From nobody Fri Dec 19 20:16:39 2025 Received: from mail.valinux.co.jp (mail.valinux.co.jp [210.128.90.3]) (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 550DF15098A for ; Mon, 12 Aug 2024 07:27:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=210.128.90.3 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723447662; cv=none; b=hc7OQ3RqWGISuWUBbozSxcVFifwFB6W0Hv+xJ5XiB+NB0C+ioJO2KU+j/qxytFiqksWT9n3DHCFZhL7Pj8qZC1/hIiA5GivCQDd9osuhxvcPbGCFXMH4yLa7K66tJiaxPqBzLzpJm8p/TUEu70dlCzJmdCpTGeL9jwI7xI2X9BQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723447662; c=relaxed/simple; bh=80BpKBUj/6IL2a36Mynw3AbqPtC9KyrQGFqkt56TbeU=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=bL4IPJvLcIlvrdIxiA3HNWHZu9X2CjHBWewnknHAkv5c1nokbmSnKzpl+X9KgZe+MP26rlrAHQEh9DaYmrLrtv8X7EVLRFlK50XPoccSmunZhk35Mm46uQFHgCqLLhZ7A7KKsmiu6VfGJlIOKExgiEEHq0Vq86/3IowPftrTlzI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=valinux.co.jp; spf=pass smtp.mailfrom=valinux.co.jp; arc=none smtp.client-ip=210.128.90.3 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=valinux.co.jp Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=valinux.co.jp Received: from localhost (localhost [127.0.0.1]) by mail.valinux.co.jp (Postfix) with ESMTP id 2D489A9E3D; Mon, 12 Aug 2024 16:27:38 +0900 (JST) X-Virus-Scanned: Debian amavisd-new at valinux.co.jp Received: from mail.valinux.co.jp ([127.0.0.1]) by localhost (mail.valinux.co.jp [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id exf96Y1OiL57; Mon, 12 Aug 2024 16:27:38 +0900 (JST) Received: from localhost.localdomain (p10213112-ipngn20001marunouchi.tokyo.ocn.ne.jp [153.220.101.112]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by mail.valinux.co.jp (Postfix) with ESMTPSA id DAE6FA9E38; Mon, 12 Aug 2024 16:27:37 +0900 (JST) From: takakura@valinux.co.jp To: pmladek@suse.com, rostedt@goodmis.org, john.ogness@linutronix.de, senozhatsky@chromium.org, akpm@linux-foundation.org, bhe@redhat.com, lukas@wunner.de, wangkefeng.wang@huawei.com, ubizjak@gmail.com, feng.tang@intel.com, j.granados@samsung.com, stephen.s.brennan@oracle.com Cc: linux-kernel@vger.kernel.org, nishimura@valinux.co.jp, taka@valinux.co.jp, Ryo Takakura Subject: [PATCH v3 1/2] Allow cpu backtraces to be written into ringbuffer during panic Date: Mon, 12 Aug 2024 16:27:03 +0900 Message-Id: <20240812072703.339690-1-takakura@valinux.co.jp> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240812072137.339644-1-takakura@valinux.co.jp> References: <20240812072137.339644-1-takakura@valinux.co.jp> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Ryo Takakura commit 779dbc2e78d7 ("printk: Avoid non-panic CPUs writing to ringbuffer") disabled non-panic CPUs to further write messages to ringbuffer after panicked. Since the commit, non-panicked CPU's are not allowed to write to ring buffer after panicked and CPU backtrace which is triggered after panicked to sample non-panicked CPUs' backtrace no longer serves its function as it has nothing to print. Fix the issue by allowing non-panicked CPUs to write into ringbuffer while CPU backtrace is in flight. Fixes: 779dbc2e78d7 ("printk: Avoid non-panic CPUs writing to ringbuffer") Signed-off-by: Ryo Takakura Reviewed-by: Petr Mladek --- include/linux/panic.h | 1 + kernel/panic.c | 8 +++++++- kernel/printk/printk.c | 2 +- 3 files changed, 9 insertions(+), 2 deletions(-) diff --git a/include/linux/panic.h b/include/linux/panic.h index 3130e0b51..54d90b6c5 100644 --- a/include/linux/panic.h +++ b/include/linux/panic.h @@ -16,6 +16,7 @@ extern void oops_enter(void); extern void oops_exit(void); extern bool oops_may_print(void); =20 +extern bool panic_triggering_all_cpu_backtrace; extern int panic_timeout; extern unsigned long panic_print; extern int panic_on_oops; diff --git a/kernel/panic.c b/kernel/panic.c index f861bedc1..2a0449144 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -64,6 +64,8 @@ unsigned long panic_on_taint; bool panic_on_taint_nousertaint =3D false; static unsigned int warn_limit __read_mostly; =20 +bool panic_triggering_all_cpu_backtrace; + int panic_timeout =3D CONFIG_PANIC_TIMEOUT; EXPORT_SYMBOL_GPL(panic_timeout); =20 @@ -253,8 +255,12 @@ 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) { + /* Temporary allow non-panic CPUs to write their backtraces. */ + panic_triggering_all_cpu_backtrace =3D true; trigger_all_cpu_backtrace(); + panic_triggering_all_cpu_backtrace =3D false; + } =20 /* * Note that smp_send_stop() is the usual SMP shutdown function, diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 054c0e778..c22b07049 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2316,7 +2316,7 @@ asmlinkage int vprintk_emit(int facility, int level, * non-panic CPUs are generating any messages, they will be * silently dropped. */ - if (other_cpu_in_panic()) + if (other_cpu_in_panic() && !panic_triggering_all_cpu_backtrace) return 0; =20 if (level =3D=3D LOGLEVEL_SCHED) { --=20 2.34.1