mut_tas.c
上传用户:romrleung
上传日期:2022-05-23
资源大小:18897k
文件大小:5k
- /*-
- * See the file LICENSE for redistribution information.
- *
- * Copyright (c) 1996-2002
- * Sleepycat Software. All rights reserved.
- */
- #include "db_config.h"
- #ifndef lint
- static const char revid[] = "$Id: mut_tas.c,v 11.32 2002/05/07 18:42:21 bostic Exp $";
- #endif /* not lint */
- #ifndef NO_SYSTEM_INCLUDES
- #include <sys/types.h>
- #include <stdlib.h>
- #include <string.h>
- #include <unistd.h>
- #endif
- /*
- * This is where we load in the actual test-and-set mutex code.
- */
- #define LOAD_ACTUAL_MUTEX_CODE
- #include "db_int.h"
- /*
- * __db_tas_mutex_init --
- * Initialize a DB_MUTEX.
- *
- * PUBLIC: int __db_tas_mutex_init __P((DB_ENV *, DB_MUTEX *, u_int32_t));
- */
- int
- __db_tas_mutex_init(dbenv, mutexp, flags)
- DB_ENV *dbenv;
- DB_MUTEX *mutexp;
- u_int32_t flags;
- {
- u_int32_t save;
- /* Check alignment. */
- DB_ASSERT(((db_alignp_t)mutexp & (MUTEX_ALIGN - 1)) == 0);
- /*
- * The only setting/checking of the MUTEX_MPOOL flags is in the mutex
- * mutex allocation code (__db_mutex_alloc/free). Preserve only that
- * flag. This is safe because even if this flag was never explicitly
- * set, but happened to be set in memory, it will never be checked or
- * acted upon.
- */
- save = F_ISSET(mutexp, MUTEX_MPOOL);
- memset(mutexp, 0, sizeof(*mutexp));
- F_SET(mutexp, save);
- /*
- * If this is a thread lock or the process has told us that there are
- * no other processes in the environment, use thread-only locks, they
- * are faster in some cases.
- *
- * This is where we decide to ignore locks we don't need to set -- if
- * the application isn't threaded, there aren't any threads to block.
- */
- if (LF_ISSET(MUTEX_THREAD) || F_ISSET(dbenv, DB_ENV_PRIVATE)) {
- if (!F_ISSET(dbenv, DB_ENV_THREAD)) {
- F_SET(mutexp, MUTEX_IGNORE);
- return (0);
- }
- }
- /* Initialize the lock. */
- if (MUTEX_INIT(&mutexp->tas))
- return (__os_get_errno());
- mutexp->spins = __os_spin(dbenv);
- #ifdef HAVE_MUTEX_SYSTEM_RESOURCES
- mutexp->reg_off = INVALID_ROFF;
- #endif
- F_SET(mutexp, MUTEX_INITED);
- return (0);
- }
- /*
- * __db_tas_mutex_lock
- * Lock on a mutex, logically blocking if necessary.
- *
- * PUBLIC: int __db_tas_mutex_lock __P((DB_ENV *, DB_MUTEX *));
- */
- int
- __db_tas_mutex_lock(dbenv, mutexp)
- DB_ENV *dbenv;
- DB_MUTEX *mutexp;
- {
- u_long ms;
- int nspins;
- if (F_ISSET(dbenv, DB_ENV_NOLOCKING) || F_ISSET(mutexp, MUTEX_IGNORE))
- return (0);
- ms = 1;
- loop: /* Attempt to acquire the resource for N spins. */
- for (nspins = mutexp->spins; nspins > 0; --nspins) {
- #ifdef HAVE_MUTEX_HPPA_MSEM_INIT
- relock:
- #endif
- if (!MUTEX_SET(&mutexp->tas))
- continue;
- #ifdef HAVE_MUTEX_HPPA_MSEM_INIT
- /*
- * HP semaphores are unlocked automatically when a holding
- * process exits. If the mutex appears to be locked
- * (mutexp->locked != 0) but we got here, assume this has
- * happened. Stick our own pid into mutexp->locked and
- * lock again. (The default state of the mutexes used to
- * block in __lock_get_internal is locked, so exiting with
- * a locked mutex is reasonable behavior for a process that
- * happened to initialize or use one of them.)
- */
- if (mutexp->locked != 0) {
- __os_id(&mutexp->locked);
- goto relock;
- }
- /*
- * If we make it here, locked == 0, the diagnostic won't fire,
- * and we were really unlocked by someone calling the
- * DB mutex unlock function.
- */
- #endif
- #ifdef DIAGNOSTIC
- if (mutexp->locked != 0)
- __db_err(dbenv,
- "__db_tas_mutex_lock: ERROR: lock currently in use: ID: %lu",
- (u_long)mutexp->locked);
- #endif
- #if defined(DIAGNOSTIC) || defined(HAVE_MUTEX_HPPA_MSEM_INIT)
- __os_id(&mutexp->locked);
- #endif
- if (ms == 1)
- ++mutexp->mutex_set_nowait;
- else
- ++mutexp->mutex_set_wait;
- return (0);
- }
- /* Yield the processor; wait 1ms initially, up to 1 second. */
- __os_yield(NULL, ms * USEC_PER_MS);
- if ((ms <<= 1) > MS_PER_SEC)
- ms = MS_PER_SEC;
- goto loop;
- }
- /*
- * __db_tas_mutex_unlock --
- * Release a lock.
- *
- * PUBLIC: int __db_tas_mutex_unlock __P((DB_ENV *, DB_MUTEX *));
- */
- int
- __db_tas_mutex_unlock(dbenv, mutexp)
- DB_ENV *dbenv;
- DB_MUTEX *mutexp;
- {
- if (F_ISSET(dbenv, DB_ENV_NOLOCKING) || F_ISSET(mutexp, MUTEX_IGNORE))
- return (0);
- #ifdef DIAGNOSTIC
- if (!mutexp->locked)
- __db_err(dbenv,
- "__db_tas_mutex_unlock: ERROR: lock already unlocked");
- #endif
- #if defined(DIAGNOSTIC) || defined(HAVE_MUTEX_HPPA_MSEM_INIT)
- mutexp->locked = 0;
- #endif
- MUTEX_UNSET(&mutexp->tas);
- return (0);
- }
- /*
- * __db_tas_mutex_destroy --
- * Destroy a DB_MUTEX.
- *
- * PUBLIC: int __db_tas_mutex_destroy __P((DB_MUTEX *));
- */
- int
- __db_tas_mutex_destroy(mutexp)
- DB_MUTEX *mutexp;
- {
- if (F_ISSET(mutexp, MUTEX_IGNORE))
- return (0);
- MUTEX_DESTROY(&mutexp->tas);
- return (0);
- }