mut_win32.c
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上传日期:2022-05-23
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文件大小:6k
- /*
- * See the file LICENSE for redistribution information.
- *
- * Copyright (c) 2002
- * Sleepycat Software. All rights reserved.
- */
- #include "db_config.h"
- #ifndef lint
- static const char revid[] = "$Id: mut_win32.c,v 1.8 2002/09/10 02:37:25 bostic Exp $";
- #endif /* not lint */
- #ifndef NO_SYSTEM_INCLUDES
- #include <sys/types.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"
- /* We don't want to run this code even in "ordinary" diagnostic mode. */
- #undef MUTEX_DIAG
- #define GET_HANDLE(mutexp, event) do {
- char idbuf[13];
-
- if (F_ISSET(mutexp, MUTEX_THREAD)) {
- event = mutexp->event;
- return (0);
- }
-
- snprintf(idbuf, sizeof idbuf, "db.m%08x", mutexp->id);
- event = CreateEvent(NULL, FALSE, FALSE, idbuf);
- if (event == NULL)
- return (__os_win32_errno());
- } while (0)
- #define RELEASE_HANDLE(mutexp, event)
- if (!F_ISSET(mutexp, MUTEX_THREAD) && event != NULL) {
- CloseHandle(event);
- event = NULL;
- }
- /*
- * __db_win32_mutex_init --
- * Initialize a DB_MUTEX.
- *
- * PUBLIC: int __db_win32_mutex_init __P((DB_ENV *, DB_MUTEX *, u_int32_t));
- */
- int
- __db_win32_mutex_init(dbenv, mutexp, flags)
- DB_ENV *dbenv;
- DB_MUTEX *mutexp;
- u_int32_t flags;
- {
- u_int32_t save;
- /*
- * 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);
- }
- F_SET(mutexp, MUTEX_THREAD);
- mutexp->event = CreateEvent(NULL, FALSE, FALSE, NULL);
- if (mutexp->event == NULL)
- return (__os_win32_errno());
- } else
- mutexp->id = ((getpid() & 0xffff) << 16) ^ P_TO_UINT32(mutexp);
- mutexp->spins = __os_spin(dbenv);
- F_SET(mutexp, MUTEX_INITED);
- return (0);
- }
- /*
- * __db_win32_mutex_lock
- * Lock on a mutex, logically blocking if necessary.
- *
- * PUBLIC: int __db_win32_mutex_lock __P((DB_ENV *, DB_MUTEX *));
- */
- int
- __db_win32_mutex_lock(dbenv, mutexp)
- DB_ENV *dbenv;
- DB_MUTEX *mutexp;
- {
- HANDLE event;
- int ret, ms, nspins;
- #ifdef MUTEX_DIAG
- LARGE_INTEGER now;
- #endif
- if (F_ISSET(dbenv, DB_ENV_NOLOCKING) || F_ISSET(mutexp, MUTEX_IGNORE))
- return (0);
- event = NULL;
- ms = 50;
- ret = 0;
- loop: /* Attempt to acquire the resource for N spins. */
- for (nspins = mutexp->spins; nspins > 0; --nspins) {
- if (!MUTEX_SET(&mutexp->tas))
- continue;
- #ifdef DIAGNOSTIC
- if (mutexp->locked)
- __db_err(dbenv,
- "__db_win32_mutex_lock: mutex double-locked!");
- __os_id(&mutexp->locked);
- #endif
- if (event == NULL)
- ++mutexp->mutex_set_nowait;
- else {
- ++mutexp->mutex_set_wait;
- RELEASE_HANDLE(mutexp, event);
- InterlockedDecrement(&mutexp->nwaiters);
- #ifdef MUTEX_DIAG
- if (ret != WAIT_OBJECT_0) {
- QueryPerformanceCounter(&now);
- printf("[%I64d]: Lost signal on mutex %p, "
- "id %d, ms %dn",
- now.QuadPart, mutexp, mutexp->id, ms);
- }
- #endif
- }
- return (0);
- }
- /*
- * Yield the processor; wait 50 ms initially, up to 1 second. This
- * loop is needed to work around a race where the signal from the
- * unlocking thread gets lost. We start at 50 ms because it's unlikely
- * to happen often and we want to avoid wasting CPU.
- */
- if (event == NULL) {
- #ifdef MUTEX_DIAG
- QueryPerformanceCounter(&now);
- printf("[%I64d]: Waiting on mutex %p, id %dn",
- now.QuadPart, mutexp, mutexp->id);
- #endif
- InterlockedIncrement(&mutexp->nwaiters);
- GET_HANDLE(mutexp, event);
- }
- if ((ret = WaitForSingleObject(event, ms)) == WAIT_FAILED)
- return (__os_win32_errno());
- if ((ms <<= 1) > MS_PER_SEC)
- ms = MS_PER_SEC;
- goto loop;
- }
- /*
- * __db_win32_mutex_unlock --
- * Release a lock.
- *
- * PUBLIC: int __db_win32_mutex_unlock __P((DB_ENV *, DB_MUTEX *));
- */
- int
- __db_win32_mutex_unlock(dbenv, mutexp)
- DB_ENV *dbenv;
- DB_MUTEX *mutexp;
- {
- int ret;
- HANDLE event;
- #ifdef MUTEX_DIAG
- LARGE_INTEGER now;
- #endif
- if (F_ISSET(dbenv, DB_ENV_NOLOCKING) || F_ISSET(mutexp, MUTEX_IGNORE))
- return (0);
- #ifdef DIAGNOSTIC
- if (!mutexp->tas || !mutexp->locked)
- __db_err(dbenv,
- "__db_win32_mutex_unlock: ERROR: lock already unlocked");
- mutexp->locked = 0;
- #endif
- MUTEX_UNSET(&mutexp->tas);
- ret = 0;
-
- if (mutexp->nwaiters > 0) {
- GET_HANDLE(mutexp, event);
- #ifdef MUTEX_DIAG
- QueryPerformanceCounter(&now);
- printf("[%I64d]: Signalling mutex %p, id %dn",
- now.QuadPart, mutexp, mutexp->id);
- #endif
- if (!PulseEvent(event))
- ret = __os_win32_errno();
- RELEASE_HANDLE(mutexp, event);
- }
- #ifdef DIAGNOSTIC
- if (ret != 0)
- __db_err(dbenv,
- "__db_win32_mutex_unlock: ERROR: unlock failed");
- #endif
- return (ret);
- }
- /*
- * __db_win32_mutex_destroy --
- * Destroy a DB_MUTEX.
- *
- * PUBLIC: int __db_win32_mutex_destroy __P((DB_MUTEX *));
- */
- int
- __db_win32_mutex_destroy(mutexp)
- DB_MUTEX *mutexp;
- {
- int ret;
- if (F_ISSET(mutexp, MUTEX_IGNORE) || !F_ISSET(mutexp, MUTEX_THREAD))
- return (0);
- ret = 0;
- if (mutexp->event != NULL) {
- if (!CloseHandle(mutexp->event))
- ret = __os_win32_errno();
- mutexp->event = NULL;
- }
- return (ret);
- }