Deadlock during remote update

Hi,

We have a cron job that runs remote update on a number of repositories. Sometimes, the processes deadlock and we have to go -TERM them. Here's a breakdown of what state the processes end up in when the deadlock happens, from one of our production systems yesterday:

31629 git --git-dir=/var/lib/jeepyb/openstack/nova/.git --work-tree=/var/lib/jeepyb/openstack/nova remote update --prune
    wait4'ing for 31630
31630 git fetch --prune --multiple --all
    wait4'ing for 31637
31637 git fetch --append --prune upstream
    waiting for read from pipe:[170381707] (fd 25)
31638 git-remote-https upstream https://git.openstack.org/openstack/nova
    has pipe:[170381707] (fd 1), waiting for read from pipe:[170384472]
31642 git fetch-pack --stateless-rpc --lock-pack --include-tag --thin --no-progress https://git.openstack.org/openstack/nova/  efs/heads/master
    has pipe:[170384472] (fd 1), waiting for read from pipe:[170384471] (fd 0) which fd 7 on 31638

31638 and 31642 are both waiting to read from a pipe that the other has, and isn't writing to.

This is git version 1.7.9.5, OS is ubuntu precise.

Any ideas, or any way I can get more useful info?

Thanks, Mike