Re: [PATCH] x86, tsc: Fix a preemption leak in restore_sched_clock_state()

[Suresh Siddha <suresh.b.siddha@intel.com>]

On Fri, 2010-09-10 at 13:32 -0700, Peter Zijlstra wrote:
> D'0h !! *facepalm*
> 
> Shame on me for not spotting that sooner.
> 
> ---
> Subject: x86, tsc: Fix a preemption leak in restore_sched_clock_state()
> 
> A real life genuine preemption leak..
> 
> Reported-by: Jeff Chua <jeff.chua.linux@gmail.com>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> ---
>  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 873a321..4496315 100644
> --- a/arch/x86/kernel/tsc.c
> +++ b/arch/x86/kernel/tsc.c
> @@ -655,7 +655,7 @@ void restore_sched_clock_state(void)
>  
>  	local_irq_save(flags);
>  
> -	get_cpu_var(cyc2ns_offset) = 0;
> +	__get_cpu_var(cyc2ns_offset) = 0;
>  	offset = cyc2ns_suspend - sched_clock();
>  
>  	for_each_possible_cpu(cpu)

Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>

Before heading for lunch, I was scratching my head and thinking that I
might be doing something wrong with the local_irq_disable() and
local_irq_enable() in that patch. But you got it right.

Thanks for looking at this and thanks to Jeff for reporting.

Original patch was marked as stable for 2.6.32+, so we need to make sure
that Greg picks up this piece too along with the original patch.