linux-kernel - [PATCH] panic: Move panic

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Message-Id: <20211230161828.121858-1-gpiccoli@igalia.com>
Date:   Thu, 30 Dec 2021 13:18:28 -0300
From:   "Guilherme G. Piccoli" <gpiccoli@...lia.com>
To:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Cc:     gpiccoli@...lia.com, kernel@...ccoli.net, pmladek@...e.com,
        senozhatsky@...omium.org, rostedt@...dmis.org,
        john.ogness@...utronix.de, feng.tang@...el.com,
        kexec@...ts.infradead.org, dyoung@...hat.com,
        keescook@...omium.org, anton@...msg.org, ccross@...roid.com,
        tony.luck@...el.com
Subject: [PATCH] panic: Move panic_print before kmsg dumpers

The panic_print setting allows users to collect more information in a
panic event, like memory stats, tasks, CPUs backtraces, etc.
This is a pretty interesting debug mechanism, but currently the print
event happens *after* kmsg_dump(), meaning that Pstore, for example,
cannot collect a dmesg with the panic_print information.

This patch changes that by moving the panic_print_sys_info() function
call up some lines, in order kmsg_dump() accounts this new information
and exposes it through Pstore or other kmsg dumpers.

Cc: Feng Tang <feng.tang@...el.com>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@...lia.com>
---

Hey folks, thanks in advance for reviews/comments!
One alternative I've considered was to move kmsg_dump() some
lines down, I'm not sure which approach is better, can't see
much difference. Opinions are very welcome =)
Cheers,

Guilherme

 kernel/panic.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/panic.c b/kernel/panic.c
index cefd7d82366f..d918da0a1c29 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -271,6 +271,8 @@ void panic(const char *fmt, ...)
 	 */
 	atomic_notifier_call_chain(&panic_notifier_list, 0, buf);

+	panic_print_sys_info();
+
 	kmsg_dump(KMSG_DUMP_PANIC);

 	/*
@@ -301,8 +303,6 @@ void panic(const char *fmt, ...)
 	debug_locks_off();
 	console_flush_on_panic(CONSOLE_FLUSH_PENDING);

-	panic_print_sys_info();
-
 	if (!panic_blink)
 		panic_blink = no_blink;

-- 
2.34.1