netdev - Re: [PATCHv3 net] xen-netback: fix race between napi

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Message-ID: <20140516112157.GI18551@zion.uk.xensource.com>
Date:	Fri, 16 May 2014 12:21:57 +0100
From:	Wei Liu <wei.liu2@...rix.com>
To:	David Vrabel <david.vrabel@...rix.com>
CC:	<netdev@...r.kernel.org>, <xen-devel@...ts.xenproject.org>,
	Ian Campbell <ian.campbell@...rix.com>,
	Wei Liu <wei.liu2@...rix.com>
Subject: Re: [PATCHv3 net] xen-netback: fix race between napi_complete() and
 interrupt handler

On Fri, May 16, 2014 at 12:20:02PM +0100, David Vrabel wrote:
> When the NAPI budget was not all used, xenvif_poll() would call
> napi_complete() /after/ enabling the interrupt.  This resulted in a
> race between the napi_complete() and the napi_schedule() in the
> interrupt handler.  The use of local_irq_save/restore() avoided by
> race iff the handler is running on the same CPU but not if it was
> running on a different CPU.
> 
> Fix this properly by calling napi_complete() before reenabling
> interrupts (in the xenvif_napi_schedule_or_enable_irq() call).
> 
> Signed-off-by: David Vrabel <david.vrabel@...rix.com>
> Acked-by: Wei Lui <wei.lui2@...rix.com>

It's "Liu". ;-)
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