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/*
* See the file LICENSE for redistribution information.
*
* Copyright (c) 2002-2004
* Sleepycat Software. All rights reserved.
*
* $Id: mut_win32.c,v 1.18 2004/07/06 21:06:39 mjc Exp $
*/
#include "db_config.h"
#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>
#include <string.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
static _TCHAR hex_digits[] = _T("0123456789abcdef");
#define GET_HANDLE(mutexp, event) do { \
_TCHAR idbuf[] = _T("db.m00000000"); \
_TCHAR *p = idbuf + 12; \
u_int32_t id; \
\
for (id = (mutexp)->id; id != 0; id >>= 4) \
*--p = hex_digits[id & 0xf]; \
event = CreateEvent(NULL, FALSE, FALSE, idbuf); \
if (event == NULL) \
return (__os_get_errno()); \
} while (0)
/*
* __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 flag 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, and 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);
}
}
mutexp->id = ((getpid() & 0xffff) << 16) ^ P_TO_UINT32(mutexp);
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;
u_int32_t nspins;
int ret, ms;
#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 = dbenv->tas_spins; nspins > 0; --nspins) {
if (!MUTEX_SET(&mutexp->tas)) {
/*
* Some systems (notably those with newer Intel CPUs)
* need a small pause here. [#6975]
*/
#ifdef MUTEX_PAUSE
MUTEX_PAUSE
#endif
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;
CloseHandle(event);
InterlockedDecrement(&mutexp->nwaiters);
#ifdef MUTEX_DIAG
if (ret != WAIT_OBJECT_0) {
QueryPerformanceCounter(&now);
printf("[%I64d]: Lost signal on mutex %p, "
"id %d, ms %d\n",
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 %d\n",
now.QuadPart, mutexp, mutexp->id);
#endif
InterlockedIncrement(&mutexp->nwaiters);
GET_HANDLE(mutexp, event);
}
if ((ret = WaitForSingleObject(event, ms)) == WAIT_FAILED)
return (__os_get_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 %d\n",
now.QuadPart, mutexp, mutexp->id);
#endif
if (!PulseEvent(event))
ret = __os_get_errno();
CloseHandle(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 - noop with this implementation.
*
* PUBLIC: int __db_win32_mutex_destroy __P((DB_MUTEX *));
*/
int
__db_win32_mutex_destroy(mutexp)
DB_MUTEX *mutexp;
{
return (0);
}
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