diff mbox series

[printk,v3,14/14] panic: Flush kernel log buffer at the end

Message ID 20231214214201.499426-15-john.ogness@linutronix.de
State New
Headers
Series fix console flushing |

Commit Message

John Ogness Dec. 14, 2023, 9:42 p.m. UTC 
  If the kernel crashes in a context where printk() calls always
defer printing (such as in NMI or inside a printk_safe section)
then the final panic messages will be deferred to irq_work. But
if irq_work is not available, the messages will not get printed
unless explicitly flushed. The result is that the final
"end Kernel panic" banner does not get printed.

Add one final flush after the last printk() call to make sure
the final panic messages make it out as well.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
 kernel/panic.c | 8 ++++++++
 1 file changed, 8 insertions(+)

Comments

Petr Mladek Feb. 2, 2024, 9:30 a.m. UTC | #1 
On Thu 2023-12-14 22:48:01, John Ogness wrote:
> If the kernel crashes in a context where printk() calls always
> defer printing (such as in NMI or inside a printk_safe section)
> then the final panic messages will be deferred to irq_work. But
> if irq_work is not available, the messages will not get printed
> unless explicitly flushed. The result is that the final
> "end Kernel panic" banner does not get printed.
> 
> Add one final flush after the last printk() call to make sure
> the final panic messages make it out as well.
> 
> Signed-off-by: John Ogness <john.ogness@linutronix.de>

Makes sense.

Reviewed-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr
diff mbox series

Patch

diff --git a/kernel/panic.c b/kernel/panic.c
index 2807639aab51..f22d8f33ea14 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -446,6 +446,14 @@  void panic(const char *fmt, ...)
 
 	/* Do not scroll important messages printed above */
 	suppress_printk = 1;
+
+	/*
+	 * The final messages may not have been printed if in a context that
+	 * defers printing (such as NMI) and irq_work is not available.
+	 * Explicitly flush the kernel log buffer one last time.
+	 */
+	console_flush_on_panic(CONSOLE_FLUSH_PENDING);
+
 	local_irq_enable();
 	for (i = 0; ; i += PANIC_TIMER_STEP) {
 		touch_softlockup_watchdog();