RE: hv_netvsc: WARNING in softirq.c

[Haiyang Zhang <haiyangz@microsoft.com>]

[-- Attachment #1: Type: text/plain, Size: 1424 bytes --]



> -----Original Message-----
> From: Richard Genoud [mailto:richard.genoud@gmail.com]
> Sent: Friday, March 01, 2013 3:39 AM
> To: Haiyang Zhang
> Cc: KY Srinivasan; devel@linuxdriverproject.org; netdev@vger.kernel.org;
> linux-kernel@vger.kernel.org
> Subject: Re: hv_netvsc: WARNING in softirq.c
> 
> 2013/2/28 Haiyang Zhang <haiyangz@microsoft.com>:
> > We will look into this. And further info around the time will also be
> helpful.
> >
> > Thanks,
> > - Haiyang
> 
> The only thing the admin sys could think about is a rsync process
> between the windows host and ANOTHER linux guest that ends at 22h30
> more or less.
> (the other linux guest is a debian 6, without any HV driver)

I have found a simple way to reproduce this kind of warning:
1) reboot the VM (because this warning can be displayed only once.)
2) login to the host and open the VM [Settings]
3) Temporarily change the Network adapter's option [Virtual Switch] to "Not connected".
4) run dmesg, you should see the warning.

The reason for the warning is -- netif_tx_disable() is called when the NIC
is disconnected. And it's called within irq context. netif_tx_disable()
calls local_bh_enable() which displays warning if in irq.

The fix is to remove the unnecessary netif_tx_disable() in the netvsc_linkstatus_callback().
I attached a patch. Would you like to test it on your side as well?

Thanks,
- Haiyang


[-- Attachment #2: net_stat_warn_test.patch --]
[-- Type: application/octet-stream, Size: 562 bytes --]

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 5f85205..8341b62 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -241,13 +241,11 @@ void netvsc_linkstatus_callback(struct hv_device *device_obj,
 
 	if (status == 1) {
 		netif_carrier_on(net);
-		netif_wake_queue(net);
 		ndev_ctx = netdev_priv(net);
 		schedule_delayed_work(&ndev_ctx->dwork, 0);
 		schedule_delayed_work(&ndev_ctx->dwork, msecs_to_jiffies(20));
 	} else {
 		netif_carrier_off(net);
-		netif_tx_disable(net);
 	}
 }