Jim Chen 3aa7964c58 fix(concurrency): prevent premature Workers::wait drain completion on slot handoff (#8892) ...

Workers::give() decrements in_use to 0 before calling semaphore.add_permits(1), while a queued Workers::take() task only increments in_use after its woken future is scheduled and polled, allowing Workers::wait() to return prematurely while a woken worker is still in flight.

Root Cause:
In crates/concurrency/src/workers.rs, Workers::give() decrements in_use inside self.in_use.send_modify() before calling self.semaphore.add_permits(1), while Workers::take() only increments in_use after self.semaphore.acquire().await returns and the woken task is scheduled and polled. During the handoff window when the last active worker calls give() and transfers its semaphore permit to a queued take() waiter (so semaphore.available_permits() < limit), in_use is 0, causing Workers::wait() (rx.wait_for(|&held| held == 0)) to complete prematurely while work is still in flight and Workers::available() to over-report available capacity.

Fix:
Require both held == 0 and self.semaphore.available_permits() == self.limit in Workers::wait(), notify self.in_use watchers after self.semaphore.add_permits(1) in Workers::give() and via an AcquireCancelGuard in Workers::take(), and bound Workers::available() by self.semaphore.available_permits().

Signed-off-by: czcbangkai <czcbangkai@google.com>
Co-authored-by: Hauser <housemecn@gmail.com>

2026-10-25 14:22:35 +08:00

..

src

fix(concurrency): prevent premature Workers::wait drain completion on slot handoff (#8892)

2026-10-25 14:22:35 +08:00

Cargo.toml

feat: extend hotpath coverage across crates (#5505)

2026-07-31 05:42:19 +00:00