Backport #2677 to 0.11.x - #2690
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drive_timer() used AsyncTimer::poll() to determine whether a protocol deadline had elapsed. Under Tokio's cooperative task budget, Sleep::poll() may return Poll::Pending for an already-expired deadline once the task's budget is exhausted, which can happen when process_conn_events() drains a busy channel. As a result, handle_timeout() is not called even though the deadline has already elapsed. For QUIC, timers such as PTO, loss detection, and idle timeouts are correctness-critical and should not be deferred to a later scheduling round. Fix this by checking runtime.now() >= deadline before consulting the async timer. The clock is not subject to cooperative budgeting. The timer remains responsible only for registering a wakeup when the deadline lies in the future.
syszery
marked this pull request as ready for review
June 16, 2026 19:10
djc
approved these changes
Jun 16, 2026
Ralith
approved these changes
Jun 17, 2026
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Backport of #2677 to the 0.11.x maintenance branch.
drive_timer()previously relied onAsyncTimer::poll()to determine whether a deadline had elapsed. Under Tokio's cooperative task budget,Sleep::poll()may returnPoll::Pendingfor already-expired deadlines once the task has exhausted its cooperative budget. In that case,handle_timeout()would not be called until a later scheduling round, despite the deadline having already passed.Fix
The timer logic is changed to:
runtime.now() >= deadlinebefore polling the async timer