/*
* ptw32_mcs_lock_acquire -- acquire an MCS lock.
*
* See:
* J. M. Mellor-Crummey and M. L. Scott.
* Algorithms for Scalable Synchronization on Shared-Memory Multiprocessors.
* ACM Transactions on Computer Systems, 9(1):21-65, Feb. 1991.
*/
INLINE void
ptw32_mcs_lock_acquire (ptw32_mcs_lock_t * lock, ptw32_mcs_local_node_t * node)
{
ptw32_mcs_local_node_t *pred;
node->lock = lock;
node->nextFlag = 0;
node->readyFlag = 0;
node->next = 0; /* initially, no successor */
/* queue for the lock */
pred = (ptw32_mcs_local_node_t *)PTW32_INTERLOCKED_EXCHANGE((LPLONG)lock,
(LONG)node);
if (0 != pred)
{
/* the lock was not free. link behind predecessor. */
pred->next = node;
ptw32_mcs_flag_set(&pred->nextFlag);
ptw32_mcs_flag_wait(&node->readyFlag);
}
}
INLINE int
pthread_mutex_unlock (pthread_mutex_t * mutex)
{
int result = 0;
pthread_mutex_t mx;
/*
* Let the system deal with invalid pointers.
*/
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 (!ptw32_static_mutex_enable || (mx < PTHREAD_ERRORCHECK_MUTEX_INITIALIZER))
{
if (mx->kind == PTHREAD_MUTEX_NORMAL)
{
LONG idx;
idx = (LONG) PTW32_INTERLOCKED_EXCHANGE ((LPLONG) &mx->lock_idx,
(LONG) 0);
if (idx != 0)
{
if (idx < 0)
{
/*
* Someone may be waiting on that mutex.
*/
if (SetEvent (mx->event) == 0)
{
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.p = NULL;
if ((LONG) PTW32_INTERLOCKED_EXCHANGE ((LPLONG) &mx->lock_idx,
(LONG) 0) < 0)
{
/* Someone may be waiting on that mutex */
if (SetEvent (mx->event) == 0)
{
result = EINVAL;
}
}
}
}
else
{
result = EPERM;
}
}
}
else
{
result = EINVAL;
}
return (result);
}
int
pthread_mutex_lock (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 ptw32_mutex_check_need_init()
* to avoid race conditions.
*/
if (*mutex >= PTHREAD_ERRORCHECK_MUTEX_INITIALIZER)
{
if ((result = ptw32_mutex_check_need_init (mutex)) != 0)
{
return (result);
}
}
mx = *mutex;
if (mx->kind == PTHREAD_MUTEX_NORMAL)
{
if ((LONG) PTW32_INTERLOCKED_EXCHANGE(
(LPLONG) &mx->lock_idx,
(LONG) 1) != 0)
{
while ((LONG) PTW32_INTERLOCKED_EXCHANGE(
(LPLONG) &mx->lock_idx,
(LONG) -1) != 0)
{
if (WAIT_OBJECT_0 != WaitForSingleObject (mx->event, INFINITE))
{
result = EINVAL;
break;
}
}
}
}
else
{
pthread_t self = pthread_self();
if ((PTW32_INTERLOCKED_LONG) PTW32_INTERLOCKED_COMPARE_EXCHANGE(
(PTW32_INTERLOCKED_LPLONG) &mx->lock_idx,
(PTW32_INTERLOCKED_LONG) 1,
(PTW32_INTERLOCKED_LONG) 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 ((LONG) PTW32_INTERLOCKED_EXCHANGE(
(LPLONG) &mx->lock_idx,
(LONG) -1) != 0)
{
if (WAIT_OBJECT_0 != WaitForSingleObject (mx->event, INFINITE))
{
result = EINVAL;
break;
}
}
if (0 == result)
{
mx->recursive_count = 1;
mx->ownerThread = self;
}
}
}
}
return (result);
}
