pipeline.py 文件源码

def _setPgid(pid, pgid):
    """set pgid of a process, ignored exception caused by race condition
    that occurs if already set by parent or child has already existed"""
    # Should just ignore on EACCES, as to handle race condition with parent
    # and child.  However some Linux kernels (seen in 2.6.18-53) report ESRCH
    # or EPERM.  To handle this is a straight-forward way, just check that the
    # change has been made.  However, in some cases the change didn't take,
    # retrying seems to make the problem go away.
    for i in xrange(0,5):
        try:
            os.setpgid(pid, pgid)
            return
        except OSError:
            if os.getpgid(pid) == pgid:
                return
            time.sleep(0.25) # sleep for retry
    # last try, let it return an error
    os.setpgid(pid, pgid)

# FIXME: why not use pipes.quote?