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To: Andi Kleen <andi@firstfloor.org>
Cc: Ingo Molnar <mingo@elte.hu>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Thomas Gleixner <tglx@linutronix.de>, x86@kernel.org,
       LKML <linux-kernel@vger.kernel.org>, jesse.brandeburg@intel.com
Subject: Re: [PATCH] Prevent nested interrupts when the IRQ stack is near overflowing v2
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From: ebiederm@xmission.com (Eric W. Biederman)
Date: Thu, 25 Mar 2010 21:55:19 -0700
In-Reply-To: <20100325182702.GR20695@one.firstfloor.org> (Andi Kleen's message of "Thu\, 25 Mar 2010 19\:27\:02 +0100")
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Andi Kleen <andi@firstfloor.org> writes:

>> I think the patch as posted solves a real problem, but also perpetuates a bad 
>> situation.
>> 
>> At minimum we should print a (one-time) warning that some badness occured. 
>> That would push us either in the direction of improving drivers, or towards 
>> improving the generic code.
>
> What should a driver do to prevent that? I don't see what it could do
> short of castrating itself (like refusing to use multiple ports)
> As Linus says the driver doesn't know if setting IRQF_DISABLED is safe.

As an aside this is happening on MSI irqs.  They can never be shared.
So in fact the driver can know it is safe.

Should we perhaps make all MSI irqs automatically set IRQF_DISABLED?

Eric