Re: [PATCH] Prevent nested interrupts when the IRQ stack is near overflowing v2 [LWN.net]

From:		Linus Torvalds <torvalds-AT-linux-foundation.org>
To:		Ingo Molnar <mingo-AT-elte.hu>
Subject:		Re: [PATCH] Prevent nested interrupts when the IRQ stack is near overflowing v2
Date:		Thu, 25 Mar 2010 12:10:22 -0700 (PDT)
Cc:		Peter Zijlstra <peterz-AT-infradead.org>, Thomas Gleixner <tglx-AT-linutronix.de>, Andi Kleen <andi-AT-firstfloor.org>, x86-AT-kernel.org, LKML <linux-kernel-AT-vger.kernel.org>, jesse.brandeburg-AT-intel.com

On Thu, 25 Mar 2010, Ingo Molnar wrote:
> 
> So the patch below should at most trigger bugs in areas that need fixing 
> anyway, and i'm quite sure that under no circumstance would it cause 
> unforeseen problems in 'thousands of drivers'.

If we do this, then we should just remove all the IRQF_DISABLED code in 
kernel/irq/manage.c too, and basically make IRQF_DISABLED a clear no-op 
(still leave it around as a #define, to not break any users). 

It won't make it any harder to revert if it causes problems, and that way 
there will be no crazy dead code (and comments) left around.

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_).

		Linus

The LWN site is currently under high scraper load, so comment display has been suppressed for anonymous users. If you are a human, you may read the comments by clicking the button below:

Note: you can avoid this step in the future by logging into your LWN account.