From: Paolo Bonzini <bonzini@gnu.org>
To: git@vger.kernel.org
Subject: Re: [PATCH] MSVC: port pthread code to native Windows threads
Date: Wed, 04 Nov 2009 12:23:15 +0100 [thread overview]
Message-ID: <hcro74$fgb$1@ger.gmane.org> (raw)
In-Reply-To: <1257331059-26344-1-git-send-email-ahaczewski@gmail.com>
The condition variable implementation seems more complicated than
necessary. The mutex can be used to protect access to cond->waiters, so
waiters_lock is not necessary. On the other hand, it seems to me that
pthread_cond_signal should be the one that decrements the waiters count.
Otherwise, a loop like
while (pthread_cond_signal (cond, mutex));
will fill the semaphore with signals and the waiters will get lots of
spurious accesses.
static __inline int pthread_cond_wait(pthread_cond_t *cond,
CRITICAL_SECTION *mutex)
{
int ret = 0;
/* the mutex protects access to waiters count */
++cond->waiters;
/*
* Unlock external mutex and wait for signal.
* NOTE: cond->waiters > 0 now. If pthread_cond_signal
* is called after leaving mutex unlocked before we wait on
* semaphore, it will add a signal to the semaphore,
* and we'll happily go on with the wait. This would not
* happen with an event, for example.
*/
LeaveCriticalSection(mutex);
if (0 != WaitForSingleObject(cond->sema, INFINITE))
ret = -1;
EnterCriticalSection(mutex);
return ret;
}
static __inline int pthread_cond_signal(pthread_cond_t *cond)
{
/* the mutex protects access to waiters count */
if (cond->waiters > 0) {
--cond->waiters;
return ReleaseSemaphore(cond->sema, 1, NULL) ? 0 : -1;
} else
return 0;
}
Paolo
next prev parent reply other threads:[~2009-11-04 11:23 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-03 21:30 [PATCH 0/1] Port of pthreads to Windows API threads Andrzej K. Haczewski
2009-11-03 21:30 ` [PATCH 1/1] MSVC: port pthread code to native Windows threads Andrzej K. Haczewski
2009-11-03 23:38 ` Johannes Schindelin
2009-11-04 2:34 ` Joshua Jensen
2009-11-04 7:44 ` Andrzej K. Haczewski
2009-11-04 8:24 ` Johannes Sixt
2009-11-04 11:02 ` Johannes Schindelin
2009-11-04 8:17 ` Andrzej K. Haczewski
2009-11-04 8:15 ` Johannes Sixt
2009-11-04 8:48 ` Michael Wookey
2009-11-04 10:53 ` Andrzej K. Haczewski
2009-11-04 10:37 ` [PATCH] " Andrzej K. Haczewski
2009-11-04 10:50 ` Erik Faye-Lund
2009-11-04 10:56 ` Andrzej K. Haczewski
2009-11-04 11:14 ` Paolo Bonzini
2009-11-04 11:23 ` Paolo Bonzini [this message]
2009-11-04 12:39 ` Johannes Sixt
2009-11-04 13:47 ` Andrzej K. Haczewski
2009-11-04 14:34 ` Johannes Sixt
2009-11-04 14:50 ` Andrzej K. Haczewski
2009-11-04 20:43 ` Daniel Barkalow
2009-11-04 21:17 ` Nicolas Pitre
2009-11-04 22:22 ` Daniel Barkalow
2009-11-05 0:27 ` Nicolas Pitre
2009-11-05 13:48 ` Dmitry Potapov
2009-11-04 14:14 ` Andrzej K. Haczewski
2009-11-04 14:19 ` Erik Faye-Lund
2009-11-04 14:04 ` Johannes Schindelin
2009-11-04 15:55 ` [PATCH] MSVC: Windows-native implementation for subset of Pthreads API Andrzej K. Haczewski
2009-11-04 18:10 ` Nicolas Pitre
2009-11-04 21:16 ` Andrzej K. Haczewski
2009-11-04 21:32 ` [PATCH] pack-objects: move thread autodetection closer to relevant code Nicolas Pitre
2009-11-06 7:20 ` Junio C Hamano
2009-11-04 21:41 ` [PATCH] MSVC: Windows-native implementation for subset of Pthreads API Erik Faye-Lund
2009-11-04 22:50 ` Andrzej K. Haczewski
2009-11-05 2:47 ` Nicolas Pitre
2009-11-05 9:00 ` Andrzej K. Haczewski
2009-11-05 9:41 ` Erik Faye-Lund
2009-11-05 10:18 ` Andrzej K. Haczewski
2009-11-05 12:27 ` Johannes Sixt
2009-11-05 12:53 ` Andrzej K. Haczewski
2009-11-05 19:25 ` Nicolas Pitre
2009-11-05 20:38 ` Andrzej K. Haczewski
2009-11-05 22:15 ` Nicolas Pitre
2009-11-04 21:52 ` Nicolas Pitre
2009-11-04 23:47 ` Andrzej K. Haczewski
2009-11-04 23:57 ` Andrzej K. Haczewski
2009-11-05 0:22 ` Nicolas Pitre
2009-11-05 8:51 ` Andrzej K. Haczewski
2009-11-05 19:22 ` Nicolas Pitre
2009-11-05 2:10 ` Nicolas Pitre
2009-11-05 8:45 ` Andrzej K. Haczewski
2009-11-05 19:17 ` Nicolas Pitre
2009-11-05 7:33 ` Johannes Sixt
2009-11-04 23:58 ` Junio C Hamano
2009-11-05 16:45 ` Andrzej K. Haczewski
2009-11-05 17:31 ` Johannes Sixt
2009-11-05 19:39 ` Nicolas Pitre
2009-11-05 20:09 ` Andrzej K. Haczewski
2009-11-05 20:36 ` Nicolas Pitre
2009-11-06 8:10 ` Andrzej K. Haczewski
2009-11-06 8:25 ` Johannes Sixt
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