linux-kernel - Re: [PATCH] irqchip/atmel-aic: Fix potential deadlock in ->xlate()

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Date:   Tue, 13 Sep 2016 14:55:20 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Boris Brezillon <boris.brezillon@...e-electrons.com>
cc:     Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>,
        Nicolas Ferre <nicolas.ferre@...el.com>,
        Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        linux-kernel@...r.kernel.org, stable@...nel.vger.org
Subject: Re: [PATCH] irqchip/atmel-aic: Fix potential deadlock in ->xlate()

On Tue, 13 Sep 2016, Boris Brezillon wrote:

> aic5_irq_domain_xlate() and aic_irq_domain_xlate() take the generic chip
> lock without disabling interrupts, which can lead to a deadlock if an
> interrupt occurs while the lock is held in one of these functions.
> 
> Replace irq_gc_{lock,unlock}() calls by
> raw_spin_{lock_irqsave,unlock_irqrestore}() ones to prevent this bug from
> happening.
> 
> Signed-off-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
> Fixes: b1479ebb7720 ("irqchip: atmel-aic: Add atmel AIC/AIC5 drivers")
> Cc: <stable@...nel.vger.org>
> ---
>  drivers/irqchip/irq-atmel-aic.c  | 5 +++--
>  drivers/irqchip/irq-atmel-aic5.c | 5 +++--
>  2 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-atmel-aic.c b/drivers/irqchip/irq-atmel-aic.c
> index 112e17c2768b..447a8b0f1395 100644
> --- a/drivers/irqchip/irq-atmel-aic.c
> +++ b/drivers/irqchip/irq-atmel-aic.c
> @@ -176,6 +176,7 @@ static int aic_irq_domain_xlate(struct irq_domain *d,
>  {
>  	struct irq_domain_chip_generic *dgc = d->gc;
>  	struct irq_chip_generic *gc;
> +	unsigned long flags;
>  	unsigned smr;
>  	int idx;
>  	int ret;
> @@ -194,11 +195,11 @@ static int aic_irq_domain_xlate(struct irq_domain *d,
>  
>  	gc = dgc->gc[idx];
>  
> -	irq_gc_lock(gc);
> +	raw_spin_lock_irqsave(&gc->lock, flags);

Please provide a primitive, i.e. irq_gc_lock_irqsave(), for it.

Thanks,

	tglx