To: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: "Pallipadi\, Venkatesh" <venkatesh.pallipadi@intel.com>,
       Shaohua Li <shaohua.li@intel.com>, Gary Hade <garyhade@us.ibm.com>,
       mingo@elte.hu, mingo@redhat.com, tglx@linutronix.de, hpa@zytor.com,
       x86@kernel.org, linux-kernel@vger.kernel.org, lcm@us.ibm.com
References: <20090408210735.GD11159@us.ibm.com>
	<m1r601fg9l.fsf@fess.ebiederm.org> <20090410200919.GA7242@us.ibm.com>
	<m1tz4wcgm8.fsf@fess.ebiederm.org>
	<86802c440904110051p3e071f8etd0792702c08d9ec5@mail.gmail.com>
From: ebiederm@xmission.com (Eric W. Biederman)
Date: Sat, 11 Apr 2009 04:01:44 -0700
In-Reply-To: <86802c440904110051p3e071f8etd0792702c08d9ec5@mail.gmail.com> (Yinghai Lu's message of "Sat\, 11 Apr 2009 00\:51\:46 -0700")
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Subject: Re: [PATCH 2/3] [BUGFIX] x86/x86_64: fix CPU offlining triggered  inactive device IRQ interrruption
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Yinghai Lu <yhlu.kernel@gmail.com> writes:

> commit 932775a4ab622e3c99bd59f14cc7d96722f79501
> Author: venkatesh.pallipadi@intel.com <venkatesh.pallipadi@intel.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@intel.com>
>     Signed-off-by: Shaohua Li <shaohua.li@intel.com>
>     Signed-off-by: Ingo Molnar <mingo@elte.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

If the goal is moving MSIs, we should modify the msi code to be safe
in process context and to set IRQ_MOVE_PCNTXT.

The only reason we migrate MSIs in interrupt context today is that there
wasn't infrastructure for support migration both in interrupt context
and outside of it.

Eric

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