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SubjectRe: fishy code in arch/x86/kernel/tsc.c:time_cpufreq_notifier()
Date
On Mon June 1 2009, Jon Masters wrote:
> On Mon, 2009-06-01 at 12:39 -0400, Christoph Hellwig wrote:
> > 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.
>
> Tiny niggle that you wind up setting lpj (loops per jiffy) twice if
> you're on SMP and have CPUFREQ_CONST_LOOPS.
>

At least it is consistent. ;)
You set lpj twice if your not on SMP and have CPUFREG_CONST_LOOPS.

Mike
> Jon.
>
>
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