mirror of https://github.com/PCSX2/pcsx2.git
111 lines
3.5 KiB
C
111 lines
3.5 KiB
C
/*
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* pthread_rwlock_tryrdlock.c
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*
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* Description:
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* This translation unit implements read/write lock primitives.
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*
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* --------------------------------------------------------------------------
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*
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* Pthreads-win32 - POSIX Threads Library for Win32
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* Copyright(C) 1998 John E. Bossom
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* Copyright(C) 1999,2005 Pthreads-win32 contributors
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*
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* Contact Email: rpj@callisto.canberra.edu.au
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*
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* The current list of contributors is contained
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* in the file CONTRIBUTORS included with the source
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* code distribution. The list can also be seen at the
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* following World Wide Web location:
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* http://sources.redhat.com/pthreads-win32/contributors.html
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library in the file COPYING.LIB;
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* if not, write to the Free Software Foundation, Inc.,
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* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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#include "ptw32pch.h"
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// FIXME : This function can return EBUSY when the rwlock is available for reading.
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// How? Because it uses a single "mtxExclusiveAccess" lock to wrangle control of the
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// RwLock's internals -- so if two read locks are attempted in parallel, this function
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// will falsely report the lock as being busy even though both locks should be allowed
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// access to the object.
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//
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// (note: double check this against OpenGroup behavior definitions -- though even if
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// OpenGroup 'allows' this behavior, we should probably strive to avoid it unless
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// it's explicitly "expected", since programs would typically have much more desirable
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// behavior if simultaneous read locks do not EBUSY.)
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int
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pthread_rwlock_tryrdlock (pthread_rwlock_t * rwlock)
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{
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int result;
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pthread_rwlock_t rwl;
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if (rwlock == NULL || *rwlock == NULL)
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{
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return EINVAL;
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}
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/*
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* We do a quick check to see if we need to do more work
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* to initialise a static rwlock. We check
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* again inside the guarded section of ptw32_rwlock_check_need_init()
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* to avoid race conditions.
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*/
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if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
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{
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result = ptw32_rwlock_check_need_init (rwlock);
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if (result != 0 && result != EBUSY)
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{
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return result;
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}
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}
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rwl = *rwlock;
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if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
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{
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return EINVAL;
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}
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if ((result = pthread_mutex_trylock (&(rwl->mtxExclusiveAccess))) != 0)
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{
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return result;
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}
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if (++rwl->nSharedAccessCount == INT_MAX)
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{
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if ((result =
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pthread_mutex_lock (&(rwl->mtxSharedAccessCompleted))) != 0)
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{
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(void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
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return result;
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}
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rwl->nSharedAccessCount -= rwl->nCompletedSharedAccessCount;
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rwl->nCompletedSharedAccessCount = 0;
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if ((result =
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pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted))) != 0)
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{
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(void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
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return result;
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}
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}
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return (pthread_mutex_unlock (&rwl->mtxExclusiveAccess));
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}
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