release_stale_claims and detect_stale_running call _terminate_reclaimed_worker
and then release the task claim unconditionally, even when the termination did
not actually kill the worker. _terminate_reclaimed_worker already reports this
via its "terminated" flag, but the callers ignore it.
When a worker is parked in uninterruptible (D) state — for example throttled by
a cgroup memory.high limit — a pending SIGTERM/SIGKILL cannot be delivered until
the throttle lifts, so the kill is a no-op. The dispatcher then frees the claim
and spawns a fresh worker beside the still-alive one. Repeated every dispatch
tick this accumulates duplicate workers without bound, deepening the memory
pressure that caused the throttle in the first place — a self-reinforcing
runaway.
Fix: gate both automatic reclaim paths on _worker_survived_termination(). When
we attempted to kill our own host-local worker and it is still alive, defer the
reclaim (_defer_reclaim_for_live_worker extends the claim a short grace and
emits a reclaim_deferred event) instead of releasing. This guarantees at most
one live worker per task and is self-correcting: not spawning a duplicate is
what relieves the pressure so the pending signal lands and the worker dies, and
the next tick reclaims cleanly. Non-host-local claims and the operator-driven
reclaim_task() path keep their existing force-release behaviour.
Related: #41448 (concurrent dispatchers amplify this by doubling reclaim
frequency); #42858 (kill the worker rather than orphan it on archive).
Tests: defer-when-worker-survives, reclaim-when-killed,
release-when-not-host-local, and the detect_stale_running path.
Sahil Saghir
b9e521da23