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Remove SIGURG blocking from maybe_grow_with to restore preemptive scheduling on grown stacks #429

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Merged
loongs-zhang merged 2 commits into from
Mar 31, 2026
Merged

Remove SIGURG blocking from maybe_grow_with to restore preemptive scheduling on grown stacks #429

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Copilot Mar 31, 2026
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Remove SIGURG blocking from maybe_grow_with to allow preemptive sched…
Copilot Mar 31, 2026
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39 changes: 2 additions & 37 deletions core/src/coroutine/korosensei.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -332,54 +332,19 @@ impl<'c, Param, Yield, Return> Coroutine<'c, Param, Yield, Return> {
return Ok(callback());
}
return DefaultStack::new(stack_size).map(|stack| {
// RAII guard to ensure stack info is popped and SIGURG mask is
// restored even if `callback` panics/unwinds during on_stack().
// RAII guard to ensure stack info is popped even if
// `callback` panics/unwinds during on_stack().
struct OnStackGuard<'a> {
stack_infos: &'a mut VecDeque<StackInfo>,
#[cfg(all(unix, feature = "preemptive"))]
old_mask: Result<SigSet, nix::Error>,
#[cfg(all(unix, feature = "preemptive"))]
sigurg_mask: SigSet,
}
impl Drop for OnStackGuard<'_> {
fn drop(&mut self) {
#[cfg(all(unix, feature = "preemptive"))]
{
// Restore original signal mask to unblock SIGURG.
// Use saved mask for correctness with nested maybe_grow_with;
// fall back to thread_unblock if the old mask wasn't saved.
match &self.old_mask {
Ok(old) => {
_ = old.thread_set_mask();
}
Err(_) => {
_ = self.sigurg_mask.thread_unblock();
}
}
}
_ = self.stack_infos.pop_back();
}
}
co.stack_infos_mut().push_back(StackInfo::from(&stack));
cfg_if::cfg_if! {
if #[cfg(all(unix, feature = "preemptive"))] {
let mut sigurg_mask = SigSet::empty();
sigurg_mask.add(Signal::SIGURG);
let old_mask = SigSet::thread_get_mask();
_ = sigurg_mask.thread_block();
}
}
// Block SIGURG during on_stack to prevent preemptive signal from
// corrupting the stack context. When the coroutine is executing on
// a grown stack via on_stack(), a SIGURG-triggered suspend would
// context-switch back to the scheduler with an inconsistent stack,
// causing SIGSEGV on resume (especially on aarch64).
let guard = OnStackGuard {
stack_infos: co.stack_infos_mut(),
#[cfg(all(unix, feature = "preemptive"))]
old_mask,
#[cfg(all(unix, feature = "preemptive"))]
sigurg_mask,
};
let r = corosensei::on_stack(stack, callback);
drop(guard);
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