X-Git-Url: http://nsz.repo.hu/git/?p=musl;a=blobdiff_plain;f=src%2Fthread%2Fpthread_barrier_wait.c;h=5e6033804033b85879ba88abdaf1d5d0b4aa14af;hp=7bfadb9532195bfad63561032e5e3f2fde376f12;hb=da8d0fc4fa3490f418a438b7e0830f9af312d41f;hpb=e882756311c7b06e59fcc8e582f03852b7dcfd30

diff --git a/src/thread/pthread_barrier_wait.c b/src/thread/pthread_barrier_wait.c
index 7bfadb95..5e603380 100644
--- a/src/thread/pthread_barrier_wait.c
+++ b/src/thread/pthread_barrier_wait.c
@@ -1,31 +1,113 @@
 #include "pthread_impl.h"
 
+void __vm_lock_impl(int);
+void __vm_unlock_impl(void);
+
+static int pshared_barrier_wait(pthread_barrier_t *b)
+{
+	int limit = (b->_b_limit & INT_MAX) + 1;
+	int ret = 0;
+	int v, w;
+
+	if (limit==1) return PTHREAD_BARRIER_SERIAL_THREAD;
+
+	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;
+		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);
+		while ((v=b->_b_count)>0)
+			__wait(&b->_b_count, &b->_b_waiters2, v, 0);
+	}
+
+	__vm_lock_impl(+1);
+
+	/* 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 {
+		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_impl();
+
+	return ret;
+}
+
+struct instance
+{
+	int count;
+	int last;
+	int waiters;
+	int finished;
+};
+
 int pthread_barrier_wait(pthread_barrier_t *b)
 {
-	int cur;
+	int limit = b->_b_limit;
+	struct instance *inst;
 
 	/* Trivial case: count was set at 1 */
-	if (!b->_b_limit) return PTHREAD_BARRIER_SERIAL_THREAD;
+	if (!limit) return PTHREAD_BARRIER_SERIAL_THREAD;
 
-	/* Wait for anyone still suspended at previous use of barrier */
-	while ((cur=b->_b_left))
-		__wait(&b->_b_left, &b->_b_waiters, cur, 0);
+	/* Process-shared barriers require a separate, inefficient wait */
+	if (limit < 0) return pshared_barrier_wait(b);
 
-	/* If we are the last to reach barrier, reset it and wake others */
-	if (a_fetch_add(&b->_b_count, 1) == b->_b_limit) {
-		b->_b_left = b->_b_limit;
-		b->_b_count = 0;
-		__wake(&b->_b_count, -1, 0);
+	/* Otherwise we need a lock on the barrier object */
+	while (a_swap(&b->_b_lock, 1))
+		__wait(&b->_b_lock, &b->_b_waiters, 1, 1);
+	inst = b->_b_inst;
+
+	/* First thread to enter the barrier becomes the "instance owner" */
+	if (!inst) {
+		struct instance new_inst = { 0 };
+		int spins = 10000;
+		b->_b_inst = inst = &new_inst;
+		a_store(&b->_b_lock, 0);
+		if (b->_b_waiters) __wake(&b->_b_lock, 1, 1);
+		while (spins-- && !inst->finished)
+			a_spin();
+		a_inc(&inst->finished);
+		while (inst->finished == 1)
+			__syscall(SYS_futex, &inst->finished, FUTEX_WAIT,1,0);
 		return PTHREAD_BARRIER_SERIAL_THREAD;
 	}
 
-	/* Wait for our peers to reach the barrier */
-	while ((cur=b->_b_count))
-		__wait(&b->_b_count, 0, cur, 0);
+	/* Last thread to enter the barrier wakes all non-instance-owners */
+	if (++inst->count == limit) {
+		b->_b_inst = 0;
+		a_store(&b->_b_lock, 0);
+		if (b->_b_waiters) __wake(&b->_b_lock, 1, 1);
+		a_store(&inst->last, 1);
+		if (inst->waiters)
+			__wake(&inst->last, -1, 1);
+	} else {
+		a_store(&b->_b_lock, 0);
+		if (b->_b_waiters) __wake(&b->_b_lock, 1, 1);
+		__wait(&inst->last, &inst->waiters, 0, 1);
+	}
 
-	/* If we're the last to wake up and barrier is awaiting reuse */
-	if (a_fetch_add(&b->_b_left, -1) == 1 && b->_b_waiters)
-		__wake(&b->_b_left, -1, 0);
+	/* Last thread to exit the barrier wakes the instance owner */
+	if (a_fetch_add(&inst->count,-1)==1 && a_fetch_add(&inst->finished,1))
+		__wake(&inst->finished, 1, 1);
 
 	return 0;
 }