Re: [RFCv5 PATCH 45/46] sched/cpufreq_sched: modify pcpu_capacity handling

Peter Zijlstra
2015-08-16T22:02:15Z

On Tue, Jul 07, 2015 at 07:24:28PM +0100, Morten Rasmussen wrote:
> From: Juri Lelli <juri.lelli@arm.com>
>
> Use the cpu argument of cpufreq_sched_set_cap() to handle per_cpu writes,
> as the thing can be called remotely (e.g., from load balacing code).
>
> cc: Ingo Molnar <mingo@redhat.com>
> cc: Peter Zijlstra <peterz@infradead.org>
>
> Signed-off-by: Juri Lelli <juri.lelli@arm.com>
> ---
> kernel/sched/cpufreq_sched.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/sched/cpufreq_sched.c b/kernel/sched/cpufreq_sched.c
> index 06ff183..b81ac779 100644
> --- a/kernel/sched/cpufreq_sched.c
> +++ b/kernel/sched/cpufreq_sched.c
> @@ -151,7 +151,7 @@ void cpufreq_sched_set_cap(int cpu, unsigned long capacity)
> unsigned long capacity_max = 0;
>
> /* update per-cpu capacity request */
> - __this_cpu_write(pcpu_capacity, capacity);
> + per_cpu(pcpu_capacity, cpu) = capacity;
>
> policy = cpufreq_cpu_get(cpu);
> if (IS_ERR_OR_NULL(policy)) {

Uhm,.. this function seems to hard assume its called for the local CPU.
It will only use the irq_queue_work_on() if the cpufreq thing requires
the thread, otherwise it will call the method directly on the calling
cpu.