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  * 3. Neither the name of the author nor the names of any co-contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * $FreeBSD$
  30  */
  31
  32 #ifndef _SYS_RWLOCK_H_
  33 #define _SYS_RWLOCK_H_
  34
  35 #include <sys/_lock.h>
  36 #include <sys/_rwlock.h>
  37 #include <sys/lock_profile.h>
  38 #include <sys/lockstat.h>
  39
  40 #ifdef _KERNEL
  41 #include <sys/pcpu.h>
  42 #include <machine/atomic.h>
  43 #endif
  44
  45 /*
  46  * The rw_lock field consists of several fields.  The low bit indicates
  47  * if the lock is locked with a read (shared) or write (exclusive) lock.
  48  * A value of 0 indicates a write lock, and a value of 1 indicates a read
  49  * lock.  Bit 1 is a boolean indicating if there are any threads waiting
  50  * for a read lock.  Bit 2 is a boolean indicating if there are any threads
  51  * waiting for a write lock.  The rest of the variable's definition is
  52  * dependent on the value of the first bit.  For a write lock, it is a
  53  * pointer to the thread holding the lock, similar to the mtx_lock field of
  54  * mutexes.  For read locks, it is a count of read locks that are held.
  55  *
  56  * When the lock is not locked by any thread, it is encoded as a read lock
  57  * with zero waiters.
  58  */
  59
  60 #define RW_LOCK_READ            0x01
  61 #define RW_LOCK_READ_WAITERS    0x02
  62 #define RW_LOCK_WRITE_WAITERS   0x04
  63 #define RW_LOCK_WRITE_SPINNER   0x08
  64 #define RW_LOCK_FLAGMASK                                                \
  65         (RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS |  \
  66         RW_LOCK_WRITE_SPINNER)
  67 #define RW_LOCK_WAITERS         (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
  68
  69 #define RW_OWNER(x)             ((x) & ~RW_LOCK_FLAGMASK)
  70 #define RW_READERS_SHIFT        4
  71 #define RW_READERS(x)           (RW_OWNER((x)) >> RW_READERS_SHIFT)
  72 #define RW_READERS_LOCK(x)      ((x) << RW_READERS_SHIFT | RW_LOCK_READ)
  73 #define RW_ONE_READER           (1 << RW_READERS_SHIFT)
  74
  75 #define RW_UNLOCKED             RW_READERS_LOCK(0)
  76 #define RW_DESTROYED            (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
  77
  78 #ifdef _KERNEL
  79
  80 #define rw_recurse      lock_object.lo_data
  81
  82 /* Very simple operations on rw_lock. */
  83
  84 /* Try to obtain a write lock once. */
  85 #define _rw_write_lock(rw, tid)                                         \
  86         atomic_cmpset_acq_ptr(&(rw)->rw_lock, RW_UNLOCKED, (tid))
  87
  88 /* Release a write lock quickly if there are no waiters. */
  89 #define _rw_write_unlock(rw, tid)                                       \
  90         atomic_cmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
  91
  92 /*
  93  * Full lock operations that are suitable to be inlined in non-debug
  94  * kernels.  If the lock cannot be acquired or released trivially then
  95  * the work is deferred to another function.
  96  */
  97
  98 /* Acquire a write lock. */
  99 #define __rw_wlock(rw, tid, file, line) do {                            \
 100         uintptr_t _tid = (uintptr_t)(tid);                              \
 101                                                                         \
 102         if (!_rw_write_lock((rw), _tid))                                \
 103                 _rw_wlock_hard((rw), _tid, (file), (line));             \
 104         else                                                            \
 105                 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_RW_WLOCK_ACQUIRE, \
 106                     rw, 0, 0, (file), (line));                          \
 107 } while (0)
 108
 109 /* Release a write lock. */
 110 #define __rw_wunlock(rw, tid, file, line) do {                          \
 111         uintptr_t _tid = (uintptr_t)(tid);                              \
 112                                                                         \
 113         if ((rw)->rw_recurse)                                           \
 114                 (rw)->rw_recurse--;                                     \
 115         else if (!_rw_write_unlock((rw), _tid))                         \
 116                 _rw_wunlock_hard((rw), _tid, (file), (line));           \
 117 } while (0)
 118
 119 /*
 120  * Function prototypes.  Routines that start with _ are not part of the
 121  * external API and should not be called directly.  Wrapper macros should
 122  * be used instead.
 123  */
 124
 125 #define rw_init(rw, name)       rw_init_flags((rw), (name), 0)
 126 void    rw_init_flags(struct rwlock *rw, const char *name, int opts);
 127 void    rw_destroy(struct rwlock *rw);
 128 void    rw_sysinit(void *arg);
 129 void    rw_sysinit_flags(void *arg);
 130 int     rw_wowned(struct rwlock *rw);
 131 void    _rw_wlock(struct rwlock *rw, const char *file, int line);
 132 int     _rw_try_wlock(struct rwlock *rw, const char *file, int line);
 133 void    _rw_wunlock(struct rwlock *rw, const char *file, int line);
 134 void    _rw_rlock(struct rwlock *rw, const char *file, int line);
 135 int     _rw_try_rlock(struct rwlock *rw, const char *file, int line);
 136 void    _rw_runlock(struct rwlock *rw, const char *file, int line);
 137 void    _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file,
 138             int line);
 139 void    _rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file,
 140             int line);
 141 int     _rw_try_upgrade(struct rwlock *rw, const char *file, int line);
 142 void    _rw_downgrade(struct rwlock *rw, const char *file, int line);
 143 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
 144 void    _rw_assert(struct rwlock *rw, int what, const char *file, int line);
 145 #endif
 146
 147 /*
 148  * Public interface for lock operations.
 149  */
 150
 151 #ifndef LOCK_DEBUG
 152 #error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/rwlock.h>
 153 #endif
 154 #if LOCK_DEBUG > 0 || defined(RWLOCK_NOINLINE)
 155 #define rw_wlock(rw)            _rw_wlock((rw), LOCK_FILE, LOCK_LINE)
 156 #define rw_wunlock(rw)          _rw_wunlock((rw), LOCK_FILE, LOCK_LINE)
 157 #else
 158 #define rw_wlock(rw)                                                    \
 159         __rw_wlock((rw), curthread, LOCK_FILE, LOCK_LINE)
 160 #define rw_wunlock(rw)                                                  \
 161         __rw_wunlock((rw), curthread, LOCK_FILE, LOCK_LINE)
 162 #endif
 163 #define rw_rlock(rw)            _rw_rlock((rw), LOCK_FILE, LOCK_LINE)
 164 #define rw_runlock(rw)          _rw_runlock((rw), LOCK_FILE, LOCK_LINE)
 165 #define rw_try_rlock(rw)        _rw_try_rlock((rw), LOCK_FILE, LOCK_LINE)
 166 #define rw_try_upgrade(rw)      _rw_try_upgrade((rw), LOCK_FILE, LOCK_LINE)
 167 #define rw_try_wlock(rw)        _rw_try_wlock((rw), LOCK_FILE, LOCK_LINE)
 168 #define rw_downgrade(rw)        _rw_downgrade((rw), LOCK_FILE, LOCK_LINE)
 169 #define rw_unlock(rw)   do {                                            \
 170         if (rw_wowned(rw))                                              \
 171                 rw_wunlock(rw);                                         \
 172         else                                                            \
 173                 rw_runlock(rw);                                         \
 174 } while (0)
 175 #define rw_sleep(chan, rw, pri, wmesg, timo)                            \
 176         _sleep((chan), &(rw)->lock_object, (pri), (wmesg), (timo))
 177
 178 #define rw_initialized(rw)      lock_initalized(&(rw)->lock_object)
 179
 180 struct rw_args {
 181         struct rwlock   *ra_rw;
 182         const char      *ra_desc;
 183 };
 184
 185 struct rw_args_flags {
 186         struct rwlock   *ra_rw;
 187         const char      *ra_desc;
 188         int             ra_flags;
 189 };
 190
 191 #define RW_SYSINIT(name, rw, desc)                                      \
 192         static struct rw_args name##_args = {                           \
 193                 (rw),                                                   \
 194                 (desc),                                                 \
 195         };                                                              \
 196         SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE,        \
 197             rw_sysinit, &name##_args);                                  \
 198         SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE,    \
 199             rw_destroy, (rw))
 200
 201
 202 #define RW_SYSINIT_FLAGS(name, rw, desc, flags)                         \
 203         static struct rw_args_flags name##_args = {                     \
 204                 (rw),                                                   \
 205                 (desc),                                                 \
 206                 (flags),                                                \
 207         };                                                              \
 208         SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE,        \
 209             rw_sysinit_flags, &name##_args);                            \
 210         SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE,    \
 211             rw_destroy, (rw))
 212
 213 /*
 214  * Options passed to rw_init_flags().
 215  */
 216 #define RW_DUPOK        0x01
 217 #define RW_NOPROFILE    0x02
 218 #define RW_NOWITNESS    0x04
 219 #define RW_QUIET        0x08
 220 #define RW_RECURSE      0x10
 221
 222 /*
 223  * The INVARIANTS-enabled rw_assert() functionality.
 224  *
 225  * The constants need to be defined for INVARIANT_SUPPORT infrastructure
 226  * support as _rw_assert() itself uses them and the latter implies that
 227  * _rw_assert() must build.
 228  */
 229 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
 230 #define RA_LOCKED               LA_LOCKED
 231 #define RA_RLOCKED              LA_SLOCKED
 232 #define RA_WLOCKED              LA_XLOCKED
 233 #define RA_UNLOCKED             LA_UNLOCKED
 234 #define RA_RECURSED             LA_RECURSED
 235 #define RA_NOTRECURSED          LA_NOTRECURSED
 236 #endif
 237
 238 #ifdef INVARIANTS
 239 #define rw_assert(rw, what)     _rw_assert((rw), (what), LOCK_FILE, LOCK_LINE)
 240 #else
 241 #define rw_assert(rw, what)
 242 #endif
 243
 244 #endif /* _KERNEL */
 245 #endif /* !_SYS_RWLOCK_H_ */