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From Ruediger Pluem <>
Subject Re: [Bug 60956] Event MPM listener thread may get blocked by SSL shutdowns
Date Fri, 30 Jun 2017 11:20:16 GMT

On 06/30/2017 12:18 PM, Yann Ylavic wrote:
> Hi Luca,
> [better/easier to talk about details on dev@]
> On Fri, Jun 30, 2017 at 11:05 AM,  <> wrote:
>> --- Comment #11 from Luca Toscano <> ---
>> Other two interesting trunk improvements that have not been backported yet:
>> IIUC these ones are meant to provide a more async behavior to most of the
>> output filters, namely setting aside buckets (on the heap) to avoid blocking.
> These are quite orthogonal I think, and don't seem to fix this particular issue.
>> After a bit of thinking it seems to me that we'd need to find a solution that
>> prevents the mod_ssl_output filter to block, but in a safe way.
> IMHO mod_ssl shoudn't (BIO_)flush unconditionally in
> modssl_smart_shutdown(), only in the "abortive" mode of
> ssl_filter_io_shutdown().

I think the issue starts before that.
ap_prep_lingering_close calls the pre_close_connection hook and modules that are registered
to this hook can perform all sort of long lasting blocking operations there.
While it can be argued that this would be a bug in the module I think the only safe way
is to have the whole start_lingering_close_nonblocking being executed by a worker thread.



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