/*
* ptw32_mcs_lock_release -- release 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_release (ptw32_mcs_local_node_t * node)
{
ptw32_mcs_lock_t *lock = node->lock;
ptw32_mcs_local_node_t *next = (ptw32_mcs_local_node_t *)
InterlockedExchangeAdd((LPLONG)&node->next, 0); /* MBR fence */
if (0 == next)
{
/* no known successor */
if (node == (ptw32_mcs_local_node_t *)
PTW32_INTERLOCKED_COMPARE_EXCHANGE((PTW32_INTERLOCKED_LPLONG)lock,
(PTW32_INTERLOCKED_LONG)0,
(PTW32_INTERLOCKED_LONG)node))
{
/* no successor, lock is free now */
return;
}
/* wait for successor */
ptw32_mcs_flag_wait(&node->nextFlag);
next = (ptw32_mcs_local_node_t *)
InterlockedExchangeAdd((LPLONG)&node->next, 0); /* MBR fence */
}
/* pass the lock */
ptw32_mcs_flag_set(&next->readyFlag);
}
int
pthread_barrier_wait (pthread_barrier_t * barrier)
{
int result;
int step;
pthread_barrier_t b;
if (barrier == NULL || *barrier == (pthread_barrier_t) PTW32_OBJECT_INVALID)
{
return EINVAL;
}
b = *barrier;
step = b->iStep;
if (0 == InterlockedDecrement ((long *) &(b->nCurrentBarrierHeight)))
{
/* Must be done before posting the semaphore. */
b->nCurrentBarrierHeight = b->nInitialBarrierHeight;
/*
* There is no race condition between the semaphore wait and post
* because we are using two alternating semas and all threads have
* entered barrier_wait and checked nCurrentBarrierHeight before this
* barrier's sema can be posted. Any threads that have not quite
* entered sem_wait below when the multiple_post has completed
* will nevertheless continue through the semaphore (barrier)
* and will not be left stranded.
*/
result = (b->nInitialBarrierHeight > 1
? sem_post_multiple (&(b->semBarrierBreeched[step]),
b->nInitialBarrierHeight - 1) : 0);
}
else
{
/*
* Use the non-cancelable version of sem_wait().
*/
result = ptw32_semwait (&(b->semBarrierBreeched[step]));
}
/*
* The first thread across will be the PTHREAD_BARRIER_SERIAL_THREAD.
* This also sets up the alternate semaphore as the next barrier.
*/
if (0 == result)
{
result = ((PTW32_INTERLOCKED_LONG) step ==
PTW32_INTERLOCKED_COMPARE_EXCHANGE ((PTW32_INTERLOCKED_LPLONG)
& (b->iStep),
(PTW32_INTERLOCKED_LONG)
(1L - step),
(PTW32_INTERLOCKED_LONG)
step) ?
PTHREAD_BARRIER_SERIAL_THREAD : 0);
}
return (result);
}
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 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 (0 == (LONG) PTW32_INTERLOCKED_COMPARE_EXCHANGE (
(PTW32_INTERLOCKED_LPLONG) &mx->lock_idx,
(PTW32_INTERLOCKED_LONG) 1,
(PTW32_INTERLOCKED_LONG) 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);
}
/*
* ptw32_mcs_flag_set -- notify another thread about an event.
*
* Set event if an event handle has been stored in the flag, and
* set flag to -1 otherwise. Note that -1 cannot be a valid handle value.
*/
INLINE void
ptw32_mcs_flag_set (LONG * flag)
{
HANDLE e = (HANDLE)PTW32_INTERLOCKED_COMPARE_EXCHANGE(
(PTW32_INTERLOCKED_LPLONG)flag,
(PTW32_INTERLOCKED_LONG)-1,
(PTW32_INTERLOCKED_LONG)0);
if ((HANDLE)0 != e)
{
/* another thread has already stored an event handle in the flag */
SetEvent(e);
}
}
int pthread_spin_trylock (pthread_spinlock_t * lock)
{
switch ((long)
PTW32_INTERLOCKED_COMPARE_EXCHANGE(lock,
PTW32_SPIN_LOCKED,
PTW32_SPIN_UNLOCKED))
{
case PTW32_SPIN_UNLOCKED:
return 0;
case PTW32_SPIN_LOCKED:
return EBUSY;
}
return EINVAL;
}
/*
* ptw32_mcs_flag_set -- wait for notification from another.
*
* Store an event handle in the flag and wait on it if the flag has not been
* set, and proceed without creating an event otherwise.
*/
INLINE void
ptw32_mcs_flag_wait (LONG * flag)
{
if (0 == InterlockedExchangeAdd((LPLONG)flag, 0)) /* MBR fence */
{
/* the flag is not set. create event. */
HANDLE e = CreateEvent(NULL, PTW32_FALSE, PTW32_FALSE, NULL);
if (0 == PTW32_INTERLOCKED_COMPARE_EXCHANGE(
(PTW32_INTERLOCKED_LPLONG)flag,
(PTW32_INTERLOCKED_LONG)e,
(PTW32_INTERLOCKED_LONG)0))
{
/* stored handle in the flag. wait on it now. */
WaitForSingleObject(e, INFINITE);
}
CloseHandle(e);
}
}
int
pthread_spin_trylock (pthread_spinlock_t * lock)
{
register pthread_spinlock_t s;
if (NULL == lock || NULL == *lock)
{
return (EINVAL);
}
if (*lock == PTHREAD_SPINLOCK_INITIALIZER)
{
int result;
if ((result = ptw32_spinlock_check_need_init (lock)) != 0)
{
return (result);
}
}
s = *lock;
switch ((long)
PTW32_INTERLOCKED_COMPARE_EXCHANGE ((PTW32_INTERLOCKED_LPLONG) &
(s->interlock),
(PTW32_INTERLOCKED_LONG)
PTW32_SPIN_LOCKED,
(PTW32_INTERLOCKED_LONG)
PTW32_SPIN_UNLOCKED))
{
case PTW32_SPIN_UNLOCKED:
return 0;
case PTW32_SPIN_LOCKED:
return EBUSY;
case PTW32_SPIN_USE_MUTEX:
return pthread_mutex_trylock (&(s->u.mutex));
}
return EINVAL;
}
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);
}
int
pthread_spin_destroy (pthread_spinlock_t * lock)
{
register pthread_spinlock_t s;
int result = 0;
if (lock == NULL || *lock == NULL)
{
return EINVAL;
}
if ((s = *lock) != PTHREAD_SPINLOCK_INITIALIZER)
{
if (s->interlock == PTW32_SPIN_USE_MUTEX)
{
result = pthread_mutex_destroy (&(s->u.mutex));
}
else if ((PTW32_INTERLOCKED_LONG) PTW32_SPIN_UNLOCKED !=
PTW32_INTERLOCKED_COMPARE_EXCHANGE ((PTW32_INTERLOCKED_LPLONG)
& (s->interlock),
(PTW32_INTERLOCKED_LONG)
PTW32_OBJECT_INVALID,
(PTW32_INTERLOCKED_LONG)
PTW32_SPIN_UNLOCKED))
{
result = EINVAL;
}
if (0 == result)
{
/*
* We are relying on the application to ensure that all other threads
* have finished with the spinlock before destroying it.
*/
*lock = NULL;
(void) free (s);
}
}
else
{
/*
* See notes in ptw32_spinlock_check_need_init() above also.
*/
EnterCriticalSection (&ptw32_spinlock_test_init_lock);
/*
* Check again.
*/
if (*lock == PTHREAD_SPINLOCK_INITIALIZER)
{
/*
* This is all we need to do to destroy a statically
* initialised spinlock that has not yet been used (initialised).
* If we get to here, another thread
* waiting to initialise this mutex will get an EINVAL.
*/
*lock = NULL;
}
else
{
/*
* The spinlock has been initialised while we were waiting
* so assume it's in use.
*/
result = EBUSY;
}
LeaveCriticalSection (&ptw32_spinlock_test_init_lock);
}
return (result);
}
