diff options
| -rw-r--r-- | library/std/src/thread/local/tests.rs | 19 |
1 files changed, 11 insertions, 8 deletions
diff --git a/library/std/src/thread/local/tests.rs b/library/std/src/thread/local/tests.rs index 964c7fc5b0c..25019b554bb 100644 --- a/library/std/src/thread/local/tests.rs +++ b/library/std/src/thread/local/tests.rs @@ -255,6 +255,9 @@ fn join_orders_after_tls_destructors() { // observe the channel in the `THREAD1_WAITING` state. If this does occur, // we switch to the “poison” state `THREAD2_JOINED` and panic all around. // (This is equivalent to “sending” from an alternate producer thread.) + // + // Relaxed memory ordering is fine because and spawn()/join() already provide all the + // synchronization we need here. const FRESH: u8 = 0; const THREAD2_LAUNCHED: u8 = 1; const THREAD1_WAITING: u8 = 2; @@ -263,7 +266,7 @@ fn join_orders_after_tls_destructors() { static SYNC_STATE: AtomicU8 = AtomicU8::new(FRESH); for _ in 0..10 { - SYNC_STATE.store(FRESH, Ordering::SeqCst); + SYNC_STATE.store(FRESH, Ordering::Relaxed); let jh = thread::Builder::new() .name("thread1".into()) @@ -272,7 +275,7 @@ fn join_orders_after_tls_destructors() { impl Drop for TlDrop { fn drop(&mut self) { - let mut sync_state = SYNC_STATE.swap(THREAD1_WAITING, Ordering::SeqCst); + let mut sync_state = SYNC_STATE.swap(THREAD1_WAITING, Ordering::Relaxed); loop { match sync_state { THREAD2_LAUNCHED | THREAD1_WAITING => thread::yield_now(), @@ -282,7 +285,7 @@ fn join_orders_after_tls_destructors() { ), v => unreachable!("sync state: {}", v), } - sync_state = SYNC_STATE.load(Ordering::SeqCst); + sync_state = SYNC_STATE.load(Ordering::Relaxed); } } } @@ -294,7 +297,7 @@ fn join_orders_after_tls_destructors() { TL_DROP.with(|_| {}); loop { - match SYNC_STATE.load(Ordering::SeqCst) { + match SYNC_STATE.load(Ordering::Relaxed) { FRESH => thread::yield_now(), THREAD2_LAUNCHED => break, v => unreachable!("sync state: {}", v), @@ -306,9 +309,9 @@ fn join_orders_after_tls_destructors() { let jh2 = thread::Builder::new() .name("thread2".into()) .spawn(move || { - assert_eq!(SYNC_STATE.swap(THREAD2_LAUNCHED, Ordering::SeqCst), FRESH); + assert_eq!(SYNC_STATE.swap(THREAD2_LAUNCHED, Ordering::Relaxed), FRESH); jh.join().unwrap(); - match SYNC_STATE.swap(THREAD2_JOINED, Ordering::SeqCst) { + match SYNC_STATE.swap(THREAD2_JOINED, Ordering::Relaxed) { MAIN_THREAD_RENDEZVOUS => return, THREAD2_LAUNCHED | THREAD1_WAITING => { panic!("Thread 2 running after thread 1 join before main thread rendezvous") @@ -322,8 +325,8 @@ fn join_orders_after_tls_destructors() { match SYNC_STATE.compare_exchange( THREAD1_WAITING, MAIN_THREAD_RENDEZVOUS, - Ordering::SeqCst, - Ordering::SeqCst, + Ordering::Relaxed, + Ordering::Relaxed, ) { Ok(_) => break, Err(FRESH) => thread::yield_now(), |