netdev - Re: [PATCH 3/4] forcedeth: napi schedule lock fix

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Message-Id: <200901271928.16783.vgusev@openvz.org>
Date:	Tue, 27 Jan 2009 19:28:16 +0300
From:	Vitaliy Gusev <vgusev@...nvz.org>
To:	Ayaz Abdulla <aabdulla@...dia.com>
Cc:	Manfred Spraul <manfred@...orfullife.com>,
	Jeff Garzik <jgarzik@...ox.com>, Andrew Morton <akpm@...l.org>,
	nedev <netdev@...r.kernel.org>
Subject: Re: [PATCH 3/4] forcedeth: napi schedule lock fix

On 10 January 2009 00:03:49 Ayaz Abdulla wrote:
> This patch fixes a potential race condition between scheduling napi and 
> completing napi poll. The call to netif_rx_schedule should be under 
> protection of the lock (as is the completion), otherwise, interrupts 
> could be masked off.

Can you explain how this issue or race can occur (interrupts can be masked off) ?

netif_rx_schedule() merely mark soft irq as waked on current CPU. So dev->poll
will not be called until irq_exit() or local_bh_enable. As nv_nic_irq() is run
under interrupt context, so napi poll will be called only during irq_exit.


> 
> Signed-off-by: Ayaz Abdulla <aabdulla@...dia.com>
> 
> 



-- 
Thank,
Vitaliy Gusev
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