netdev - Re: [PATCH] igb: completely disable interrupts during netpoll

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Message-ID: <20080626024927.GC32408@gospo.rdu.redhat.com>
Date:	Wed, 25 Jun 2008 22:49:27 -0400
From:	Andy Gospodarek <andy@...yhouse.net>
To:	David Miller <davem@...emloft.net>
Cc:	andy@...yhouse.net, jeffrey.t.kirsher@...el.com,
	jesse.brandeburg@...el.com, bruce.w.allan@...el.com,
	john.ronciak@...el.com, netdev@...r.kernel.org
Subject: Re: [PATCH] igb: completely disable interrupts during netpoll

On Wed, Jun 25, 2008 at 03:27:51PM -0700, David Miller wrote:
> From: Andy Gospodarek <andy@...yhouse.net>
> Date: Wed, 25 Jun 2008 10:15:11 -0400
> 
> > 
> > Globally disable the interrupt during netpoll rather than simply
> > disabling it on the hardware.  This will ensure all pending operations
> > are complete and no more will execute.  I've seen reports of deadlocks
> > with the current driver and this patch resolves them.
> 
> I don't want to see network drivers start getting into the habit
> of doing this.  This operation could be extremely expensive with
> certain IRQ controllers.
> 
> It's better to have a good understanding of why the deadlocks
> happen, and this was decidedly missing from your commit message.
> 

I thought this was a pretty common problem that cannot simply be solved
with a call to synchronize_irq since you might get one that pops on
another CPU and doesn't set the in-progress bit before your
synchronize_irq call completes?

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