linux-kernel - [tip: sched/core] sched: Split out __schedule() deactivate task logic into a helper

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Message-ID: <172923526117.1442.11641248208406837165.tip-bot2@tip-bot2>
Date: Fri, 18 Oct 2024 07:07:41 -0000
From: "tip-bot2 for John Stultz" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: John Stultz <jstultz@...gle.com>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Metin Kaya <metin.kaya@....com>, Qais Yousef <qyousef@...alina.io>,
 K Prateek Nayak <kprateek.nayak@....com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched: Split out __schedule() deactivate task logic
 into a helper

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     7b3d61f6578ab06f130ecc13cd2f3010a6c295bb
Gitweb:        https://git.kernel.org/tip/7b3d61f6578ab06f130ecc13cd2f3010a6c295bb
Author:        John Stultz <jstultz@...gle.com>
AuthorDate:    Wed, 09 Oct 2024 16:53:39 -07:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 14 Oct 2024 12:52:41 +02:00

sched: Split out __schedule() deactivate task logic into a helper

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

Signed-off-by: John Stultz <jstultz@...gle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Metin Kaya <metin.kaya@....com>
Reviewed-by: Qais Yousef <qyousef@...alina.io>
Tested-by: K Prateek Nayak <kprateek.nayak@....com>
Tested-by: Metin Kaya <metin.kaya@....com>
Link: https://lore.kernel.org/r/20241009235352.1614323-7-jstultz@google.com
---
 kernel/sched/core.c | 67 ++++++++++++++++++++++++++------------------
 1 file changed, 40 insertions(+), 27 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ab0b775..b534de6 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6491,6 +6491,45 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 #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 bool try_to_block_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 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);
+	return true;
+}
+
+/*
  * __schedule() is the main scheduler function.
  *
  * The main means of driving the scheduler and thus entering this function are:
@@ -6598,33 +6637,7 @@ 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);
-			block = true;
-		}
+		block = try_to_block_task(rq, prev, prev_state);
 		switch_count = &prev->nvcsw;
 	}