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 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. -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://issues.apache.org/jira/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira