linux-kernel - [tip:sched/core] sched/core: Streamle calls to task_rq

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Message-ID: <tip-4b211f2b129dd1f6a6956bbc76e2f232c1ec3ad8@git.kernel.org>
Date:   Thu, 25 Jul 2019 09:20:28 -0700
From:   tip-bot for Mathieu Poirier <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     peterz@...radead.org, mingo@...nel.org, dietmar.eggemann@....com,
        linux-kernel@...r.kernel.org, mathieu.poirier@...aro.org,
        torvalds@...ux-foundation.org, tglx@...utronix.de,
        rostedt@...dmis.org, hpa@...or.com, tj@...nel.org
Subject: [tip:sched/core] sched/core: Streamle calls to task_rq_unlock()

Commit-ID:  4b211f2b129dd1f6a6956bbc76e2f232c1ec3ad8
Gitweb:     https://git.kernel.org/tip/4b211f2b129dd1f6a6956bbc76e2f232c1ec3ad8
Author:     Mathieu Poirier <mathieu.poirier@...aro.org>
AuthorDate: Fri, 19 Jul 2019 15:59:54 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 25 Jul 2019 15:51:57 +0200

sched/core: Streamle calls to task_rq_unlock()

Calls to task_rq_unlock() are done several times in the
__sched_setscheduler() function.  This is fine when only the rq lock needs to be
handled but not so much when other locks come into play.

This patch streamlines the release of the rq lock so that only one
location need to be modified when dealing with more than one lock.

No change of functionality is introduced by this patch.

Tested-by: Dietmar Eggemann <dietmar.eggemann@....com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Acked-by: Tejun Heo <tj@...nel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: bristot@...hat.com
Cc: claudio@...dence.eu.com
Cc: lizefan@...wei.com
Cc: longman@...hat.com
Cc: luca.abeni@...tannapisa.it
Cc: tommaso.cucinotta@...tannapisa.it
Link: https://lkml.kernel.org/r/20190719140000.31694-3-juri.lelli@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/core.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 0b22e55cebe8..1af3d2dc6b29 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4712,8 +4712,8 @@ recheck:
 	 * Changing the policy of the stop threads its a very bad idea:
 	 */
 	if (p == rq->stop) {
-		task_rq_unlock(rq, p, &rf);
-		return -EINVAL;
+		retval = -EINVAL;
+		goto unlock;
 	}
 
 	/*
@@ -4731,8 +4731,8 @@ recheck:
 			goto change;
 
 		p->sched_reset_on_fork = reset_on_fork;
-		task_rq_unlock(rq, p, &rf);
-		return 0;
+		retval = 0;
+		goto unlock;
 	}
 change:
 
@@ -4745,8 +4745,8 @@ change:
 		if (rt_bandwidth_enabled() && rt_policy(policy) &&
 				task_group(p)->rt_bandwidth.rt_runtime == 0 &&
 				!task_group_is_autogroup(task_group(p))) {
-			task_rq_unlock(rq, p, &rf);
-			return -EPERM;
+			retval = -EPERM;
+			goto unlock;
 		}
 #endif
 #ifdef CONFIG_SMP
@@ -4761,8 +4761,8 @@ change:
 			 */
 			if (!cpumask_subset(span, p->cpus_ptr) ||
 			    rq->rd->dl_bw.bw == 0) {
-				task_rq_unlock(rq, p, &rf);
-				return -EPERM;
+				retval = -EPERM;
+				goto unlock;
 			}
 		}
 #endif
@@ -4781,8 +4781,8 @@ change:
 	 * is available.
 	 */
 	if ((dl_policy(policy) || dl_task(p)) && sched_dl_overflow(p, policy, attr)) {
-		task_rq_unlock(rq, p, &rf);
-		return -EBUSY;
+		retval = -EBUSY;
+		goto unlock;
 	}
 
 	p->sched_reset_on_fork = reset_on_fork;
@@ -4840,6 +4840,10 @@ change:
 	preempt_enable();
 
 	return 0;
+
+unlock:
+	task_rq_unlock(rq, p, &rf);
+	return retval;
 }
 
 static int _sched_setscheduler(struct task_struct *p, int policy,