linux-kernel - Re: [PATCH] Prevent nested interrupts when the IRQ stack is near overflowing v2

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Message-ID: <alpine.LFD.2.00.1003251349500.3721@i5.linux-foundation.org>
Date:	Thu, 25 Mar 2010 13:53:25 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andi Kleen <andi@...stfloor.org>, x86@...nel.org,
	LKML <linux-kernel@...r.kernel.org>, jesse.brandeburg@...el.com
Subject: Re: [PATCH] Prevent nested interrupts when the IRQ stack is near
 overflowing v2



On Thu, 25 Mar 2010, Linus Torvalds wrote:
> 
> And I just checked: even the 8250 serial driver doesn't use IRQF_DISABLED 
> any more, so doing that shouldn't cause any latency issues (sure, the 
> serial driver may interrupt another irq, but another irq can also 
> interrupt the serial driver as things stand now, so the original latency 
> issue with fast irq handlers doesn't actually work these days _anyway_).

Btw, if we really do decide that everybody is IRQF_DISABLED, that really 
should make the whole mask-and-ack issue for the irq controllers go away.

We'd still need it, but only for the very special IDE controller case and 
others who _explicitly_ re-enable interrupts. Those would really have to 
cause the irq to be masked so that we don't get issues with recursive irqs 
of the same kind.

		Linus
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