Subject: Re: [PATCH RFC] virtio_net: fix refill related races

From: Tejun Heo <[email-masked]>
Date: Tue, 20 Dec 2011 11:09:46 -0800

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.

-- 
tejun