[PATCH v2 0/2] sched/core: Cleanup leftovers in __schedule()

[PATCH v2 0/2] sched/core: Cleanup leftovers in __schedule()

[Alexander Gordeev]

Changes since v1:
  - cover letter BLURB added :)
  - forgotten Suggested-by Oleg field added to patch 1
  - raw_smp_processor_id() returned instead of mistaken smp_processor_id()
  - kbuild excess function parameter 'cpu' description warning fixed

Alexander Gordeev (2):
  sched/core: Get rid of 'cpu' argument in wq_worker_sleeping()
  sched/core: Get rid of 'cpu' variable in __schedule()

 kernel/sched/core.c         | 7 ++-----
 kernel/workqueue.c          | 5 ++---
 kernel/workqueue_internal.h | 2 +-
 3 files changed, 5 insertions(+), 9 deletions(-)

-- 
1.8.3.1

[PATCH v2 1/2] sched/core: Get rid of 'cpu' argument in wq_worker_sleeping()

[Alexander Gordeev]

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@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Alexander Gordeev <agordeev@redhat.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 9503d59..4e56a4d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3257,7 +3257,7 @@ 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

[PATCH v2 2/2] sched/core: Get rid of 'cpu' variable in __schedule()

[Alexander Gordeev]

'cpu' variable is only used to acquire the current runqueue.
By using this_rq() instead, we can get rid of that variable.

Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
---
 kernel/sched/core.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4e56a4d..82206f0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3205,10 +3205,8 @@ static void __sched notrace __schedule(bool preempt)
 	struct task_struct *prev, *next;
 	unsigned long *switch_count;
 	struct rq *rq;
-	int cpu;
 
-	cpu = smp_processor_id();
-	rq = cpu_rq(cpu);
+	rq = this_rq();
 	prev = rq->curr;
 
 	/*
@@ -3280,7 +3278,6 @@ static void __sched notrace __schedule(bool preempt)
 
 		trace_sched_switch(preempt, prev, next);
 		rq = context_switch(rq, prev, next); /* unlocks the rq */
-		cpu = cpu_of(rq);
 	} else {
 		lockdep_unpin_lock(&rq->lock);
 		raw_spin_unlock_irq(&rq->lock);
-- 
1.8.3.1

Re: [PATCH v2 2/2] sched/core: Get rid of 'cpu' variable in __schedule()

[Peter Zijlstra]

On Tue, Mar 01, 2016 at 01:01:42PM +0100, Alexander Gordeev wrote:
> 'cpu' variable is only used to acquire the current runqueue.
> By using this_rq() instead, we can get rid of that variable.

Does not apply to tip/sched/core