From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [patch 20/47] x86: Remove useless reinitialization of irq
 descriptors
Date: Sun, 3 Oct 2010 20:26:25 +0200 (CEST)
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References: <20100930221351.682772535@linutronix.de> <20100930221740.449419120@linutronix.de> <m14od3l2th.fsf@fess.ebiederm.org>
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To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: LKML <linux-kernel@vger.kernel.org>, linux-arch@vger.kernel.org, Linus Torvalds <torvalds@osdl.org>, Andrew Morton <akpm@linux-foundation.org>, x86@kernel.org, Peter Zijlstra <peterz@infradead.org>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Paul Mundt <lethal@linux-sh.org>, Russell King <linux@arm.linux.org.uk>, David Woodhouse <dwmw2@infradead.org>, Jesse Barnes <jbarnes@virtuousgeek.org>, Yinghai Lu <yinghai@kernel.org>, Grant Likely <grant.likely@secretlab.ca>

On Sun, 3 Oct 2010, Eric W. Biederman wrote:

> Thomas Gleixner <tglx@linutronix.de> writes:
> 
> > The descriptors are already initialized in exaclty this way.
> 
> They aren't only status is initialized exactly that way.

Err.

SPARSE_IRQ=n:

struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_in_smp = {
        [0 ... NR_IRQS-1] = {
                .status = IRQ_DISABLED,
		.chip = &no_irq_chip,
                .handle_irq = handle_bad_irq,
                .depth = 1,
                .lock = __RAW_SPIN_LOCK_UNLOCKED(irq_desc->lock),
        }
};

So action == NULL and depth == 1

SPARSE_IRQ=y:

allocates with kzalloc which makes action == NULL and depth is set in
the init function to 1.

That's true for mainline and after the rework as well.

Thanks,

	tglx