Re: [PATCH] virtio_net: enable tx after resuming from suspend

[Jason Wang]

On 2018å10æ11æ 18:22, ake wrote:
> On 2018å10æ11æ 18:44, Jason Wang wrote:
> > On 2018å10æ11æ 15:51, Ake Koomsin wrote:
> > > commit 713a98d90c5e ("virtio-net: serialize tx routine during reset")
> > > disabled the virtio tx before going to suspend to avoid a use after free.
> > > However, after resuming, it causes the virtio_net device to lose its
> > > network connectivity.
> > >
> > > To solve the issue, we need to enable tx after resuming.
> > >
> > > Fixes commit 713a98d90c5e ("virtio-net: serialize tx routine during
> > > reset")
> > > Signed-off-by: Ake Koomsin <ake@xxxxxxxxxx>
> > > ---
> > >  Â drivers/net/virtio_net.c | 1 +
> > >  Â 1 file changed, 1 insertion(+)
> > >
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index dab504ec5e50..3453d80f5f81 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -2256,6 +2256,7 @@ static int virtnet_restore_up(struct
> > > virtio_device *vdev)
> > >  ÂÂÂÂÂ }
> > >  Â ÂÂÂÂÂ netif_device_attach(vi->dev);
> > > +ÂÂÂ netif_start_queue(vi->dev);
> > I believe this is duplicated with netif_tx_wake_all_queues() in
> > netif_device_attach() above?
> Thank you for your review.
>
> If both netif_tx_wake_all_queues() and netif_start_queue() result in
> clearing __QUEUE_STATE_DRV_XOFF, then is it possible that some
> conditions in netif_device_attach() is not satisfied?

Yes, maybe. One case I can see now is when the device is down, in this 
case netif_device_attach() won't try to wakeup the queue.

>   Without
> netif_start_queue(), the virtio_net device does not resume properly
> after waking up.

How do you trigger the issue? Just do suspend/resume?

> Is it better to report this as a bug first?

Nope, you're very welcome to post patch directly.

> If I am to do more
> investigation, what areas should I look into?

As you've figured out, you can start with why netif_tx_wake_all_queues() 
were not executed?

(Btw, does the issue disappear if you move netif_tx_disable() under the 
check of netif_running() in virtnet_freeze_down()?)

Thanks

> Best Regards
> Ake Koomsin