void __vm_unlock(void)
{
- if (vmlock[0]>0) a_dec(vmlock);
- else a_inc(vmlock);
- if (vmlock[1]) __wake(vmlock, 1, 1);
+ int inc = vmlock[0]>0 ? -1 : 1;
+ if (a_fetch_add(vmlock, inc)==-inc && vmlock[1])
+ __wake(vmlock, -1, 1);
}
static int pshared_barrier_wait(pthread_barrier_t *b)
{
int limit = (b->_b_limit & INT_MAX) + 1;
- int seq;
int ret = 0;
+ int v, w;
- if (!limit) return PTHREAD_BARRIER_SERIAL_THREAD;
-
- while (a_swap(&b->_b_lock, 1))
- __wait(&b->_b_lock, &b->_b_waiters, 1, 0);
+ if (limit==1) return PTHREAD_BARRIER_SERIAL_THREAD;
- seq = b->_b_seq;
+ while ((v=a_cas(&b->_b_lock, 0, limit)))
+ __wait(&b->_b_lock, &b->_b_waiters, v, 0);
+ /* Wait for <limit> threads to get to the barrier */
if (++b->_b_count == limit) {
+ a_store(&b->_b_count, 0);
ret = PTHREAD_BARRIER_SERIAL_THREAD;
- b->_b_seq++;
- __wake(&b->_b_seq, -1, 0);
+ if (b->_b_waiters2) __wake(&b->_b_count, -1, 0);
} else {
a_store(&b->_b_lock, 0);
if (b->_b_waiters) __wake(&b->_b_lock, 1, 0);
- __wait(&b->_b_seq, 0, seq, 0);
+ while ((v=b->_b_count)>0)
+ __wait(&b->_b_count, &b->_b_waiters2, v, 0);
}
__vm_lock(+1);
- if (a_fetch_add(&b->_b_count, -1)==1) {
- b->_b_seq++;
- __wake(&b->_b_seq, -1, 0);
- a_store(&b->_b_lock, 0);
- if (b->_b_waiters) __wake(&b->_b_lock, 1, 0);
+ /* Ensure all threads have a vm lock before proceeding */
+ if (a_fetch_add(&b->_b_count, -1)==1-limit) {
+ a_store(&b->_b_count, 0);
+ if (b->_b_waiters2) __wake(&b->_b_count, -1, 0);
} else {
- __wait(&b->_b_seq, 0, seq+1, 0);
+ while ((v=b->_b_count))
+ __wait(&b->_b_count, &b->_b_waiters2, v, 0);
}
+ /* Perform a recursive unlock suitable for self-sync'd destruction */
+ do {
+ v = b->_b_lock;
+ w = b->_b_waiters;
+ } while (a_cas(&b->_b_lock, v, v==INT_MIN+1 ? 0 : v-1) != v);
+
+ /* Wake a thread waiting to reuse or destroy the barrier */
+ if (v==INT_MIN+1 || (v==1 && w))
+ __wake(&b->_b_lock, 1, 0);
+
__vm_unlock();
return ret;