X-Git-Url: http://nsz.repo.hu/git/?p=musl;a=blobdiff_plain;f=src%2Fthread%2Fpthread_barrier_wait.c;h=6052925a819a5280f627572d8a6b6455dcfa0b71;hp=db432ba30a21bf1b30c8bbd52daaad387b6271d5;hb=de543b05c87d79a9313991810e9ee8ecdaad8f19;hpb=60164570111873175111cf8a5b973375e492eee9

diff --git a/src/thread/pthread_barrier_wait.c b/src/thread/pthread_barrier_wait.c
index db432ba3..6052925a 100644
--- a/src/thread/pthread_barrier_wait.c
+++ b/src/thread/pthread_barrier_wait.c
@@ -13,48 +13,58 @@ void __vm_lock(int inc)
 
 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 0;
+	return ret;
 }
 
 struct instance