linux-kernel - Re: [PATCH 1/4] irq: correct CPUMASKS

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Date:	Wed, 15 Apr 2009 12:01:05 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Cc:	Yinghai Lu <yinghai@...nel.org>, rusty@...tcorp.com.au,
	tglx@...utronix.de, hpa@...or.com, ebiederm@...ssion.com,
	garyhade@...ibm.com, lcm@...ibm.com, venkatesh.pallipadi@...el.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] irq: correct CPUMASKS_OFFSTACK typo -v2


* Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Tue, 14 Apr 2009 13:41:55 -0700
> Yinghai Lu <yinghai@...nel.org> wrote:
> 
> > irq
> 
> Speaking of which, could someone please take a look at
> http://www.gossamer-threads.com/lists/linux/kernel/1060580?do=post_view_threaded#1060580
> ?
[...]

> But try_one_irq() is running tifm_7xx1_isr() with local interrupts 
> enabled, which upsets lockdep.

It doesnt just upset lockdep, it could also cause real lockups. 
Lockdep is just the canary, the lockup is the methane explosion.

> But I suspect that the code as it stands is non-buggy. Unless the 
> interrupt can magically come back to life. In which case any 
> change we make is purely a make-lockdep-shut-up thing.

Hm, i'd suggest we go for the methane leak instead of squashing the 
canary. Which in this case would be try_one_irq() ignoring 
IRQF_DISABLED or so? Affecting (much) more ISRs than just 
tifm_7xx1_isr()?

Thomas?

	Ingo
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