/*
* pthread_mutex.c
*
* Description:
* This translation unit implements mutual exclusion (mutex) primitives.
*
* --------------------------------------------------------------------------
*
* Pthreads-embedded (PTE) - POSIX Threads Library for embedded systems
* Copyright(C) 2008 Jason Schmidlapp
*
* Contact Email: jschmidlapp@users.sourceforge.net
*
*
* Based upon 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 original list of contributors to the Pthreads-win32 project
* is contained in the file CONTRIBUTORS.ptw32 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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <pte_osal.h>
#include "pthread.h"
#include "implement.h"
#define TEST_IE InterlockedExchange
int pthread_mutex_destroy (pthread_mutex_t * mutex)
{
int result = 0;
pthread_mutex_t mx;
/*
* Let the system deal with invalid pointers.
*/
/*
* Check to see if we have something to delete.
*/
if (*mutex < PTHREAD_ERRORCHECK_MUTEX_INITIALIZER)
{
mx = *mutex;
result = pthread_mutex_trylock (&mx);
/*
* If trylock succeeded and the mutex is not recursively locked it
* can be destroyed.
*/
if (result == 0)
{
if (mx->kind != PTHREAD_MUTEX_RECURSIVE || 1 == mx->recursive_count)
{
/*
* FIXME!!!
* The mutex isn't held by another thread but we could still
* be too late invalidating the mutex below since another thread
* may already have entered mutex_lock and the check for a valid
* *mutex != NULL.
*
* Note that this would be an unusual situation because it is not
* common that mutexes are destroyed while they are still in
* use by other threads.
*/
*mutex = NULL;
result = pthread_mutex_unlock (&mx);
if (result == 0)
{
pte_osSemaphoreDelete(mx->handle);
free(mx);
}
else
{
/*
* Restore the mutex before we return the error.
*/
*mutex = mx;
}
}
else /* mx->recursive_count > 1 */
{
/*
* The mutex must be recursive and already locked by us (this thread).
*/
mx->recursive_count--; /* Undo effect of pthread_mutex_trylock() above */
result = EBUSY;
}
}
}
else
{
/*
* See notes in pte_mutex_check_need_init() above also.
*/
pte_osMutexLock (pte_mutex_test_init_lock);
/*
* Check again.
*/
if (*mutex >= PTHREAD_ERRORCHECK_MUTEX_INITIALIZER)
{
/*
* 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;
}
pte_osMutexUnlock(pte_mutex_test_init_lock);
}
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;
else
{
mx->lock_idx = 0;
mx->recursive_count = 0;
mx->kind = (attr == NULL || *attr == NULL
? PTHREAD_MUTEX_DEFAULT : (*attr)->kind);
mx->ownerThread = NULL;
pte_osSemaphoreCreate(0,&mx->handle);
}
*mutex = mx;
return (result);
}
int pthread_mutex_lock (pthread_mutex_t * mutex)
{
int result = 0;
pthread_mutex_t mx;
/*
* Let the system deal with invalid pointers.
*/
if (*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 pte_mutex_check_need_init()
* to avoid race conditions.
*/
if (*mutex >= PTHREAD_ERRORCHECK_MUTEX_INITIALIZER)
{
if ((result = pte_mutex_check_need_init (mutex)) != 0)
return (result);
}
mx = *mutex;
if (mx->kind == PTHREAD_MUTEX_NORMAL)
{
if (PTE_ATOMIC_EXCHANGE(
&mx->lock_idx,
1) != 0)
{
while (PTE_ATOMIC_EXCHANGE(&mx->lock_idx,-1) != 0)
{
if (pte_osSemaphorePend(mx->handle,NULL) != PTE_OS_OK)
{
result = EINVAL;
break;
}
}
}
}
else
{
pthread_t self = pthread_self();
if (PTE_ATOMIC_COMPARE_EXCHANGE(&mx->lock_idx,1,0) == 0)
{
mx->recursive_count = 1;
mx->ownerThread = self;
}
else
{
if (pthread_equal (mx->ownerThread, self))
{
if (mx->kind == PTHREAD_MUTEX_RECURSIVE)
mx->recursive_count++;
else
result = EDEADLK;
}
else
{
while (PTE_ATOMIC_EXCHANGE(&mx->lock_idx,-1) != 0)
{
if (pte_osSemaphorePend(mx->handle,NULL) != PTE_OS_OK)
{
result = EINVAL;
break;
}
}
if (0 == result)
{
mx->recursive_count = 1;
mx->ownerThread = self;
}
}
}
}
return (result);
}
static int pte_timed_eventwait (pte_osSemaphoreHandle event, const struct timespec *abstime)
/*
* ------------------------------------------------------
* DESCRIPTION
* This function waits on an event until signaled or until
* abstime passes.
* If abstime has passed when this routine is called then
* it returns a result to indicate this.
*
* If 'abstime' is a NULL pointer then this function will
* block until it can successfully decrease the value or
* until interrupted by a signal.
*
* This routine is not a cancelation point.
*
* RESULTS
* 0 successfully signaled,
* ETIMEDOUT abstime passed
* EINVAL 'event' is not a valid event,
*
* ------------------------------------------------------
*/
{
unsigned int milliseconds;
pte_osResult status;
int retval;
if (abstime == NULL)
status = pte_osSemaphorePend(event, NULL);
else
{
/*
* Calculate timeout as milliseconds from current system time.
*/
milliseconds = pte_relmillisecs (abstime);
status = pte_osSemaphorePend(event, &milliseconds);
}
if (status == PTE_OS_TIMEOUT)
{
retval = ETIMEDOUT;
}
else
{
retval = 0;
}
return retval;
}
int pthread_mutex_timedlock (pthread_mutex_t * mutex,
const struct timespec *abstime)
{
int result;
pthread_mutex_t mx;
/*
* Let the system deal with invalid pointers.
*/
/*
* 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 pte_mutex_check_need_init()
* to avoid race conditions.
*/
if (*mutex >= PTHREAD_ERRORCHECK_MUTEX_INITIALIZER)
{
if ((result = pte_mutex_check_need_init (mutex)) != 0)
return (result);
}
mx = *mutex;
if (mx->kind == PTHREAD_MUTEX_NORMAL)
{
if (PTE_ATOMIC_EXCHANGE(&mx->lock_idx,1) != 0)
{
while (PTE_ATOMIC_EXCHANGE(&mx->lock_idx,-1) != 0)
{
if (0 != (result = pte_timed_eventwait (mx->handle, abstime)))
return result;
}
}
}
else
{
pthread_t self = pthread_self();
if (PTE_ATOMIC_COMPARE_EXCHANGE(&mx->lock_idx,1,0) == 0)
{
mx->recursive_count = 1;
mx->ownerThread = self;
}
else
{
if (pthread_equal (mx->ownerThread, self))
{
if (mx->kind == PTHREAD_MUTEX_RECURSIVE)
mx->recursive_count++;
else
return EDEADLK;
}
else
{
while (PTE_ATOMIC_EXCHANGE(&mx->lock_idx,-1) != 0)
{
if (0 != (result = pte_timed_eventwait (mx->handle, abstime)))
return result;
}
mx->recursive_count = 1;
mx->ownerThread = self;
}
}
}
return 0;
}
int pthread_mutex_trylock (pthread_mutex_t * mutex)
{
int result = 0;
pthread_mutex_t mx;
/*
* Let the system deal with invalid pointers.
*/
/*
* 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 pte_mutex_check_need_init()
* to avoid race conditions.
*/
if (*mutex >= PTHREAD_ERRORCHECK_MUTEX_INITIALIZER)
{
if ((result = pte_mutex_check_need_init (mutex)) != 0)
return (result);
}
mx = *mutex;
if (0 == PTE_ATOMIC_COMPARE_EXCHANGE (&mx->lock_idx,1,0))
{
if (mx->kind != PTHREAD_MUTEX_NORMAL)
{
mx->recursive_count = 1;
mx->ownerThread = pthread_self ();
}
}
else
{
if (mx->kind == PTHREAD_MUTEX_RECURSIVE &&
pthread_equal (mx->ownerThread, pthread_self ()))
mx->recursive_count++;
else
result = EBUSY;
}
return (result);
}
int pthread_mutex_unlock (pthread_mutex_t * mutex)
{
int result = 0;
pthread_mutex_t mx = *mutex;
/*
* Let the system deal with invalid pointers.
*/
/*
* 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_ERRORCHECK_MUTEX_INITIALIZER)
{
if (mx->kind == PTHREAD_MUTEX_NORMAL)
{
int idx;
idx = PTE_ATOMIC_EXCHANGE (&mx->lock_idx,0);
if (idx != 0)
{
if (idx < 0)
{
/*
* Someone may be waiting on that mutex.
*/
if (pte_osSemaphorePost(mx->handle,1) != PTE_OS_OK)
result = EINVAL;
}
}
else
{
/*
* Was not locked (so can't be owned by us).
*/
result = EPERM;
}
}
else
{
if (pthread_equal (mx->ownerThread, pthread_self ()))
{
if (mx->kind != PTHREAD_MUTEX_RECURSIVE
|| 0 == --mx->recursive_count)
{
mx->ownerThread = NULL;
if (PTE_ATOMIC_EXCHANGE (&mx->lock_idx,0) < 0)
{
if (pte_osSemaphorePost(mx->handle,1) != PTE_OS_OK)
result = EINVAL;
}
}
}
else
result = EPERM;
}
}
else
result = EINVAL;
return (result);
}