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_barrier_wait (pthread_barrier_t * barrier)
{
int result;
pthread_barrier_t b;
ptw32_mcs_local_node_t node;
if (barrier == NULL || *barrier == (pthread_barrier_t) PTW32_OBJECT_INVALID)
{
return EINVAL;
}
ptw32_mcs_lock_acquire(&(*barrier)->lock, &node);
b = *barrier;
if (--b->nCurrentBarrierHeight == 0)
{
ptw32_mcs_node_transfer(&b->proxynode, &node);
result = (b->nInitialBarrierHeight > 1
? sem_post_multiple (&(b->semBarrierBreeched),
b->nInitialBarrierHeight - 1) : 0);
}
else
{
ptw32_mcs_lock_release(&node);
result = ptw32_semwait (&(b->semBarrierBreeched));
}
if ((PTW32_INTERLOCKED_LONG)PTW32_INTERLOCKED_INCREMENT_LONG((PTW32_INTERLOCKED_LONGPTR)&b->nCurrentBarrierHeight)
== (PTW32_INTERLOCKED_LONG)b->nInitialBarrierHeight)
{
ptw32_mcs_lock_release(&b->proxynode);
if (0 == result)
{
result = PTHREAD_BARRIER_SERIAL_THREAD;
}
}
return (result);
}
int
pthread_barrier_wait (pthread_barrier_t * barrier)
{
int result;
pthread_barrier_t b;
ptw32_mcs_local_node_t node;
if (barrier == NULL || *barrier == (pthread_barrier_t) PTW32_OBJECT_INVALID)
{
return EINVAL;
}
ptw32_mcs_lock_acquire(&(*barrier)->lock, &node);
b = *barrier;
if (--b->nCurrentBarrierHeight == 0)
{
/*
* We are the last thread to arrive at the barrier before it releases us.
* Move our MCS local node to the global scope barrier handle so that the
* last thread out (not necessarily us) can release the lock.
*/
ptw32_mcs_node_transfer(&b->proxynode, &node);
/*
* Any threads that have not quite entered sem_wait below when the
* multiple_post has completed will nevertheless continue through
* the semaphore (barrier).
*/
result = (b->nInitialBarrierHeight > 1
? sem_post_multiple (&(b->semBarrierBreeched),
b->nInitialBarrierHeight - 1) : 0);
}
else
{
ptw32_mcs_lock_release(&node);
/*
* Use the non-cancelable version of sem_wait().
*
* It is possible that all nInitialBarrierHeight-1 threads are
* at this point when the last thread enters the barrier, resets
* nCurrentBarrierHeight = nInitialBarrierHeight and leaves.
* If pthread_barrier_destroy is called at that moment then the
* barrier will be destroyed along with the semas.
*/
result = ptw32_semwait (&(b->semBarrierBreeched));
}
if ((PTW32_INTERLOCKED_LONG)PTW32_INTERLOCKED_INCREMENT_LONG((PTW32_INTERLOCKED_LONGPTR)&b->nCurrentBarrierHeight)
== (PTW32_INTERLOCKED_LONG)b->nInitialBarrierHeight)
{
/*
* We are the last thread to cross this barrier
*/
ptw32_mcs_lock_release(&b->proxynode);
if (0 == result)
{
result = PTHREAD_BARRIER_SERIAL_THREAD;
}
}
return (result);
}
static INLINE int
ptw32_cond_unblock (pthread_cond_t * cond, int unblockAll)
/*
* Notes.
*
* Does not use the external mutex for synchronisation,
* therefore semBlockLock is needed.
* mtxUnblockLock is for LEVEL-2 synch. LEVEL-2 is the
* state where the external mutex is not necessarily locked by
* any thread, ie. between cond_wait unlocking and re-acquiring
* the lock after having been signaled or a timeout or
* cancellation.
*
* Uses the following CV elements:
* nWaitersBlocked
* nWaitersToUnblock
* nWaitersGone
* mtxUnblockLock
* semBlockLock
* semBlockQueue
*/
{
int result;
pthread_cond_t cv;
int nSignalsToIssue;
if (cond == NULL || *cond == NULL)
{
return EINVAL;
}
cv = *cond;
/*
* No-op if the CV is static and hasn't been initialised yet.
* Assuming that any race condition is harmless.
*/
if (cv == PTHREAD_COND_INITIALIZER)
{
return 0;
}
if ((result = pthread_mutex_lock (&(cv->mtxUnblockLock))) != 0)
{
return result;
}
if (0 != cv->nWaitersToUnblock)
{
if (0 == cv->nWaitersBlocked)
{
return pthread_mutex_unlock (&(cv->mtxUnblockLock));
}
if (unblockAll)
{
cv->nWaitersToUnblock += (nSignalsToIssue = cv->nWaitersBlocked);
cv->nWaitersBlocked = 0;
}
else
{
nSignalsToIssue = 1;
cv->nWaitersToUnblock++;
cv->nWaitersBlocked--;
}
}
else if (cv->nWaitersBlocked > cv->nWaitersGone)
{
/* Use the non-cancellable version of sem_wait() */
if (ptw32_semwait (&(cv->semBlockLock)) != 0)
{
result = errno;
(void) pthread_mutex_unlock (&(cv->mtxUnblockLock));
return result;
}
if (0 != cv->nWaitersGone)
{
cv->nWaitersBlocked -= cv->nWaitersGone;
cv->nWaitersGone = 0;
}
if (unblockAll)
{
nSignalsToIssue = cv->nWaitersToUnblock = cv->nWaitersBlocked;
cv->nWaitersBlocked = 0;
}
else
{
nSignalsToIssue = cv->nWaitersToUnblock = 1;
cv->nWaitersBlocked--;
}
}
else
{
return pthread_mutex_unlock (&(cv->mtxUnblockLock));
}
if ((result = pthread_mutex_unlock (&(cv->mtxUnblockLock))) == 0)
{
if (sem_post_multiple (&(cv->semBlockQueue), nSignalsToIssue) != 0)
{
result = errno;
}
}
return result;
} /* ptw32_cond_unblock */
static void PTW32_CDECL
ptw32_cond_wait_cleanup (void *args)
{
ptw32_cond_wait_cleanup_args_t *cleanup_args =
(ptw32_cond_wait_cleanup_args_t *) args;
pthread_cond_t cv = cleanup_args->cv;
int *resultPtr = cleanup_args->resultPtr;
int nSignalsWasLeft;
int result;
/*
* Whether we got here as a result of signal/broadcast or because of
* timeout on wait or thread cancellation we indicate that we are no
* longer waiting. The waiter is responsible for adjusting waiters
* (to)unblock(ed) counts (protected by unblock lock).
*/
if ((result = pthread_mutex_lock (&(cv->mtxUnblockLock))) != 0)
{
*resultPtr = result;
return;
}
if (0 != (nSignalsWasLeft = cv->nWaitersToUnblock))
{
--(cv->nWaitersToUnblock);
}
else if (INT_MAX / 2 == ++(cv->nWaitersGone))
{
/* Use the non-cancellable version of sem_wait() */
if (ptw32_semwait (&(cv->semBlockLock)) != 0)
{
*resultPtr = errno;
/*
* This is a fatal error for this CV,
* so we deliberately don't unlock
* cv->mtxUnblockLock before returning.
*/
return;
}
cv->nWaitersBlocked -= cv->nWaitersGone;
if (sem_post (&(cv->semBlockLock)) != 0)
{
*resultPtr = errno;
/*
* This is a fatal error for this CV,
* so we deliberately don't unlock
* cv->mtxUnblockLock before returning.
*/
return;
}
cv->nWaitersGone = 0;
}
if ((result = pthread_mutex_unlock (&(cv->mtxUnblockLock))) != 0)
{
*resultPtr = result;
return;
}
if (1 == nSignalsWasLeft)
{
if (sem_post (&(cv->semBlockLock)) != 0)
{
*resultPtr = errno;
return;
}
}
/*
* XSH: Upon successful return, the mutex has been locked and is owned
* by the calling thread.
*/
if ((result = pthread_mutex_lock (cleanup_args->mutexPtr)) != 0)
{
*resultPtr = result;
}
} /* ptw32_cond_wait_cleanup */
int
pthread_cond_destroy (pthread_cond_t * cond)
/*
* ------------------------------------------------------
* DOCPUBLIC
* This function destroys a condition variable
*
*
* PARAMETERS
* cond
* pointer to an instance of pthread_cond_t
*
*
* DESCRIPTION
* This function destroys a condition variable.
*
* NOTES:
* 1) A condition variable can be destroyed
* immediately after all the threads that
* are blocked on it are awakened. e.g.
*
* struct list {
* pthread_mutex_t lm;
* ...
* }
*
* struct elt {
* key k;
* int busy;
* pthread_cond_t notbusy;
* ...
* }
*
*
* struct elt *
* list_find(struct list *lp, key k)
* {
* struct elt *ep;
*
* pthread_mutex_lock(&lp->lm);
* while ((ep = find_elt(l,k) != NULL) && ep->busy)
* pthread_cond_wait(&ep->notbusy, &lp->lm);
* if (ep != NULL)
* ep->busy = 1;
* pthread_mutex_unlock(&lp->lm);
* return(ep);
* }
*
* delete_elt(struct list *lp, struct elt *ep)
* {
* pthread_mutex_lock(&lp->lm);
* assert(ep->busy);
* ... remove ep from list ...
* ep->busy = 0;
* (A) pthread_cond_broadcast(&ep->notbusy);
* pthread_mutex_unlock(&lp->lm);
* (B) pthread_cond_destroy(&rp->notbusy);
* free(ep);
* }
*
* In this example, the condition variable
* and its list element may be freed (line B)
* immediately after all threads waiting for
* it are awakened (line A), since the mutex
* and the code ensure that no other thread
* can touch the element to be deleted.
*
* RESULTS
* 0 successfully released condition variable,
* EINVAL 'cond' is invalid,
* EBUSY 'cond' is in use,
*
* ------------------------------------------------------
*/
{
pthread_cond_t cv;
int result = 0, result1 = 0, result2 = 0;
/*
* Assuming any race condition here is harmless.
*/
if (cond == NULL || *cond == NULL)
{
return EINVAL;
}
if (*cond != PTHREAD_COND_INITIALIZER)
{
ptw32_mcs_local_node_t node;
ptw32_mcs_lock_acquire(&ptw32_cond_list_lock, &node);
cv = *cond;
/*
* Close the gate; this will synchronize this thread with
* all already signaled waiters to let them retract their
* waiter status - SEE NOTE 1 ABOVE!!!
*/
if (ptw32_semwait (&(cv->semBlockLock)) != 0) /* Non-cancelable */
{
result = PTW32_GET_ERRNO();
}
else
{
/*
* !TRY! lock mtxUnblockLock; try will detect busy condition
* and will not cause a deadlock with respect to concurrent
* signal/broadcast.
*/
if ((result = pthread_mutex_trylock (&(cv->mtxUnblockLock))) != 0)
{
(void) sem_post (&(cv->semBlockLock));
}
}
if (result != 0)
{
ptw32_mcs_lock_release(&node);
return result;
}
/*
* Check whether cv is still busy (still has waiters)
*/
if (cv->nWaitersBlocked > cv->nWaitersGone)
{
if (sem_post (&(cv->semBlockLock)) != 0)
{
result = PTW32_GET_ERRNO();
}
result1 = pthread_mutex_unlock (&(cv->mtxUnblockLock));
result2 = EBUSY;
}
else
{
/*
* Now it is safe to destroy
*/
*cond = NULL;
if (sem_destroy (&(cv->semBlockLock)) != 0)
{
result = PTW32_GET_ERRNO();
}
if (sem_destroy (&(cv->semBlockQueue)) != 0)
{
result1 = PTW32_GET_ERRNO();
}
if ((result2 = pthread_mutex_unlock (&(cv->mtxUnblockLock))) == 0)
{
result2 = pthread_mutex_destroy (&(cv->mtxUnblockLock));
}
/* Unlink the CV from the list */
if (ptw32_cond_list_head == cv)
{
ptw32_cond_list_head = cv->next;
}
else
{
cv->prev->next = cv->next;
}
if (ptw32_cond_list_tail == cv)
{
ptw32_cond_list_tail = cv->prev;
}
else
{
cv->next->prev = cv->prev;
}
(void) free (cv);
}
ptw32_mcs_lock_release(&node);
}
else
{
ptw32_mcs_local_node_t node;
/*
* See notes in ptw32_cond_check_need_init() above also.
*/
ptw32_mcs_lock_acquire(&ptw32_cond_test_init_lock, &node);
/*
* Check again.
*/
if (*cond == PTHREAD_COND_INITIALIZER)
{
/*
* This is all we need to do to destroy a statically
* initialised cond that has not yet been used (initialised).
* If we get to here, another thread waiting to initialise
* this cond will get an EINVAL. That's OK.
*/
*cond = NULL;
}
else
{
/*
* The cv has been initialised while we were waiting
* so assume it's in use.
*/
result = EBUSY;
}
ptw32_mcs_lock_release(&node);
}
return ((result != 0) ? result : ((result1 != 0) ? result1 : result2));
}
