docs: explain why the post-force-kill reboot wait must stay unbounded - #2577
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dunglas wants to merge 1 commit into
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docs: explain why the post-force-kill reboot wait must stay unbounded#2577dunglas wants to merge 1 commit into
dunglas wants to merge 1 commit into
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Bounding this wait and giving up on the stuck thread looks like the obvious fix for #2553 (one stuck thread wedging every reboot forever), and #2573 tried exactly that. It's unsafe: php_main() calls tsrm_shutdown() on every reboot cycle, which requires every PHP thread to have already exited. Giving up on a thread whose OS thread is still alive violates that and crashes the process (confirmed by CI on #2573). Leave a comment so the same fix isn't attempted again without this context.
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Comment-only change, no behavior change.
#2573 tried to bound this wait and abandon an unresponsive thread instead of blocking the whole reboot forever — a reasonable-looking fix for #2553's escalating hang. It's unsafe:
php_main()infrankenphp.cruns the same SAPI/TSRM teardown on every reboot cycle (not just final shutdown), andtsrm_shutdown()requires every PHP thread to have already exited first. Giving up on a thread whose OS thread is still alive and registered in TSRM tears down global engine state out from under it — a use-after-free confirmed by CI segfaults on that PR (see the discussion on #2573, now closed).Adding this as a comment so the next attempt at #2553 doesn't rediscover the same crash the hard way. #2570 and #2574 remain the correct lever: reduce how often a thread ever gets stuck like this, since recovering from it after the fact isn't safely possible.