Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753430AbdLMQbm (ORCPT ); Wed, 13 Dec 2017 11:31:42 -0500 Received: from mail.kernel.org ([198.145.29.99]:53886 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752811AbdLMQbi (ORCPT ); Wed, 13 Dec 2017 11:31:38 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BEE6921877 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Wed, 13 Dec 2017 11:31:35 -0500 From: Steven Rostedt To: Peter Zijlstra Cc: Ilia Mirkin , Ingo Molnar , "linux-kernel@vger.kernel.org" , Pekka Paalanen , Lyude , Thomas Gleixner , Karol Herbst , Linus Torvalds , hpa@zytor.com, linux-tip-commits@vger.kernel.org, Karol Herbst Subject: Re: [tip:x86/urgent] x86/mm/kmmio: Fix mmiotrace for page unaligned addresses Message-ID: <20171213113135.1a8af60d@gandalf.local.home> In-Reply-To: <20171212145105.6rfbdbty6e5ajron@hirez.programming.kicks-ass.net> References: <20171127075139.4928-1-kherbst@redhat.com> <20171212134952.2hok6754245qshv3@hirez.programming.kicks-ass.net> <20171212140418.56xld2lxja5rywp7@gmail.com> <20171212144334.slrpfdtptr5nhuhx@hirez.programming.kicks-ass.net> <20171212145105.6rfbdbty6e5ajron@hirez.programming.kicks-ass.net> X-Mailer: Claws Mail 3.14.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1204 Lines: 42 On Tue, 12 Dec 2017 15:51:05 +0100 Peter Zijlstra wrote: > On Tue, Dec 12, 2017 at 09:47:05AM -0500, Ilia Mirkin wrote: > > > So this 'thing' has huge gaping SMP holes in. > > > > Sure does! Probably why the following happens when mmiotrace is enabled: > > > > void enable_mmiotrace(void) > > { > > mutex_lock(&mmiotrace_mutex); > > if (is_enabled()) > > goto out; > > > > if (nommiotrace) > > pr_info("MMIO tracing disabled.\n"); > > kmmio_init(); > > enter_uniprocessor(); > > ^^^^^ > > Ah! I completely missed that. OK, that makes it much less broken :-) /me just saw this thread. Once I saw your initial complaint, my first thought was "I think he doesn't know that it causes the system to turn into a uniprocessor first". My ftrace tests have a test that switches to each tracer, and this mmiotrace catches the most bugs after an rc1 release. The bugs are triggered by switching to and from uniprocessor mode. Hopefully, with the new hotplug code, that will be a thing of the past. > > If I don't forget, I'll add some comments to this file to clarify that. Great, thanks! -- Steve >