From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752553AbaDQPci (ORCPT ); Thu, 17 Apr 2014 11:32:38 -0400 Received: from mail-qa0-f41.google.com ([209.85.216.41]:44257 "EHLO mail-qa0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751076AbaDQPc3 (ORCPT ); Thu, 17 Apr 2014 11:32:29 -0400 Date: Thu, 17 Apr 2014 11:35:45 -0400 (EDT) From: Vince Weaver To: Peter Zijlstra cc: Vince Weaver , Ingo Molnar , linux-kernel@vger.kernel.org, Thomas Gleixner Subject: Re: [perf] more perf_fuzzer memory corruption In-Reply-To: <20140417145418.GM11096@twins.programming.kicks-ass.net> Message-ID: References: <20140416141514.GS11182@twins.programming.kicks-ass.net> <20140417094815.GA9348@gmail.com> <20140417114533.GJ11096@twins.programming.kicks-ass.net> <20140417142213.GA29338@gmail.com> <20140417145418.GM11096@twins.programming.kicks-ass.net> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 17 Apr 2014, Peter Zijlstra wrote: > > Meh.. my machine keeps locking up with 15-rc1 and your fuzzer. It looks > to get stuck a finish_task_switch() from a preemption while waiting for > a perf IPI. > > Which is complete crack because we have preemption disabled over > issueing and waiting for the IPI :/ > > I tried reverting some of the IPI related patches, but no joy so far, > I'm about to go try a git-bisect on this. Bisecting can be a pain, as if you go too far back you start running into other bugs that have been fixed due to the fuzzer. Over the past year there's been at least 10 perf_fuzzer-related crash fixes that have gotten into the kernel. It used to be I could crash things in seconds, it's now up to minutes-hours but the bugs are that much harder to isolate :( And I still am not fuzzing with signal-overflow enabled, which causes even more pain. Vince