Re: 2.6.32.21 - uptime related crashes?

[Nikola Ciprich]

Hi,
thanks for the patch! I'll put this on our testing boxes...
Are You going to push this upstream so we can ask Greg to push this to -stable?
or do You plan to wait for more complex patch?
n.


On Thu, Jul 21, 2011 at 02:24:58PM +0200, Peter Zijlstra wrote:
> On Thu, 2011-07-21 at 09:22 +0200, Ingo Molnar wrote:
> > 
> > Ping, what's going on with this bug? Systems are crashing so we need 
> > a quick fix ASAP ... 
> 
> Something as simple as the below ought to cure things for now. Once we
> get __cycles_2_ns() fixed up we can enable it again.
> 
> (patch against -tip, .32 code is different but equally simple to fix)
> 
> ---
> Subject: x86, intel: Don't mark sched_clock() as stable
> 
> Because the x86 sched_clock() implementation wraps at 54 bits and the
> scheduler code assumes it wraps at the full 64bits we can get into
> trouble after 208 days (~7 months) of uptime. 
> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> ---
>  arch/x86/kernel/cpu/intel.c |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
> index ed6086e..c8dc48b 100644
> --- a/arch/x86/kernel/cpu/intel.c
> +++ b/arch/x86/kernel/cpu/intel.c
> @@ -91,8 +91,15 @@ static void __cpuinit early_init_intel(struct cpuinfo_x86 *c)
>  	if (c->x86_power & (1 << 8)) {
>  		set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
>  		set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
> +		/*
> +		 * Unfortunately our __cycles_2_ns() implementation makes
> +		 * the raw sched_clock() interface wrap at 54-bits, which
> +		 * makes it unsuitable for direct use, so disable this
> +		 * for now.
> +		 *
>  		if (!check_tsc_unstable())
>  			sched_clock_stable = 1;
> +		 */
>  	}
>  
>  	/*
> 
> 

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