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-rw-r--r--library/std/src/sync/once/tests.rs116
1 files changed, 116 insertions, 0 deletions
diff --git a/library/std/src/sync/once/tests.rs b/library/std/src/sync/once/tests.rs
new file mode 100644
index 000000000..0c35597e1
--- /dev/null
+++ b/library/std/src/sync/once/tests.rs
@@ -0,0 +1,116 @@
+use super::Once;
+use crate::panic;
+use crate::sync::mpsc::channel;
+use crate::thread;
+
+#[test]
+fn smoke_once() {
+ static O: Once = Once::new();
+ let mut a = 0;
+ O.call_once(|| a += 1);
+ assert_eq!(a, 1);
+ O.call_once(|| a += 1);
+ assert_eq!(a, 1);
+}
+
+#[test]
+fn stampede_once() {
+ static O: Once = Once::new();
+ static mut RUN: bool = false;
+
+ let (tx, rx) = channel();
+ for _ in 0..10 {
+ let tx = tx.clone();
+ thread::spawn(move || {
+ for _ in 0..4 {
+ thread::yield_now()
+ }
+ unsafe {
+ O.call_once(|| {
+ assert!(!RUN);
+ RUN = true;
+ });
+ assert!(RUN);
+ }
+ tx.send(()).unwrap();
+ });
+ }
+
+ unsafe {
+ O.call_once(|| {
+ assert!(!RUN);
+ RUN = true;
+ });
+ assert!(RUN);
+ }
+
+ for _ in 0..10 {
+ rx.recv().unwrap();
+ }
+}
+
+#[test]
+fn poison_bad() {
+ static O: Once = Once::new();
+
+ // poison the once
+ let t = panic::catch_unwind(|| {
+ O.call_once(|| panic!());
+ });
+ assert!(t.is_err());
+
+ // poisoning propagates
+ let t = panic::catch_unwind(|| {
+ O.call_once(|| {});
+ });
+ assert!(t.is_err());
+
+ // we can subvert poisoning, however
+ let mut called = false;
+ O.call_once_force(|p| {
+ called = true;
+ assert!(p.is_poisoned())
+ });
+ assert!(called);
+
+ // once any success happens, we stop propagating the poison
+ O.call_once(|| {});
+}
+
+#[test]
+fn wait_for_force_to_finish() {
+ static O: Once = Once::new();
+
+ // poison the once
+ let t = panic::catch_unwind(|| {
+ O.call_once(|| panic!());
+ });
+ assert!(t.is_err());
+
+ // make sure someone's waiting inside the once via a force
+ let (tx1, rx1) = channel();
+ let (tx2, rx2) = channel();
+ let t1 = thread::spawn(move || {
+ O.call_once_force(|p| {
+ assert!(p.is_poisoned());
+ tx1.send(()).unwrap();
+ rx2.recv().unwrap();
+ });
+ });
+
+ rx1.recv().unwrap();
+
+ // put another waiter on the once
+ let t2 = thread::spawn(|| {
+ let mut called = false;
+ O.call_once(|| {
+ called = true;
+ });
+ assert!(!called);
+ });
+
+ tx2.send(()).unwrap();
+
+ assert!(t1.join().is_ok());
+ assert!(t2.join().is_ok());
+}