linux-kernel - [PATCH] prinkt/nbcon: Add a scheduling point to nbcon_kthread

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Message-ID: <20240620094300.YJlW043f@linutronix.de>
Date: Thu, 20 Jun 2024 11:43:00 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Derek Barbosa <debarbos@...hat.com>, john.ogness@...utronix.de
Cc: pmladek@...e.com, rostedt@...dmis.org, senozhatsky@...omium.org,
	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	williams@...hat.com, jlelli@...hat.com, ahalaney@...hat.com,
	lgoncalv@...hat.com, jwyatt@...hat.com, aubaker@...hat.com
Subject: [PATCH] prinkt/nbcon: Add a scheduling point to nbcon_kthread_func().

Constant printing can lead to a CPU hog in nbcon_kthread_func(). The
context is preemptible but on !PREEMPT kernels there is no explicit
preemption point which leads softlockup warnings.

Add an explicit preemption point in nbcon_kthread_func().

Reported-by: Derek Barbosa <debarbos@...hat.com>
Link: https://lore.kernel.org/ZnHF5j1DUDjN1kkq@debarbos-thinkpadt14sgen2i.remote.csb
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 kernel/printk/nbcon.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
index bb9689f94d302..0813ce88a49c5 100644
--- a/kernel/printk/nbcon.c
+++ b/kernel/printk/nbcon.c
@@ -1119,6 +1119,7 @@ static int nbcon_kthread_func(void *__console)
 		}
 
 		console_srcu_read_unlock(cookie);
+		cond_resched();
 
 	} while (backlog);
 
-- 
2.45.2