Subject: [PATCH 34/48] printk: Atomic print in printk context on shutdown
From: John Ogness <[email-masked]>
Date: Mon, 23 Oct 2023 17:43:48 +0000

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 <[email-masked]>
Signed-off-by: Sebastian Andrzej Siewior <[email-masked]>
---
 kernel/printk/printk.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Index: linux-6.8.2-rt10/kernel/printk/printk.c
===================================================================
--- linux-6.8.2-rt10.orig/kernel/printk/printk.c
+++ linux-6.8.2-rt10/kernel/printk/printk.c
@@ -2402,12 +2402,17 @@ 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/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_pending();
+		}
 	}
 
 	if (do_trylock_unlock) {