Graham Dumpleton commented on MODPYTHON-109:

Better fix for this if calling of Py_Finalize() is to be eliminated would be 
simply not to register python_finalize() function against the child init pool. 
This would be done by deleting line:

  apr_pool_cleanup_register(p, NULL, python_finalize, apr_pool_cleanup_null);

from PythonChildInitHandler() function. The whole python_finalize() function 
would then no longer be needed and could also be deleted.

If the functionality of registering Python based server cleanup functions were 
to be removed, the server register_cleanup() functions should probably be left 
in place as stubs. That is, they would no longer do anything. They should 
though log a message indicating that they are now deprecated. By not removing 
them completely, existing code will at least still run. Given that the cleanup 
functions would not have been reliably called in the past and couldn't be 
relied upon, it shouldn't adversely affect any actual web application that used 

Feedback on this issue is needed. Any decision about what is done should be 
made by all core developers.

> 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
>         Type: Bug
>   Components: core
>     Versions: 3.2
>     Reporter: Graham Dumpleton
>     Assignee: Graham Dumpleton

> 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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