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-/*
- * condvar_signal.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"
-
-
-static INLINE int
-ptw32_cond_unblock (pthread_cond_t * cond,
- int unblockAll)
- /*
- * Notes.
- *
- * Does not use the external mutex for synchronisation,
- * therefore semBlockLock is needed.
- * mtxUnblockLock is for LEVEL-2 synch. LEVEL-2 is the
- * state where the external mutex is not necessarily locked by
- * any thread, ie. between cond_wait unlocking and re-acquiring
- * the lock after having been signaled or a timeout or
- * cancellation.
- *
- * Uses the following CV elements:
- * nWaitersBlocked
- * nWaitersToUnblock
- * nWaitersGone
- * mtxUnblockLock
- * semBlockLock
- * semBlockQueue
- */
-{
- int result;
- pthread_cond_t cv;
- int nSignalsToIssue;
-
- if (cond == NULL || *cond == NULL)
- {
- return EINVAL;
- }
-
- cv = *cond;
-
- /*
- * No-op if the CV is static and hasn't been initialised yet.
- * Assuming that any race condition is harmless.
- */
- if (cv == PTHREAD_COND_INITIALIZER)
- {
- return 0;
- }
-
- if ((result = pthread_mutex_lock(&(cv->mtxUnblockLock))) != 0)
- {
- return result;
- }
-
- if ( 0 != cv->nWaitersToUnblock )
- {
- if ( 0 == cv->nWaitersBlocked )
- {
- return pthread_mutex_unlock( &(cv->mtxUnblockLock) );
- }
- if (unblockAll)
- {
- cv->nWaitersToUnblock += (nSignalsToIssue = cv->nWaitersBlocked);
- cv->nWaitersBlocked = 0;
- }
- else
- {
- nSignalsToIssue = 1;
- cv->nWaitersToUnblock++;
- cv->nWaitersBlocked--;
- }
- }
- else if ( cv->nWaitersBlocked > cv->nWaitersGone )
- {
- if (sem_wait( &(cv->semBlockLock) ) != 0)
- {
- result = errno;
- (void) pthread_mutex_unlock( &(cv->mtxUnblockLock) );
- return result;
- }
- if ( 0 != cv->nWaitersGone )
- {
- cv->nWaitersBlocked -= cv->nWaitersGone;
- cv->nWaitersGone = 0;
- }
- if (unblockAll)
- {
- nSignalsToIssue = cv->nWaitersToUnblock = cv->nWaitersBlocked;
- cv->nWaitersBlocked = 0;
- }
- else
- {
- nSignalsToIssue = cv->nWaitersToUnblock = 1;
- cv->nWaitersBlocked--;
- }
- }
- else
- {
- return pthread_mutex_unlock( &(cv->mtxUnblockLock) );
- }
-
- if ((result = pthread_mutex_unlock( &(cv->mtxUnblockLock) )) == 0)
- {
- if (sem_post_multiple( &(cv->semBlockQueue), nSignalsToIssue ) != 0)
- {
- result = errno;
- }
- }
-
- return result;
-
-} /* ptw32_cond_unblock */
-
-int
-pthread_cond_signal (pthread_cond_t * cond)
- /*
- * ------------------------------------------------------
- * DOCPUBLIC
- * This function signals a condition variable, waking
- * one waiting thread.
- * If SCHED_FIFO or SCHED_RR policy threads are waiting
- * the highest priority waiter is awakened; otherwise,
- * an unspecified waiter is awakened.
- *
- * PARAMETERS
- * cond
- * pointer to an instance of pthread_cond_t
- *
- *
- * DESCRIPTION
- * This function signals a condition variable, waking
- * one waiting thread.
- * If SCHED_FIFO or SCHED_RR policy threads are waiting
- * the highest priority waiter is awakened; otherwise,
- * an unspecified waiter is awakened.
- *
- * NOTES:
- *
- * 1) Use when any waiter can respond and only one need
- * respond (all waiters being equal).
- *
- * RESULTS
- * 0 successfully signaled condition,
- * EINVAL 'cond' is invalid,
- *
- * ------------------------------------------------------
- */
-{
- /*
- * The '0'(FALSE) unblockAll arg means unblock ONE waiter.
- */
- return (ptw32_cond_unblock(cond, 0));
-
-} /* pthread_cond_signal */
-
-int
-pthread_cond_broadcast (pthread_cond_t * cond)
- /*
- * ------------------------------------------------------
- * DOCPUBLIC
- * This function broadcasts the condition variable,
- * waking all current waiters.
- *
- * PARAMETERS
- * cond
- * pointer to an instance of pthread_cond_t
- *
- *
- * DESCRIPTION
- * This function signals a condition variable, waking
- * all waiting threads.
- *
- * NOTES:
- *
- * 1) Use when more than one waiter may respond to
- * predicate change or if any waiting thread may
- * not be able to respond
- *
- * RESULTS
- * 0 successfully signalled condition to all
- * waiting threads,
- * EINVAL 'cond' is invalid
- * ENOSPC a required resource has been exhausted,
- *
- * ------------------------------------------------------
- */
-{
- /*
- * The '1'(TRUE) unblockAll arg means unblock ALL waiters.
- */
- return (ptw32_cond_unblock(cond, 1));
-
-} /* pthread_cond_broadcast */
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