netdev - Re: [PATCH] macb: Add support of the netpoll API

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Date:	Fri, 17 Apr 2009 02:08:41 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	haavard.skinnemoen@...el.com
Cc:	thomas.petazzoni@...e-electrons.com, netdev@...r.kernel.org,
	michael@...e-electrons.com
Subject: Re: [PATCH] macb: Add support of the netpoll API

From: Haavard Skinnemoen <haavard.skinnemoen@...el.com>
Date: Fri, 17 Apr 2009 11:07:03 +0200

> David Miller wrote:
>> And in response to this Haavard explained the potential deadlock
>> (sorry I deleted that email) and suggested to use local_irq_save()
>> 
>> But that won't work either, because it doesn't prevent the interrupt
>> handler from running on other cpus, it only prevents that on the
>> local cpu.
> 
> The interrupt handler takes bp->lock. Isn't that sufficient to prevent
> it from running on other cpus?

We don't necessarily hold bp->lock here, we could be called from
the netpoll code.  Another cpu could easily hold bp->lock and be
in the middle of the interrupt handler.

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