From e6f1797e9e9925ae7f9dda54806ef8f52ae3ed07 Mon Sep 17 00:00:00 2001 From: rpj Date: Mon, 11 Feb 2002 01:53:22 +0000 Subject: Splitting files. See ChangeLog file for details. --- condvar_signal.c | 355 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 355 insertions(+) create mode 100644 condvar_signal.c (limited to 'condvar_signal.c') diff --git a/condvar_signal.c b/condvar_signal.c new file mode 100644 index 0000000..604ef4d --- /dev/null +++ b/condvar_signal.c @@ -0,0 +1,355 @@ +/* + * 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 */ -- cgit v1.2.3