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

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Message-Id: <20140516.162759.1966063113769346927.davem@davemloft.net>
Date:	Fri, 16 May 2014 16:27:59 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	david.vrabel@...rix.com
Cc:	wei.liu2@...rix.com, netdev@...r.kernel.org,
	xen-devel@...ts.xenproject.org, ian.campbell@...rix.com
Subject: Re: [PATCHv3 net] xen-netback: fix race between napi_complete()
 and interrupt handler

From: David Vrabel <david.vrabel@...rix.com>
Date: Fri, 16 May 2014 12:26:04 +0100

> Dave, can you take this instead:
> 
> 8<--------------
> xen-netback: fix race between napi_complete() and interrupt handler
> 
> 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 Liu <wei.liu2@...rix.com>
> Acked-by: Ian Campbell <ian.campbell@...rix.com>

Applied, thanks everyone.
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