linux-kernel - Re: [PATCH v4 09/12] virtio: net: Add freeze, restore handlers to support S4

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Date:	Wed, 7 Dec 2011 13:46:03 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Amit Shah <amit.shah@...hat.com>
Cc:	Virtualization List <virtualization@...ts.linux-foundation.org>,
	Rusty Russell <rusty@...tcorp.com.au>, levinsasha928@...il.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 09/12] virtio: net: Add freeze, restore handlers to
 support S4

On Wed, Dec 07, 2011 at 04:05:29PM +0530, Amit Shah wrote:
> On (Wed) 07 Dec 2011 [12:28:24], Michael S. Tsirkin wrote:
> > On Wed, Dec 07, 2011 at 01:18:47AM +0530, Amit Shah wrote:
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index 697a0fc..1378f3c 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -1151,6 +1151,38 @@ static void __devexit virtnet_remove(struct virtio_device *vdev)
> > >  	free_netdev(vi->dev);
> > >  }
> > >  
> > > +#ifdef CONFIG_PM
> > > +static int virtnet_freeze(struct virtio_device *vdev)
> > > +{
> > > +	struct virtnet_info *vi = vdev->priv;
> > > +
> > > +	netif_device_detach(vi->dev);
> > > +	if (netif_running(vi->dev))
> > > +		napi_disable(&vi->napi);
> > > +
> > 
> > Could refill_work still be running at this point?
> 
> Yes, it could.  So moving the cancel_delayed_work_sync() before
> disabling napi would work fine?

No, because napi poll can schedule that.
Further, refill can reschedule itself.

It also looks like we have a bug in virtio net cleanup now:
cancel_delayed_work_sync is called after unregister, so
it will be calling napi API on an invalid device.
And, if it schedules itself it will run after device is gone.

I think we need some locking to fix this.

>  Anything else that might similar treatment?
> 
> 		Amit



-- 
MST
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