Re: [libvirt] [PATCH] [RFC] nwfilter: resolve deadlock between VM operations and filter update
On 10/07/2010 09:52 AM, Daniel Veillard wrote:
On Wed, Oct 06, 2010 at 05:56:36PM -0400, Stefan Berger wrote:
> V2:
> remove the locks from qemudVMFilterRebuild& umlVMFilterRebuild
> For now I want to put this out as an RFC patch. I have tested it by
> 'stretching' the critical section after the define/undefine
> functions each lock the filter so I can (easily) concurrently
> execute another VM operation (suspend,start). That code is in this
> patch and if you want you can de-activate it. It seems to work ok
> and operations are being blocked while the update is being done.
> I still also want to verify the other assumption above that locking
> filter and qemu_domain always has a preceding qemu_driver lock.
I looked at the patch and the only thing that need to be cleaned up
is the stretching blocki below, otherwise looks fine to me.
Yes, I'll remove that.
> +if (true) {
> + fprintf(stderr,"sleep in %s\n", __FUNCTION__);
> + sleep(CRITICAL_SECTION_STRETCH);
> + fprintf(stderr,"continue in %s\n", __FUNCTION__);
> +}
> +
It would be good to have some ways to exercise all code paths
in the locking (okay error handling specific paths aside because
it's really hard), before applying.
It will take some time, but I'll try to write a TCK test that does
something like Soren was testing:
- concurrently create/destroy 2 vms
- concurrently modify their filters
- plus occasionally shoot a SIGHUP at libvirt ( if possible )
That would test some of the code paths.
Stefan