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From: John Ogness <john.ogness@linutronix.de>
To: Mukesh Ojha <quic_mojha@quicinc.com>, pmladek@suse.com,
 rostedt@goodmis.org, senozhatsky@chromium.org
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH] printk: Update @console_may_schedule in
 console_trylock_spinning()
In-Reply-To: <e5474801-53c1-6bbb-8781-e5cee42d6a90@quicinc.com>
References: <20240222090538.23017-1-quic_mojha@quicinc.com>
 <87plwo5z4k.fsf@jogness.linutronix.de>
 <e5474801-53c1-6bbb-8781-e5cee42d6a90@quicinc.com>
Date: Mon, 26 Feb 2024 13:07:24 +0106
Message-ID: <875xybmo2z.fsf@jogness.linutronix.de>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain

console_trylock_spinning() may takeover the console lock from a
schedulable context. Update @console_may_schedule to make sure it
reflects a trylock acquire.

Reported-by: Mukesh Ojha <quic_mojha@quicinc.com>
Link: https://lore.kernel.org/lkml/20240222090538.23017-1-quic_mojha@quicinc.com
Fixes: dbdda842fe96 ("printk: Add console owner and waiter logic to load balance console writes")
Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
 kernel/printk/printk.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 1685a71f3f71..1612b50b2374 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2020,6 +2020,12 @@ static int console_trylock_spinning(void)
 	 */
 	mutex_acquire(&console_lock_dep_map, 0, 1, _THIS_IP_);
 
+	/*
+	 * Update @console_may_schedule for trylock because the previous
+	 * owner may have been schedulable.
+	 */
+	console_may_schedule = 0;
+
 	return 1;
 }
 

base-commit: e7081d5a9d976b84f61f497316d7c940a4a2e67a
-- 
2.30.2