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 87EFEC54EE9 for ; Sun, 18 Sep 2022 14:14:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229495AbiIROOL (ORCPT ); Sun, 18 Sep 2022 10:14:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57390 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229572AbiIROOK (ORCPT ); Sun, 18 Sep 2022 10:14:10 -0400 Received: from fanzine2.igalia.com (fanzine.igalia.com [178.60.130.6]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1A7E923BF5; Sun, 18 Sep 2022 07:14:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:From: References:Cc:To:Subject:MIME-Version:Date:Message-ID:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=aDVyle5G3wtqIccxn/cBaHSZXXYVPnL6YNcpcqqbsXA=; b=I91NEcebw/ZpGroEZ11QU1CmBe qxInUn7rIoCX3CLVXGhhGfuz+ZmBv0nnIWJh9TyhqERtkoI6T0q2tisSnIhmcbyHxJNdNYDBf6A1N gTXmzClAfzBC6LtN7rIjPVIzVgYFHk9nHdF582Rl4jILjOuN6k+loxnoLdkCmi5LdumVTOSZpDK+q Y9ZtTZSPLNeG5QmwQkdpsdADSwd10DInYUGS44hH9YkaF7zoTcmDEKMFJKQSo+EaCUbjvmfZRaOT+ Fslvq1PhA/2XIP1FVDJ6gsObNe9jSJWV0qymX9tQ4eqaV/F9OhxifebTXFFT52vNbBeWX0rN5rjcI bBzgCpTg==; Received: from 201-27-35-168.dsl.telesp.net.br ([201.27.35.168] helo=[192.168.1.60]) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_128_GCM:128) (Exim) id 1oZv3a-0081yC-2g; Sun, 18 Sep 2022 16:14:02 +0200 Message-ID: <09016e20-5b38-3650-24bf-5fd649ee9b93@igalia.com> Date: Sun, 18 Sep 2022 11:13:28 -0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Subject: Re: [PATCH V3 11/11] panic: Fixes the panic_print NMI backtrace setting Content-Language: en-US To: akpm@linux-foundation.org, kexec@lists.infradead.org Cc: bhe@redhat.com, pmladek@suse.com, linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org, netdev@vger.kernel.org, x86@kernel.org, kernel-dev@igalia.com, kernel@gpiccoli.net, halves@canonical.com, fabiomirmar@gmail.com, alejandro.j.jimenez@oracle.com, andriy.shevchenko@linux.intel.com, arnd@arndb.de, bp@alien8.de, corbet@lwn.net, d.hatayama@jp.fujitsu.com, dave.hansen@linux.intel.com, dyoung@redhat.com, feng.tang@intel.com, gregkh@linuxfoundation.org, mikelley@microsoft.com, hidehiro.kawai.ez@hitachi.com, jgross@suse.com, john.ogness@linutronix.de, keescook@chromium.org, luto@kernel.org, mhiramat@kernel.org, mingo@redhat.com, paulmck@kernel.org, peterz@infradead.org, rostedt@goodmis.org, senozhatsky@chromium.org, stern@rowland.harvard.edu, tglx@linutronix.de, vgoyal@redhat.com, vkuznets@redhat.com, will@kernel.org, xuqiang36@huawei.com References: <20220819221731.480795-1-gpiccoli@igalia.com> <20220819221731.480795-12-gpiccoli@igalia.com> From: "Guilherme G. Piccoli" In-Reply-To: <20220819221731.480795-12-gpiccoli@igalia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org On 19/08/2022 19:17, Guilherme G. Piccoli wrote: > Commit 8d470a45d1a6 ("panic: add option to dump all CPUs backtraces in panic_print") > introduced a setting for the "panic_print" kernel parameter to allow > users to request a NMI backtrace on panic. Problem is that the panic_print > handling happens after the secondary CPUs are already disabled, hence > this option ended-up being kind of a no-op - kernel skips the NMI trace > in idling CPUs, which is the case of offline CPUs. > > Fix it by checking the NMI backtrace bit in the panic_print prior to > the CPU disabling function. > > Fixes: 8d470a45d1a6 ("panic: add option to dump all CPUs backtraces in panic_print") > Cc: Feng Tang > Cc: Petr Mladek > Signed-off-by: Guilherme G. Piccoli > > --- > > V3: > - No changes. > > V2: > - new patch, there was no V1 of this one. > > Hi folks, thanks upfront for reviews. This is a new patch, fixing an issue > I found in my tests, so I shoved it into this fixes series. > > Notice that while at it, I got rid of the "crash_kexec_post_notifiers" > local copy in panic(). This was introduced by commit b26e27ddfd2a > ("kexec: use core_param for crash_kexec_post_notifiers boot option"), > but it is not clear from comments or commit message why this local copy > is required. > > My understanding is that it's a mechanism to prevent some concurrency, > in case some other CPU modify this variable while panic() is running. > I find it very unlikely, hence I removed it - but if people consider > this copy needed, I can respin this patch and keep it, even providing a > comment about that, in order to be explict about its need. > > Let me know your thoughts! Cheers, > > Guilherme > > > kernel/panic.c | 47 +++++++++++++++++++++++++++-------------------- > 1 file changed, 27 insertions(+), 20 deletions(-) > [...] Hi Andrew, sorry for the ping. Does the patch makes sense for you? Any comments are much appreciated! Tnx in advance, Guilherme