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Date:   Mon,  6 Nov 2023 19:34:58 +0000
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Subject: [PATCH v6 15/20] sched: Add proxy deactivate helper
From:   John Stultz <jstultz@google.com>
To:     LKML <linux-kernel@vger.kernel.org>
Cc:     John Stultz <jstultz@google.com>,
        Joel Fernandes <joelaf@google.com>,
        Qais Yousef <qyousef@google.com>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Valentin Schneider <vschneid@redhat.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>,
        Zimuzo Ezeozue <zezeozue@google.com>,
        Youssef Esmat <youssefesmat@google.com>,
        Mel Gorman <mgorman@suse.de>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Will Deacon <will@kernel.org>,
        Waiman Long <longman@redhat.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        "Paul E . McKenney" <paulmck@kernel.org>, kernel-team@android.com
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Add small helper for deactivating the selected task

Cc: Joel Fernandes <joelaf@google.com>
Cc: Qais Yousef <qyousef@google.com>
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: Youssef Esmat <youssefesmat@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
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: kernel-team@android.com
Signed-off-by: John Stultz <jstultz@google.com>
---
 kernel/sched/core.c | 43 +++++++++++++++++++++----------------------
 1 file changed, 21 insertions(+), 22 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5770656b898d..1b84d612332e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6612,6 +6612,22 @@ static bool try_to_deactivate_task(struct rq *rq, struct task_struct *p,
 }
 
 #ifdef CONFIG_PROXY_EXEC
+
+bool proxy_deactivate(struct rq *rq, struct task_struct *next)
+{
+	unsigned long state = READ_ONCE(next->__state);
+
+	/* Don't deactivate if the state has been changed to TASK_RUNNING */
+	if (!state)
+		return false;
+	if (!try_to_deactivate_task(rq, next, state, true))
+		return false;
+	put_prev_task(rq, next);
+	rq_set_selected(rq, rq->idle);
+	resched_curr(rq);
+	return true;
+}
+
 /*
  * Initial simple proxy that just returns the task if its waking
  * or deactivates the blocked task so we can pick something that
@@ -6620,10 +6636,9 @@ static bool try_to_deactivate_task(struct rq *rq, struct task_struct *p,
 static struct task_struct *
 proxy(struct rq *rq, struct task_struct *next, struct rq_flags *rf)
 {
+	struct task_struct *ret = NULL;
 	struct task_struct *p = next;
 	struct mutex *mutex;
-	unsigned long state;
-
 	mutex = p->blocked_on;
 	/* Something changed in the chain, pick_again */
 	if (!mutex)
@@ -6645,30 +6660,14 @@ proxy(struct rq *rq, struct task_struct *next, struct rq_flags *rf)
 		 */
 		raw_spin_unlock(&p->blocked_lock);
 		raw_spin_unlock(&mutex->wait_lock);
-		return NULL;
-	}
-
-	state = READ_ONCE(p->__state);
-	/* Don't deactivate if the state has been changed to TASK_RUNNING */
-	if (!state) {
-		raw_spin_unlock(&p->blocked_lock);
-		raw_spin_unlock(&mutex->wait_lock);
-		return p;
+		return ret;
 	}
 
-	try_to_deactivate_task(rq, next, state, true);
-
-	/*
-	 * If next is the selected task, then remove lingering
-	 * references to it from rq and sched_class structs after
-	 * dequeueing.
-	 */
-	put_prev_task(rq, next);
-	rq_set_selected(rq, rq->idle);
-	resched_curr(rq);
+	if (!proxy_deactivate(rq, next))
+		ret = p;
 	raw_spin_unlock(&p->blocked_lock);
 	raw_spin_unlock(&mutex->wait_lock);
-	return NULL;
+	return ret;
 }
 #else /* PROXY_EXEC */
 static struct task_struct *
-- 
2.42.0.869.gea05f2083d-goog