linux-kernel - Re: [PATCH v2 1/2] x86: skip migrating IRQF_PER_CPU irq in fixup

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Message-ID: <20110506135828.GC5500@dumpdata.com>
Date:	Fri, 6 May 2011 09:58:28 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	"Tian, Kevin" <kevin.tian@...el.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	Ian Campbell <Ian.Campbell@...citrix.com>,
	"JBeulich@...ell.com" <JBeulich@...ell.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>
Subject: Re: [PATCH v2 1/2] x86: skip migrating IRQF_PER_CPU irq in fixup_irqs

On Fri, May 06, 2011 at 02:43:36PM +0800, Tian, Kevin wrote:
> x86: skip migrating IRQF_PER_CPU irq in fixup_irqs
> 
> IRQF_PER_CPU marks a irq binding to a specific cpu, and can never be
> moved away from that cpu. So it shouldn't be migrated when fixup irqs
> to offline a cpu. Xen pvops guest is one source using IRQF_PER_CPU
  ^- are called 
> on a set of virtual interrupts. Previously no error is observed 
                                                      ^^- was
 Which ones? Can you be more specific here of which type of virtual interrupts?
 spinlock? timer? 
> because Xen event chip silently fails the set_affinity ops, and
> logically IRQF_PER_CPU should be recognized here.

OK, so what if the set_affinity ops was implemented?
> 
> Signed-off-by: Fengzhe Zhang <fengzhe.zhang@...el.com>
> Signed-off-by: Kevin Tian <kevin.tian@...el.com>
> CC: Thomas Gleixner <tglx@...utronix.de>
> CC: Ingo Molnar <mingo@...hat.com>
> CC: H. Peter Anvin <hpa@...or.com>
> CC: Ian Campbell <Ian.Campbell@...rix.com>
> CC: Jan Beulich <JBeulich@...ell.com>
> 
> --- linux-2.6.39-rc6.orig/arch/x86/kernel/irq.c	2011-05-04 10:59:13.000000000 +0800
> +++ linux-2.6.39-rc6/arch/x86/kernel/irq.c	2011-05-06 09:20:25.563963000 +0800
> @@ -249,7 +250,7 @@ void fixup_irqs(void)
>  
>  		data = irq_desc_get_irq_data(desc);
>  		affinity = data->affinity;
> -		if (!irq_has_action(irq) ||
> +		if (!irq_has_action(irq) || irqd_is_per_cpu(data) ||
>  		    cpumask_subset(affinity, cpu_online_mask)) {
>  			raw_spin_unlock(&desc->lock);
>  			continue;
> --
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