linux-kernel - [PATCH v2 1/2] Handle flushing of CPU backtraces during panic

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Message-Id: <20240803081230.223512-1-takakura@valinux.co.jp>
Date: Sat,  3 Aug 2024 17:12:30 +0900
From: takakura@...inux.co.jp
To: pmladek@...e.com,
	rostedt@...dmis.org,
	john.ogness@...utronix.de,
	senozhatsky@...omium.org,
	akpm@...ux-foundation.org,
	bhe@...hat.com,
	lukas@...ner.de,
	wangkefeng.wang@...wei.com,
	ubizjak@...il.com,
	feng.tang@...el.com,
	j.granados@...sung.com,
	stephen.s.brennan@...cle.com
Cc: linux-kernel@...r.kernel.org,
	nishimura@...inux.co.jp,
	taka@...inux.co.jp,
	Ryo Takakura <takakura@...inux.co.jp>
Subject: [PATCH v2 1/2] Handle flushing of CPU backtraces during panic

From: Ryo Takakura <takakura@...inux.co.jp>

After panic, non-panicked CPU's has been unable to flush ringbuffer 
while they can still write into it. This can affect CPU backtrace 
triggered in panic only able to write into ringbuffer incapable of 
flushing them.

Fix the issue by letting the panicked CPU handle the flushing of 
ringbuffer right after non-panicked CPUs finished writing their
backtraces.

Signed-off-by: Ryo Takakura <takakura@...inux.co.jp>
---
 kernel/panic.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/panic.c b/kernel/panic.c
index 7e2070925..f94923a63 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -252,8 +252,10 @@ void check_panic_on_warn(const char *origin)
  */
 static void panic_other_cpus_shutdown(bool crash_kexec)
 {
-	if (panic_print & PANIC_PRINT_ALL_CPU_BT)
+	if (panic_print & PANIC_PRINT_ALL_CPU_BT) {
 		trigger_all_cpu_backtrace();
+		console_flush_on_panic(CONSOLE_FLUSH_PENDING);
+	}
 
 	/*
 	 * Note that smp_send_stop() is the usual SMP shutdown function,
-- 
2.34.1