pthread_rwlock_wrlock.c

/*
 * pthread_rwlock_wrlock.c
 *
 * Description:
 * This translation unit implements read/write lock primitives.
 *
 * --------------------------------------------------------------------------
 *
 *      Pthreads4w - POSIX Threads for Windows
 *      Copyright 1998 John E. Bossom
 *      Copyright 1999-2018, Pthreads4w contributors
 *
 *      Homepage: https://sourceforge.net/projects/pthreads4w/
 *
 *      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:
 *
 *      https://sourceforge.net/p/pthreads4w/wiki/Contributors/
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <limits.h>

#include "pthread.h"
#include "implement.h"

int
pthread_rwlock_wrlock (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_lock (&(rwl->mtxExclusiveAccess))) != 0)
    {
      return result;
    }

  if ((result = pthread_mutex_lock (&(rwl->mtxSharedAccessCompleted))) != 0)
    {
      (void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
      return result;
    }

  if (rwl->nExclusiveAccessCount == 0)
    {
      if (rwl->nCompletedSharedAccessCount > 0)
	{
	  rwl->nSharedAccessCount -= rwl->nCompletedSharedAccessCount;
	  rwl->nCompletedSharedAccessCount = 0;
	}

      if (rwl->nSharedAccessCount > 0)
	{
	  rwl->nCompletedSharedAccessCount = -rwl->nSharedAccessCount;

	  /*
	   * This routine may be a cancellation point
	   * according to POSIX 1003.1j section 18.1.2.
	   */
#if defined (__PTW32_CONFIG_MSVC7)
#pragma inline_depth(0)
#endif
	  pthread_cleanup_push (__ptw32_rwlock_cancelwrwait, (void *) rwl);

	  do
	    {
	      result = pthread_cond_wait (&(rwl->cndSharedAccessCompleted),
					  &(rwl->mtxSharedAccessCompleted));
	    }
	  while (result == 0 && rwl->nCompletedSharedAccessCount < 0);

	  pthread_cleanup_pop ((result != 0) ? 1 : 0);
#if defined (__PTW32_CONFIG_MSVC7)
#pragma inline_depth()
#endif

	  if (result == 0)
	    {
	      rwl->nSharedAccessCount = 0;
	    }
	}
    }

  if (result == 0)
    {
      rwl->nExclusiveAccessCount++;
    }

  return result;
}