startup failure, Can't check status of PID <nnnn> from pidfile .../buildslave/twistd.pid: Operation not permitted

[Erno Kuusela]

Binary package hint: python-twisted-core

After an unclean shutdown, I got an error message like this on "buildbot start ." in the buildslave dir:

Can't check status of PID <nnnn> from pidfile .../buildslave/twistd.pid: Operation not permitted

Interestingly the pid turned out to be a thread id beloning to another process and it seems kill(2) always returns EPERM for it, even when i tried it as root from the shell...

The relevant code is around lines 74-82 of /usr/share/pyshared/twisted/scripts/_twistd_unix.py:

        try:
            os.kill(pid, 0)
        except OSError, why:
            if why[0] == errno.ESRCH:
                # The pid doesnt exists.
                log.msg('Removing stale pidfile %s' % pidfile, isError=True)
                os.remove(pidfile)
            else:
                sys.exit("Can't check status of PID %s from pidfile %s: %s" %
                         (pid, pidfile, why[1]))

and the EPERM as shown by strace:

2702 kill(1403, SIG_0) = -1 EPERM (Operation not permitted)
2702 write(2, "Can't check status of PID 1403 f"..., 107) = 107

Details per guidelines:

> 1) The release of Ubuntu you are using, via 'lsb_release -rd' or System -> About Ubuntu.

Release: 9.10

> 2) The version of the package you are using, via 'apt-cache policy packagename' or by checking in Synaptic

Source: twisted
Version: 8.2.0-3

> 3) What you expected to happen

buildbot to start

> 4) What happened instead

buildbot didn't start