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Fix thread-safety in GC, type cache, and instruction cache #7355

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Merged
youknowone merged 6 commits into from
Mar 5, 2026
Merged

Fix thread-safety in GC, type cache, and instruction cache #7355

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70169e8
Fix thread-safety in GC, type cache, and instruction cache
youknowone Mar 5, 2026
b0ad917
Fix RLock _acquire_restore tuple handling and unxfail threading test
youknowone Mar 5, 2026
de01099
Align type cache seqlock writer protocol with CPython
youknowone Mar 5, 2026
8683977
RLock: use single parking_lot level, track recursion manually
youknowone Mar 5, 2026
3e31d22
Add try_to_owned_from_ptr to avoid &PyObject on stale ptrs
youknowone Mar 5, 2026
b3de227
Fix CI: spelling typo and xfail flaky test_thread_safety
youknowone Mar 5, 2026
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RLock: use single parking_lot level, track recursion manually 
Instead of calling lock()/unlock() N times for recursion depth N,
keep parking_lot at 1 level and manage the count ourselves.
This makes acquire/release O(1) and matches CPython's
_PyRecursiveMutex approach (lock once + set level directly).
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@youknowone
youknowone committed Mar 5, 2026
commit 8683977378340ee67501bb85d997b8407e440aaa
3 changes: 0 additions & 3 deletions Lib/test/test_threading.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2141,9 +2141,6 @@ def __init__(self, a, *, b) -> None:
CustomRLock(1, b=2)
self.assertEqual(warnings_log, [])

def test_release_save_unacquired(self):
return super().test_release_save_unacquired()

@unittest.skip('TODO: RUSTPYTHON; flaky test')
def test_different_thread(self):
return super().test_different_thread()
Expand Down
30 changes: 16 additions & 14 deletions crates/vm/src/stdlib/thread.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -221,10 +221,16 @@ pub(crate) mod _thread {
#[pymethod(name = "acquire_lock")]
#[pymethod(name = "__enter__")]
fn acquire(&self, args: AcquireArgs, vm: &VirtualMachine) -> PyResult<bool> {
let result = acquire_lock_impl!(&self.mu, args, vm)?;
if result {
if self.mu.is_owned_by_current_thread() {
// Re-entrant acquisition: just increment our count.
// parking_lot stays at 1 level; we track recursion ourselves.
self.count
.fetch_add(1, core::sync::atomic::Ordering::Relaxed);
return Ok(true);
}
let result = acquire_lock_impl!(&self.mu, args, vm)?;
if result {
self.count.store(1, core::sync::atomic::Ordering::Relaxed);
}
Ok(result)
}
Expand All @@ -234,13 +240,13 @@ pub(crate) mod _thread {
if !self.mu.is_owned_by_current_thread() {
return Err(vm.new_runtime_error("cannot release un-acquired lock"));
}
debug_assert!(
self.count.load(core::sync::atomic::Ordering::Relaxed) > 0,
"RLock count underflow"
);
self.count
let prev = self
.count
.fetch_sub(1, core::sync::atomic::Ordering::Relaxed);
unsafe { self.mu.unlock() };
debug_assert!(prev > 0, "RLock count underflow");
if prev == 1 {
unsafe { self.mu.unlock() };
}
Ok(())
}

Expand Down Expand Up @@ -285,9 +291,7 @@ pub(crate) mod _thread {
}
let count = self.count.swap(0, core::sync::atomic::Ordering::Relaxed);
debug_assert!(count > 0, "RLock count underflow");
for _ in 0..count {
unsafe { self.mu.unlock() };
}
unsafe { self.mu.unlock() };
Ok((count, current_thread_id()))
}

Expand All @@ -303,9 +307,7 @@ pub(crate) mod _thread {
if count == 0 {
return Ok(());
}
for _ in 0..count {
self.mu.lock();
}
self.mu.lock();
self.count
.store(count, core::sync::atomic::Ordering::Relaxed);
Ok(())
Expand Down