[PATCH v26 02/10] sched: Minimise repeated sched_proxy_exec() checking

[John Stultz <jstultz@google.com>]

Peter noted: Compilers are really bad (as in they utterly refuse)
optimizing (even when marked with __pure) the static branch
things, and will happily emit multiple identical in a row.

So pull out the one obvious sched_proxy_exec() branch in
__schedule() and remove some of the 'implicit' ones in that
path.

Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: John Stultz <jstultz@google.com>
---
Cc: Joel Fernandes <joelagnelf@nvidia.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: Suleiman Souhlal <suleiman@google.com>
Cc: kuyo chang <kuyo.chang@mediatek.com>
Cc: hupu <hupu.gm@gmail.com>
Cc: kernel-team@android.com
---
 kernel/sched/core.c | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 92b1807c05a4e..dc044a405f83b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6600,11 +6600,7 @@ find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf)
 	struct mutex *mutex;
 
 	/* Follow blocked_on chain. */
-	for (p = donor; task_is_blocked(p); p = owner) {
-		mutex = p->blocked_on;
-		/* Something changed in the chain, so pick again */
-		if (!mutex)
-			return NULL;
+	for (p = donor; (mutex = p->blocked_on); p = owner) {
 		/*
 		 * By taking mutex->wait_lock we hold off concurrent mutex_unlock()
 		 * and ensure @owner sticks around.
@@ -6835,12 +6831,14 @@ static void __sched notrace __schedule(int sched_mode)
 	next = pick_next_task(rq, rq->donor, &rf);
 	rq_set_donor(rq, next);
 	rq->next_class = next->sched_class;
-	if (unlikely(task_is_blocked(next))) {
-		next = find_proxy_task(rq, next, &rf);
-		if (!next)
-			goto pick_again;
-		if (next == rq->idle)
-			goto keep_resched;
+	if (sched_proxy_exec()) {
+		if (unlikely(next->blocked_on)) {
+			next = find_proxy_task(rq, next, &rf);
+			if (!next)
+				goto pick_again;
+			if (next == rq->idle)
+				goto keep_resched;
+		}
 	}
 picked:
 	clear_tsk_need_resched(prev);
-- 
2.53.0.1018.g2bb0e51243-goog