Re: [PATCH 1/3] sched: Add new API wake_up_if_idle() to wake up the idle cpu

Daniel Lezcano
2014-08-21T01:54:22Z

On 08/18/2014 10:37 AM, Chuansheng Liu wrote:
> Implementing one new API wake_up_if_idle(), which is used to
> wake up the idle CPU.

Is this patchset tested ? Did you check it solves the issue you were
facing ?

> Suggested-by: Andy Lutomirski <luto@amacapital.net>
> Signed-off-by: Chuansheng Liu <chuansheng.liu@intel.com>
> ---
> include/linux/sched.h | 1 +
> kernel/sched/core.c | 16 ++++++++++++++++
> 2 files changed, 17 insertions(+)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 857ba40..3f89ac1 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1024,6 +1024,7 @@ struct sched_domain_topology_level {
> extern struct sched_domain_topology_level *sched_domain_topology;
>
> extern void set_sched_topology(struct sched_domain_topology_level *tl);
> +extern void wake_up_if_idle(int cpu);
>
> #ifdef CONFIG_SCHED_DEBUG
> # define SD_INIT_NAME(type) .name = #type
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 1211575..adf104f 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1620,6 +1620,22 @@ static void ttwu_queue_remote(struct task_struct *p, int cpu)
> }
> }
>
> +void wake_up_if_idle(int cpu)
> +{
> + struct rq *rq = cpu_rq(cpu);
> + unsigned long flags;
> +
> + if (set_nr_if_polling(rq->idle)) {
> + trace_sched_wake_idle_without_ipi(cpu);
> + } else {
> + raw_spin_lock_irqsave(&rq->lock, flags);
> + if (rq->curr == rq->idle)
> + smp_send_reschedule(cpu);
> + /* Else cpu is not in idle, do nothing here */
> + raw_spin_unlock_irqrestore(&rq->lock, flags);
> + }
> +}
> +
> bool cpus_share_cache(int this_cpu, int that_cpu)
> {
> return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
>

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