[tsan] Replace pthread_yield with sched_yield in lit tests

OS X doesn't have `pthread_yield`. Let's use `sched_yield` instead.

Differential Revision: http://reviews.llvm.org/D14428

llvm-svn: 252283

compiler-rt/test/tsan/atomic_free3.cc

@@ -13,7 +13,7 @@ int main() {
   pthread_t t;
   pthread_create(&t, 0, Thread, a);
   while (__atomic_load_n(a, __ATOMIC_RELAXED) == 0)
-    pthread_yield();
+    sched_yield();
   delete a;
   pthread_join(t, 0);
 }

compiler-rt/test/tsan/real_deadlock_detector_stress_test.cc

@@ -59,7 +59,7 @@ void *Thread(void *seed) {
       for (;;) {
         int old = __atomic_load_n(&m->state, __ATOMIC_RELAXED);
         if (old == kStateLocked) {
-          pthread_yield();
+          sched_yield();
           continue;
         }
         int newv = old + 1;

compiler-rt/test/tsan/signal_errno.cc

@@ -24,7 +24,7 @@ static __attribute__((noinline)) void loop() {
     volatile char *p = (char*)malloc(1);
     p[0] = 0;
     free((void*)p);
-    pthread_yield();
+    sched_yield();
   }
 }