[PATCH v13 6/7] sched: Split out __schedule() deactivate task logic into a helper

[John Stultz <jstultz@google.com>]

As we're going to re-use the deactivation logic,
split it into a helper.

Cc: Joel Fernandes <joelaf@google.com>
Cc: Qais Yousef <qyousef@layalina.io>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Zimuzo Ezeozue <zezeozue@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Will Deacon <will@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Metin Kaya <Metin.Kaya@arm.com>
Cc: Xuewen Yan <xuewen.yan94@gmail.com>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: kernel-team@android.com
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Tested-by: Metin Kaya <metin.kaya@arm.com>
Reviewed-by: Metin Kaya <metin.kaya@arm.com>
Reviewed-by: Qais Yousef <qyousef@layalina.io>
Signed-off-by: John Stultz <jstultz@google.com>
---
v6:
* Define function as static to avoid "no previous prototype"
  warnings as Reported-by: kernel test robot <lkp@intel.com>
v7:
* Rename state task_state to be more clear, as suggested by
  Metin Kaya
v11:
* Return early to simplify indentation, and drop unused bool
  return (will be introduced later when its needed) as sugggested
  by Qais.
---
 kernel/sched/core.c | 65 +++++++++++++++++++++++++++------------------
 1 file changed, 39 insertions(+), 26 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 615fc7a7b17c..7f949bb9e2a8 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6483,6 +6483,44 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 #define SM_PREEMPT		1
 #define SM_RTLOCK_WAIT		2
 
+/*
+ * Helper function for __schedule()
+ *
+ * If a task does not have signals pending, deactivate it
+ * Otherwise marks the task's __state as RUNNING
+ */
+static void try_to_deactivate_task(struct rq *rq, struct task_struct *p,
+				   unsigned long task_state)
+{
+	int flags = DEQUEUE_NOCLOCK;
+
+	if (signal_pending_state(task_state, p)) {
+		WRITE_ONCE(p->__state, TASK_RUNNING);
+		return;
+	}
+
+	p->sched_contributes_to_load =
+		(task_state & TASK_UNINTERRUPTIBLE) &&
+		!(task_state & TASK_NOLOAD) &&
+		!(task_state & TASK_FROZEN);
+
+	if (unlikely(is_special_task_state(task_state)))
+		flags |= DEQUEUE_SPECIAL;
+
+	/*
+	 * __schedule()			ttwu()
+	 *   prev_state = prev->state;    if (p->on_rq && ...)
+	 *   if (prev_state)		    goto out;
+	 *     p->on_rq = 0;		  smp_acquire__after_ctrl_dep();
+	 *				  p->state = TASK_WAKING
+	 *
+	 * Where __schedule() and ttwu() have matching control dependencies.
+	 *
+	 * After this, schedule() must not care about p->state any more.
+	 */
+	block_task(rq, p, flags);
+}
+
 /*
  * __schedule() is the main scheduler function.
  *
@@ -6590,32 +6628,7 @@ static void __sched notrace __schedule(int sched_mode)
 			goto picked;
 		}
 	} else if (!preempt && prev_state) {
-		if (signal_pending_state(prev_state, prev)) {
-			WRITE_ONCE(prev->__state, TASK_RUNNING);
-		} else {
-			int flags = DEQUEUE_NOCLOCK;
-
-			prev->sched_contributes_to_load =
-				(prev_state & TASK_UNINTERRUPTIBLE) &&
-				!(prev_state & TASK_NOLOAD) &&
-				!(prev_state & TASK_FROZEN);
-
-			if (unlikely(is_special_task_state(prev_state)))
-				flags |= DEQUEUE_SPECIAL;
-
-			/*
-			 * __schedule()			ttwu()
-			 *   prev_state = prev->state;    if (p->on_rq && ...)
-			 *   if (prev_state)		    goto out;
-			 *     p->on_rq = 0;		  smp_acquire__after_ctrl_dep();
-			 *				  p->state = TASK_WAKING
-			 *
-			 * Where __schedule() and ttwu() have matching control dependencies.
-			 *
-			 * After this, schedule() must not care about p->state any more.
-			 */
-			block_task(rq, prev, flags);
-		}
+		try_to_deactivate_task(rq, prev, prev_state);
 		switch_count = &prev->nvcsw;
 	}
 
-- 
2.47.0.rc1.288.g06298d1525-goog