linux-kernel - Re: [BISECTED][REGRESSION] Loading Hyper-V network drivers is racy in 3.14+ on Hyper-V 2012 R2

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Date:	Mon, 14 Jul 2014 22:30:32 +0100
From:	Sitsofe Wheeler <sitsofe@...il.com>
To:	Haiyang Zhang <haiyangz@...rosoft.com>
Cc:	KY Srinivasan <kys@...rosoft.com>,
	"David S. Miller" <davem@...emloft.net>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [BISECTED][REGRESSION] Loading Hyper-V network drivers is racy
 in 3.14+ on Hyper-V 2012 R2

On Fri, Jul 11, 2014 at 03:25:11PM +0000, Haiyang Zhang wrote:
> 
> > -----Original Message-----
> > From: Sitsofe Wheeler [mailto:sitsofe@...il.com]
> > Sent: Friday, July 11, 2014 1:53 AM
> > To: Haiyang Zhang
> > Cc: KY Srinivasan; David S. Miller; devel@...uxdriverproject.org; linux-
> > kernel@...r.kernel.org; netdev@...r.kernel.org
> > Subject: Re: [BISECTED][REGRESSION] Loading Hyper-V network drivers is
> > racy in 3.14+ on Hyper-V 2012 R2
> 
> > Oops that should have been
> > https://bugzilla.kernel.org/attachment.cgi?id=142351 (either way it's
> > information linked off
> > https://bugzilla.kernel.org/show_bug.cgi?id=78771 ).
> 
> Thanks for the dmesg. By looking at it, seems the netvsc driver was
> loaded properly, and 2 NICs are up, one NIC is down (probably not set
> to connected in HyperV manager?). Or, this dmesg wasn't the one when
> bug happens?

This was a dmesg where the bug did happen and your first guess is right
- there are 3 NICs but only the first two are connected and the last is
set to "Not connected" in Hyper-V Manager.

> Since you found the commit b679ef73edc is related to this problem,
> could you do a simple test:
>   Reduce the receive buffer size back to 2MB, like below, then re-test
>   it, see if the problem goes away?
> 	drivers/net/hyperv/hyperv_net.h
> 	#define NETVSC_RECEIVE_BUFFER_SIZE		(1024*1024*2)	/* 2MB */

After doing this I was able to reach over 900 reboots where the network
connected properly.

-- 
Sitsofe | http://sucs.org/~sits/
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