From: John Ogness <john.ogness@linutronix.de>
Date: Mon, 23 Oct 2023 17:43:48 +0000
Subject: [PATCH 122/134] printk: Atomic print in printk context on shutdown
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.6/older/patches-6.6.7-rt18.tar.xz

For nbcon consoles, normally the printing is handled by the
dedicated console printing threads. However, on shutdown the
printing threads may not get a chance to print the final
messages.

When shutting down or rebooting (system_state > SYSTEM_RUNNING),
perform atomic printing from the printk() caller context.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/printk/printk.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2389,13 +2389,18 @@ asmlinkage int vprintk_emit(int facility
 		 *
 		 * - When this CPU is in panic.
 		 *
+		 * - During shutdown, since the printing threads may not get
+		 *   a chance to print the final messages.
+		 *
 		 * Note that if boot consoles are registered, the
 		 * console_lock/console_unlock dance must be relied upon
 		 * instead because nbcon consoles cannot print simultaneously
 		 * with boot consoles.
 		 */
-		if (is_panic_context)
+		if (is_panic_context ||
+		    (system_state > SYSTEM_RUNNING)) {
 			nbcon_atomic_flush_all();
+		}
 	}
 
 	if (do_trylock_unlock) {
