Re: [PATCH 4/4] nohz: Convert a few places to use local per cpu accesses

[Peter Zijlstra <peterz@infradead.org>]

OK so these patches look ok to me -- didn't read in detail though.

On Fri, Aug 16, 2013 at 05:42:33PM +0200, Frederic Weisbecker wrote:
> A few functions use remote per CPU access APIs when they
> deal with local values.
> 
> Just to the right conversion to improve performance, code
> readability and debug checks.

> @@ -410,7 +408,7 @@ static void tick_nohz_update_jiffies(ktime_t now)
>  
>  static void tick_nohz_stop_idle(int cpu, ktime_t now)
>  {
> -	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
> +	struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);

What's there from stopping someone from calling this with cpu !=
smp_processor_id() ? 

> @@ -1020,7 +1018,7 @@ static void tick_nohz_kick_tick(int cpu, ktime_t now)
>  
>  static inline void tick_check_nohz(int cpu)
>  {
> -	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
> +	struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
>  	ktime_t now;
>  
>  	if (!ts->idle_active && !ts->tick_stopped)

idem