[PATCH v29 4/9] sched: Rework block_task so it can be directly called

[John Stultz]

Pull most of the logic out of try_to_block_task() and put it
into block_task() directly, so that we can call block_task() and
not have to worry about the failing cases in try_to_block_task()

Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: John Stultz <jstultz@xxxxxxxxxx>
---
Cc: Joel Fernandes <joelagnelf@xxxxxxxxxx>
Cc: Qais Yousef <qyousef@xxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: Valentin Schneider <vschneid@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Ben Segall <bsegall@xxxxxxxxxx>
Cc: Zimuzo Ezeozue <zezeozue@xxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Waiman Long <longman@xxxxxxxxxx>
Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Cc: Metin Kaya <Metin.Kaya@xxxxxxx>
Cc: Xuewen Yan <xuewen.yan94@xxxxxxxxx>
Cc: K Prateek Nayak <kprateek.nayak@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Cc: Suleiman Souhlal <suleiman@xxxxxxxxxx>
Cc: kuyo chang <kuyo.chang@xxxxxxxxxxxx>
Cc: hupu <hupu.gm@xxxxxxxxx>
Cc: kernel-team@xxxxxxxxxxx
---
 kernel/sched/core.c | 45 +++++++++++++++++++++++----------------------
 1 file changed, 23 insertions(+), 22 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 90267454077ea..7440bd7c05ca8 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2223,8 +2223,29 @@ void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
 	dequeue_task(rq, p, flags);
 }
 
-static void block_task(struct rq *rq, struct task_struct *p, int flags)
+static void block_task(struct rq *rq, struct task_struct *p, unsigned long task_state)
 {
+	int flags = DEQUEUE_NOCLOCK;
+
+	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.
+	 */
 	if (dequeue_task(rq, p, DEQUEUE_SLEEP | flags))
 		__block_task(rq, p);
 }
@@ -6582,7 +6603,6 @@ static bool try_to_block_task(struct rq *rq, struct task_struct *p,
 			      unsigned long *task_state_p, bool should_block)
 {
 	unsigned long task_state = *task_state_p;
-	int flags = DEQUEUE_NOCLOCK;
 
 	if (signal_pending_state(task_state, p)) {
 		WRITE_ONCE(p->__state, TASK_RUNNING);
@@ -6602,26 +6622,7 @@ static bool try_to_block_task(struct rq *rq, struct task_struct *p,
 	if (!should_block)
 		return false;
 
-	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);
+	block_task(rq, p, task_state);
 	return true;
 }
 
-- 
2.54.0.563.g4f69b47b94-goog