Apache SIGTERM causes module shutdown to run at runtime

[bwoebi]

Description

Apache workers tends to sometimes crash when killed via SIGTERM:

Sample trace:

#2 php_module_shutdown () at ./main/main.c:2455
#3 0x00007fee0fbfc83d in php_module_shutdown_wrapper (sapi_globals=<optimized out>) at ./main/main.c:2448
#4 0x00007fee0fce6d05 in php_apache_child_shutdown (tmp=<optimized out>) at ./sapi/apache2handler/sapi_apache2.c:422
#5 0x00007fee11324d2e in apr_pool_destroy () from /usr/lib/x86_64-linux-gnu/libapr-1.so.0
#6 0x00007fee10f83303 in clean_child_exit () from /usr/lib/apache2/modules/mod_mpm_prefork.so
#7 0x00007fee10f83341 in just_die () from /usr/lib/apache2/modules/mod_mpm_prefork.so
#8 0x00007fee0fc866cd in zend_signal_handler (signo=signo@entry=15, siginfo=siginfo@entry=0x7fffe103fc30, context=context@entry=0x7fffe103fb00) at ./Zend/zend_signal.c:217
#9 0x00007fee0fc86873 in zend_signal_handler_defer (signo=15, siginfo=0x7fffe103fc30, context=0x7fffe103fb00) at ./Zend/zend_signal.c:102
#10 <signal handler called>
#11 0x00007fee11203bbf in __GI___poll (fds=fds@entry=0x7fffe1040890, nfds=nfds@entry=1, timeout=86400000) at ../sysdeps/unix/sysv/linux/poll.c:29
<a mysql function here>

The specific crash location within php_module_shutdown can vary quite a bit, depending on when exactly the signal handler was called.
But in particular, PHP does quite a lot of cleanup during module shutdown, and most is neither signal safe, nor can refcounts be relied on being correct.

I'd expect PHP to avoid any complex operations (like a module shutdown) upon receiving a SIGTERM signal. (Just like PHP also avoids doing special handling for CLI processes receiving a SIGTERM.)

PHP Version

PHP 7.4 - 8.4

Operating System

No response

[bukka]

Possibly related to https://bugs.php.net/bug.php?id=78619

[bukka]

Well it's probably duplicate of the above but better to keep this open as GH issues are open for comments to anybody (with GH account).

[bwoebi]

@bukka It's not quite a dupe of that, as there it crashes in zend_signal_handler_defer directly (IIRC that is actually fixed?), but it crashes in the shutdown sequence initiated by apache in its sigterm handler.