linux-kernel - Re: [PATCH 2/3] [BUGFIX] x86/x86_64: fix CPU offlining triggered inactive device IRQ interrruption

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Date:	Sat, 11 Apr 2009 00:51:46 -0700
From:	Yinghai Lu <yhlu.kernel@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	Shaohua Li <shaohua.li@...el.com>
Cc:	Gary Hade <garyhade@...ibm.com>, mingo@...e.hu, mingo@...hat.com,
	tglx@...utronix.de, hpa@...or.com, x86@...nel.org,
	linux-kernel@...r.kernel.org, lcm@...ibm.com
Subject: Re: [PATCH 2/3] [BUGFIX] x86/x86_64: fix CPU offlining triggered 
	inactive device IRQ interrruption

On Fri, Apr 10, 2009 at 3:02 PM, Eric W. Biederman
<ebiederm@...ssion.com> wrote:
> Gary Hade <garyhade@...ibm.com> writes:
>
> It looks like some additional bugs have slipped in since last I looked.
>
> set_irq_affinity does this:
> ifdef CONFIG_GENERIC_PENDING_IRQ
>        if (desc->status & IRQ_MOVE_PCNTXT || desc->status & IRQ_DISABLED) {
>                cpumask_copy(desc->affinity, cpumask);
>                desc->chip->set_affinity(irq, cpumask);
>        } else {
>                desc->status |= IRQ_MOVE_PENDING;
>                cpumask_copy(desc->pending_mask, cpumask);
>        }
> #else
>
> That IRQ_DISABLED case is a software state and as such it has nothing to
> do with how safe it is to move an irq in process context.
>

commit 932775a4ab622e3c99bd59f14cc7d96722f79501
Author: venkatesh.pallipadi@...el.com <venkatesh.pallipadi@...el.com>
Date:   Fri Sep 5 18:02:15 2008 -0700

    x86: HPET_MSI change IRQ affinity in process context when it is disabled

    Change the IRQ affinity in the process context when the IRQ is disabled.

    Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
    Signed-off-by: Shaohua Li <shaohua.li@...el.com>
    Signed-off-by: Ingo Molnar <mingo@...e.hu>

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index ddc9568..ad2ce72 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -87,10 +87,11 @@ int irq_set_affinity(unsigned int irq, cpumask_t cpumask)
                return -EINVAL;

 #ifdef CONFIG_GENERIC_PENDING_IRQ
-       if (desc->status & IRQ_MOVE_PCNTXT) {
+       if (desc->status & IRQ_MOVE_PCNTXT || desc->status & IRQ_DISABLED) {
                unsigned long flags;

                spin_lock_irqsave(&desc->lock, flags);
+               desc->affinity = cpumask;
                desc->chip->set_affinity(irq, cpumask);
                spin_unlock_irqrestore(&desc->lock, flags);
        } else
--
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