Rollup merge of #102773 - joboet:apple_parker, r=thomcc

Use semaphores for thread parking on Apple platforms

Currently we use a mutex-condvar pair for thread parking on Apple systems. Unfortunately, `pthread_cond_timedwait` uses the real-time clock for measuring time, which causes problems when the system time changes. The parking implementation in this PR uses a semaphore instead, which measures monotonic time by default, avoiding these issues. As a further benefit, this has the potential to improve performance a bit, since `unpark` does not need to wait for a lock to be released.

Since the Mach semaphores are poorly documented (I could not find availability or stability guarantees for instance), this uses a [dispatch semaphore](https://developer.apple.com/documentation/dispatch/dispatch_semaphore?language=objc) instead. While it adds a layer of indirection (it uses Mach semaphores internally), the overhead is probably negligible.

Tested on macOS 12.5.

r? ``````@thomcc``````

1 files changed, 22 insertions, 0 deletions

diff --git a/library/std/src/thread/tests.rs b/library/std/src/thread/tests.rs
index 130e47c8d44..dfb8765ab4e 100644
--- a/library/std/src/thread/tests.rs
+++ b/library/std/src/thread/tests.rs
@@ -245,6 +245,28 @@ fn test_try_panic_any_message_unit_struct() {
 }
 
 #[test]
+fn test_park_unpark_before() {
+    for _ in 0..10 {
+        thread::current().unpark();
+        thread::park();
+    }
+}
+
+#[test]
+fn test_park_unpark_called_other_thread() {
+    for _ in 0..10 {
+        let th = thread::current();
+
+        let _guard = thread::spawn(move || {
+            super::sleep(Duration::from_millis(50));
+            th.unpark();
+        });
+
+        thread::park();
+    }
+}
+
+#[test]
 fn test_park_timeout_unpark_before() {
     for _ in 0..10 {
         thread::current().unpark();