The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/sys/rwlock.h

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    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: releng/8.1/sys/sys/rwlock.h 199583 2009-11-20 15:27:52Z jhb $
   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_ */

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