/*
* pthread_cond_signal.c
*
* Description:
* This translation unit implements condition variables and their primitives.
*
*
* --------------------------------------------------------------------------
*
* Pthreads-embedded (PTE) - POSIX Threads Library for embedded systems
* Copyright(C) 2008 Jason Schmidlapp
*
* Contact Email: jschmidlapp@users.sourceforge.net
*
*
* Based upon 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 original list of contributors to the Pthreads-win32 project
* is contained in the file CONTRIBUTORS.ptw32 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 int
pte_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 (sem_wait_nocancel (&(cv->semBlockLock)) != 0)
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;
} /* pte_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 (pte_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 (pte_cond_unblock (cond, PTE_TRUE));
} /* pthread_cond_broadcast */