}
StatInc(thr, StatShadowAnotherThread);
if (HappensBefore(old, thr)) {
- StoreIfNotYetStored(sp, &store_word);
+ if (old.IsRWWeakerOrEqual(kAccessIsWrite, kIsAtomic))
+ StoreIfNotYetStored(sp, &store_word);
break;
}
if (old.IsBothReadsOrAtomic(kAccessIsWrite, kIsAtomic))
--- /dev/null
+// RUN: %clang_tsan -O1 %s -o %t && %deflake %run %t | FileCheck %s
+#include "test.h"
+
+// We want to establish the following sequence of accesses to X:
+// - main thread writes X
+// - thread2 reads X, this read happens-before the write in main thread
+// - thread1 reads X, this read is concurrent with the write in main thread
+// Write in main thread and read in thread1 should be detected as a race.
+// Previously tsan replaced write by main thread with read by thread1,
+// as the result the race was not detected.
+
+volatile long X, Y, Z;
+
+void *Thread1(void *x) {
+ barrier_wait(&barrier);
+ barrier_wait(&barrier);
+ Y = X;
+ return NULL;
+}
+
+void *Thread2(void *x) {
+ Z = X;
+ barrier_wait(&barrier);
+ return NULL;
+}
+
+int main() {
+ barrier_init(&barrier, 2);
+ pthread_t t[2];
+ pthread_create(&t[0], 0, Thread1, 0);
+ X = 42;
+ barrier_wait(&barrier);
+ pthread_create(&t[1], 0, Thread2, 0);
+ pthread_join(t[0], 0);
+ pthread_join(t[1], 0);
+ return 0;
+}
+
+// CHECK: WARNING: ThreadSanitizer: data race
+