fix excessive/insufficient wakes in __vm_unlock

[musl] / src / thread / pthread_barrier_wait.c

diff --git a/src/thread/pthread_barrier_wait.c b/src/thread/pthread_barrier_wait.c
index 71f7b5f..6052925 100644 (file)
--- a/src/thread/pthread_barrier_wait.c
+++ b/src/thread/pthread_barrier_wait.c
@@ -13,9 +13,9 @@ 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)