From mboxrd@z Thu Jan 1 00:00:00 1970 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 9622FC433FE for ; Fri, 25 Mar 2022 01:35:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1357467AbiCYBhO (ORCPT ); Thu, 24 Mar 2022 21:37:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39210 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357527AbiCYBf5 (ORCPT ); Thu, 24 Mar 2022 21:35:57 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2147B3BBDD for ; Thu, 24 Mar 2022 18:34:18 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id B093860A50 for ; Fri, 25 Mar 2022 01:34:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1572CC340EC; Fri, 25 Mar 2022 01:34:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1648172057; bh=Bz5i+bJPmuKlGzOPWuwa9RpNzSx9IdzcjOzodhLio9c=; h=Date:To:From:Subject:From; b=xmiE+3pHRbZJ9e28lVAIfDDpkBqSR2esWXPDmlE5aVeGIYCOvpx10d6MyW2lWX+q4 ruGBWrhmn9gHLW8WUKcCoua0vAnIM0Xa1lAcjJJkIAyfDXuOHbZ/mh45AjhrHqj9K4 kmjFiVYZ8lDEakGZfMSDzyZMYf/xudAH0PUXoDhc= Date: Thu, 24 Mar 2022 18:34:16 -0700 To: mm-commits@vger.kernel.org, senozhatsky@chromium.org, pmladek@suse.com, feng.tang@intel.com, bhe@redhat.com, gpiccoli@igalia.com, akpm@linux-foundation.org From: Andrew Morton Subject: [merged] panic-move-panic_print-before-kmsg-dumpers.patch removed from -mm tree Message-Id: <20220325013417.1572CC340EC@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: panic: move panic_print before kmsg dumpers has been removed from the -mm tree. Its filename was panic-move-panic_print-before-kmsg-dumpers.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: "Guilherme G. Piccoli" Subject: 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 an 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 extra information. This patch changes that in 2 steps: (a) The panic_print setting allows to replay the existing kernel log buffer to the console (bit 5), besides the extra information dump. This functionality makes sense only at the end of the panic() function. So, we hereby allow to distinguish the two situations by a new boolean parameter in the function panic_print_sys_info(). (b) With the above change, we can safely call panic_print_sys_info() before kmsg_dump(), allowing to dump the extra information when using pstore or other kmsg dumpers. The additional messages from panic_print could overwrite the oldest messages when the buffer is full. The only reasonable solution is to use a large enough log buffer, hence we added an advice into the kernel parameters documentation about that. Link: https://lkml.kernel.org/r/20220214141308.841525-1-gpiccoli@igalia.com Signed-off-by: Guilherme G. Piccoli Acked-by: Baoquan He Reviewed-by: Petr Mladek Reviewed-by: Sergey Senozhatsky Cc: Feng Tang Signed-off-by: Andrew Morton --- Documentation/admin-guide/kernel-parameters.txt | 4 ++++ kernel/panic.c | 13 +++++++++---- 2 files changed, 13 insertions(+), 4 deletions(-) --- a/Documentation/admin-guide/kernel-parameters.txt~panic-move-panic_print-before-kmsg-dumpers +++ a/Documentation/admin-guide/kernel-parameters.txt @@ -3727,6 +3727,10 @@ bit 4: print ftrace buffer bit 5: print all printk messages in buffer bit 6: print all CPUs backtrace (if available in the arch) + *Be aware* that this option may print a _lot_ of lines, + so there are risks of losing older messages in the log. + Use this option carefully, maybe worth to setup a + bigger log buffer with "log_buf_len" along with this. panic_on_taint= Bitmask for conditionally calling panic() in add_taint() Format: [,nousertaint] --- a/kernel/panic.c~panic-move-panic_print-before-kmsg-dumpers +++ a/kernel/panic.c @@ -148,10 +148,13 @@ void nmi_panic(struct pt_regs *regs, con } EXPORT_SYMBOL(nmi_panic); -static void panic_print_sys_info(void) +static void panic_print_sys_info(bool console_flush) { - if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG) - console_flush_on_panic(CONSOLE_REPLAY_ALL); + if (console_flush) { + if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG) + console_flush_on_panic(CONSOLE_REPLAY_ALL); + return; + } if (panic_print & PANIC_PRINT_ALL_CPU_BT) trigger_all_cpu_backtrace(); @@ -286,6 +289,8 @@ void panic(const char *fmt, ...) */ atomic_notifier_call_chain(&panic_notifier_list, 0, buf); + panic_print_sys_info(false); + kmsg_dump(KMSG_DUMP_PANIC); /* @@ -316,7 +321,7 @@ void panic(const char *fmt, ...) debug_locks_off(); console_flush_on_panic(CONSOLE_FLUSH_PENDING); - panic_print_sys_info(); + panic_print_sys_info(true); if (!panic_blink) panic_blink = no_blink; _ Patches currently in -mm which might be from gpiccoli@igalia.com are