linux-kernel - Re: fishy code in arch/x86/kernel/tsc.c:time_cpufreq

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Message-ID: <20090601163914.GA6098@infradead.org>
Date:	Mon, 1 Jun 2009 12:39:14 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	Dave Jones <davej@...hat.com>,
	Christoph Hellwig <hch@...radead.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: fishy code in arch/x86/kernel/tsc.c:time_cpufreq_notifier()

On Mon, Jun 01, 2009 at 12:29:55PM -0400, Dave Jones wrote:
> diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
> index d57de05..78c54ea 100644
> --- a/arch/x86/kernel/tsc.c
> +++ b/arch/x86/kernel/tsc.c
> @@ -631,17 +631,15 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
>  				void *data)
>  {
>  	struct cpufreq_freqs *freq = data;
> -	unsigned long *lpj, dummy;
> +	unsigned long *lpj;
>  
>  	if (cpu_has(&cpu_data(freq->cpu), X86_FEATURE_CONSTANT_TSC))
>  		return 0;
>  
> -	lpj = &dummy;
> -	if (!(freq->flags & CPUFREQ_CONST_LOOPS))
> +	lpj = &boot_cpu_data.loops_per_jiffy;
>  #ifdef CONFIG_SMP
> +	if (!(freq->flags & CPUFREQ_CONST_LOOPS))
>  		lpj = &cpu_data(freq->cpu).loops_per_jiffy;
> -#else
> -	lpj = &boot_cpu_data.loops_per_jiffy;
>  #endif

This makes the code look a lot more sane and should fix the potential
issue.

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