[ http://issues.apache.org/jira/browse/MODPYTHON-109?page=all ]
Graham Dumpleton updated MODPYTHON-109:
---------------------------------------
Fix Version/s: 3.3
Mark to be addressed in 3.3. Specifically, unless good reasons are found not
to, the apache.register_cleanup() and req.server.register_cleanup() methods
will be deprecated and implementations stubbed out to log a message to Apache
error log indicate they are no longer supported. The current code is just too
unreliable, can't be guaranteed to run and causes problems in shutdown of
Apache child processes.
> Signal handler calling Py_Finalize() when child processes being killed.
> -----------------------------------------------------------------------
>
> Key: MODPYTHON-109
> URL: http://issues.apache.org/jira/browse/MODPYTHON-109
> Project: mod_python
> Issue Type: Bug
> Components: core
> Affects Versions: 3.2.7
> Reporter: Graham Dumpleton
> Assigned To: Graham Dumpleton
> Fix For: 3.3
>
> Attachments: MP109_20060308_grahamd_1.diff
>
>
> When Apache is killing off child processes as part of actions taken when the
> "apachectl restart" or "apachectl graceful" command is run, it sends a
> SIGTERM signal to the child processes. This causes a signal handler
> registered by Apache to be run. That signal handler destroys the main child
> memory pool. That memory pool has though a cleanup handler associated with it
> which was registered by mod_python. That cleanup handler ultimately calls
> Py_Finalize().
> The problem with this is that Py_Finalize() isn't safe to be called from a
> signal handler and if a handler is still executing or there is a separate
> thread running in the context of Python, a deadlock will likely ensue. This
> will prevent the child process exiting due to the SIGTERM causing the Apache
> parent process to send it a SIGKILL to really kill it.
> For a more detailed assessment of the problem and what lead to this
> conclusion see:
> http://www.modpython.org/pipermail/mod_python/2006-January/019865.html
> http://www.modpython.org/pipermail/mod_python/2006-January/019866.html
> http://www.modpython.org/pipermail/mod_python/2006-January/019870.html
> To avoid the problem, the only choice seems to be avoid calling Py_Finalize()
> from the signal handler. The simplistic way of doing this seems to be to add:
> if (child_init_pool)
> return APR_SUCCESS;
> at the start of python_finalize(). This will mean that Py_Finalize() is never
> called in child processes. The full consequences of this is unknown, but on
> face value it would seem that it might be a reasonable thing to do. More
> research may be required.
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