linux-kernel - Re: [PATCH] Calling check_system_tsc_reliable before unsynchronized

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Date:   Mon, 12 Jun 2017 18:03:45 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Zhenzhong Duan <zhenzhong.duan@...cle.com>
cc:     mingo@...hat.com, hpa@...or.com, x86@...nel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Calling check_system_tsc_reliable before
 unsynchronized_tsc

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@...cle.com>
> ---
>  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.

Thanks,

	tglx