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Make wrapped thread mutex acquisition unwind-safe #9813

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Merged
youknowone merged 6 commits into from
Nov 12, 2026
+38 −29
Merged

Make wrapped thread mutex acquisition unwind-safe #9813

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7cc324e
Make wrapped thread mutex acquisition unwind-safe
youknowdot Nov 12, 2026
c7ef4f7
Follow test-module and core-import lint conventions
youknowdot Nov 12, 2026
eedb181
Detach I/O threads only for contended locks
youknowdot Nov 12, 2026
d46f621
Preserve stop-the-world checkpoints on I/O lock fast paths
youknowdot Nov 12, 2026
0c04579
Cover reentrant I/O acquisition with a pending stop
youknowdot Nov 12, 2026
000a31e
Return real guards from wrapped thread mutex callbacks
youknowone Nov 12, 2026
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67 changes: 38 additions & 29 deletions crates/common/src/lock/thread_mutex.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,10 @@ impl<R: RawMutex, G: GetThreadId> RawThreadMutex<R, G> {
get_thread_id: G::INIT,
};

fn is_owned_by_current_thread(&self) -> bool {
self.owner.load(Ordering::Relaxed) == self.get_thread_id.nonzero_thread_id().get()
}

#[inline]
fn lock_internal<F: FnOnce() -> bool>(&self, try_lock: F) -> Option<bool> {
let id = self.get_thread_id.nonzero_thread_id().get();
Expand All @@ -53,18 +57,6 @@ impl<R: RawMutex, G: GetThreadId> RawThreadMutex<R, G> {
.is_some()
}

/// Like `lock()` but wraps the blocking wait in `wrap_fn`.
/// The caller can use this to detach thread state while waiting.
pub fn lock_wrapped<F: FnOnce(&dyn Fn())>(&self, wrap_fn: F) -> bool {
let id = self.get_thread_id.nonzero_thread_id().get();
if self.owner.load(Ordering::Relaxed) == id {
return false;
}
wrap_fn(&|| self.mutex.lock());
self.owner.store(id, Ordering::Relaxed);
true
}

/// Returns `Some(true)` if able to successfully lock without blocking, `Some(false)`
/// otherwise, and `None` when the mutex is already locked on the current thread.
pub fn try_lock(&self) -> Option<bool> {
Expand Down Expand Up @@ -149,18 +141,16 @@ impl<R: RawMutex, G: GetThreadId, T: ?Sized> ThreadMutex<R, G, T> {

/// Like `lock()` but wraps the blocking wait in `wrap_fn`.
/// The caller can use this to detach thread state while waiting.
pub fn lock_wrapped<F: FnOnce(&dyn Fn())>(
&self,
wrap_fn: F,
) -> Option<ThreadMutexGuard<'_, R, G, T>> {
if self.raw.lock_wrapped(wrap_fn) {
Some(ThreadMutexGuard {
mu: self,
marker: PhantomData,
})
} else {
None
pub fn lock_wrapped<'a, F>(&'a self, wrap_fn: F) -> Option<ThreadMutexGuard<'a, R, G, T>>
where
F: FnOnce(
&dyn Fn() -> Option<ThreadMutexGuard<'a, R, G, T>>,
) -> Option<ThreadMutexGuard<'a, R, G, T>>,
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{
if self.raw.is_owned_by_current_thread() {
return None;
}
wrap_fn(&|| self.lock())
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}

pub fn try_lock(&self) -> Result<ThreadMutexGuard<'_, R, G, T>, TryLockThreadError> {
Expand All @@ -177,25 +167,31 @@ impl<R: RawMutex, G: GetThreadId, T: ?Sized> ThreadMutex<R, G, T> {

impl<R: RawMutexTimed, G: GetThreadId, T: ?Sized> ThreadMutex<R, G, T> {
/// Wait at most `timeout`, wrapping only the blocking acquisition.
pub fn try_lock_for_wrapped<F: FnOnce(&dyn Fn() -> bool) -> bool>(
&self,
pub fn try_lock_for_wrapped<'a, F>(
&'a self,
timeout: R::Duration,
wrap_fn: F,
) -> Result<ThreadMutexGuard<'_, R, G, T>, TryLockThreadError>
) -> Result<ThreadMutexGuard<'a, R, G, T>, TryLockThreadError>
where
F: FnOnce(
&dyn Fn() -> Result<ThreadMutexGuard<'a, R, G, T>, TryLockThreadError>,
) -> Result<ThreadMutexGuard<'a, R, G, T>, TryLockThreadError>,
R::Duration: Copy,
{
match self
if self.raw.is_owned_by_current_thread() {
return Err(TryLockThreadError::Current);
}
wrap_fn(&|| match self
.raw
.lock_internal(|| wrap_fn(&|| self.raw.mutex.try_lock_for(timeout)))
.lock_internal(|| self.raw.mutex.try_lock_for(timeout))
{
Some(true) => Ok(ThreadMutexGuard {
mu: self,
marker: PhantomData,
}),
Some(false) => Err(TryLockThreadError::Other),
None => Err(TryLockThreadError::Current),
}
})
}
}

Expand Down Expand Up @@ -409,4 +405,17 @@ mod tests {
drop(guard);
assert_eq!(*mutex.lock().unwrap(), 1);
}

#[test]
fn wrapped_lock_releases_on_panic() {
let mutex = PyThreadMutex::new(0);
let result = std::panic::catch_unwind(core::panic::AssertUnwindSafe(|| {
mutex.lock_wrapped(|wait| {
let _g = wait();
panic!()
})
}));
assert!(result.is_err());
assert!(mutex.try_lock().is_ok());
}
}
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