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Drop racy STOP_BIT assertion from eval-breaker test #8789

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Merged
youknowone merged 2 commits into from
Sep 23, 2026
Merged

Drop racy STOP_BIT assertion from eval-breaker test #8789

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f1fef34
Drop racy STOP_BIT assertion from eval-breaker test
youknowone Sep 22, 2026
26731c2
Merge branch 'main' into fix/sendall-deadline-stw-test
youknowone Sep 23, 2026
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7 changes: 0 additions & 7 deletions crates/vm/src/signal.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -182,11 +182,6 @@ mod mt {
EVAL_BREAKER.fetch_and(!STOP_BIT, Ordering::Release);
}

#[cfg(test)]
pub(crate) fn stop_bit_set() -> bool {
EVAL_BREAKER.load(Ordering::Relaxed) & STOP_BIT != 0
}

/// Record that finalization has begun. See `FINALIZING_BIT`.
pub(crate) fn set_finalizing_bit() {
EVAL_BREAKER.fetch_or(FINALIZING_BIT, Ordering::Release);
Expand All @@ -203,8 +198,6 @@ mod mt {
}
}

#[cfg(all(test, feature = "threading"))]
pub(crate) use mt::stop_bit_set;
#[cfg(feature = "threading")]
pub(crate) use mt::{
clear_qsbr_bit, clear_stop_bit, qsbr_bit_set, schedule_gc, set_finalizing_bit, set_qsbr_bit,
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26 changes: 5 additions & 21 deletions crates/vm/src/vm/interpreter.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1851,36 +1851,20 @@ for _ in range(40):
worker.join().expect("worker panicked");
}

/// Per-thread `stop_requested` must trip the eval breaker even when the
/// process-wide `STOP_BIT` is clear.
/// Per-thread `stop_requested` must trip the eval breaker on its own.
/// Do not touch or assert the process-wide eval-breaker word: other tests
/// in this process may be flickering `STOP_BIT` at the same time.
#[cfg(feature = "threading")]
#[test]
fn eval_breaker_tripped_when_stop_requested_and_stop_bit_clear() {
fn eval_breaker_tripped_when_stop_requested() {
let interp = Interpreter::without_stdlib(Default::default());
interp.enter(|vm| {
assert!(
crate::vm::thread::set_stop_requested_for_current_thread(true),
"current thread has no stop_requested flag"
);
// STOP_BIT is process-wide; a parallel stop-the-world test can
// set it between the clear and the load. Retry until this thread
// observes it clear, then sample `eval_breaker_tripped`.
let (stop_bit, tripped) = {
let mut stop_bit = true;
let mut tripped = false;
for _ in 0..10_000 {
crate::signal::clear_stop_bit();
stop_bit = crate::signal::stop_bit_set();
tripped = vm.eval_breaker_tripped();
if !stop_bit {
break;
}
std::thread::yield_now();
}
(stop_bit, tripped)
};
let tripped = vm.eval_breaker_tripped();
crate::vm::thread::set_stop_requested_for_current_thread(false);
assert!(!stop_bit, "process-wide STOP_BIT was set");
assert!(tripped);
});
}
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