linux-kernel - Re: [PATCH] gpio/msm-v1: re-read IRQ flags on each iteration

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Message-Id: <20120511174112.D9EEE3E0791@localhost>
Date:	Fri, 11 May 2012 11:41:12 -0600
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Linus Walleij <linus.walleij@...ricsson.com>,
	linux-kernel@...r.kernel.org
Cc:	Julia Lawall <julia.lawall@...6.fr>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH] gpio/msm-v1: re-read IRQ flags on each iteration

On Fri, 11 May 2012 14:07:12 +0200, Linus Walleij <linus.walleij@...ricsson.com> wrote:
> From: Linus Walleij <linus.walleij@...aro.org>
> 
> We have recently found a number or erroneous IRQ handlers in
> the kernel where the flag iterator loop miss IRQs that get
> raised when the loop is executing. This was spotted in the
> MSM v1 GPIO driver by Julia Lawall using this cocinelle
> snippet:
> 
> @@
> expression pending,gedr,e1;
> statement S;
> @@
> 
> *pending = readl(gedr);
> ... when != pending = e1
> while (pending) S
> 
> Reported-by: Julia Lawall <julia.lawall@...6.fr>
> Signed-off-by: Linus Walleij <linus.walleij@...aro.org>

Thanks Linus,

I'll need an ack from an msm developer before applying this.

g.

> ---
>  drivers/gpio/gpio-msm-v1.c |    6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpio/gpio-msm-v1.c b/drivers/gpio/gpio-msm-v1.c
> index 52a4d42..68ca760 100644
> --- a/drivers/gpio/gpio-msm-v1.c
> +++ b/drivers/gpio/gpio-msm-v1.c
> @@ -567,9 +567,9 @@ static void msm_gpio_irq_handler(unsigned int irq, struct irq_desc *desc)
>  
>  	for (i = 0; i < msm_gpio_count; i++) {
>  		struct msm_gpio_chip *msm_chip = &msm_gpio_chips[i];
> -		val = readl(msm_chip->regs.int_status);
> -		val &= msm_chip->int_enable[0];
> -		while (val) {
> +
> +		while (val = (readl(msm_chip->regs.int_status) &
> +			      msm_chip->int_enable[0])) {
>  			mask = val & -val;
>  			j = fls(mask) - 1;
>  			/* printk("%s %08x %08x bit %d gpio %d irq %d\n",
> -- 
> 1.7.9.2
> 

-- 
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies, Ltd.
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