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From Ruediger Pluem <>
Subject Re: new watchdog module
Date Wed, 04 Feb 2009 22:02:36 GMT

On 02/04/2009 10:44 PM, Jeff Trawick wrote:
> On Wed, Feb 4, 2009 at 11:09 AM, Mladen Turk <> wrote:
>> Hi,
>> I would like to commit this module to trunk.
>> It's a watchdog module that creates a worker threads
>> either in parent, child via an API, and it's not for
>> standalone use, but for other module usage like
>> mod_heartbeat, probably mod_jk and others that need
>> maintenance threads.
> It seems scary to me to have the MPM parent on Unix forking children while a
> separate thread in that same process is running arbitrary code.  Surprising
> problems can crop up when this arbitrary code is in certain states (maybe a
> mutex gets inherited in held state by the new MPM child?)

This seems to be a very valid concern to me. Plus in the parent it runs with root
privileges and we should minimize the code that runs with these privileges, even
more so as an author of code that uses the watchdog may not really be aware that
its code is running under root (in contrast to people who develop modules like
mod_unixd and mod_privileges).

So we shouldn't run this in the parent process but only in the childs or fork a
separate child (like mod_cgid does) that only runs the watchdog if a
single-instance-non-locking watchdog is needed.



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