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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D4506C433DF for ; Fri, 29 May 2020 16:15:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BA99F2077D for ; Fri, 29 May 2020 16:15:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727024AbgE2QPW convert rfc822-to-8bit (ORCPT ); Fri, 29 May 2020 12:15:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57206 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725601AbgE2QPV (ORCPT ); Fri, 29 May 2020 12:15:21 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 762A2C03E969; Fri, 29 May 2020 09:15:21 -0700 (PDT) Received: from bigeasy by Galois.linutronix.de with local (Exim 4.80) (envelope-from ) id 1jehfC-0000nm-H5; Fri, 29 May 2020 18:15:18 +0200 Date: Fri, 29 May 2020 18:15:18 +0200 From: Sebastian Andrzej Siewior To: Mark Marshall Cc: linux-rt-users , Mark Marshall , thomas.graziadei@omicronenergy.com, Thomas Gleixner , linux-kernel@vger.kernel.org, rostedt@goodmis.org Subject: Re: Kernel crash due to memory corruption with v5.4.26-rt17 and PowerPC e500 Message-ID: <20200529161518.svpxhkeljafbtdz2@linutronix.de> References: <20200529131452.pgj7mx7xaz7n4kz3@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8BIT In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-05-29 17:38:39 [+0200], Mark Marshall wrote: > Hi Sebastian & list, Hi, > I had assumed that my e-mail had got lost or overlooked, I was meaning to > post a follow up message this week... > > All I could find from the debugging and tracing that we added was that > something was going wrong with the mm data structures somewhere in the > exec code. In the end I just spent a week or two pouring over the diffs > of this code between the versions that I new worked and didn't work. > > I eventually found the culprit. On the working kernel versions there is > a patch called "mm: Protect activate_mm() by preempt_[disable&enable]_rt()". > This is commit f0b4a9cb253a on the V4.19.82-rt30 branch, for instance. > Although the commit message talks about ARM, it seems that we need this for > PowerPC too (I guess, any PowerPC with the "nohash" MMU?). Could you drop me your config, please? I need to dig here a little and I should have seen this on qemu, right? > Could you please add this commit back to the RT branch? I'm not sure how > to find out the history of this commit. For instance, why has it been > removed from the RT patchset? How are these things tracked, generally? I dropped that patch in v5.4.3-rt1. I couldn't reproduce the issue that was documented in the patch and the code that triggered the warning was removed / reworked in commit b5466f8728527 ("ARM: mm: remove IPI broadcasting on ASID rollover") So it looked like no longer needed and then got dropped during the rebase. In order to get it back into the RT queue I need to understand why it is required. What exactly is it fixing. Let me stare at for a little… > Best regards, > Mark Sebastian