Miss Islington (bot) c8c08cfe29 [3.15] gh-115634: Fix ProcessPoolExecutor deadlock with max_tasks_per_child (GH-140900) (#152926) ...

gh-115634: Fix ProcessPoolExecutor deadlock with max_tasks_per_child (GH-140900)

The idle worker semaphore counts task completions, not idle workers, so
it can hold a stale token released by a worker that later exited upon
reaching its max_tasks_per_child limit. The worker replacement path
consumed such tokens and skipped spawning a replacement, deadlocking
the remaining queued tasks once no workers were left.

Replace dead workers based on len(self._processes) without consulting
the semaphore. The submit() path is unchanged, preserving on-demand
spawning and idle worker reuse.

Replace the documentation note added in GH-140897 with a versionchanged
entry now that the bug is fixed.

Based on a fix proposed by Tabrez Mohammed.
(cherry picked from commit b706767d8f)

Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com>

2026-07-03 06:37:25 +00:00

..

futures

[3.15] gh-115634: Fix ProcessPoolExecutor deadlock with max_tasks_per_child (GH-140900) (#152926)

2026-07-03 06:37:25 +00:00

interpreters

[3.15] gh-150285: Fix too long docstrings in the concurrent package (GH-151076) (GH-151173)

2026-06-09 16:41:26 +00:00

__init__.py

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