/*
* mutex.c
*
* Description:
* This translation unit implements mutual exclusion (mutex) primitives.
*
* Pthreads-win32 - POSIX Threads Library for Win32
* Copyright (C) 1998
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library 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
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the Free
* Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA
*/
/* errno.h or a replacement file is included by pthread.h */
//#include <errno.h>
#include "pthread.h"
#include "implement.h"
static int
ptw32_mutex_check_need_init(pthread_mutex_t *mutex)
{
int result = 0;
/*
* The following guarded test is specifically for statically
* initialised mutexes (via PTHREAD_MUTEX_INITIALIZER).
*
* Note that by not providing this synchronisation we risk
* introducing race conditions into applications which are
* correctly written.
*
* Approach
* --------
* We know that static mutexes will not be PROCESS_SHARED
* so we can serialise access to internal state using
* Win32 Critical Sections rather than Win32 Mutexes.
*
* If using a single global lock slows applications down too much,
* multiple global locks could be created and hashed on some random
* value associated with each mutex, the pointer perhaps. At a guess,
* a good value for the optimal number of global locks might be
* the number of processors + 1.
*
*/
EnterCriticalSection(&ptw32_mutex_test_init_lock);
/*
* We got here possibly under race
* conditions. Check again inside the critical section
* and only initialise if the mutex is valid (not been destroyed).
* If a static mutex has been destroyed, the application can
* re-initialise it only by calling pthread_mutex_init()
* explicitly.
*/
if (*mutex == (pthread_mutex_t) PTW32_OBJECT_AUTO_INIT)
{
result = pthread_mutex_init(mutex, NULL);
}
else if (*mutex == NULL)
{
/*
* The mutex has been destroyed while we were waiting to
* initialise it, so the operation that caused the
* auto-initialisation should fail.
*/
result = EINVAL;
}
LeaveCriticalSection(&ptw32_mutex_test_init_lock);
return(result);
}
/*
* The following internal versions of *CriticalSection()
* include an implementation of TryEnterCriticalSection
* for platforms on which that function has not been
* provided by Microsoft (eg. W95/98). This allows us
* to use critical sections exclusively as the basis
* of our implementation of POSIX mutex locks.
*
* Where TryEnterCriticalSection() is provided by the
* platform, these routines act as wrappers with
* minimal additional overhead. Otherwise, these
* routines manage additional state in order to
* properly emulate TryEnterCriticalSection().
*
* In any case, using of critical sections exclusively
* should still be much faster than using Win32 mutex
* locks as our POSIX mutex locks.
*/
static void
ptw32_InitializeCriticalSection (ptw32_cs_t * csect)
/*
* ------------------------------------------------------
*
* PARAMETERS
* csect
* pointer to an instance of ptw32_cs_t
*
* DESCRIPTION
* Internal implementation of InitializeCriticalSection.
*
* ------------------------------------------------------
*/
{
ptw32_cs_t cs = *csect;
cs->owner = NULL;
cs->lock_idx = -1;
cs->entered_count = 0;
InitializeCriticalSection(&cs->cs);
cs->valid = 1;
}
static void
ptw32_DeleteCriticalSection (ptw32_cs_t * csect)
/*
* ------------------------------------------------------
*
* PARAMETERS
* csect
* pointer to an instance of ptw32_cs_t
*
* DESCRIPTION
* Internal implementation of DeleteCriticalSection.
*
* ------------------------------------------------------
*/
{
ptw32_cs_t cs = *csect;
cs->valid = 0;
DeleteCriticalSection(&cs->cs);
}
static void
ptw32_EnterCriticalSection(ptw32_cs_t * csect)
/*
* ------------------------------------------------------
*
* PARAMETERS
* csect
* pointer to an instance of ptw32_cs_t
*
* DESCRIPTION
* Internal implementation of EnterCriticalSection.
*
* ------------------------------------------------------
*/
{
ptw32_cs_t cs = *csect;
if (!cs->valid)
{
return;
}
if (NULL != ptw32_try_enter_critical_section)
{
EnterCriticalSection(&cs->cs);
}
else
{
while (InterlockedIncrement(&cs->lock_idx) > 0)
{
InterlockedDecrement(&cs->lock_idx);
Sleep(0);
}
EnterCriticalSection(&cs->cs);
cs->entered_count++;
cs->owner = pthread_self();
InterlockedDecrement(&cs->lock_idx);
}
}
static void
ptw32_LeaveCriticalSection (ptw32_cs_t * csect)
/*
* ------------------------------------------------------
*
* PARAMETERS
* csect
* pointer to an instance of ptw32_cs_t
*
* DESCRIPTION
* Internal implementation of LeaveCriticalSection.
*
* ------------------------------------------------------
*/
{
ptw32_cs_t cs = *csect;
if (!cs->valid)
{
return;
}
if (NULL != ptw32_try_enter_critical_section)
{
LeaveCriticalSection(&cs->cs);
}
else
{
while (InterlockedIncrement(&cs->lock_idx) > 0)
{
InterlockedDecrement(&cs->lock_idx);
Sleep(0);
}
LeaveCriticalSection(&cs->cs);
cs->entered_count--;
if (cs->entered_count == 0)
{
cs->owner = NULL;
}
InterlockedDecrement(&cs->lock_idx);
}
}
static BOOL
ptw32_TryEnterCriticalSection (ptw32_cs_t * csect)
/*
* ------------------------------------------------------
*
* PARAMETERS
* csect
* pointer to an instance of ptw32_cs_t
*
* DESCRIPTION
* Internal implementation of TryEnterCriticalSection.
*
* RETURNS
* FALSE Current thread doesn't own the
* lock,
* TRUE Current thread owns the lock
* (if the current thread already
* held the lock then we recursively
* enter).
* ------------------------------------------------------
*/
{
ptw32_cs_t cs = *csect;
BOOL result = FALSE;
if (!cs->valid)
{
return (FALSE);
}
if (NULL != ptw32_try_enter_critical_section)
{
result = (*ptw32_try_enter_critical_section)(&cs->cs);
}
else
{
pthread_t self = pthread_self();
while (InterlockedIncrement(&cs->lock_idx) > 0)
{
InterlockedDecrement(&cs->lock_idx);
Sleep(0);
}
if (cs->owner == NULL || pthread_equal(cs->owner, self))
{
/* The semantics of TryEnterCriticalSection
* (according to the documentation at MS)
* are that the CS is entered recursively
* if the thread is the current owner.
*/
EnterCriticalSection(&cs->cs);
cs->entered_count++;
cs->owner = self;
result = TRUE;
}
InterlockedDecrement(&cs->lock_idx);
}
return (result);
}
int
pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *attr)
{
int result = 0;
pthread_mutex_t mx;
if (mutex == NULL)
{
return EINVAL;
}
mx = (pthread_mutex_t) calloc(1, sizeof(*mx));
if (mx == NULL)
{
result = ENOMEM;
goto FAIL0;
}
ptw32_InitializeCriticalSection(&mx->cs);
mx->lockCount = 0;
mx->ownerThread = NULL;
if (attr != NULL && *attr != NULL)
{
mx->type = (*attr)->type;
if ((*attr)->pshared == PTHREAD_PROCESS_SHARED)
{
/*
* Creating mutex that can be shared between
* processes.
*/
#if _POSIX_THREAD_PROCESS_SHARED
/*
* Not implemented yet.
*/
#error ERROR [__FILE__, line __LINE__]: Process shared mutexes are not supported yet.
#else
result = ENOSYS;
#endif /* _POSIX_THREAD_PROCESS_SHARED */
}
}
if (result != 0 && mx != NULL)
{
free(mx);
mx = NULL;
}
FAIL0:
*mutex = mx;
return(result);
}
int
pthread_mutex_destroy(pthread_mutex_t *mutex)
{
int result = 0;
pthread_mutex_t mx;
if (mutex == NULL || *mutex == NULL)
{
return EINVAL;
}
/*
* Check to see if we have something to delete.
*/
if (*mutex != (pthread_mutex_t) PTW32_OBJECT_AUTO_INIT)
{
mx = *mutex;
result = pthread_mutex_trylock(&mx);
if (result == 0 || result == EDEADLK)
{
/*
* FIXME!!!
* The mutex isn't held by another thread but we could still
* be too late invalidating the mutex below. Yet we can't do it
* earlier in case another thread needs to unlock the mutex
* that it's holding.
*/
*mutex = NULL;
result = pthread_mutex_unlock(&mx);
if (result == 0)
{
ptw32_DeleteCriticalSection(&mx->cs);
free(mx);
}
else
{
/*
* Restore the mutex before we return the error.
*/
*mutex = mx;
}
}
}
else
{
/*
* See notes in ptw32_mutex_check_need_init() above also.
*/
EnterCriticalSection(&ptw32_mutex_test_init_lock);
/*
* Check again.
*/
if (*mutex == (pthread_mutex_t) PTW32_OBJECT_AUTO_INIT)
{
/*
* This is all we need to do to destroy a statically
* initialised mutex that has not yet been used (initialised).
* If we get to here, another thread
* waiting to initialise this mutex will get an EINVAL.
*/
*mutex = NULL;
}
else
{
/*
* The mutex has been initialised while we were waiting
* so assume it's in use.
*/
result = EBUSY;
}
LeaveCriticalSection(&ptw32_mutex_test_init_lock);
}
return(result);
}
int
pthread_mutexattr_init (pthread_mutexattr_t * attr)
/*
* ------------------------------------------------------
* DOCPUBLIC
* Initializes a mutex attributes object with default
* attributes.
*
* PARAMETERS
* attr
* pointer to an instance of pthread_mutexattr_t
*
*
* DESCRIPTION
* Initializes a mutex attributes object with default
* attributes.
*
* NOTES:
* 1) Used to define mutex types
*
* RESULTS
* 0 successfully initialized attr,
* ENOMEM insufficient memory for attr.
*
* ------------------------------------------------------
*/
{
pthread_mutexattr_t ma;
int result = 0;
ma = (pthread_mutexattr_t) calloc (1, sizeof (*ma));
if (ma == NULL)
{
result = ENOMEM;
}
ma->pshared = PTHREAD_PROCESS_PRIVATE;
ma->type = PTHREAD_MUTEX_DEFAULT;
*attr = ma;
return (result);
} /* pthread_mutexattr_init */
int
pthread_mutexattr_destroy (pthread_mutexattr_t * attr)
/*
* ------------------------------------------------------
* DOCPUBLIC
* Destroys a mutex attributes object. The object can
* no longer be used.
*
* PARAMETERS
* attr
* pointer to an instance of pthread_mutexattr_t
*
*
* DESCRIPTION
* Destroys a mutex attributes object. The object can
* no longer be used.
*
* NOTES:
* 1) Does not affect mutexes created using 'attr'
*
* RESULTS
* 0 successfully released attr,
* EINVAL 'attr' is invalid.
*
* ------------------------------------------------------
*/
{
int result = 0;
if (attr == NULL || *attr == NULL)
{
result = EINVAL;
}
else
{
pthread_mutexattr_t ma = *attr;
*attr = NULL;
free (ma);
result = 0;
}
return (result);
} /* pthread_mutexattr_destroy */
int
pthread_mutexattr_getpshared (const pthread_mutexattr_t * attr,
int *pshared)
/*
* ------------------------------------------------------
* DOCPUBLIC
* Determine whether mutexes created with 'attr' can be
* shared between processes.
*
* PARAMETERS
* attr
* pointer to an instance of pthread_mutexattr_t
*
* pshared
* will be set to one of:
*
* PTHREAD_PROCESS_SHARED
* May be shared if in shared memory
*
* PTHREAD_PROCESS_PRIVATE
* Cannot be shared.
*
*
* DESCRIPTION
* Mutexes creatd with 'attr' can be shared between
* processes if pthread_mutex_t variable is allocated
* in memory shared by these processes.
* NOTES:
* 1) pshared mutexes MUST be allocated in shared
* memory.
* 2) The following macro is defined if shared mutexes
* are supported:
* _POSIX_THREAD_PROCESS_SHARED
*
* RESULTS
* 0 successfully retrieved attribute,
* EINVAL 'attr' is invalid,
*
* ------------------------------------------------------
*/
{
int result;
if ((attr != NULL && *attr != NULL) &&
(pshared != NULL))
{
*pshared = (*attr)->pshared;
result = 0;
}
else
{
*pshared = PTHREAD_PROCESS_PRIVATE;
result = EINVAL;
}
return (result);
} /* pthread_mutexattr_getpshared */
int
pthread_mutexattr_setpshared (pthread_mutexattr_t * attr,
int pshared)
/*
* ------------------------------------------------------
* DOCPUBLIC
* Mutexes created with 'attr' can be shared between
* processes if pthread_mutex_t variable is allocated
* in memory shared by these processes.
*
* PARAMETERS
* attr
* pointer to an instance of pthread_mutexattr_t
*
* pshared
* must be one of:
*
* PTHREAD_PROCESS_SHARED
* May be shared if in shared memory
*
* PTHREAD_PROCESS_PRIVATE
* Cannot be shared.
*
* DESCRIPTION
* Mutexes creatd with 'attr' can be shared between
* processes if pthread_mutex_t variable is allocated
* in memory shared by these processes.
*
* NOTES:
* 1) pshared mutexes MUST be allocated in shared
* memory.
*
* 2) The following macro is defined if shared mutexes
* are supported:
* _POSIX_THREAD_PROCESS_SHARED
*
* RESULTS
* 0 successfully set attribute,
* EINVAL 'attr' or pshared is invalid,
* ENOSYS PTHREAD_PROCESS_SHARED not supported,
*
* ------------------------------------------------------
*/
{
int result;
if ((attr != NULL && *attr != NULL) &&
((pshared == PTHREAD_PROCESS_SHARED) ||
(pshared == PTHREAD_PROCESS_PRIVATE)))
{
if (pshared == PTHREAD_PROCESS_SHARED)
{
#if !defined( _POSIX_THREAD_PROCESS_SHARED )
result = ENOSYS;
pshared = PTHREAD_PROCESS_PRIVATE;
#else
result = 0;
#endif /* _POSIX_THREAD_PROCESS_SHARED */
}
else
{
result = 0;
}
(*attr)->pshared = pshared;
}
else
{
result = EINVAL;
}
return (result);
} /* pthread_mutexattr_setpshared */
int
pthread_mutexattr_settype (pthread_mutexattr_t * attr,
int type)
/*
* ------------------------------------------------------
*
* PARAMETERS
* attr
* pointer to an instance of pthread_mutexattr_t
*
* type
* must be one of:
*
* PTHREAD_MUTEX_DEFAULT
*
* PTHREAD_MUTEX_NORMAL
*
* PTHREAD_MUTEX_ERRORCHECK
*
* PTHREAD_MUTEX_RECURSIVE
*
* DESCRIPTION
* The pthread_mutexattr_gettype() and
* pthread_mutexattr_settype() functions respectively get and
* set the mutex type attribute. This attribute is set in the
* type parameter to these functions. The default value of the
* type attribute is PTHREAD_MUTEX_DEFAULT.
*
* The type of mutex is contained in the type attribute of the
* mutex attributes. Valid mutex types include:
*
* PTHREAD_MUTEX_NORMAL
* This type of mutex does not detect deadlock. A
* thread attempting to relock this mutex without
* first unlocking it will deadlock. Attempting to
* unlock a mutex locked by a different thread
* results in undefined behavior. Attempting to
* unlock an unlocked mutex results in undefined
* behavior.
*
* PTHREAD_MUTEX_ERRORCHECK
* This type of mutex provides error checking. A
* thread attempting to relock this mutex without
* first unlocking it will return with an error. A
* thread attempting to unlock a mutex which another
* thread has locked will return with an error. A
* thread attempting to unlock an unlocked mutex will
* return with an error.
*
* PTHREAD_MUTEX_RECURSIVE
* A thread attempting to relock this mutex without
* first unlocking it will succeed in locking the
* mutex. The relocking deadlock which can occur with
* mutexes of type PTHREAD_MUTEX_NORMAL cannot occur
* with this type of mutex. Multiple locks of this
* mutex require the same number of unlocks to
* release the mutex before another thread can
* acquire the mutex. A thread attempting to unlock a
* mutex which another thread has locked will return
* with an error. A thread attempting to unlock an
* unlocked mutex will return with an error. This
* type of mutex is only supported for mutexes whose
* process shared attribute is
* PTHREAD_PROCESS_PRIVATE.
*
* RESULTS
* 0 successfully set attribute,
* EINVAL 'attr' or 'type' is invalid,
*
* ------------------------------------------------------
*/
{
int result = 0;
if ((attr != NULL && *attr != NULL))
{
switch (type)
{
case PTHREAD_MUTEX_DEFAULT:
case PTHREAD_MUTEX_NORMAL:
case PTHREAD_MUTEX_ERRORCHECK:
case PTHREAD_MUTEX_RECURSIVE:
(*attr)->type = type;
break;
default:
result = EINVAL;
break;
}
}
else
{
result = EINVAL;
}
return (result);
} /* pthread_mutexattr_settype */
int
pthread_mutexattr_gettype (pthread_mutexattr_t * attr,
int type)
{
int result = 0;
if ((attr != NULL && *attr != NULL))
{
result = (*attr)->type;
}
else
{
result = EINVAL;
}
return (result);
}
int
pthread_mutex_lock(pthread_mutex_t *mutex)
{
int result = 0;
pthread_mutex_t mx;
pthread_t self;
if (mutex == NULL || *mutex == NULL)
{
return EINVAL;
}
/*
* We do a quick check to see if we need to do more work
* to initialise a static mutex. We check
* again inside the guarded section of ptw32_mutex_check_need_init()
* to avoid race conditions.
*/
if (*mutex == (pthread_mutex_t) PTW32_OBJECT_AUTO_INIT)
{
result = ptw32_mutex_check_need_init(mutex);
}
mx = *mutex;
self = pthread_self();
ptw32_EnterCriticalSection(&mx->cs);
switch (mx->type)
{
case PTHREAD_MUTEX_NORMAL:
if (pthread_equal(mx->ownerThread, self))
{
ptw32_LeaveCriticalSection(&mx->cs);
/*
* Pretend to be deadlocked but release the
* mutex if we are canceled.
*/
pthread_cleanup_push(pthread_mutex_unlock, (void *) mutex);
while (TRUE)
{
Sleep(0);
}
pthread_cleanup_pop(1);
}
break;
case PTHREAD_MUTEX_DEFAULT:
case PTHREAD_MUTEX_ERRORCHECK:
if (pthread_equal(mx->ownerThread, self))
{
ptw32_LeaveCriticalSection(&mx->cs);
result = EDEADLK;
}
break;
case PTHREAD_MUTEX_RECURSIVE:
/*
* Nothing more to do.
*/
break;
default:
result = EINVAL;
break;
}
if (result == 0)
{
mx->ownerThread = self;
mx->lockCount++;
}
return(result);
}
int
pthread_mutex_unlock(pthread_mutex_t *mutex)
{
int result = 0;
pthread_mutex_t mx;
if (mutex == NULL || *mutex == NULL)
{
return EINVAL;
}
mx = *mutex;
/*
* If the thread calling us holds the mutex then there is no
* race condition. If another thread holds the
* lock then we shouldn't be in here.
*/
if (mx != (pthread_mutex_t) PTW32_OBJECT_AUTO_INIT)
{
if (pthread_equal(mx->ownerThread, pthread_self()))
{
mx->lockCount--;
if (mx->lockCount == 0)
{
mx->ownerThread = NULL;
}
ptw32_LeaveCriticalSection(&mx->cs);
}
else
{
result = EPERM;
}
}
else
{
result = EINVAL;
}
return(result);
}
int
pthread_mutex_trylock(pthread_mutex_t *mutex)
{
int result = 0;
pthread_mutex_t mx;
pthread_t self;
if (mutex == NULL || *mutex == NULL)
{
return EINVAL;
}
/*
* We do a quick check to see if we need to do more work
* to initialise a static mutex. We check
* again inside the guarded section of ptw32_mutex_check_need_init()
* to avoid race conditions.
*/
if (*mutex == (pthread_mutex_t) PTW32_OBJECT_AUTO_INIT)
{
result = ptw32_mutex_check_need_init(mutex);
}
mx = *mutex;
self = pthread_self();
if (result == 0)
{
/*
* TryEnterCriticalSection is a little different to
* the POSIX trylock semantics. Trylock returns
* EBUSY even if the calling thread already owns
* the mutex - it doesn't lock it recursively, even
* if the mutex type is PTHREAD_MUTEX_RECURSIVE.
*/
if (ptw32_TryEnterCriticalSection(&mx->cs))
{
/*
* We now own the lock, but check that we don't
* already own the mutex.
*/
if (pthread_equal(mx->ownerThread, self))
{
ptw32_LeaveCriticalSection(&mx->cs);
result = EBUSY;
}
}
else
{
result = EBUSY;
}
}
if (result == 0)
{
mx->ownerThread = self;
mx->lockCount++;
}
return (result);
}