linux-kernel - Re: [PATCH 14/14] genirq: Mask irqs when migrating them.

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Date:	Fri, 23 Feb 2007 18:06:55 -0800
From:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org,
	Zwane Mwaikambo <zwane@...radead.org>,
	Ashok Raj <ashok.raj@...el.com>, Ingo Molnar <mingo@...e.hu>,
	"Lu, Yinghai" <yinghai.lu@....com>,
	Natalie Protasevich <protasnb@...il.com>,
	Andi Kleen <ak@...e.de>,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 14/14] genirq: Mask irqs when migrating them.

Andrew, This is a bug fix and must go in before 2.6.21.

Acked-by: Suresh Siddha <suresh.b.siddha@...el.com>

On Fri, Feb 23, 2007 at 04:46:20AM -0700, Eric W. Biederman wrote:
> 
> move_native_irqs tries to do the right thing when migrating irqs
> by disabling them.  However disabling them is a software logical
> thing, not a hardware thing.  This has always been a little flaky
> and after Ingo's latest round of changes it is guaranteed to not
> mask the apic.
> 
> So this patch fixes move_native_irq to directly call the mask and
> unmask chip methods to guarantee that we mask the irq when we
> are migrating it.  We must do this as it is required by
> all code that call into the path.
> 
> Since we don't know the masked status when IRQ_DISABLED is
> set so we will not be able to restore it.   The patch makes the code
> just give up and trying again the next time this routing is called.
> 
> Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
> ---
>  kernel/irq/migration.c |    9 ++++-----
>  1 files changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/irq/migration.c b/kernel/irq/migration.c
> index 4baa3bb..77b7acc 100644
> --- a/kernel/irq/migration.c
> +++ b/kernel/irq/migration.c
> @@ -65,12 +65,11 @@ void move_native_irq(int irq)
>  	if (likely(!(desc->status & IRQ_MOVE_PENDING)))
>  		return;
>  
> -	if (likely(!(desc->status & IRQ_DISABLED)))
> -		desc->chip->disable(irq);
> +	if (unlikely(desc->status & IRQ_DISABLED))
> +		return;
>  
> +	desc->chip->mask(irq);
>  	move_masked_irq(irq);
> -
> -	if (likely(!(desc->status & IRQ_DISABLED)))
> -		desc->chip->enable(irq);
> +	desc->chip->unmask(irq);
>  }
>  
> -- 
> 1.5.0.g53756
-
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