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-/*
- * condvar_wait.c
- *
- * Description:
- * This translation unit implements condition variables and their primitives.
- *
- *
- * --------------------------------------------------------------------------
- *
- * Pthreads-win32 - POSIX Threads Library for Win32
- * Copyright(C) 1998 John E. Bossom
- * Copyright(C) 1999,2002 Pthreads-win32 contributors
- *
- * Contact Email: rpj@ise.canberra.edu.au
- *
- * The current list of contributors is contained
- * in the file CONTRIBUTORS included with the source
- * code distribution. The list can also be seen at the
- * following World Wide Web location:
- * http://sources.redhat.com/pthreads-win32/contributors.html
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; either
- * version 2 of the License, or (at your option) any later version.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library in the file COPYING.LIB;
- * if not, write to the Free Software Foundation, Inc.,
- * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
- *
- * -------------------------------------------------------------
- * Algorithm:
- * The algorithm used in this implementation is that developed by
- * Alexander Terekhov in colaboration with Louis Thomas. The bulk
- * of the discussion is recorded in the file README.CV, which contains
- * several generations of both colaborators original algorithms. The final
- * algorithm used here is the one referred to as
- *
- * Algorithm 8a / IMPL_SEM,UNBLOCK_STRATEGY == UNBLOCK_ALL
- *
- * presented below in pseudo-code as it appeared:
- *
- *
- * given:
- * semBlockLock - bin.semaphore
- * semBlockQueue - semaphore
- * mtxExternal - mutex or CS
- * mtxUnblockLock - mutex or CS
- * nWaitersGone - int
- * nWaitersBlocked - int
- * nWaitersToUnblock - int
- *
- * wait( timeout ) {
- *
- * [auto: register int result ] // error checking omitted
- * [auto: register int nSignalsWasLeft ]
- * [auto: register int nWaitersWasGone ]
- *
- * sem_wait( semBlockLock );
- * nWaitersBlocked++;
- * sem_post( semBlockLock );
- *
- * unlock( mtxExternal );
- * bTimedOut = sem_wait( semBlockQueue,timeout );
- *
- * lock( mtxUnblockLock );
- * if ( 0 != (nSignalsWasLeft = nWaitersToUnblock) ) {
- * if ( bTimeout ) { // timeout (or canceled)
- * if ( 0 != nWaitersBlocked ) {
- * nWaitersBlocked--;
- * }
- * else {
- * nWaitersGone++; // count spurious wakeups.
- * }
- * }
- * if ( 0 == --nWaitersToUnblock ) {
- * if ( 0 != nWaitersBlocked ) {
- * sem_post( semBlockLock ); // open the gate.
- * nSignalsWasLeft = 0; // do not open the gate
- * // below again.
- * }
- * else if ( 0 != (nWaitersWasGone = nWaitersGone) ) {
- * nWaitersGone = 0;
- * }
- * }
- * }
- * else if ( INT_MAX/2 == ++nWaitersGone ) { // timeout/canceled or
- * // spurious semaphore :-)
- * sem_wait( semBlockLock );
- * nWaitersBlocked -= nWaitersGone; // something is going on here
- * // - test of timeouts? :-)
- * sem_post( semBlockLock );
- * nWaitersGone = 0;
- * }
- * unlock( mtxUnblockLock );
- *
- * if ( 1 == nSignalsWasLeft ) {
- * if ( 0 != nWaitersWasGone ) {
- * // sem_adjust( semBlockQueue,-nWaitersWasGone );
- * while ( nWaitersWasGone-- ) {
- * sem_wait( semBlockQueue ); // better now than spurious later
- * }
- * } sem_post( semBlockLock ); // open the gate
- * }
- *
- * lock( mtxExternal );
- *
- * return ( bTimedOut ) ? ETIMEOUT : 0;
- * }
- *
- * signal(bAll) {
- *
- * [auto: register int result ]
- * [auto: register int nSignalsToIssue]
- *
- * lock( mtxUnblockLock );
- *
- * if ( 0 != nWaitersToUnblock ) { // the gate is closed!!!
- * if ( 0 == nWaitersBlocked ) { // NO-OP
- * return unlock( mtxUnblockLock );
- * }
- * if (bAll) {
- * nWaitersToUnblock += nSignalsToIssue=nWaitersBlocked;
- * nWaitersBlocked = 0;
- * }
- * else {
- * nSignalsToIssue = 1;
- * nWaitersToUnblock++;
- * nWaitersBlocked--;
- * }
- * }
- * else if ( nWaitersBlocked > nWaitersGone ) { // HARMLESS RACE CONDITION!
- * sem_wait( semBlockLock ); // close the gate
- * if ( 0 != nWaitersGone ) {
- * nWaitersBlocked -= nWaitersGone;
- * nWaitersGone = 0;
- * }
- * if (bAll) {
- * nSignalsToIssue = nWaitersToUnblock = nWaitersBlocked;
- * nWaitersBlocked = 0;
- * }
- * else {
- * nSignalsToIssue = nWaitersToUnblock = 1;
- * nWaitersBlocked--;
- * }
- * }
- * else { // NO-OP
- * return unlock( mtxUnblockLock );
- * }
- *
- * unlock( mtxUnblockLock );
- * sem_post( semBlockQueue,nSignalsToIssue );
- * return result;
- * }
- * -------------------------------------------------------------
- *
- */
-
-#include "pthread.h"
-#include "implement.h"
-
-
-/*
- * Arguments for cond_wait_cleanup, since we can only pass a
- * single void * to it.
- */
-typedef struct {
- pthread_mutex_t * mutexPtr;
- pthread_cond_t cv;
- int * resultPtr;
- int signaled;
-} ptw32_cond_wait_cleanup_args_t;
-
-static void
-ptw32_cond_wait_cleanup(void * args)
-{
- ptw32_cond_wait_cleanup_args_t * cleanup_args = (ptw32_cond_wait_cleanup_args_t *) args;
- pthread_cond_t cv = cleanup_args->cv;
- int * resultPtr = cleanup_args->resultPtr;
- int nSignalsWasLeft;
- int nWaitersWasGone = 0; /* Initialised to quell warnings. */
- int result;
-
- /*
- * Whether we got here as a result of signal/broadcast or because of
- * timeout on wait or thread cancellation we indicate that we are no
- * longer waiting. The waiter is responsible for adjusting waiters
- * (to)unblock(ed) counts (protected by unblock lock).
- */
- if ((result = pthread_mutex_lock(&(cv->mtxUnblockLock))) != 0)
- {
- *resultPtr = result;
- return;
- }
-
- if ( 0 != (nSignalsWasLeft = cv->nWaitersToUnblock) )
- {
- if ( !cleanup_args->signaled )
- {
- if ( 0 != cv->nWaitersBlocked )
- {
- (cv->nWaitersBlocked)--;
- }
- else
- {
- (cv->nWaitersGone)++;
- }
- }
- if ( 0 == --(cv->nWaitersToUnblock) )
- {
- if ( 0 != cv->nWaitersBlocked )
- {
- if (sem_post( &(cv->semBlockLock) ) != 0)
- {
- *resultPtr = errno;
- /*
- * This is a fatal error for this CV,
- * so we deliberately don't unlock
- * cv->mtxUnblockLock before returning.
- */
- return;
- }
- nSignalsWasLeft = 0;
- }
- else if ( 0 != (nWaitersWasGone = cv->nWaitersGone) )
- {
- cv->nWaitersGone = 0;
- }
- }
- }
- else if ( INT_MAX/2 == ++(cv->nWaitersGone) )
- {
- if (sem_wait( &(cv->semBlockLock) ) != 0)
- {
- *resultPtr = errno;
- /*
- * This is a fatal error for this CV,
- * so we deliberately don't unlock
- * cv->mtxUnblockLock before returning.
- */
- return;
- }
- cv->nWaitersBlocked -= cv->nWaitersGone;
- if (sem_post( &(cv->semBlockLock) ) != 0)
- {
- *resultPtr = errno;
- /*
- * This is a fatal error for this CV,
- * so we deliberately don't unlock
- * cv->mtxUnblockLock before returning.
- */
- return;
- }
- cv->nWaitersGone = 0;
- }
-
- if ((result = pthread_mutex_unlock(&(cv->mtxUnblockLock))) != 0)
- {
- *resultPtr = result;
- return;
- }
-
- if ( 1 == nSignalsWasLeft )
- {
- if ( 0 != nWaitersWasGone )
- {
- // sem_adjust( &(cv->semBlockQueue), -nWaitersWasGone );
- while ( nWaitersWasGone-- )
- {
- if (sem_wait( &(cv->semBlockQueue)) != 0 )
- {
- *resultPtr = errno;
- return;
- }
- }
- }
- if (sem_post(&(cv->semBlockLock)) != 0)
- {
- *resultPtr = errno;
- return;
- }
- }
-
- /*
- * XSH: Upon successful return, the mutex has been locked and is owned
- * by the calling thread
- */
- if ((result = pthread_mutex_lock(cleanup_args->mutexPtr)) != 0)
- {
- *resultPtr = result;
- }
-
-} /* ptw32_cond_wait_cleanup */
-
-static INLINE int
-ptw32_cond_timedwait (pthread_cond_t * cond,
- pthread_mutex_t * mutex,
- const struct timespec *abstime)
-{
- int result = 0;
- pthread_cond_t cv;
- ptw32_cond_wait_cleanup_args_t cleanup_args;
-
- if (cond == NULL || *cond == NULL)
- {
- return EINVAL;
- }
-
- /*
- * We do a quick check to see if we need to do more work
- * to initialise a static condition variable. We check
- * again inside the guarded section of ptw32_cond_check_need_init()
- * to avoid race conditions.
- */
- if (*cond == PTHREAD_COND_INITIALIZER)
- {
- result = ptw32_cond_check_need_init(cond);
- }
-
- if (result != 0 && result != EBUSY)
- {
- return result;
- }
-
- cv = *cond;
-
- if (sem_wait(&(cv->semBlockLock)) != 0)
- {
- return errno;
- }
-
- cv->nWaitersBlocked++;
-
- if (sem_post(&(cv->semBlockLock)) != 0)
- {
- return errno;
- }
-
- /*
- * Setup this waiter cleanup handler
- */
- cleanup_args.mutexPtr = mutex;
- cleanup_args.cv = cv;
- cleanup_args.resultPtr = &result;
- /*
- * If we're canceled, or the cancelable wait fails for any reason,
- * including a timeout, then tell the cleanup routine that we
- * have not been signaled.
- */
- cleanup_args.signaled = 0;
-
-#ifdef _MSC_VER
-#pragma inline_depth(0)
-#endif
- pthread_cleanup_push(ptw32_cond_wait_cleanup, (void *) &cleanup_args);
-
- /*
- * Now we can release 'mutex' and...
- */
- if ((result = pthread_mutex_unlock(mutex)) == 0)
- {
-
- /*
- * ...wait to be awakened by
- * pthread_cond_signal, or
- * pthread_cond_broadcast, or
- * timeout, or
- * thread cancellation
- *
- * Note:
- *
- * sem_timedwait is a cancellation point,
- * hence providing the mechanism for making
- * pthread_cond_wait a cancellation point.
- * We use the cleanup mechanism to ensure we
- * re-lock the mutex and adjust (to)unblock(ed) waiters
- * counts if we are cancelled, timed out or signalled.
- */
- if (sem_timedwait(&(cv->semBlockQueue), abstime) != 0)
- {
- result = errno;
- }
- }
-
- /*
- * Not executed if we're canceled. Signaled is false if we timed out.
- */
- cleanup_args.signaled = (result == 0);
-
- /*
- * Always cleanup
- */
- pthread_cleanup_pop(1);
-#ifdef _MSC_VER
-#pragma inline_depth()
-#endif
-
- /*
- * "result" can be modified by the cleanup handler.
- */
- return result;
-
-} /* ptw32_cond_timedwait */
-
-
-int
-pthread_cond_wait (pthread_cond_t * cond,
- pthread_mutex_t * mutex)
- /*
- * ------------------------------------------------------
- * DOCPUBLIC
- * This function waits on a condition variable until
- * awakened by a signal or broadcast.
- *
- * Caller MUST be holding the mutex lock; the
- * lock is released and the caller is blocked waiting
- * on 'cond'. When 'cond' is signaled, the mutex
- * is re-acquired before returning to the caller.
- *
- * PARAMETERS
- * cond
- * pointer to an instance of pthread_cond_t
- *
- * mutex
- * pointer to an instance of pthread_mutex_t
- *
- *
- * DESCRIPTION
- * This function waits on a condition variable until
- * awakened by a signal or broadcast.
- *
- * NOTES:
- *
- * 1) The function must be called with 'mutex' LOCKED
- * by the calling thread, or undefined behaviour
- * will result.
- *
- * 2) This routine atomically releases 'mutex' and causes
- * the calling thread to block on the condition variable.
- * The blocked thread may be awakened by
- * pthread_cond_signal or
- * pthread_cond_broadcast.
- *
- * Upon successful completion, the 'mutex' has been locked and
- * is owned by the calling thread.
- *
- *
- * RESULTS
- * 0 caught condition; mutex released,
- * EINVAL 'cond' or 'mutex' is invalid,
- * EINVAL different mutexes for concurrent waits,
- * EINVAL mutex is not held by the calling thread,
- *
- * ------------------------------------------------------
- */
-{
- /*
- * The NULL abstime arg means INFINITE waiting.
- */
- return (ptw32_cond_timedwait(cond, mutex, NULL));
-
-} /* pthread_cond_wait */
-
-
-int
-pthread_cond_timedwait (pthread_cond_t * cond,
- pthread_mutex_t * mutex,
- const struct timespec *abstime)
- /*
- * ------------------------------------------------------
- * DOCPUBLIC
- * This function waits on a condition variable either until
- * awakened by a signal or broadcast; or until the time
- * specified by abstime passes.
- *
- * PARAMETERS
- * cond
- * pointer to an instance of pthread_cond_t
- *
- * mutex
- * pointer to an instance of pthread_mutex_t
- *
- * abstime
- * pointer to an instance of (const struct timespec)
- *
- *
- * DESCRIPTION
- * This function waits on a condition variable either until
- * awakened by a signal or broadcast; or until the time
- * specified by abstime passes.
- *
- * NOTES:
- * 1) The function must be called with 'mutex' LOCKED
- * by the calling thread, or undefined behaviour
- * will result.
- *
- * 2) This routine atomically releases 'mutex' and causes
- * the calling thread to block on the condition variable.
- * The blocked thread may be awakened by
- * pthread_cond_signal or
- * pthread_cond_broadcast.
- *
- *
- * RESULTS
- * 0 caught condition; mutex released,
- * EINVAL 'cond', 'mutex', or abstime is invalid,
- * EINVAL different mutexes for concurrent waits,
- * EINVAL mutex is not held by the calling thread,
- * ETIMEDOUT abstime ellapsed before cond was signaled.
- *
- * ------------------------------------------------------
- */
-{
- if (abstime == NULL)
- {
- return EINVAL;
- }
-
- return (ptw32_cond_timedwait(cond, mutex, abstime));
-
-} /* pthread_cond_timedwait */
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