linux-kernel - Re: [PATCH] intel_idle: Check cpu_idle_get_driver() for NULL before dereferencing it.

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Message-Id: <201208042356.35884.rjw@sisk.pl>
Date:	Sat, 4 Aug 2012 23:56:35 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	lenb@...nel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] intel_idle: Check cpu_idle_get_driver() for NULL before dereferencing it.

On Thursday, August 02, 2012, Konrad Rzeszutek Wilk wrote:
> If the machine is booted without any cpu_idle driver set
> (b/c disable_cpuidle() has been called) we should follow
> other users of cpu_idle API and check the return value
> for NULL before using it.
> 
> Reported-by: Mark van Dijk <mark@...ernecto.net>
> Tested-by: Mark van Dijk <mark@...ernecto.net>
> Suggested-by: Jan Beulich <JBeulich@...e.com>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> ---
>  drivers/idle/intel_idle.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
> index f559088..7383aa0 100644
> --- a/drivers/idle/intel_idle.c
> +++ b/drivers/idle/intel_idle.c
> @@ -607,7 +607,7 @@ static int __init intel_idle_init(void)
>  	retval = cpuidle_register_driver(&intel_idle_driver);
>  	if (retval) {

What about:

  		struct cpuidle_driver *drv = cpuidle_get_driver();

  		printk(KERN_DEBUG PREFIX "intel_idle yielding to %s",
			drv ? drv->name : "none");

>  		printk(KERN_DEBUG PREFIX "intel_idle yielding to %s",
> -			cpuidle_get_driver()->name);
> +			cpuidle_get_driver() ? cpuidle_get_driver()->name : "none");
>  		return retval;
>  	}
>  
> 

Rafael
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