linux-kernel - Re: [PATCH] virtio: remove overzealous BUG

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Message-ID: <47FA26A0.3020701@codemonkey.ws>
Date:	Mon, 07 Apr 2008 08:50:24 -0500
From:	Anthony Liguori <anthony@...emonkey.ws>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	Balaji Rao <balajirrao@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH] virtio: remove overzealous BUG_ON.

Rusty Russell wrote:
> The 'disable_cb' callback is designed as an optimization to tell the host
> we don't need callbacks now.  As it is not reliable, the debug check is
> overzealous: it can happen on two CPUs at the same time.  Document this.
> 
> Even if it were reliable, the virtio_net driver doesn't disable
> callbacks on transmit so the START_USE/END_USE debugging reentrance
> protection can be easily tripped even on UP.
> 
> Thanks to Balaji Rao for the bug report and testing.

I think the printk() in start_xmit should be removed too (or at least 
rate limited).

Regards,

Anthony Liguori
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