[Python-Dev] mysterious hangs in socket code

Barry A. Warsaw barry@python.org
Tue, 3 Sep 2002 21:35:27 -0400

>>>>> "JH" == Jeremy Hylton <jeremy@alum.mit.edu> writes:

    JH> I've been running a small, multi-threaded program to retrieve
    JH> web pages today.  The entire program appears to hang when I
    JH> perform a slow DNS operation, even there is no
    JH> application-level coordinate between the threads.

Does strace'ing the program provide any clues?  Also, if it's a DNS
thing, you should definitely try to run it on different networks (or
at least pointing to different DNS servers).

<type> <type>

Ok, running it now as "strace python foo.py" (Py2.2.1) and I see
similar behavior.  It seems to mostly be sitting in select() calls and
rt_sigsuspend() which I guess is a wrapper around sigsuspend().  When
I use Python 2.1.3 I never see it sit in sigsuspend().