rts: Annotate benign race in pthread ticker's exit test wip/T20690

Previously TSAN would report spurious data races due to
the unsynchronized access of `exited`. I would have thought
that using a relaxed load on `exited` would be enough to convince
TSAN that the race was intentional, but apparently not.

Closes #20690.

1 files changed, 1 insertions, 0 deletions

diff --git a/rts/posix/ticker/Pthread.c b/rts/posix/ticker/Pthread.c
index f07d000dac..7d39fd1b10 100644
--- a/rts/posix/ticker/Pthread.c
+++ b/rts/posix/ticker/Pthread.c
@@ -109,6 +109,7 @@ static void *itimer_thread_func(void *_handle_tick)
 
     // Relaxed is sufficient: If we don't see that exited was set in one iteration we will
     // see it next time.
+    TSAN_ANNOTATE_BENIGN_RACE(&exited, "itimer_thread_func");
     while (!RELAXED_LOAD(&exited)) {
         if (USE_TIMERFD_FOR_ITIMER) {
             ssize_t r = read(timerfd, &nticks, sizeof(nticks));