Re: [PATCH] Calling check_system_tsc_reliable before unsynchronized_tsc

[Zhenzhong Duan]

在 2017/6/13 0:03, Thomas Gleixner 写道:
> On Thu, 8 Jun 2017, Zhenzhong Duan wrote:
>
> > unsynchronized_tsc() checks value of tsc_clocksource_reliable which is set by
> > check_system_tsc_reliable(). It's better to move check_system_tsc_reliable()
> > at
> > front, or else this check makes no sense.
> >
> > Though X86_FEATURE_CONSTANT_TSC is usually set for TSC reliable system, just
> > in
> > case.
> >
> > Signed-off-by: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx>
> > ---
> >   arch/x86/kernel/tsc.c |    4 ++--
> >   1 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
> > index 714dfba..a316bdd 100644
> > --- a/arch/x86/kernel/tsc.c
> > +++ b/arch/x86/kernel/tsc.c
> > @@ -1412,11 +1412,11 @@ void __init tsc_init(void)
> >    	use_tsc_delay();
> >   +	check_system_tsc_reliable();
> > +
> >   	if (unsynchronized_tsc())
> >   		mark_tsc_unstable("TSCs unsynchronized");
> >   -	check_system_tsc_reliable();
> > -
> What kind of patch is that? Definitely nothing which can be applied.
To avoid using unassigned variable tsc_clocksource_reliable.
Or what's the purpose of if (tsc_clocksource_reliable) check in 
unsynchronized_tsc()?

--
thanks
zduan