linux-kernel - RE: [hyperv] BUG at drivers/hv/channel.c:462 while changing MTU

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Message-ID: <cf94fd58947d4c5aa6d0d369c1126d7f@BY2PR0301MB0711.namprd03.prod.outlook.com>
Date:	Mon, 25 Aug 2014 17:34:27 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Dan Carpenter <dan.carpenter@...cle.com>,
	Sitsofe Wheeler <sitsofe@...il.com>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jason Wang <jasowang@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Daniel Borkmann <dborkman@...hat.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	Haiyang Zhang <haiyangz@...rosoft.com>
Subject: RE: [hyperv] BUG at drivers/hv/channel.c:462 while changing MTU



> -----Original Message-----
> From: Dan Carpenter [mailto:dan.carpenter@...cle.com]
> Sent: Monday, August 25, 2014 2:37 AM
> To: Sitsofe Wheeler
> Cc: KY Srinivasan; Greg Kroah-Hartman; Jason Wang; linux-
> kernel@...r.kernel.org; David S. Miller; Daniel Borkmann;
> netdev@...r.kernel.org; devel@...uxdriverproject.org; Haiyang Zhang
> Subject: Re: [hyperv] BUG at drivers/hv/channel.c:462 while changing MTU
> 
> The code here is:
> 
> drivers/hv/channel.c
>    460          BUG_ON(ret != 0);
>    461          t = wait_for_completion_timeout(&info->waitevent, 5*HZ);
>    462          BUG_ON(t == 0);
> 
> So it calls BUG_ON() if the teardown takes more than 5 seconds.  It's most
> likely that there is a race condition somewhere.  It's also possible that it's just
> taking longer than 5 seconds for some odd reason and the bug would go
> away if we raised it to 60 seconds.
> 
> BUG_ON() after 5 seconds seems like a very aggressive thing.

Dan,

I am going to audit all BUG_ON() instances.

Thanks,

K. Y
> 
> regards,
> dan carpenter

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