From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 561DE6ABA for ; Wed, 23 Mar 2022 23:07:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 20A52C340E9; Wed, 23 Mar 2022 23:07:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1648076827; bh=VqhygAS1t2nG4D0I4BLfEi0GaTUbQew/QgIBNQ+wk84=; h=Date:To:From:In-Reply-To:Subject:From; b=VUH+4Wn3UGxrIFstuc6TQW0EWOHBu6fooelqo+Sx1DK0XH75WVjcC9qRcVncsaAZ5 qWsg/4yISElhV6WqFenc5EmcH2Fj92McDeoz5uj0vIOuETBopmEPsg8/HaS3DzFwS1 RgduCnkET99292/h2Yj+c2fXKIW9Ed9g4eDUSqME= Date: Wed, 23 Mar 2022 16:07:06 -0700 To: yzaikin@google.com,siglesias@igalia.com,mcgrof@kernel.org,keescook@chromium.org,feng.tang@intel.com,gpiccoli@igalia.com,akpm@linux-foundation.org,patches@lists.linux.dev,linux-mm@kvack.org,mm-commits@vger.kernel.org,torvalds@linux-foundation.org,akpm@linux-foundation.org From: Andrew Morton In-Reply-To: <20220323160453.65922ced539cbf445b191555@linux-foundation.org> Subject: [patch 36/41] panic: add option to dump all CPUs backtraces in panic_print Message-Id: <20220323230707.20A52C340E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: From: "Guilherme G. Piccoli" Subject: panic: add option to dump all CPUs backtraces in panic_print Currently the "panic_print" parameter/sysctl allows some interesting debug information to be printed during a panic event. This is useful for example in cases the user cannot kdump due to resource limits, or if the user collects panic logs in a serial output (or pstore) and prefers a fast reboot instead of a kdump. Happens that currently there's no way to see all CPUs backtraces in a panic using "panic_print" on architectures that support that. We do have "oops_all_cpu_backtrace" sysctl, but although partially overlapping in the functionality, they are orthogonal in nature: "panic_print" is a panic tuning (and we have panics without oopses, like direct calls to panic() or maybe other paths that don't go through oops_enter() function), and the original purpose of "oops_all_cpu_backtrace" is to provide more information on oopses for cases in which the users desire to continue running the kernel even after an oops, i.e., used in non-panic scenarios. So, we hereby introduce an additional bit for "panic_print" to allow dumping the CPUs backtraces during a panic event. Link: https://lkml.kernel.org/r/20211109202848.610874-3-gpiccoli@igalia.com Signed-off-by: Guilherme G. Piccoli Reviewed-by: Feng Tang Cc: Iurii Zaikin Cc: Kees Cook Cc: Luis Chamberlain Cc: Samuel Iglesias Gonsalvez Signed-off-by: Andrew Morton --- Documentation/admin-guide/kernel-parameters.txt | 1 + Documentation/admin-guide/sysctl/kernel.rst | 1 + kernel/panic.c | 4 ++++ 3 files changed, 6 insertions(+) --- a/Documentation/admin-guide/kernel-parameters.txt~panic-add-option-to-dump-all-cpus-backtraces-in-panic_print +++ a/Documentation/admin-guide/kernel-parameters.txt @@ -3726,6 +3726,7 @@ bit 3: print locks info if CONFIG_LOCKDEP is on bit 4: print ftrace buffer bit 5: print all printk messages in buffer + bit 6: print all CPUs backtrace (if available in the arch) panic_on_taint= Bitmask for conditionally calling panic() in add_taint() Format: [,nousertaint] --- a/Documentation/admin-guide/sysctl/kernel.rst~panic-add-option-to-dump-all-cpus-backtraces-in-panic_print +++ a/Documentation/admin-guide/sysctl/kernel.rst @@ -807,6 +807,7 @@ bit 2 print timer info bit 3 print locks info if ``CONFIG_LOCKDEP`` is on bit 4 print ftrace buffer bit 5 print all printk messages in buffer +bit 6 print all CPUs backtrace (if available in the arch) ===== ============================================ So for example to print tasks and memory info on panic, user can:: --- a/kernel/panic.c~panic-add-option-to-dump-all-cpus-backtraces-in-panic_print +++ a/kernel/panic.c @@ -66,6 +66,7 @@ EXPORT_SYMBOL_GPL(panic_timeout); #define PANIC_PRINT_LOCK_INFO 0x00000008 #define PANIC_PRINT_FTRACE_INFO 0x00000010 #define PANIC_PRINT_ALL_PRINTK_MSG 0x00000020 +#define PANIC_PRINT_ALL_CPU_BT 0x00000040 unsigned long panic_print; ATOMIC_NOTIFIER_HEAD(panic_notifier_list); @@ -152,6 +153,9 @@ static void panic_print_sys_info(void) if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG) console_flush_on_panic(CONSOLE_REPLAY_ALL); + if (panic_print & PANIC_PRINT_ALL_CPU_BT) + trigger_all_cpu_backtrace(); + if (panic_print & PANIC_PRINT_TASK_INFO) show_state(); _ 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 72677C433FE for ; Wed, 23 Mar 2022 23:07:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345451AbiCWXIt (ORCPT ); Wed, 23 Mar 2022 19:08:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54916 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345430AbiCWXIi (ORCPT ); Wed, 23 Mar 2022 19:08:38 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2ED5690CC0 for ; Wed, 23 Mar 2022 16:07:08 -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 BA3D0617C1 for ; Wed, 23 Mar 2022 23:07:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 20A52C340E9; Wed, 23 Mar 2022 23:07:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1648076827; bh=VqhygAS1t2nG4D0I4BLfEi0GaTUbQew/QgIBNQ+wk84=; h=Date:To:From:In-Reply-To:Subject:From; b=VUH+4Wn3UGxrIFstuc6TQW0EWOHBu6fooelqo+Sx1DK0XH75WVjcC9qRcVncsaAZ5 qWsg/4yISElhV6WqFenc5EmcH2Fj92McDeoz5uj0vIOuETBopmEPsg8/HaS3DzFwS1 RgduCnkET99292/h2Yj+c2fXKIW9Ed9g4eDUSqME= Date: Wed, 23 Mar 2022 16:07:06 -0700 To: yzaikin@google.com, siglesias@igalia.com, mcgrof@kernel.org, keescook@chromium.org, feng.tang@intel.com, gpiccoli@igalia.com, akpm@linux-foundation.org, patches@lists.linux.dev, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org From: Andrew Morton In-Reply-To: <20220323160453.65922ced539cbf445b191555@linux-foundation.org> Subject: [patch 36/41] panic: add option to dump all CPUs backtraces in panic_print Message-Id: <20220323230707.20A52C340E9@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: "Guilherme G. Piccoli" Subject: panic: add option to dump all CPUs backtraces in panic_print Currently the "panic_print" parameter/sysctl allows some interesting debug information to be printed during a panic event. This is useful for example in cases the user cannot kdump due to resource limits, or if the user collects panic logs in a serial output (or pstore) and prefers a fast reboot instead of a kdump. Happens that currently there's no way to see all CPUs backtraces in a panic using "panic_print" on architectures that support that. We do have "oops_all_cpu_backtrace" sysctl, but although partially overlapping in the functionality, they are orthogonal in nature: "panic_print" is a panic tuning (and we have panics without oopses, like direct calls to panic() or maybe other paths that don't go through oops_enter() function), and the original purpose of "oops_all_cpu_backtrace" is to provide more information on oopses for cases in which the users desire to continue running the kernel even after an oops, i.e., used in non-panic scenarios. So, we hereby introduce an additional bit for "panic_print" to allow dumping the CPUs backtraces during a panic event. Link: https://lkml.kernel.org/r/20211109202848.610874-3-gpiccoli@igalia.com Signed-off-by: Guilherme G. Piccoli Reviewed-by: Feng Tang Cc: Iurii Zaikin Cc: Kees Cook Cc: Luis Chamberlain Cc: Samuel Iglesias Gonsalvez Signed-off-by: Andrew Morton --- Documentation/admin-guide/kernel-parameters.txt | 1 + Documentation/admin-guide/sysctl/kernel.rst | 1 + kernel/panic.c | 4 ++++ 3 files changed, 6 insertions(+) --- a/Documentation/admin-guide/kernel-parameters.txt~panic-add-option-to-dump-all-cpus-backtraces-in-panic_print +++ a/Documentation/admin-guide/kernel-parameters.txt @@ -3726,6 +3726,7 @@ bit 3: print locks info if CONFIG_LOCKDEP is on bit 4: print ftrace buffer bit 5: print all printk messages in buffer + bit 6: print all CPUs backtrace (if available in the arch) panic_on_taint= Bitmask for conditionally calling panic() in add_taint() Format: [,nousertaint] --- a/Documentation/admin-guide/sysctl/kernel.rst~panic-add-option-to-dump-all-cpus-backtraces-in-panic_print +++ a/Documentation/admin-guide/sysctl/kernel.rst @@ -807,6 +807,7 @@ bit 2 print timer info bit 3 print locks info if ``CONFIG_LOCKDEP`` is on bit 4 print ftrace buffer bit 5 print all printk messages in buffer +bit 6 print all CPUs backtrace (if available in the arch) ===== ============================================ So for example to print tasks and memory info on panic, user can:: --- a/kernel/panic.c~panic-add-option-to-dump-all-cpus-backtraces-in-panic_print +++ a/kernel/panic.c @@ -66,6 +66,7 @@ EXPORT_SYMBOL_GPL(panic_timeout); #define PANIC_PRINT_LOCK_INFO 0x00000008 #define PANIC_PRINT_FTRACE_INFO 0x00000010 #define PANIC_PRINT_ALL_PRINTK_MSG 0x00000020 +#define PANIC_PRINT_ALL_CPU_BT 0x00000040 unsigned long panic_print; ATOMIC_NOTIFIER_HEAD(panic_notifier_list); @@ -152,6 +153,9 @@ static void panic_print_sys_info(void) if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG) console_flush_on_panic(CONSOLE_REPLAY_ALL); + if (panic_print & PANIC_PRINT_ALL_CPU_BT) + trigger_all_cpu_backtrace(); + if (panic_print & PANIC_PRINT_TASK_INFO) show_state(); _