Subject: [PATCH 30/48] panic: Mark emergency section in oops
From: John Ogness <[email-masked]>
Date: Tue, 19 Sep 2023 17:07:34 +0000

Mark an emergency section beginning with oops_enter() until the
end of oops_exit(). In this section, the CPU will not perform
console output for the printk() calls. Instead, a flushing of the
console output is triggered when exiting the emergency section.

The very end of oops_exit() performs a kmsg_dump(). This is not
included in the emergency section because it is another
flushing mechanism that should occur after the consoles have
been triggered to flush.

Signed-off-by: John Ogness <[email-masked]>
Signed-off-by: Sebastian Andrzej Siewior <[email-masked]>
---
 kernel/panic.c |    2 ++
 1 file changed, 2 insertions(+)

Index: linux-6.8.2-rt10/kernel/panic.c
===================================================================
--- linux-6.8.2-rt10.orig/kernel/panic.c
+++ linux-6.8.2-rt10/kernel/panic.c
@@ -634,6 +634,7 @@ bool oops_may_print(void)
  */
 void oops_enter(void)
 {
+	nbcon_cpu_emergency_enter();
 	tracing_off();
 	/* can't trust the integrity of the kernel anymore: */
 	debug_locks_off();
@@ -656,6 +657,7 @@ void oops_exit(void)
 {
 	do_oops_enter_exit();
 	print_oops_end_marker();
+	nbcon_cpu_emergency_exit();
 	kmsg_dump(KMSG_DUMP_OOPS);
 }