linux-kernel - Re: [PATCH] genirq: Set initial default irq affinity to just CPU0

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Message-Id: <8440180C-A3B1-4436-9CDF-C6BA9A01F8CD@kernel.crashing.org>
Date:	Mon, 27 Oct 2008 08:43:11 -0500
From:	Kumar Gala <galak@...nel.crashing.org>
To:	benh@...nel.crashing.org
Cc:	David Miller <davem@...emloft.net>, akpm@...l.org,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
	torvalds@...l.org, maxk@...lcomm.com, tglx@...utronix.de
Subject: Re: [PATCH] genirq: Set initial default irq affinity to just CPU0


On Oct 26, 2008, at 1:33 AM, Benjamin Herrenschmidt wrote:

> On Sat, 2008-10-25 at 21:04 -0700, David Miller wrote:
>> But back to my original wonder, since I've always tipped off of this
>> generic IRQ layer cpu mask, when was it ever defaulting to zero
>> and causing the behvaior your powerpc guys actually want? :-)
>
> Well, I'm not sure what Kumar wants. Most powerpc SMP setups actually
> want to spread interrupts to all CPUs, and those who can't tend to  
> just
> not implement set_affinity... So Kumar must have a special case of  
> MPIC
> usage here on FSL platforms.
>
> In any case, the platform limitations should be dealt with there or  
> the
> user could break it by manipulating affinity via /proc anyway.
>
> By yeah, I do expect default affinity to be all CPUs and in fact, I  
> even
> have an -OLD- comment in the code that says
>
> 	/* let the mpic know we want intrs. default affinitya is  
> 0xffffffff ...

While we have the comment the code appears not to really follow it.   
We appear to write 1 << hard_smp_processor_id().

- k
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