> Am 25.02.2022 um 14:15 schrieb Graham Leggett <minf...@sharp.fm>:
>
> On 23 Feb 2022, at 12:39, Stefan Eissing <ste...@eissing.org> wrote:
>
>> One thing that is currently missing is a way to shutdown/reap/join module
>> threads when the mpm exits.
>>
>> Example:
>>
>> mod_watchdog creates several threads post_config which are only joined on
>> pool destruction.
>>
>> Problem:
>>
>> pool destruction is not ordered between modules and dependencies on order
>> are not
>> fully known. This leads to crashes in OpenSSL, for example, when mod_ssl is
>> destructed
>> before all watchdogs using OpenSSL are joined (OpenSSL 3.x seems to do
>> better on this,
>> but the point remains valid).
>
> A note on OpenSSL termination - in old versions of OpenSSL, there was this
> wrong assumption that an application would only ever initialise OpenSSL once,
> and in turn shut down OpenSSL once, but this scenario doesn’t exist in the
> real world (like ours, where modules that have no idea about each other
> independently use OpenSSL).
>
> OpenSSL 3 (and I think earlier versions, I don’t remember) have gone further
> than “do better”, they have (to my knowledge) 100% fixed this problem by
> turning all OpenSSL init functions into noops and using reference counting
> internally to ensure sanity is maintained at all times.
>
> If any of this doesn't work, we need to let OpenSSL know.
>
>> There has been attempts by Yann to make a patch that make the OpenSSL
>> termination
>> way later (adding it to a 'higher' pool destruction). But that would only
>> solve
>> this particular problem and not any other 3rd party dependency.
>>
>> Proposal:
>>
>> Add a hook 'child_exiting(int graceful)' where modules can register
>> and do their own thread join/reap.
>>
>>
>> On a graceful shutdown, this would allow watchdogs to fully complete any
>> ongoing task
>> before things start to disappear in the process.
>
> +1 - will be very useful.
Thanks. I added this and support in mod_watchdog. Results from mpm_event seem to
indicate that this works.
However, I get strange failures/crashes with mpm_prefork. Seemingly when
clean_child_exit()
is directly invoked from the signal handler. I have not been able to wrap my
head around
what is causing this.
I disabled calling the child_stopping/child_stopped hooks when this is invoked
by the signal
handler. This should revert mpm_prefork to the state before and have it again
passing in out
Travis CI. If this still fails, I screwed up somewhere else.
Kind Regards,
Stefan
>
> Regards,
> Graham
> —
