset_acq_ptr(&(rw)->rw_lock, RW_UNLOCKED, (tid))
  84
  85 /* Release a write lock quickly if there are no waiters. */
  86 #define _rw_write_unlock(rw, tid)                                       \
  87         atomic_cmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
  88
  89 /*
  90  * Full lock operations that are suitable to be inlined in non-debug
  91  * kernels.  If the lock cannot be acquired or released trivially then
  92  * the work is deferred to another function.
  93  */
  94
  95 /* Acquire a write lock. */
  96 #define __rw_wlock(rw, tid, file, line) do {                            \
  97         uintptr_t _tid = (uintptr_t)(tid);                              \
  98                                                                         \
  99         if (!_rw_write_lock((rw), _tid))                                \
 100                 _rw_wlock_hard((rw), _tid, (file), (line));             \
 101         else                                                            \
 102                 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_RW_WLOCK_ACQUIRE, \
 103                     rw, 0, 0, (file), (line));                          \
 104 } while (0)
 105
 106 /* Release a write lock. */
 107 #define __rw_wunlock(rw, tid, file, line) do {                          \
 108         uintptr_t _tid = (uintptr_t)(tid);                              \
 109                                                                         \
 110         if ((rw)->rw_recurse)                                           \
 111                 (rw)->rw_recurse--;                                     \
 112         else if (!_rw_write_unlock((rw), _tid))                         \
 113                 _rw_wunlock_hard((rw), _tid, (file), (line));           \
 114 } while (0)
 115
 116 /*
 117  * Function prototypes.  Routines that start with _ are not part of the
 118  * external API and should not be called directly.  Wrapper macros should
 119  * be used instead.
 120  */
 121
 122 #define rw_init(rw, name)       rw_init_flags((rw), (name), 0)
 123 void    rw_init_flags(struct rwlock *rw, const char *name, int opts);
 124 void    rw_destroy(struct rwlock *rw);
 125 void    rw_sysinit(void *arg);
 126 void    rw_sysinit_flags(void *arg);
 127 int     rw_wowned(struct rwlock *rw);
 128 void    _rw_wlock(struct rwlock *rw, const char *file, int line);
 129 int     _rw_try_wlock(struct rwlock *rw, const char *file, int line);
 130 void    _rw_wunlock(struct rwlock *rw, const char *file, int line);
 131 void    _rw_rlock(struct rwlock *rw, const char *file, int line);
 132 int     _rw_try_rlock(struct rwlock *rw, const char *file, int line);
 133 void    _rw_runlock(struct rwlock *rw, const char *file, int line);
 134 void    _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file,
 135             int line);
 136 void    _rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file,
 137             int line);
 138 int     _rw_try_upgrade(struct rwlock *rw, const char *file, int line);
 139 void    _rw_downgrade(struct rwlock *rw, const char *file, int line);
 140 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
 141 void    _rw_assert(struct rwlock *rw, int what, const char *file, int line);
 142 #endif
 143
 144 /*
 145  * Public interface for lock operations.
 146  */
 147
 148 #ifndef LOCK_DEBUG
 149 #error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/rwlock.h>
 150 #endif
 151 #if LOCK_DEBUG > 0 || defined(RWLOCK_NOINLINE)
 152 #define rw_wlock(rw)            _rw_wlock((rw), LOCK_FILE, LOCK_LINE)
 153 #define rw_wunlock(rw)          _rw_wunlock((rw), LOCK_FILE, LOCK_LINE)
 154 #else
 155 #define rw_wlock(rw)                                                    \
 156         __rw_wlock((rw), curthread, LOCK_FILE, LOCK_LINE)
 157 #define rw_wunlock(rw)                                                  \
 158         __rw_wunlock((rw), curthread, LOCK_FILE, LOCK_LINE)
 159 #endif
 160 #define rw_rlock(rw)            _rw_rlock((rw), LOCK_FILE, LOCK_LINE)
 161 #define rw_runlock(rw)          _rw_runlock((rw), LOCK_FILE, LOCK_LINE)
 162 #define rw_try_rlock(rw)        _rw_try_rlock((rw), LOCK_FILE, LOCK_LINE)
 163 #define rw_try_upgrade(rw)      _rw_try_upgrade((rw), LOCK_FILE, LOCK_LINE)
 164 #define rw_try_wlock(rw)        _rw_try_wlock((rw), LOCK_FILE, LOCK_LINE)
 165 #define rw_downgrade(rw)        _rw_downgrade((rw), LOCK_FILE, LOCK_LINE)
 166 #define rw_unlock(rw)   do {                                            \
 167         if (rw_wowned(rw))                                              \
 168                 rw_wunlock(rw);                                         \
 169         else                                                            \
 170                 rw_runlock(rw);                                         \
 171 } while (0)
 172 #define rw_sleep(chan, rw, pri, wmesg, timo)                            \
 173         _sleep((chan), &(rw)->lock_object, (pri), (wmesg), (timo))
 174
 175 #define rw_initialized(rw)      lock_initalized(&(rw)->lock_object)
 176
 177 struct rw_args {
 178         struct rwlock   *ra_rw;
 179         const char      *ra_desc;
 180 };
 181
 182 struct rw_args_flags {
 183         struct rwlock   *ra_rw;
 184         const char      *ra_desc;
 185         int             ra_flags;
 186 };
 187
 188 #define RW_SYSINIT(name, rw, desc)                                      \
 189         static struct rw_args name##_args = {                           \
 190                 (rw),                                                   \
 191                 (desc),                                                 \
 192         };                                                              \
 193         SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE,        \
 194             rw_sysinit, &name##_args);                                  \
 195         SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE,    \
 196             rw_destroy, (rw))
 197
 198
 199 #define RW_SYSINIT_FLAGS(name, rw, desc, flags)                         \
 200         static struct rw_args_flags name##_args = {                     \
 201                 (rw),                                                   \
 202                 (desc),                                                 \
 203                 (flags),                                                \
 204         };                                                              \
 205         SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE,        \
 206             rw_sysinit_flags, &name##_args);                            \
 207         SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE,    \
 208             rw_destroy, (rw))
 209
 210 /*
 211  * Options passed to rw_init_flags().
 212  */
 213 #define RW_DUPOK        0x01
 214 #define RW_NOPROFILE    0x02
 215 #define RW_NOWITNESS    0x04
 216 #define RW_QUIET        0x08
 217 #define RW_RECURSE      0x10
 218
 219 /*
 220  * The INVARIANTS-enabled rw_assert() functionality.
 221  *
 222  * The constants need to be defined for INVARIANT_SUPPORT infrastructure
 223  * support as _rw_assert() itself uses them and the latter implies that
 224  * _rw_assert() must build.
 225  */
 226 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
 227 #define RA_LOCKED               LA_LOCKED
 228 #define RA_RLOCKED              LA_SLOCKED
 229 #define RA_WLOCKED              LA_XLOCKED
 230 #define RA_UNLOCKED             LA_UNLOCKED
 231 #define RA_RECURSED             LA_RECURSED
 232 #define RA_NOTRECURSED          LA_NOTRECURSED
 233 #endif
 234
 235 #ifdef INVARIANTS
 236 #define rw_assert(rw, what)     _rw_assert((rw), (what), LOCK_FILE, LOCK_LINE)
 237 #else
 238 #define rw_assert(rw, what)
 239 #endif
 240
 241 #endif /* _KERNEL */
 242 #endif /* !_SYS_RWLOCK_H_ */