linux-kernel - Re: Question related to patch: x86/irq: Remove x86_io_apic_ops.set

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Date:	Tue, 8 Sep 2015 17:21:18 +0300
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Jiang Liu <jiang.liu@...ux.intel.com>,
	jarkko.nikula@...ux.intel.com, linux-kernel@...r.kernel.org
Subject: Re: Question related to patch: x86/irq: Remove
 x86_io_apic_ops.set_affinity and related interfaces

On Tue, Sep 08, 2015 at 04:02:29PM +0200, Thomas Gleixner wrote:
> On Tue, 8 Sep 2015, Mika Westerberg wrote:
> > It says that there are no users for x86_io_apic_ops.set_affinity but then
> > it does this:
> > 
> > -               x86_io_apic_ops.set_affinity(idata, mask, false);
> > +               irq_set_affinity(irq, mask);
> > 
> > The difference is that x86_io_apic_ops.set_affinity() programs affinity
> > directly to the hardware (if I understand it right) but irq_set_affinity()
> > calls irqd_set_move_pending() which defers programming the hardware later.
> > 
> > Now when an interrupt triggers we end up calling irq_move_masked_irq() with
> > unlocked descriptor.
> > 
> > Without the above change we never do that and the crash does not happen.
> 
> Right. Patch below should fix that issue.
> 
> Thanks,
> 
> 	tglx
> 
> diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
> index 38a76f826530..d2ea50c5e936 100644
> --- a/arch/x86/kernel/apic/io_apic.c
> +++ b/arch/x86/kernel/apic/io_apic.c
> @@ -2522,6 +2522,7 @@ void __init setup_ioapic_dest(void)
>  	int pin, ioapic, irq, irq_entry;
>  	const struct cpumask *mask;
>  	struct irq_data *idata;
> +	struct irq_chip *chip;
>  
>  	if (skip_ioapic_setup == 1)
>  		return;
> @@ -2545,9 +2546,9 @@ void __init setup_ioapic_dest(void)
>  		else
>  			mask = apic->target_cpus();
>  
> -		irq_set_affinity(irq, mask);
> +		chip = irq_data_get_chip(idata);

There seems to be no irq_data_get_chip() helper in current mainline. So
I replaced this with:

		chip = idata->chip;

> +		chip->irq_set_affinity(idata, mask, false);
>  	}
> -
>  }
>  #endif

With the above change the patch fixes the problem, thanks!

Tested-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
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