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From: John Ogness <john.ogness@linutronix.de>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Josh Poimboeuf <jpoimboe@kernel.org>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	"Guilherme G. Piccoli" <gpiccoli@igalia.com>,
	Kefeng Wang <wangkefeng.wang@huawei.com>,
	Uros Bizjak <ubizjak@gmail.com>,
	Arnd Bergmann <arnd@arndb.de>
Subject: [PATCH printk v4 13/14] panic: Flush kernel log buffer at the end
Date: Wed,  7 Feb 2024 14:47:02 +0106
Message-Id: <20240207134103.1357162-14-john.ogness@linutronix.de>
In-Reply-To: <20240207134103.1357162-1-john.ogness@linutronix.de>
References: <20240207134103.1357162-1-john.ogness@linutronix.de>
Precedence: bulk
MIME-Version: 1.0
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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>
Reviewed-by: Petr Mladek <pmladek@suse.com>
---
 kernel/panic.c | 8 ++++++++
 1 file changed, 8 insertions(+)

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();
-- 
2.39.2