linux-kernel - Re: [PATCH -next] hrtimer: Fix hang seen if tick_init

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Message-ID: <20150822142550.254aec3a@redhat.com>
Date:	Sat, 22 Aug 2015 14:25:50 -0700
From:	Luiz Capitulino <lcapitulino@...hat.com>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] hrtimer: Fix hang seen if tick_init_highres()
 failed

On Sat, 22 Aug 2015 01:10:47 -0700
Guenter Roeck <linux@...ck-us.net> wrote:

> Commit 75e3b37d0598 ("hrtimer: Drop return code of hrtimer_switch_to_hres()")
> drops the return code of hrtimer_switch_to_hres(). While doing so, it also
> drops the return statement itself on failure. This may cause a system hang.
> Seen when running arm:multi_v7_defconfig in qemu with devicetree file
> vexpress-v2p-ca9.
> 
> Fixes: 75e3b37d0598 ("hrtimer: Drop return code of hrtimer_switch_to_hres()")
> Cc: Luiz Capitulino <lcapitulino@...hat.com>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>

Thanks for catching it Guenter!

Reviewed-by: Luiz Capitulino <lcapitulino@...hat.com>

> ---
>  kernel/time/hrtimer.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
> index 5c4fe50e47d3..457a373e2181 100644
> --- a/kernel/time/hrtimer.c
> +++ b/kernel/time/hrtimer.c
> @@ -695,6 +695,7 @@ static void hrtimer_switch_to_hres(void)
>  	if (tick_init_highres()) {
>  		printk(KERN_WARNING "Could not switch to high resolution "
>  				    "mode on CPU %d\n", base->cpu);
> +		return;
>  	}
>  	base->hres_active = 1;
>  	hrtimer_resolution = HIGH_RES_NSEC;

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