id	summary	reporter	owner	description	type	status	priority	milestone	component	resolution	keywords	cc	branch	branch_author	launchpad_bug
5151	_SIGCHLDWaker in twisted.internet.posixbase doesn't check its pipe is still open when registering signal handlers	hodgestar	hodgestar	"The function install in _SIGCHLDWaker looks like:
{{{
    def install(self):
        """"""
        Install the handler necessary to make this waker active.
        """"""
        _signals.installHandler(self.o)
}}}
Here self.o may evaluate to None causing installHandler to throw an exception. This may happen if connectionLost is somehow called before installHandler.

One possible fix is:
{{{
    def install(self):
        """"""
        Install the handler necessary to make this waker active.
        """"""
        if self.o is not None:
            _signals.installHandler(self.o)
}}}

I've observed this in the wild inside a moderately complex test suite. Assistance in understanding the ""somehow"" that causes self.o to become None would be appreciated.

The following note inside _handleSignals in posixbase might be relevant since it explains one possible scenario in which related code may be executed before the event handlers are installed:
{{{
# Also reap all processes right now, in case we missed any
# signals before we installed the SIGCHLD waker/handler.
# This should only happen if someone used spawnProcess
# before calling reactor.run (and the process also exited
# already).
}}}"	defect	new	normal		core			itamar@…	branches/process-exited-errors-5151	hodgestar