semaphore.c

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/*
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%        SS     E      MM MM  A   A  P   P  H   H  O   O  R   R  E            %
%         SSS   EEE    M M M  AAAAA  PPPP   HHHHH  O   O  RRRR   EEE          %
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%                        MagickCore Semaphore Methods                         %
%                                                                             %
%                              Software Design                                %
%                             William Radcliffe                               %
%                                John Cristy                                  %
%                                 June 2000                                   %
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%  Copyright 1999-2009 ImageMagick Studio LLC, a non-profit organization      %
%  dedicated to making software imaging solutions freely available.           %
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%  You may not use this file except in compliance with the License.  You may  %
%  obtain a copy of the License at                                            %
%                                                                             %
%    http://www.imagemagick.org/script/license.php                            %
%                                                                             %
%  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.                                             %
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*/

/*
  Include declarations.
*/
#include "magick/studio.h"
#include "magick/exception.h"
#include "magick/exception-private.h"
#include "magick/memory_.h"
#include "magick/semaphore.h"
#include "magick/string_.h"
#include "magick/thread_.h"
#include "magick/thread-private.h"

/*
  Struct declaractions.
*/
struct SemaphoreInfo
{
  MagickMutexType
    mutex;

  MagickThreadType
    id;

  long
    reference_count;

  unsigned long
    signature;
};

/*
  Static declaractions.
*/
#if defined(MAGICKCORE_HAVE_PTHREAD)
static pthread_mutex_t
  semaphore_mutex = PTHREAD_MUTEX_INITIALIZER;
#elif defined(MAGICKCORE_HAVE_WINTHREADS)
static LONG
  semaphore_mutex = 0;
#else
static long
  semaphore_mutex = 0;
#endif

/*
  Forward declaractions.
*/
static void
  LockMagickMutex(void),
  UnlockMagickMutex(void);

/*
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%  AcquireSemaphoreInfo() acquires a semaphore.
%
%  The format of the AcquireSemaphoreInfo method is:
%
%      void AcquireSemaphoreInfo(SemaphoreInfo **semaphore_info)
%
%  A description of each parameter follows:
%
%    o semaphore_info: Specifies a pointer to an SemaphoreInfo structure.
%
*/
MagickExport void AcquireSemaphoreInfo(SemaphoreInfo **semaphore_info)
{
  assert(semaphore_info != (SemaphoreInfo **) NULL);
  if (*semaphore_info == (SemaphoreInfo *) NULL)
    {
      LockMagickMutex();
      if (*semaphore_info == (SemaphoreInfo *) NULL)
        *semaphore_info=AllocateSemaphoreInfo();
      UnlockMagickMutex();
    }
}

/*
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%  AllocateSemaphoreInfo() initializes the SemaphoreInfo structure.
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%  The format of the AllocateSemaphoreInfo method is:
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%      SemaphoreInfo *AllocateSemaphoreInfo(void)
%
*/
MagickExport SemaphoreInfo *AllocateSemaphoreInfo(void)
{
  SemaphoreInfo
    *semaphore_info;

  /*
    Allocate semaphore.
  */
  semaphore_info=(SemaphoreInfo *) AcquireAlignedMemory(1,
    sizeof(SemaphoreInfo));
  if (semaphore_info == (SemaphoreInfo *) NULL)
    ThrowFatalException(ResourceLimitFatalError,"MemoryAllocationFailed");
  (void) ResetMagickMemory(semaphore_info,0,sizeof(SemaphoreInfo));
  /*
    Initialize the semaphore.
  */
#if defined(MAGICKCORE_HAVE_PTHREAD)
  {
    int
      status;

    pthread_mutexattr_t
      mutex_info;

    status=pthread_mutexattr_init(&mutex_info);
    if (status != 0)
      {
        semaphore_info=(SemaphoreInfo *) RelinquishAlignedMemory(
          semaphore_info);
        ThrowFatalException(ResourceLimitFatalError,
          "UnableToInitializeSemaphore");
      }
    status=pthread_mutex_init(&semaphore_info->mutex,&mutex_info);
    (void) pthread_mutexattr_destroy(&mutex_info);
    if (status != 0)
      {
        semaphore_info=(SemaphoreInfo *) RelinquishAlignedMemory(
          semaphore_info);
        ThrowFatalException(ResourceLimitFatalError,
          "UnableToInitializeSemaphore");
      }
  }
#elif defined(MAGICKCORE_HAVE_WINTHREADS)
  InitializeCriticalSection(&semaphore_info->mutex);
#endif
  semaphore_info->id=GetMagickThreadId();
  semaphore_info->reference_count=0;
  semaphore_info->signature=MagickSignature;
  return(semaphore_info);
}

/*
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%  DestroySemaphoreInfo() destroys a semaphore.
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%  The format of the DestroySemaphoreInfo method is:
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%      void DestroySemaphoreInfo(SemaphoreInfo **semaphore_info)
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%  A description of each parameter follows:
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%    o semaphore_info: Specifies a pointer to an SemaphoreInfo structure.
%
*/
MagickExport void DestroySemaphoreInfo(SemaphoreInfo **semaphore_info)
{
  assert(semaphore_info != (SemaphoreInfo **) NULL);
  assert((*semaphore_info) != (SemaphoreInfo *) NULL);
  assert((*semaphore_info)->signature == MagickSignature);
  LockMagickMutex();
#if defined(MAGICKCORE_HAVE_PTHREAD)
  (void) pthread_mutex_destroy(&(*semaphore_info)->mutex);
#elif defined(MAGICKCORE_HAVE_WINTHREADS)
  DeleteCriticalSection(&(*semaphore_info)->mutex);
#endif
  (*semaphore_info)->signature=(~MagickSignature);
  *semaphore_info=(SemaphoreInfo *) RelinquishAlignedMemory(*semaphore_info);
  UnlockMagickMutex();
}

/*
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%  LockMagickMutex() locks a global mutex.  If it is already locked, the
%  calling thread blocks until the mutex becomes available.
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%  The format of the LockMagickMutex method is:
%
%      void LockMagickMutex(void)
%
*/
static void LockMagickMutex(void)
{
#if defined(MAGICKCORE_HAVE_PTHREAD)
  if (pthread_mutex_lock(&semaphore_mutex) != 0)
    (void) fprintf(stderr,"pthread_mutex_lock failed %s\n",
      GetExceptionMessage(errno));
#elif defined(MAGICKCORE_HAVE_WINTHREADS)
  while (InterlockedCompareExchange(&semaphore_mutex,1L,0L) != 0)
    Sleep(10);
#endif
}

/*
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%  LockSemaphoreInfo() locks a semaphore.
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%  The format of the LockSemaphoreInfo method is:
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%      MagickBooleanType LockSemaphoreInfo(SemaphoreInfo *semaphore_info)
%
%  A description of each parameter follows:
%
%    o semaphore_info: Specifies a pointer to an SemaphoreInfo structure.
%
*/
MagickExport MagickBooleanType LockSemaphoreInfo(SemaphoreInfo *semaphore_info)
{
  assert(semaphore_info != (SemaphoreInfo *) NULL);
#if defined(MAGICKCORE_HAVE_PTHREAD)
  {
    int
      status;

    status=pthread_mutex_lock(&semaphore_info->mutex);
    if (status != 0)
      return(MagickFalse);
#if defined(MAGICKCORE_DEBUG)
    {
      if ((semaphore_info->reference_count > 0) &&
          (IsMagickThreadEqual(semaphore_info->id) != MagickFalse))
        {
          (void) fprintf(stderr,"Warning: unexpected recursive lock!\n");
          (void) fflush(stderr);
        }
    }
#endif
  }
#elif defined(MAGICKCORE_HAVE_WINTHREADS)
  {
    EnterCriticalSection(&semaphore_info->mutex);
#if defined(MAGICKCORE_DEBUG)
    {
      if ((semaphore_info->reference_count > 0) &&
          (IsMagickThreadEqual(semaphore_info->id) != MagickFalse))
        {
          (void) fprintf(stderr,"Warning: unexpected recursive lock!\n");
          (void) fflush(stderr);
        }
    }
#endif
  }
#endif
  semaphore_info->id=GetMagickThreadId();
  semaphore_info->reference_count++;
  return(MagickTrue);
}

/*
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%  RelinquishSemaphoreInfo() relinquishes a semaphore.
%
%  The format of the RelinquishSemaphoreInfo method is:
%
%      RelinquishSemaphoreInfo(SemaphoreInfo *semaphore_info)
%
%  A description of each parameter follows:
%
%    o semaphore_info: Specifies a pointer to an SemaphoreInfo structure.
%
*/
MagickExport void RelinquishSemaphoreInfo(SemaphoreInfo *semaphore_info)
{
  assert(semaphore_info != (SemaphoreInfo *) NULL);
  assert(semaphore_info->signature == MagickSignature);
  (void) UnlockSemaphoreInfo(semaphore_info);
}

/*
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%   S e m a p h o r e C o m p o n e n t G e n e s i s                         %
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%  SemaphoreComponentGenesis() instantiates the semaphore environment.
%
%  The format of the SemaphoreComponentGenesis method is:
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%      MagickBooleanType SemaphoreComponentGenesis(void)
%
*/
MagickExport MagickBooleanType SemaphoreComponentGenesis(void)
{
  LockMagickMutex();
  UnlockMagickMutex();
  return(MagickTrue);
}

/*
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%  SemaphoreComponentTerminus() destroys the semaphore component.
%
%  The format of the SemaphoreComponentTerminus method is:
%
%      SemaphoreComponentTerminus(void)
%
*/
MagickExport void SemaphoreComponentTerminus(void)
{
}

/*
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%  UnlockMagickMutex() releases a global mutex.
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%  The format of the LockMagickMutex method is:
%
%      void UnlockMagickMutex(void)
%
*/
static void UnlockMagickMutex(void)
{
#if defined(MAGICKCORE_HAVE_PTHREAD)
  if (pthread_mutex_unlock(&semaphore_mutex) != 0)
    (void) fprintf(stderr,"pthread_mutex_unlock failed %s\n",
      GetExceptionMessage(errno));
#elif defined(MAGICKCORE_HAVE_WINTHREADS)
  InterlockedExchange(&semaphore_mutex,0L);
#endif
}

/*
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%  UnlockSemaphoreInfo() unlocks a semaphore.
%
%  The format of the UnlockSemaphoreInfo method is:
%
%      MagickBooleanType UnlockSemaphoreInfo(SemaphoreInfo *semaphore_info)
%
%  A description of each parameter follows:
%
%    o semaphore_info: Specifies a pointer to an SemaphoreInfo structure.
%
*/
MagickExport MagickBooleanType UnlockSemaphoreInfo(
  SemaphoreInfo *semaphore_info)
{
  assert(semaphore_info != (SemaphoreInfo *) NULL);
#if defined(MAGICKCORE_DEBUG)
  assert(IsMagickThreadEqual(semaphore_info->id) != MagickFalse);
  if (semaphore_info->reference_count == 0)
    {
      (void) fprintf(stderr,"Warning: semaphore lock already unlocked!\n");
      (void) fflush(stderr);
      return(MagickFalse);
    }
  semaphore_info->reference_count--;
#endif
#if defined(MAGICKCORE_HAVE_PTHREAD)
  {
    int
      status;

    status=pthread_mutex_unlock(&semaphore_info->mutex);
    if (status != 0)
      {
        semaphore_info->reference_count++;
        return(MagickFalse);
      }
  }
#elif defined(MAGICKCORE_HAVE_WINTHREADS)
  LeaveCriticalSection(&semaphore_info->mutex);
#endif
  return(MagickTrue);
}