Comment 6 for bug 1094076

Reviewed: https://review.openstack.org/18689
Committed: http://github.com/openstack/oslo-incubator/commit/ffeb0855085617095f19296770a1223cb5641d1c
Submitter: Jenkins
Branch: master

commit ffeb0855085617095f19296770a1223cb5641d1c
Author: Davanum Srinivas <email address hidden>
Date: Thu Dec 27 12:22:56 2012 -0500

    Don't rely on os.wait() blocking

    Before this fix which was included in eventlet 0.10.0:

    https://bitbucket.org/which_linden/eventlet/issue/92/eventletgreen-override-of-oswaitpid

    the os.wait() wrapper in eventlet would not block if no child processes
    had exited. This was clearly buggy behaviour and os.wait() no blocks
    correctly. However, it appears it now does not return if the parent process
    was interrupted by a signal. This means that you can't kill the parent process
    and have the child processes cleaned up gracefully.

    To avoid all these issues, switch to non-blocking wait behaviour. We use
    WNOHANG with waitpid() to poll for an exited child process and, if there
    is none, we yield to other green threads and sleep for a short period.
    This means excessive CPU usage, though, which will be tracked by
    bug #1095346.

    Check pid to avoid some unnecessary warning/info messages in the logs

    Fixes LP #1094076

    Change-Id: I783fac652376c2daa9d591403b9f4c1fe9523043