Re: [PATCH v3 09/11] virtio: net: Add freeze, restore handlers to support S4

Michael S. Tsirkin
2011-11-17T12:31:46Z

On Thu, Nov 17, 2011 at 05:57:06PM +0530, Amit Shah wrote:
> On (Thu) 17 Nov 2011 [14:19:09], Michael S. Tsirkin wrote:
> > On Thu, Nov 17, 2011 at 05:27:40PM +0530, Amit Shah wrote:
>
> > > +#ifdef CONFIG_PM
> > > +static int virtnet_freeze(struct virtio_device *vdev)
> > > +{
> > > + struct virtnet_info *vi = vdev->priv;
> > > +
> > > + netif_device_detach(vi->dev);
> > > + remove_vq_common(vi);
> >
> > This stops TX in progress, if any, but not RX
> > which might use the RX VQ. Then remove_vq_common
> > might delete this VQ while it's still in use.
> >
> > So I think we need to call something like napi_disable.
> > However, the subtle twist is that we need to call that
> > *after interrupts have been disabled*.
> > Otherwise we might schedule another napi callback.
>
> resetting the vqs will mean the host won't pass us any data in the
> vqs. Plus we're removing the vqs altogether. Also, we're disabling
> the pci device in virtio_pci.c, so all of these actions will take
> care of that, isn't it?

I don't think so.

> In addition, once the vqs are taken off, there's no chance for any
> other rx to happen, so napi_disable() after plugging off vqs doesn't
> make sense.
>
> Amit

Yes but napi might have been scheduled before remove_vq_common was
called, and run afterwards.

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