linux-kernel - Re: [RFC] [PATCH] Fix misrouted interrupts deadlocks

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Date:	Fri, 10 Nov 2006 17:31:26 +0300
From:	Pavel Emelianov <xemul@...nvz.org>
To:	Ingo Molnar <mingo@...hat.com>
CC:	Andrew Morton <akpm@...l.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	mingo@...e.hu, Kirill Korotaev <dev@...nvz.org>
Subject: Re: [RFC] [PATCH] Fix misrouted interrupts deadlocks

Ingo Molnar wrote:
> On Fri, 2006-11-10 at 16:55 +0300, Pavel Emelianov wrote:
>> -                       int ok = misrouted_irq(irq);
>> +                       int ok;
>> +
>> +                       spin_unlock(&desc->lock);
>> +                       ok = misrouted_irq(irq);
>> +                       spin_lock(&desc->lock); 
> 
> your fix looks reasonable to me - it's a thinko to call misrouted_irq()
> with the descriptor lock still held. (btw., how did you find it -
> lockdep spinlock debugging or NMI watchdog?)

It was NMI watchdog who reported the deadlock. With lockdep
turned on it wouldn't be caught - local_irq_enable_in_hardirq()
is nothing but a "do { } while (0)" if CONFIG_LOCKDEP=y :)

The second issue (with 2 cpus involved) was discovered
by code examining.

> Acked-by: Ingo Molnar <mingo@...hat.com>
> 
> 	Ingo
> 
> -
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