linux-kernel - [PATCH] sched/core: Fix setup_preempt

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Date:   Wed, 24 Nov 2021 16:42:46 +0100
From:   Nicolas Saenz Julienne <nsaenzju@...hat.com>
To:     peterz@...radead.org
Cc:     mingo@...hat.com, juri.lelli@...hat.com, frederic@...nel.org,
        linux-kernel@...r.kernel.org, mtosatti@...hat.com, mgorman@...e.de,
        bsegall@...gle.com, rostedt@...dmis.org, dietmar.eggemann@....com,
        bristot@...hat.com, vincent.guittot@...aro.org,
        Nicolas Saenz Julienne <nsaenzju@...hat.com>
Subject: [PATCH] sched/core: Fix setup_preempt_mode() return values

__setup() expects its setup_func() implementations to return 1 on
success and 0 otherwise. So let's honor that.

This gets rid of the following kernel log:
"Unknown kernel command line parameters "preempt=full", will be
passed to user space."

Fixes: 826bfeb37bb4 ("preempt/dynamic: Support dynamic preempt with preempt= boot option")
Signed-off-by: Nicolas Saenz Julienne <nsaenzju@...hat.com>

---
An alternative fix would be using early_param() instead of __setup(),
which actually takes 0 as success. But I figure __setup() was chosen for
a reason.

 kernel/sched/core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index cd61e4109eecc..0d6eab5eeb4c9 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6657,11 +6657,11 @@ static int __init setup_preempt_mode(char *str)
 	int mode = sched_dynamic_mode(str);
 	if (mode < 0) {
 		pr_warn("Dynamic Preempt: unsupported mode: %s\n", str);
-		return 1;
+		return 0;
 	}
 
 	sched_dynamic_update(mode);
-	return 0;
+	return 1;
 }
 __setup("preempt=", setup_preempt_mode);
 
-- 
2.33.1