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169 lines
3.4 KiB
169 lines
3.4 KiB
/*-
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* See the file LICENSE for redistribution information.
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*
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* Copyright (c) 1996, 1997, 1998, 1999
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* Sleepycat Software. All rights reserved.
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*/
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#include "db_config.h"
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#ifdef HAVE_MUTEX_TAS
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#ifndef lint
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static const char sccsid[] = "@(#)mut_tas.c 11.4 (Sleepycat) 10/1/99";
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#endif /* not lint */
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#ifndef NO_SYSTEM_INCLUDES
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#include <sys/types.h>
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#ifndef _MSC_VER /* _WIN32 */
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#include <unistd.h>
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#endif
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#endif
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#include "db_int.h"
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#ifdef HAVE_MUTEX_68K_GCC_ASSEMBLY
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#include "68K.gcc"
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#endif
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#ifdef HAVE_MUTEX_ALPHA_GCC_ASSEMBLY
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#include "alpha.gcc"
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#endif
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#ifdef HAVE_MUTEX_HPPA_GCC_ASSEMBLY
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#include "parisc.gcc"
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#endif
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#ifdef HAVE_MUTEX_SCO_X86_CC_ASSEMBLY
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#include "sco.cc"
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#endif
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#ifdef HAVE_MUTEX_SPARC_GCC_ASSEMBLY
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#include "sparc.gcc"
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#endif
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#ifdef HAVE_MUTEX_X86_GCC_ASSEMBLY
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#include "x86.gcc"
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#endif
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#ifdef DIAGNOSTIC
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#undef MSG1
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#define MSG1 "mutex_lock: ERROR: lock currently in use: pid: %lu.\n"
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#undef MSG2
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#define MSG2 "mutex_unlock: ERROR: lock already unlocked\n"
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#ifndef STDERR_FILENO
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#define STDERR_FILENO 2
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#endif
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#endif
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/*
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* CDB___db_tas_mutex_init --
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* Initialize a MUTEX.
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*
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* PUBLIC: int CDB___db_tas_mutex_init __P((DB_ENV *, MUTEX *, u_int32_t));
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*/
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int
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CDB___db_tas_mutex_init(dbenv, mutexp, flags)
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DB_ENV *dbenv;
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MUTEX *mutexp;
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u_int32_t flags;
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{
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memset(mutexp, 0, sizeof(*mutexp));
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/*
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* If this is a thread lock or the process has told us that there are
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* no other processes in the environment, use thread-only locks, they
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* are faster in some cases.
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*
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* This is where we decide to ignore locks we don't need to set -- if
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* the application isn't threaded, there aren't any threads to block.
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*/
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if (LF_ISSET(MUTEX_THREAD) || F_ISSET(dbenv, DB_ENV_PRIVATE)) {
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if (!F_ISSET(dbenv, DB_ENV_THREAD)) {
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F_SET(mutexp, MUTEX_IGNORE);
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return (0);
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}
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F_SET(mutexp, MUTEX_THREAD);
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}
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/* Initialize the lock. */
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if (MUTEX_INIT(&mutexp->tas))
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return (CDB___os_get_errno());
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mutexp->spins = CDB___os_spin();
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return (0);
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}
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/*
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* CDB___db_tas_mutex_lock
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* Lock on a mutex, logically blocking if necessary.
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*
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* PUBLIC: int CDB___db_tas_mutex_lock __P((MUTEX *));
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*/
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int
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CDB___db_tas_mutex_lock(mutexp)
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MUTEX *mutexp;
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{
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u_long ms;
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int nspins;
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if (!DB_GLOBAL(db_mutexlocks) || F_ISSET(mutexp, MUTEX_IGNORE))
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return (0);
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ms = 1;
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loop: /* Attempt to acquire the resource for N spins. */
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for (nspins = mutexp->spins; nspins > 0; --nspins) {
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if (!MUTEX_SET(&mutexp->tas))
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continue;
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#ifdef DIAGNOSTIC
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if (mutexp->locked != 0) {
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char msgbuf[128];
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(void)snprintf(msgbuf,
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sizeof(msgbuf), MSG1, (u_long)mutexp->locked);
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(void)write(STDERR_FILENO, msgbuf, strlen(msgbuf));
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}
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mutexp->locked = (u_int32_t)getpid();
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#endif
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if (ms == 1)
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++mutexp->mutex_set_nowait;
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else
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++mutexp->mutex_set_wait;
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return (0);
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}
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/* Yield the processor; wait 1ms initially, up to 1 second. */
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CDB___os_yield(ms * USEC_PER_MS);
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if ((ms <<= 1) > MS_PER_SEC)
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ms = MS_PER_SEC;
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goto loop;
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}
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/*
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* CDB___db_tas_mutex_unlock --
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* Release a lock.
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*
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* PUBLIC: int CDB___db_tas_mutex_unlock __P((MUTEX *));
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*/
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int
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CDB___db_tas_mutex_unlock(mutexp)
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MUTEX *mutexp;
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{
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if (!DB_GLOBAL(db_mutexlocks) || F_ISSET(mutexp, MUTEX_IGNORE))
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return (0);
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#ifdef DIAGNOSTIC
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if (!mutexp->locked)
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(void)write(STDERR_FILENO, MSG2, sizeof(MSG2) - 1);
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mutexp->locked = 0;
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#endif
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MUTEX_UNSET(&mutexp->tas);
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return (0);
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}
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#endif /* HAVE_MUTEX_TAS */
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