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Diffstat (limited to 'pthreads/pthread_cond_signal.c')
| -rw-r--r-- | pthreads/pthread_cond_signal.c | 231 |
1 files changed, 231 insertions, 0 deletions
diff --git a/pthreads/pthread_cond_signal.c b/pthreads/pthread_cond_signal.c new file mode 100644 index 000000000..2b4f6d4d4 --- /dev/null +++ b/pthreads/pthread_cond_signal.c @@ -0,0 +1,231 @@ +/* + * pthread_cond_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) 1999,2005 Pthreads-win32 contributors + * + * Contact Email: rpj@callisto.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: + * See the comments at the top of pthread_cond_wait.c. + */ + +#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) + { + /* Use the non-cancellable version of sem_wait() */ + if (ptw32_semwait (&(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 TRUE unblockAll arg means unblock ALL waiters. + */ + return (ptw32_cond_unblock (cond, PTW32_TRUE)); + +} /* pthread_cond_broadcast */ |