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  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    3  *
    4  * Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org>
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   26  * SUCH DAMAGE.
   27  *
   28  * $FreeBSD: releng/12.0/sys/sys/rwlock.h 326256 2017-11-27 15:01:59Z pfg $
   29  */
   30 
   31 #ifndef _SYS_RWLOCK_H_
   32 #define _SYS_RWLOCK_H_
   33 
   34 #include <sys/_lock.h>
   35 #include <sys/_rwlock.h>
   36 #include <sys/lock_profile.h>
   37 #include <sys/lockstat.h>
   38 
   39 #ifdef _KERNEL
   40 #include <sys/pcpu.h>
   41 #include <machine/atomic.h>
   42 #endif
   43 
   44 /*
   45  * The rw_lock field consists of several fields.  The low bit indicates
   46  * if the lock is locked with a read (shared) or write (exclusive) lock.
   47  * A value of 0 indicates a write lock, and a value of 1 indicates a read
   48  * lock.  Bit 1 is a boolean indicating if there are any threads waiting
   49  * for a read lock.  Bit 2 is a boolean indicating if there are any threads
   50  * waiting for a write lock.  The rest of the variable's definition is
   51  * dependent on the value of the first bit.  For a write lock, it is a
   52  * pointer to the thread holding the lock, similar to the mtx_lock field of
   53  * mutexes.  For read locks, it is a count of read locks that are held.
   54  *
   55  * When the lock is not locked by any thread, it is encoded as a read lock
   56  * with zero waiters.
   57  */
   58 
   59 #define RW_LOCK_READ            0x01
   60 #define RW_LOCK_READ_WAITERS    0x02
   61 #define RW_LOCK_WRITE_WAITERS   0x04
   62 #define RW_LOCK_WRITE_SPINNER   0x08
   63 #define RW_LOCK_WRITER_RECURSED 0x10
   64 #define RW_LOCK_FLAGMASK                                                \
   65         (RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS |  \
   66         RW_LOCK_WRITE_SPINNER | RW_LOCK_WRITER_RECURSED)
   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        5
   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 #define RW_READ_VALUE(x)        ((x)->rw_lock)
   83 
   84 /* Very simple operations on rw_lock. */
   85 
   86 /* Try to obtain a write lock once. */
   87 #define _rw_write_lock(rw, tid)                                         \
   88         atomic_cmpset_acq_ptr(&(rw)->rw_lock, RW_UNLOCKED, (tid))
   89 
   90 #define _rw_write_lock_fetch(rw, vp, tid)                               \
   91         atomic_fcmpset_acq_ptr(&(rw)->rw_lock, vp, (tid))
   92 
   93 /* Release a write lock quickly if there are no waiters. */
   94 #define _rw_write_unlock(rw, tid)                                       \
   95         atomic_cmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
   96 
   97 #define _rw_write_unlock_fetch(rw, tid)                                 \
   98         atomic_fcmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
   99 
  100 /*
  101  * Full lock operations that are suitable to be inlined in non-debug
  102  * kernels.  If the lock cannot be acquired or released trivially then
  103  * the work is deferred to another function.
  104  */
  105 
  106 /* Acquire a write lock. */
  107 #define __rw_wlock(rw, tid, file, line) do {                            \
  108         uintptr_t _tid = (uintptr_t)(tid);                              \
  109         uintptr_t _v = RW_UNLOCKED;                                     \
  110                                                                         \
  111         if (__predict_false(LOCKSTAT_PROFILE_ENABLED(rw__acquire) ||    \
  112             !_rw_write_lock_fetch((rw), &_v, _tid)))                    \
  113                 _rw_wlock_hard((rw), _v, (file), (line));               \
  114 } while (0)
  115 
  116 /* Release a write lock. */
  117 #define __rw_wunlock(rw, tid, file, line) do {                          \
  118         uintptr_t _v = (uintptr_t)(tid);                                \
  119                                                                         \
  120         if (__predict_false(LOCKSTAT_PROFILE_ENABLED(rw__release) ||    \
  121             !_rw_write_unlock_fetch((rw), &_v)))                        \
  122                 _rw_wunlock_hard((rw), _v, (file), (line));             \
  123 } while (0)
  124 
  125 /*
  126  * Function prototypes.  Routines that start with _ are not part of the
  127  * external API and should not be called directly.  Wrapper macros should
  128  * be used instead.
  129  */
  130 void    _rw_init_flags(volatile uintptr_t *c, const char *name, int opts);
  131 void    _rw_destroy(volatile uintptr_t *c);
  132 void    rw_sysinit(void *arg);
  133 void    rw_sysinit_flags(void *arg);
  134 int     _rw_wowned(const volatile uintptr_t *c);
  135 void    _rw_wlock_cookie(volatile uintptr_t *c, const char *file, int line);
  136 int     __rw_try_wlock_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
  137 int     __rw_try_wlock(volatile uintptr_t *c, const char *file, int line);
  138 void    _rw_wunlock_cookie(volatile uintptr_t *c, const char *file, int line);
  139 void    __rw_rlock_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
  140 void    __rw_rlock(volatile uintptr_t *c, const char *file, int line);
  141 int     __rw_try_rlock_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
  142 int     __rw_try_rlock(volatile uintptr_t *c, const char *file, int line);
  143 void    _rw_runlock_cookie_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
  144 void    _rw_runlock_cookie(volatile uintptr_t *c, const char *file, int line);
  145 void    __rw_wlock_hard(volatile uintptr_t *c, uintptr_t v
  146             LOCK_FILE_LINE_ARG_DEF);
  147 void    __rw_wunlock_hard(volatile uintptr_t *c, uintptr_t v
  148             LOCK_FILE_LINE_ARG_DEF);
  149 int     __rw_try_upgrade_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
  150 int     __rw_try_upgrade(volatile uintptr_t *c, const char *file, int line);
  151 void    __rw_downgrade_int(struct rwlock *rw LOCK_FILE_LINE_ARG_DEF);
  152 void    __rw_downgrade(volatile uintptr_t *c, const char *file, int line);
  153 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
  154 void    __rw_assert(const volatile uintptr_t *c, int what, const char *file,
  155             int line);
  156 #endif
  157 
  158 /*
  159  * Top-level macros to provide lock cookie once the actual rwlock is passed.
  160  * They will also prevent passing a malformed object to the rwlock KPI by
  161  * failing compilation as the rw_lock reserved member will not be found.
  162  */
  163 #define rw_init(rw, n)                                                  \
  164         _rw_init_flags(&(rw)->rw_lock, n, 0)
  165 #define rw_init_flags(rw, n, o)                                         \
  166         _rw_init_flags(&(rw)->rw_lock, n, o)
  167 #define rw_destroy(rw)                                                  \
  168         _rw_destroy(&(rw)->rw_lock)
  169 #define rw_wowned(rw)                                                   \
  170         _rw_wowned(&(rw)->rw_lock)
  171 #define _rw_wlock(rw, f, l)                                             \
  172         _rw_wlock_cookie(&(rw)->rw_lock, f, l)
  173 #define _rw_try_wlock(rw, f, l)                                         \
  174         __rw_try_wlock(&(rw)->rw_lock, f, l)
  175 #define _rw_wunlock(rw, f, l)                                           \
  176         _rw_wunlock_cookie(&(rw)->rw_lock, f, l)
  177 #define _rw_try_rlock(rw, f, l)                                         \
  178         __rw_try_rlock(&(rw)->rw_lock, f, l)
  179 #if LOCK_DEBUG > 0
  180 #define _rw_rlock(rw, f, l)                                             \
  181         __rw_rlock(&(rw)->rw_lock, f, l)
  182 #define _rw_runlock(rw, f, l)                                           \
  183         _rw_runlock_cookie(&(rw)->rw_lock, f, l)
  184 #else
  185 #define _rw_rlock(rw, f, l)                                             \
  186         __rw_rlock_int((struct rwlock *)rw)
  187 #define _rw_runlock(rw, f, l)                                           \
  188         _rw_runlock_cookie_int((struct rwlock *)rw)
  189 #endif
  190 #if LOCK_DEBUG > 0
  191 #define _rw_wlock_hard(rw, v, f, l)                                     \
  192         __rw_wlock_hard(&(rw)->rw_lock, v, f, l)
  193 #define _rw_wunlock_hard(rw, v, f, l)                                   \
  194         __rw_wunlock_hard(&(rw)->rw_lock, v, f, l)
  195 #define _rw_try_upgrade(rw, f, l)                                       \
  196         __rw_try_upgrade(&(rw)->rw_lock, f, l)
  197 #define _rw_downgrade(rw, f, l)                                         \
  198         __rw_downgrade(&(rw)->rw_lock, f, l)
  199 #else
  200 #define _rw_wlock_hard(rw, v, f, l)                                     \
  201         __rw_wlock_hard(&(rw)->rw_lock, v)
  202 #define _rw_wunlock_hard(rw, v, f, l)                                   \
  203         __rw_wunlock_hard(&(rw)->rw_lock, v)
  204 #define _rw_try_upgrade(rw, f, l)                                       \
  205         __rw_try_upgrade_int(rw)
  206 #define _rw_downgrade(rw, f, l)                                         \
  207         __rw_downgrade_int(rw)
  208 #endif
  209 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
  210 #define _rw_assert(rw, w, f, l)                                         \
  211         __rw_assert(&(rw)->rw_lock, w, f, l)
  212 #endif
  213 
  214 
  215 /*
  216  * Public interface for lock operations.
  217  */
  218 
  219 #ifndef LOCK_DEBUG
  220 #error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/rwlock.h>
  221 #endif
  222 #if LOCK_DEBUG > 0 || defined(RWLOCK_NOINLINE)
  223 #define rw_wlock(rw)            _rw_wlock((rw), LOCK_FILE, LOCK_LINE)
  224 #define rw_wunlock(rw)          _rw_wunlock((rw), LOCK_FILE, LOCK_LINE)
  225 #else
  226 #define rw_wlock(rw)                                                    \
  227         __rw_wlock((rw), curthread, LOCK_FILE, LOCK_LINE)
  228 #define rw_wunlock(rw)                                                  \
  229         __rw_wunlock((rw), curthread, LOCK_FILE, LOCK_LINE)
  230 #endif
  231 #define rw_rlock(rw)            _rw_rlock((rw), LOCK_FILE, LOCK_LINE)
  232 #define rw_runlock(rw)          _rw_runlock((rw), LOCK_FILE, LOCK_LINE)
  233 #define rw_try_rlock(rw)        _rw_try_rlock((rw), LOCK_FILE, LOCK_LINE)
  234 #define rw_try_upgrade(rw)      _rw_try_upgrade((rw), LOCK_FILE, LOCK_LINE)
  235 #define rw_try_wlock(rw)        _rw_try_wlock((rw), LOCK_FILE, LOCK_LINE)
  236 #define rw_downgrade(rw)        _rw_downgrade((rw), LOCK_FILE, LOCK_LINE)
  237 #define rw_unlock(rw)   do {                                            \
  238         if (rw_wowned(rw))                                              \
  239                 rw_wunlock(rw);                                         \
  240         else                                                            \
  241                 rw_runlock(rw);                                         \
  242 } while (0)
  243 #define rw_sleep(chan, rw, pri, wmesg, timo)                            \
  244         _sleep((chan), &(rw)->lock_object, (pri), (wmesg),              \
  245             tick_sbt * (timo), 0, C_HARDCLOCK)
  246 
  247 #define rw_initialized(rw)      lock_initialized(&(rw)->lock_object)
  248 
  249 struct rw_args {
  250         void            *ra_rw;
  251         const char      *ra_desc;
  252         int             ra_flags;
  253 };
  254 
  255 #define RW_SYSINIT_FLAGS(name, rw, desc, flags)                         \
  256         static struct rw_args name##_args = {                           \
  257                 (rw),                                                   \
  258                 (desc),                                                 \
  259                 (flags),                                                \
  260         };                                                              \
  261         SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE,        \
  262             rw_sysinit, &name##_args);                                  \
  263         SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE,    \
  264             _rw_destroy, __DEVOLATILE(void *, &(rw)->rw_lock))
  265 
  266 #define RW_SYSINIT(name, rw, desc)      RW_SYSINIT_FLAGS(name, rw, desc, 0)
  267 
  268 /*
  269  * Options passed to rw_init_flags().
  270  */
  271 #define RW_DUPOK        0x01
  272 #define RW_NOPROFILE    0x02
  273 #define RW_NOWITNESS    0x04
  274 #define RW_QUIET        0x08
  275 #define RW_RECURSE      0x10
  276 #define RW_NEW          0x20
  277 
  278 /*
  279  * The INVARIANTS-enabled rw_assert() functionality.
  280  *
  281  * The constants need to be defined for INVARIANT_SUPPORT infrastructure
  282  * support as _rw_assert() itself uses them and the latter implies that
  283  * _rw_assert() must build.
  284  */
  285 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
  286 #define RA_LOCKED               LA_LOCKED
  287 #define RA_RLOCKED              LA_SLOCKED
  288 #define RA_WLOCKED              LA_XLOCKED
  289 #define RA_UNLOCKED             LA_UNLOCKED
  290 #define RA_RECURSED             LA_RECURSED
  291 #define RA_NOTRECURSED          LA_NOTRECURSED
  292 #endif
  293 
  294 #ifdef INVARIANTS
  295 #define rw_assert(rw, what)     _rw_assert((rw), (what), LOCK_FILE, LOCK_LINE)
  296 #else
  297 #define rw_assert(rw, what)
  298 #endif
  299 
  300 #endif /* _KERNEL */
  301 #endif /* !_SYS_RWLOCK_H_ */

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