linux-kernel - Re: [PATCH][RFC] x86: Fix the irq affinity in fixup

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Message-ID: <alpine.DEB.2.20.1706042158160.3517@nanos>
Date:   Sun, 4 Jun 2017 22:04:53 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Chen Yu <yu.c.chen@...el.com>
cc:     Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
        Borislav Petkov <bp@...e.de>, Len Brown <len.brown@...el.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][RFC] x86: Fix the irq affinity in fixup_cpus

On Mon, 24 Apr 2017, Chen Yu wrote:

> fixup_cpus() is to set appropriate irq affinity once the CPU
> has been brought down, however we should also adjust the
> desc->irq_common_data.affinity otherwise we will get an
> incorrect irqmask during cpu offline:
> 
> cat /proc/irq/31/smp_affinity
> 00000000,80000000
> echo 0 > /sys/devices/system/cpu/cpu31/online
> cat /proc/irq/31/smp_affinity
> 00000000,80000000
> 
> This might bring potential problems, as reported we
> saw plenty of irq flood during hibernation restore:
> do_IRQ: 1.51 No irq handler for vector
> Maybe it is due to some drivers get incorrect irq mask
> during hibernation.
> 
> Fix this by invoking the interface of irq_set_affinity_locked()
> to also update the desc->irq_common_data.affinity.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=188281
> Reported-and-tested-by: Thomas Mitterfellner <thomas@...terfellner.at>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Borislav Petkov <bp@...e.de>
> Cc: Len Brown <len.brown@...el.com>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Cc: x86@...nel.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> ---
>  arch/x86/kernel/irq.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
> index 4d8183b..a108ed2 100644
> --- a/arch/x86/kernel/irq.c
> +++ b/arch/x86/kernel/irq.c
> @@ -480,13 +480,14 @@ void fixup_irqs(void)
>  		if (!irqd_can_move_in_process_context(data) && chip->irq_mask)
>  			chip->irq_mask(data);
>  
> -		if (chip->irq_set_affinity) {
> -			ret = chip->irq_set_affinity(data, affinity, true);
> -			if (ret == -ENOSPC)
> +		ret = irq_set_affinity_locked(data, affinity, true);

This can't work. For interrupts which cannot set the affinity in normal
context irq_set_affinity_locked() will queue the interrupt to move at the
next arrival of an interrupt. So the irq stays affine to the dying
CPU.

After looking at the callsites, it's safe to change
irq_set_affinity_locked() so that it uses the direct affinity setter
function when force == true.

So we need that change first, before we can switch fixups_irqs() over.

Thanks,

	tglx