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

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Message-ID: <20090417115011.5c3d17e1@hskinnemoen-d830>
Date:	Fri, 17 Apr 2009 11:50:11 +0200
From:	Haavard Skinnemoen <haavard.skinnemoen@...el.com>
To:	David Miller <davem@...emloft.net>
Cc:	thomas.petazzoni@...e-electrons.com, netdev@...r.kernel.org,
	michael@...e-electrons.com
Subject: Re: [PATCH] macb: Add support of the netpoll API

David Miller wrote:
> From: Haavard Skinnemoen <haavard.skinnemoen@...el.com>
> Date: Fri, 17 Apr 2009 11:25:53 +0200
> 
> > I guess you're right -- we just have to be careful about calling
> > printk() from within the driver. But it seems a lot easier to just drop
> > the lock before dumping an error message than it is to work around that
> > disable_irq() deadlock. And if you're running with verbose debugging
> > enabled, you probably shouldn't be using netconsole anyway.  
> 
> Therefore, do you agree to add Thomas's patch as-is?

No, therefore, I'd prefer local_irq_save() :-)

When using disable_irq(), there's no way we can call printk() from the
interrupt handler ever. When using local_irq_save() we can call
printk() from the interrupt handler provided that we drop the lock
first.

And since poll_controller() ends up taking the lock in both cases, we
need to be careful about calling printk() while holding the lock
anyway. So local_irq_save() means one less thing that might kill the
driver.

Haavard
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