Re: [Xen-devel] caif: Fix napi poll list corruption

[Jason Wang <jasowang@xxxxxxxxxx>]

On Mon, Dec 22, 2014 at 5:35 PM, Herbert Xu 
<herbert@xxxxxxxxxxxxxxxxxxx> wrote:
> On Mon, Dec 22, 2014 at 04:18:33PM +0800, Jason Wang wrote:
> >  btw, looks like at least caif_virtio has the same issue.
> Good catch.
>
> -- >8 --
> The commit d75b1ade567ffab085e8adbbdacf0092d10cd09c (net: less
> interrupt masking in NAPI) breaks caif.
>
> It is now required that if the entire budget is consumed when poll
> returns, the napi poll_list must remain empty.  However, like some
> other drivers caif tries to do a last-ditch check and if there is
> more work it will call napi_schedule and then immediately process
> some of this new work.  Should the entire budget be consumed while
> processing such new work then we will violate the new caller
> contract.
>
> This patch fixes this by not touching any work when we reschedule
> in caif.
>
> Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>

Thanks.
> diff --git a/drivers/net/caif/caif_virtio.c 
> b/drivers/net/caif/caif_virtio.c
> index a5fefb9..b306210 100644
> --- a/drivers/net/caif/caif_virtio.c
> +++ b/drivers/net/caif/caif_virtio.c
> @@ -257,7 +257,6 @@ static int cfv_rx_poll(struct napi_struct *napi, 
> int quota)
>         struct vringh_kiov *riov = &cfv->ctx.riov;
>         unsigned int skb_len;
>  
> -again:
>         do {
>                 skb = NULL;
>  
> @@ -322,7 +321,6 @@ exit:
>                     napi_schedule_prep(napi)) {
>                         vringh_notify_disable_kern(cfv->vr_rx);
>                         __napi_schedule(napi);
> -                       goto again;
>                 }
>                 break;
>
> Thanks,
> --
> Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

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