Merge pull request #62 from geoffreyblake/fix_race

Fix race condition in synchronize_threads()

Author: rpgolshan

benchmarks/lockhammer/include/atomics.h

@@ -494,8 +494,8 @@ void synchronize_threads(uint64_t *barrier, unsigned long nthrds)
     uint64_t tmp_sense = ~global_sense & SENSE_BIT_MASK;
     uint32_t local_sense = (uint32_t)(tmp_sense >> 32);
 
-    fetchadd64_acquire(barrier, 2);
-    if (*barrier == ((nthrds * 2) | global_sense)) {
+    uint64_t old_barrier = fetchadd64_acquire(barrier, 2);
+    if (old_barrier == (((nthrds - 1) * 2) | global_sense)) {
         // Make sure the store gets observed by the system. Reset count
         // to zero and flip the sense bit.
         __atomic_store_n(barrier, tmp_sense, __ATOMIC_RELEASE);