linux-kernel - Re: [RFC][PATCH] irq: remove IRQF

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Message-Id: <1236333909.7260.141.camel@pasglop>
Date:	Fri, 06 Mar 2009 21:05:09 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	lkml <linux-kernel@...r.kernel.org>,
	linux-arch <linux-arch@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC][PATCH] irq: remove IRQF_DISABLED


> No, you don't get unlimited IRQ nesting, at least not on sane archs with
> a decent PIC that does things like what I described above :-)

Note that if unlimited nesting is what you are afraid of, you can do
something along the lines of:

-        if (!(action->flags & IRQF_DISABLED))
+        if (arch_nest_irq() && !(action->flags & IRQF_DISABLED))
                local_irq_enable_in_hardirq();

With arch_nest_irq() then set to always return 0 if you want, or be
smarter and check how much stack space is left, and return 1 only if
above a reasonable threshold.

Cheers,
Ben.


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