extra-dependencies/debian/htdig/htdig-3.2.0b6/db/mut_pthread.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1999
 *	Sleepycat Software.  All rights reserved.
 */

#include "db_config.h"

#ifdef HAVE_MUTEX_PTHREAD

#ifndef lint
static const char sccsid[] = "@(#)mut_pthread.c	11.15 (Sleepycat) 11/9/99";
#endif /* not lint */

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>

#include <errno.h>
#include <string.h>
#include <unistd.h>
#endif

#include "db_int.h"

#ifdef DIAGNOSTIC
#undef	MSG1
#define	MSG1		"mutex_lock: ERROR: lock currently in use: pid: %lu.\n"
#undef	MSG2
#define	MSG2		"mutex_unlock: ERROR: lock already unlocked\n"
#ifndef	STDERR_FILENO
#define	STDERR_FILENO	2
#endif
#endif

#ifdef HAVE_MUTEX_SOLARIS_LWP
#define	pthread_cond_signal	_lwp_cond_signal
#define	pthread_cond_wait	_lwp_cond_wait
#define	pthread_mutex_lock	_lwp_mutex_lock
#define	pthread_mutex_trylock	_lwp_mutex_trylock
#define	pthread_mutex_unlock	_lwp_mutex_unlock
#endif
#ifdef HAVE_MUTEX_UI_THREADS
#define	pthread_cond_signal	cond_signal
#define	pthread_cond_wait	cond_wait
#define	pthread_mutex_lock	mutex_lock
#define	pthread_mutex_trylock	mutex_trylock
#define	pthread_mutex_unlock	mutex_unlock
#endif

/*
 * CDB___db_pthread_mutex_init --
 *	Initialize a MUTEX.
 *
 * PUBLIC: int CDB___db_pthread_mutex_init __P((DB_ENV *, MUTEX *, u_int32_t));
 */
int
CDB___db_pthread_mutex_init(dbenv, mutexp, flags)
	DB_ENV *dbenv;
	MUTEX *mutexp;
	u_int32_t flags;
{
	int ret;

	ret = 0;
	memset(mutexp, 0, sizeof(*mutexp));

	/*
	 * 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);
	}

#ifdef HAVE_MUTEX_PTHREADS
	{
	pthread_condattr_t condattr, *condattrp = NULL;
	pthread_mutexattr_t mutexattr, *mutexattrp = NULL;

	if (!F_ISSET(mutexp, MUTEX_THREAD)) {
		ret = pthread_condattr_init(&condattr);
		if (ret == 0)
			ret = pthread_condattr_setpshared(
			    &condattr, PTHREAD_PROCESS_SHARED);
		condattrp = &condattr;

		if (ret == 0)
			ret = pthread_mutexattr_init(&mutexattr);
		if (ret == 0)
			ret = pthread_mutexattr_setpshared(
			    &mutexattr, PTHREAD_PROCESS_SHARED);
		mutexattrp = &mutexattr;
	}

	if (ret == 0)
		ret = pthread_mutex_init(&mutexp->mutex, mutexattrp);
	if (mutexattrp != NULL)
		pthread_mutexattr_destroy(mutexattrp);
	if (LF_ISSET(MUTEX_SELF_BLOCK)) {
		if (ret == 0)
			ret = pthread_cond_init(&mutexp->cond, condattrp);

		F_SET(mutexp, MUTEX_SELF_BLOCK);
		if (condattrp != NULL)
			pthread_condattr_destroy(condattrp);
	}}
#endif
#ifdef HAVE_MUTEX_SOLARIS_LWP
	if (F_ISSET(mutexp, MUTEX_THREAD)) {
		static lwp_mutex_t mi = DEFAULTMUTEX;

		/*
		 * !!!
		 * Gcc attempts to use special Sparc instructions to do a fast
		 * copy of the structures, but the structures aren't
		 * necessarily appropriately aligned for the Sparc instructions
		 * to work.  We don't use memcpy instead of structure assignment
		 * because gcc figures that one out and drops core anyway.
		 */
		CDB___ua_memcpy(&mutexp->mutex, &mi, sizeof(mi));
	} else {
		static lwp_mutex_t mi = SHAREDMUTEX;

		CDB___ua_memcpy(&mutexp->mutex, &mi, sizeof(mi));
	}
	if (LF_ISSET(MUTEX_SELF_BLOCK)) {
		if (F_ISSET(mutexp, MUTEX_THREAD)) {
			static lwp_cond_t ci = DEFAULTCV;

			CDB___ua_memcpy(&mutexp->cond, &ci, sizeof(ci));
		} else {
			static lwp_cond_t ci = SHAREDCV;

			CDB___ua_memcpy(&mutexp->cond, &ci, sizeof(ci));
		}
		F_SET(mutexp, MUTEX_SELF_BLOCK);
	}
#endif
#ifdef HAVE_MUTEX_UI_THREADS
	{
	int type;

	type = F_ISSET(mutexp, MUTEX_THREAD) ? USYNC_THREAD : USYNC_PROCESS;

	ret = mutex_init(&mutexp->mutex, type, NULL);
	if (ret == 0 && LF_ISSET(MUTEX_SELF_BLOCK)) {
		ret = cond_init(&mutexp->cond, type, NULL);

		F_SET(mutexp, MUTEX_SELF_BLOCK);
	}}
#endif

	mutexp->spins = CDB___os_spin();

	return (ret);
}

/*
 * CDB___db_pthread_mutex_lock
 *	Lock on a mutex, logically blocking if necessary.
 *
 * PUBLIC: int CDB___db_pthread_mutex_lock __P((MUTEX *));
 */
int
CDB___db_pthread_mutex_lock(mutexp)
	MUTEX *mutexp;
{
	u_int32_t nspins;
	int ret, waited;

	if (!DB_GLOBAL(db_mutexlocks) || F_ISSET(mutexp, MUTEX_IGNORE))
		return (0);

	/* Attempt to acquire the resource for N spins. */
	for (nspins = mutexp->spins; nspins > 0; --nspins)
		if (pthread_mutex_trylock(&mutexp->mutex) == 0)
			break;

	if (nspins == 0 && (ret = pthread_mutex_lock(&mutexp->mutex)) != 0)
		return (ret);

	if (F_ISSET(mutexp, MUTEX_SELF_BLOCK)) {
		for (waited = 0; mutexp->locked != 0; waited = 1) {
			ret = pthread_cond_wait(&mutexp->cond, &mutexp->mutex);
			/*
			 * !!!
			 * Solaris bug workaround:
			 * pthread_cond_wait() sometimes returns ETIME -- out
			 * of sheer paranoia, check both ETIME and ETIMEDOUT.
			 * We believe this happens when the application uses
			 * SIGALRM for some purpose, e.g., the C library sleep
			 * call, and Solaris delivers the signal to the wrong
			 * LWP.
			 */
			if (ret != 0 && ret != ETIME && ret != ETIMEDOUT)
				return (ret);
		}

		if (waited)
			++mutexp->mutex_set_wait;
		else
			++mutexp->mutex_set_nowait;

#ifdef DIAGNOSTIC
		mutexp->locked = (u_int32_t)pthread_self();
#else
		mutexp->locked = 1;
#endif
		if ((ret = pthread_mutex_unlock(&mutexp->mutex)) != 0)
			return (ret);
	} else {
		if (nspins == mutexp->spins)
			++mutexp->mutex_set_nowait;
		else
			++mutexp->mutex_set_wait;
#ifdef DIAGNOSTIC
		if (mutexp->locked) {
			char msgbuf[128];
			(void)snprintf(msgbuf,
			    sizeof(msgbuf), MSG1, (u_long)mutexp->locked);
			(void)write(STDERR_FILENO, msgbuf, strlen(msgbuf));
		}
		mutexp->locked = (u_int32_t)pthread_self();
#else
		mutexp->locked = 1;
#endif
	}
	return (0);
}

/*
 * CDB___db_pthread_mutex_unlock --
 *	Release a lock.
 *
 * PUBLIC: int CDB___db_pthread_mutex_unlock __P((MUTEX *));
 */
int
CDB___db_pthread_mutex_unlock(mutexp)
	MUTEX *mutexp;
{
	int ret;

	if (!DB_GLOBAL(db_mutexlocks) || F_ISSET(mutexp, MUTEX_IGNORE))
		return (0);

#ifdef DIAGNOSTIC
	if (!mutexp->locked)
		(void)write(STDERR_FILENO, MSG2, sizeof(MSG2) - 1);
#endif

	if (F_ISSET(mutexp, MUTEX_SELF_BLOCK)) {
		if ((ret = pthread_mutex_lock(&mutexp->mutex)) != 0)
			return (ret);

		mutexp->locked = 0;

		if ((ret = pthread_mutex_unlock(&mutexp->mutex)) != 0)
			return (ret);

		if ((ret = pthread_cond_signal(&mutexp->cond)) != 0)
			return (ret);
	} else {
		mutexp->locked = 0;

		if ((ret = pthread_mutex_unlock(&mutexp->mutex)) != 0)
			return (ret);
	}

	return (0);
}

#endif /* HAVE_MUTEX_PTHREAD */