linux-kernel - Re: [PATCH v3 1/2] sched/core: Get rid of 'cpu' argument in wq_worker

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Date:	Wed, 2 Mar 2016 13:03:16 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Alexander Gordeev <agordeev@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>,
	Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH v3 1/2] sched/core: Get rid of 'cpu' argument in
 wq_worker_sleeping()


This really should also have been Cc'ed to TJ, doing so now.

On Wed, Mar 02, 2016 at 12:53:31PM +0100, Alexander Gordeev wrote:
> Given that wq_worker_sleeping() could only be called for a
> CPU it is running on, we do not need passing a CPU ID as an
> argument.
> 
> Suggested-by: Oleg Nesterov <oleg@...hat.com>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Alexander Gordeev <agordeev@...hat.com>
> ---
>  kernel/sched/core.c         | 2 +-
>  kernel/workqueue.c          | 5 ++---
>  kernel/workqueue_internal.h | 2 +-
>  3 files changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 423452c..735e87c 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3183,7 +3183,7 @@ static void __sched notrace __schedule(bool preempt)
>  			if (prev->flags & PF_WQ_WORKER) {
>  				struct task_struct *to_wakeup;
>  
> -				to_wakeup = wq_worker_sleeping(prev, cpu);
> +				to_wakeup = wq_worker_sleeping(prev);
>  				if (to_wakeup)
>  					try_to_wake_up_local(to_wakeup);
>  			}
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 7ff5dc7..2fa8d26 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -858,7 +858,6 @@ void wq_worker_waking_up(struct task_struct *task, int cpu)
>  /**
>   * wq_worker_sleeping - a worker is going to sleep
>   * @task: task going to sleep
> - * @cpu: CPU in question, must be the current CPU number
>   *
>   * This function is called during schedule() when a busy worker is
>   * going to sleep.  Worker on the same cpu can be woken up by
> @@ -870,7 +869,7 @@ void wq_worker_waking_up(struct task_struct *task, int cpu)
>   * Return:
>   * Worker task on @cpu to wake up, %NULL if none.
>   */
> -struct task_struct *wq_worker_sleeping(struct task_struct *task, int cpu)
> +struct task_struct *wq_worker_sleeping(struct task_struct *task)
>  {
>  	struct worker *worker = kthread_data(task), *to_wakeup = NULL;
>  	struct worker_pool *pool;
> @@ -886,7 +885,7 @@ struct task_struct *wq_worker_sleeping(struct task_struct *task, int cpu)
>  	pool = worker->pool;
>  
>  	/* this can only happen on the local cpu */
> -	if (WARN_ON_ONCE(cpu != raw_smp_processor_id() || pool->cpu != cpu))
> +	if (WARN_ON_ONCE(pool->cpu != raw_smp_processor_id()))
>  		return NULL;
>  
>  	/*
> diff --git a/kernel/workqueue_internal.h b/kernel/workqueue_internal.h
> index 4521587..8635417 100644
> --- a/kernel/workqueue_internal.h
> +++ b/kernel/workqueue_internal.h
> @@ -69,6 +69,6 @@ static inline struct worker *current_wq_worker(void)
>   * sched/core.c and workqueue.c.
>   */
>  void wq_worker_waking_up(struct task_struct *task, int cpu);
> -struct task_struct *wq_worker_sleeping(struct task_struct *task, int cpu);
> +struct task_struct *wq_worker_sleeping(struct task_struct *task);
>  
>  #endif /* _KERNEL_WORKQUEUE_INTERNAL_H */
> -- 
> 1.8.3.1
>