From mboxrd@z Thu Jan  1 00:00:00 1970
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [RFC][PATCH] irq: remove IRQF_DISABLED
Date: Fri, 06 Mar 2009 21:05:09 +1100
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To: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>, Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>, lkml <linux-kernel@vger.kernel.org>, linux-arch <linux-arch@vger.kernel.org>, Andrew Morton <akpm@linux-foundation.org>


> 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.