deadloop in zdrun.py leaves parent process hung

[Darryl Dixon]

Under certain conditions, the runforever() function in zdrun.py will deadloop attempting to kill.SIGKILL a defunct child process (which will never suceed). It can be triggered by starting and stopping a zope instance from code running in another zope instance (both instances running as the same unprivileged user account) with the 'zopectl start' and 'zopectl stop' commands.
Sample workflow:
Have two zope instances.
Have code in one instance that executes a shell command to start, then executes another shell command to stop the other instance.
The stop command will fail - the child processes are left as 'defunct' and the parent will loop forever sending KILL commands to them (which will obviously not succeed).

Suggested fix: set the child pid to '0' with self.proc.setstatus(0) immediately after sending the SIGKILL (the only conditions under which SIGKILL will not remove the process from the process table is when it is a zombie, as per above). This correctly fixes the problem (tested OK).

[Darryl Dixon (esrever-otua)]

PATCH:
--- app/zope-stable/lib/python/zdaemon/zdrun.py 2006-07-07 15:00:13.246377264 +1200
+++ /u01/app/zope-stable/lib/python/zdaemon/zdrun.py 2006-07-07 13:59:46.502932790 +1200
@@ -421,6 +421,7 @@
                     if self.killing and self.proc.pid:
                         self.proc.kill(signal.SIGKILL)
                         self.delay = time.time() + self.options.backofflimit
+ self.proc.setstatus(0)
             try:
                 r, w, x = select.select(r, w, x, timeout)
             except select.error, err:

[Colin Watson (cjwatson)]

The zope2 project on Launchpad has been archived at the request of the Zope developers (see https://answers.launchpad.net/launchpad/+question/683589 and https://answers.launchpad.net/launchpad/+question/685285). If this bug is still relevant, please refile it at https://github.com/zopefoundation/zope2.