linux-kernel - Re: [tip:x86/urgent] x86: tsc: Prevent delayed init if initial tsc calibration failed

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Date:	Tue, 11 Jan 2011 07:46:46 -0800
From:	John Stultz <john.stultz@...aro.org>
To:	linux-kernel@...r.kernel.org, mingo@...hat.com, hpa@...or.com,
	tglx@...utronix.de, kas@...nvz.org
Cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/urgent] x86: tsc: Prevent delayed init if initial tsc
 calibration failed

On Tue, 2011-01-11 at 10:51 +0000, tip-bot for Thomas Gleixner wrote:
> Commit-ID:  29fe359ca20326e57b25e8545c49ed9ff5e830c7
> Gitweb:     http://git.kernel.org/tip/29fe359ca20326e57b25e8545c49ed9ff5e830c7
> Author:     Thomas Gleixner <tglx@...utronix.de>
> AuthorDate: Tue, 11 Jan 2011 11:40:48 +0100
> Committer:  Thomas Gleixner <tglx@...utronix.de>
> CommitDate: Tue, 11 Jan 2011 11:48:39 +0100
> 
> x86: tsc: Prevent delayed init if initial tsc calibration failed
> 
> commit a8760ec (x86: Check tsc available/disabled in the delayed init
> function) missed to prevent the setup of the delayed init function in
> case the initial tsc calibration failed. This results in the same
> divide by zero bug as we have seen without the tsc disabled check.
> 
> Skip the delayed work setup when tsc_khz (the initial calibration
> value) is 0.
> 
> Bisected-and-tested-by: Kirill A. Shutemov <kas@...nvz.org>
> Cc: John Stultz <john.stultz@...aro.org>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

Krill: Thanks for reporting and testing!

Thomas: Thanks for the fix. I'll see if we can't condense the invalid
states a bit more. If tsc_khz=0, we probably should set tsc_disabled.

Acked-by: John Stultz <johnstul@...ibm.com>

> ---
>  arch/x86/kernel/tsc.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
> index 356a0d4..463901e 100644
> --- a/arch/x86/kernel/tsc.c
> +++ b/arch/x86/kernel/tsc.c
> @@ -965,7 +965,7 @@ out:
> 
>  static int __init init_tsc_clocksource(void)
>  {
> -	if (!cpu_has_tsc || tsc_disabled > 0)
> +	if (!cpu_has_tsc || tsc_disabled > 0 || !tsc_khz)
>  		return 0;
> 
>  	if (tsc_clocksource_reliable)


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