On Wed, May 04, 2011 at 08:18:04AM -0700, Shirley Ma wrote:
> > > +void vhost_zerocopy_callback(struct sk_buff *skb)
> > > +{
> > > + int idx = skb_shinfo(skb)->ubuf.desc;
> > > + struct vhost_virtqueue *vq = skb_shinfo(skb)->ubuf.arg;
> > > +
> > > + /* set len = 1 to mark this desc buffers done DMA */
> > > + vq->heads[idx].len = 1;
> > > +}
> >
> > So any kind of callback like that, that goes into the skb,
> > will be racy wrt module unloading because module can go away
> > after you mark dma done and before this function returns.
> > Solution is to have a core function that does the
> > final signalling (e.g. sock_wfree is in core).
> > Would be nice to fix, even though this race is
> > completely theoretical, I don't believe it will
> > trigger in practice.
>
> I run lots of stress tests, and never hit this.
>
> But I can try to fix it.
Yes, it's a theoretical thing. Nice to have but not a must.
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