linux-kernel - Re: [PATCH RESEND] x86/fixup_irq: Clean the offlining CPU from the irq affinity mask

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Date:	Wed, 26 Sep 2012 14:32:38 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	"Liu, Chuansheng" <chuansheng.liu@...el.com>
CC:	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"yanmin_zhang@...ux.intel.com" <yanmin_zhang@...ux.intel.com>
Subject: Re: [PATCH RESEND] x86/fixup_irq: Clean the offlining CPU from the
 irq affinity mask

On 09/26/2012 02:26 PM, Liu, Chuansheng wrote:
>> A return value of 0 and 1 are acceptable. So this check isn't correct.
>>
>> Regards,
>> Srivatsa S. Bhat
>>
> Which case value 1 is acceptable, could you share? Thanks.

I can see the following in include/linux/irq.h:

/*
 * Return value for chip->irq_set_affinity()
 *
 * IRQ_SET_MASK_OK      - OK, core updates irq_data.affinity
 * IRQ_SET_MASK_NOCPY   - OK, chip did update irq_data.affinity
 */
enum {
        IRQ_SET_MASK_OK = 0,
        IRQ_SET_MASK_OK_NOCOPY,
};

And see some of those ->irq_set_affinity() implementations at various
places.

Regards,
Srivatsa S. Bhat

> 
>> OMG, why did you drop the other hunk which cleared the cpu *before*
>> invoking ->irq_set_affinity()? IMO, altering irq affinity involves more work
>> than just altering the mask; that's why you have that ->irq_set_affinity()
>> function. So, if you alter the mask *after* calling ->irq_set_affinity(),
>> its not right..
> Sorry the mistake, will update.
> 

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