linux-kernel - RE: hv_netvsc: WARNING in softirq.c

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Message-ID: <4147bb5a7cf547c19c6a5a6b459a957d@DFM-DB3MBX15-06.exchange.corp.microsoft.com>
Date:	Wed, 6 Mar 2013 22:45:11 +0000
From:	Haiyang Zhang <haiyangz@...rosoft.com>
To:	Richard Genoud <richard.genoud@...il.com>
CC:	KY Srinivasan <kys@...rosoft.com>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: hv_netvsc: WARNING in softirq.c

> -----Original Message-----
> From: Richard Genoud [mailto:richard.genoud@...il.com]
> Sent: Friday, March 01, 2013 3:39 AM
> To: Haiyang Zhang
> Cc: KY Srinivasan; devel@...uxdriverproject.org; netdev@...r.kernel.org;
> linux-kernel@...r.kernel.org
> Subject: Re: hv_netvsc: WARNING in softirq.c
> 
> 2013/2/28 Haiyang Zhang <haiyangz@...rosoft.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

Download attachment "net_stat_warn_test.patch" of type "application/octet-stream" (562 bytes)