pcsx2/3rdparty/w32pthreads/pthread_rwlock_tryrdlock.c

111 lines
3.5 KiB
C

/*
* pthread_rwlock_tryrdlock.c
*
* Description:
* This translation unit implements read/write lock 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
*/
#include "ptw32pch.h"
// FIXME : This function can return EBUSY when the rwlock is available for reading.
// How? Because it uses a single "mtxExclusiveAccess" lock to wrangle control of the
// RwLock's internals -- so if two read locks are attempted in parallel, this function
// will falsely report the lock as being busy even though both locks should be allowed
// access to the object.
//
// (note: double check this against OpenGroup behavior definitions -- though even if
// OpenGroup 'allows' this behavior, we should probably strive to avoid it unless
// it's explicitly "expected", since programs would typically have much more desirable
// behavior if simultaneous read locks do not EBUSY.)
int
pthread_rwlock_tryrdlock (pthread_rwlock_t * rwlock)
{
int result;
pthread_rwlock_t rwl;
if (rwlock == NULL || *rwlock == NULL)
{
return EINVAL;
}
/*
* We do a quick check to see if we need to do more work
* to initialise a static rwlock. We check
* again inside the guarded section of ptw32_rwlock_check_need_init()
* to avoid race conditions.
*/
if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
{
result = ptw32_rwlock_check_need_init (rwlock);
if (result != 0 && result != EBUSY)
{
return result;
}
}
rwl = *rwlock;
if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
{
return EINVAL;
}
if ((result = pthread_mutex_trylock (&(rwl->mtxExclusiveAccess))) != 0)
{
return result;
}
if (++rwl->nSharedAccessCount == INT_MAX)
{
if ((result =
pthread_mutex_lock (&(rwl->mtxSharedAccessCompleted))) != 0)
{
(void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
return result;
}
rwl->nSharedAccessCount -= rwl->nCompletedSharedAccessCount;
rwl->nCompletedSharedAccessCount = 0;
if ((result =
pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted))) != 0)
{
(void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
return result;
}
}
return (pthread_mutex_unlock (&rwl->mtxExclusiveAccess));
}