On Tue, Dec 20, 2011 at 11:09:46AM -0800, Tejun Heo wrote: > Hello, Michael. > > On Tue, Dec 20, 2011 at 09:09:08PM +0200, Michael S. Tsirkin wrote: > > Another question, wanted to make sure: > > virtnet_poll does schedule_delayed_work(&vi->refill, 0); > > separately refill work itself also does > > schedule_delayed_work(&vi->refill, HZ/2); > > If two such events happen twice, on different CPUs, we are still guaranteed > > the work will only run once, right? > > No, it's not. Normal workqueues only guarantee non-reentrance on > local CPU. If you want to guarantee that only one instance of a given > item is executing across all CPUs, you need to use the nrt workqueue. > > Thanks. Hmm, in that case it looks like a nasty race could get triggered, with try_fill_recv run on multiple CPUs in parallel, corrupting the linked list within the vq. Using the mutex as my patch did will fix that naturally, as well. Rusty, am I missing something? > -- > tejun _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
