Add park/park_timeout/unpark test.

tests/run-pass/concurrency/parking.rs

@@ -0,0 +1,37 @@
+// ignore-windows: Concurrency on Windows is not supported yet.
+// compile-flags: -Zmiri-disable-isolation
+
+use std::thread;
+use std::time::{Duration, Instant};
+
+// Normally, waiting in park/park_timeout may spuriously wake up early, but we
+// know Miri's timed synchronization primitives do not do that.
+
+fn park_timeout() {
+    let start = Instant::now();
+
+    thread::park_timeout(Duration::from_millis(200));
+
+    assert!((200..500).contains(&start.elapsed().as_millis()));
+}
+
+fn park_unpark() {
+    let t1 = thread::current();
+    let t2 = thread::spawn(move || {
+        thread::park();
+        thread::sleep(Duration::from_millis(200));
+        t1.unpark();
+    });
+
+    let start = Instant::now();
+
+    t2.thread().unpark();
+    thread::park();
+
+    assert!((200..500).contains(&start.elapsed().as_millis()));
+}
+
+fn main() {
+    park_timeout();
+    park_unpark();
+}

tests/run-pass/concurrency/parking.stderr

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+warning: thread support is experimental. For example, Miri does not detect data races yet.
+