On 06/02/2012 02:12 AM, Michal Privoznik wrote:
On 01.06.2012 17:41, Eric Blake wrote:
It is possible to deadlock libvirt by having a domain with XML longer than PIPE_BUF, and by writing a hook script that closes stdin early. This is because libvirt was keeping a copy of the child's stdin read fd open, which means the write fd in the parent will never see EPIPE (remember, libvirt should always be run with SIGPIPE ignored, so we should never get a SIGPIPE signal). Since there is no error, libvirt blocks waiting for a write to complete, even though the only reader is also libvirt. The solution is to ensure that only the child can act as a reader before the parent does any writes; and then dealing with the fallout of dealing with EPIPE.
So we have now covered this case in tests. Awesome.
ACK
Thanks; pushed. -- Eric Blake eblake@redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org