linux-kernel - [PATCH sched_ext/for-6.11] sched, sched_ext: Simplify dl_prio() case handling in sched

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Message-ID: <ZnncZcJFbN86-b4Y@slm.duckdns.org>
Date: Mon, 24 Jun 2024 10:51:49 -1000
From: Tejun Heo <tj@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>, mingo@...hat.com,
	juri.lelli@...hat.com, vincent.guittot@...aro.org,
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
	mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com,
	ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
	martin.lau@...nel.org, joshdon@...gle.com, brho@...gle.com,
	pjt@...gle.com, derkling@...gle.com, haoluo@...gle.com,
	dvernet@...a.com, dschatzberg@...a.com, dskarlat@...cmu.edu,
	riel@...riel.com, changwoo@...lia.com, himadrics@...ia.fr,
	memxor@...il.com, andrea.righi@...onical.com,
	joel@...lfernandes.org, linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org, kernel-team@...a.com
Subject: [PATCH sched_ext/for-6.11] sched, sched_ext: Simplify dl_prio() case
 handling in sched_fork()

From: Tejun Heo <tj@...nel.org>

sched_fork() returns with -EAGAIN if dl_prio(@p). a7a9fc549293 ("sched_ext:
Add boilerplate for extensible scheduler class") added scx_pre_fork() call
before it and then scx_cancel_fork() on the exit path. This is silly as the
dl_prio() block can just be moved above the scx_pre_fork() call.

Move the dl_prio() block above the scx_pre_fork() call and remove the now
unnecessary scx_cancel_fork() invocation.

Signed-off-by: Tejun Heo <tj@...nel.org>
Suggested-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: David Vernet <void@...ifault.com>
---
Hello,

As this is pretty trivial, if no one objects, I'll apply this to
sched_ext/for-6.11 after a bit.

Thanks.

 kernel/sched/core.c |   14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4583,8 +4583,6 @@ late_initcall(sched_core_sysctl_init);
  */
 int sched_fork(unsigned long clone_flags, struct task_struct *p)
 {
-	int ret;
-
 	__sched_fork(clone_flags, p);
 	/*
 	 * We mark the process as NEW here. This guarantees that
@@ -4621,12 +4619,12 @@ int sched_fork(unsigned long clone_flags
 		p->sched_reset_on_fork = 0;
 	}
 
+	if (dl_prio(p->prio))
+		return -EAGAIN;
+
 	scx_pre_fork(p);
 
-	if (dl_prio(p->prio)) {
-		ret = -EAGAIN;
-		goto out_cancel;
-	} else if (rt_prio(p->prio)) {
+	if (rt_prio(p->prio)) {
 		p->sched_class = &rt_sched_class;
 #ifdef CONFIG_SCHED_CLASS_EXT
 	} else if (task_should_scx(p)) {
@@ -4652,10 +4650,6 @@ int sched_fork(unsigned long clone_flags
 	RB_CLEAR_NODE(&p->pushable_dl_tasks);
 #endif
 	return 0;
-
-out_cancel:
-	scx_cancel_fork(p);
-	return ret;
 }
 
 int sched_cgroup_fork(struct task_struct *p, struct kernel_clone_args *kargs)