From nobody Wed Dec 31 02:42:25 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C92F0C4332F for ; Sun, 12 Nov 2023 13:41:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231864AbjKLNl7 (ORCPT ); Sun, 12 Nov 2023 08:41:59 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38562 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231441AbjKLNln (ORCPT ); Sun, 12 Nov 2023 08:41:43 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E328B7D8C; Sun, 12 Nov 2023 05:30:28 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C6832C43391; Sun, 12 Nov 2023 13:30:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1699795807; bh=tNC/DsCjLvIyEu8EYISzzrl6+JlkcbjlQUsWvWqeMGM=; h=From:To:Cc:Subject:Date:From; b=Qzd4OfTQ3qtpvrDWH/qllCR4nfFbh2+JJXxgpe/1Fh7Bm8TRunpgqviXK+zOONA25 mYmWIPf8tmOKr8Ovz2YAs6nFQlXJsy6bjz7AG4csQgXeC71jkAndO8iBaUs/l0rOKW iyxX4L4UruCxl+VLKASnWVTN/B7uJXgLUPExbsT8WYX+d3lkCpHkPg00E5hUfyZnkU 9szUGFycTlAxUoOuffsawMQMqdBZTmtik5B74dJV/txS+OnNBuGUUVSAyhlEMEHFS9 8blMaZ4vbMeTehsnBNMlAMUh4pte/xkcvw4tOkggiU6B8qaIgk/ZnvmmEwIbLjLPYS p6syiwBVsU97g== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Douglas Anderson , Daniel Thompson , Sasha Levin , jason.wessel@windriver.com, kgdb-bugreport@lists.sourceforge.net Subject: [PATCH AUTOSEL 6.1] kgdb: Flush console before entering kgdb on panic Date: Sun, 12 Nov 2023 08:30:04 -0500 Message-ID: <20231112133005.177227-1-sashal@kernel.org> X-Mailer: git-send-email 2.42.0 MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.1.62 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Douglas Anderson [ Upstream commit dd712d3d45807db9fcae28a522deee85c1f2fde6 ] When entering kdb/kgdb on a kernel panic, it was be observed that the console isn't flushed before the `kdb` prompt came up. Specifically, when using the buddy lockup detector on arm64 and running: echo HARDLOCKUP > /sys/kernel/debug/provoke-crash/DIRECT I could see: [ 26.161099] lkdtm: Performing direct entry HARDLOCKUP [ 32.499881] watchdog: Watchdog detected hard LOCKUP on cpu 6 [ 32.552865] Sending NMI from CPU 5 to CPUs 6: [ 32.557359] NMI backtrace for cpu 6 ... [backtrace for cpu 6] ... [ 32.558353] NMI backtrace for cpu 5 ... [backtrace for cpu 5] ... [ 32.867471] Sending NMI from CPU 5 to CPUs 0-4,7: [ 32.872321] NMI backtrace forP cpuANC: Hard LOCKUP Entering kdb (current=3D..., pid 0) on processor 5 due to Keyboard Entry [5]kdb> As you can see, backtraces for the other CPUs start printing and get interleaved with the kdb PANIC print. Let's replicate the commands to flush the console in the kdb panic entry point to avoid this. Signed-off-by: Douglas Anderson Link: https://lore.kernel.org/r/20230822131945.1.I5b460ae8f954e4c4f628a373d= 6e74713c06dd26f@changeid Signed-off-by: Daniel Thompson Signed-off-by: Sasha Levin --- kernel/debug/debug_core.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c index d5e9ccde3ab8e..3a904d8697c8f 100644 --- a/kernel/debug/debug_core.c +++ b/kernel/debug/debug_core.c @@ -1006,6 +1006,9 @@ void kgdb_panic(const char *msg) if (panic_timeout) return; =20 + debug_locks_off(); + console_flush_on_panic(CONSOLE_FLUSH_PENDING); + if (dbg_kdb_mode) kdb_printf("PANIC: %s\n", msg); =20 --=20 2.42.0