From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933268AbcIOMsI (ORCPT ); Thu, 15 Sep 2016 08:48:08 -0400 Received: from mail-it0-f45.google.com ([209.85.214.45]:35114 "EHLO mail-it0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933906AbcIOMsE (ORCPT ); Thu, 15 Sep 2016 08:48:04 -0400 From: Vince Weaver X-Google-Original-From: Vince Weaver Date: Thu, 15 Sep 2016 08:47:25 -0400 (EDT) X-X-Sender: vince@macbook-air To: Stephane Eranian cc: LKML , Alexander Shishkin , Peter Zijlstra , Ingo Molnar Subject: Re: perf: perf_fuzzer lockup in perf_cgroup_attach In-Reply-To: Message-ID: References: User-Agent: Alpine 2.20 (DEB 67 2015-01-07) 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 Wed, 14 Sep 2016, Stephane Eranian wrote: > I would think there is a way to disable KASLR for this kind of testing! yes, it's just I hadn't realized I had it enabled until I couldn't figure out why addr2line wasn't working. > Which of your fuzzer scripts are you using? fast_repro99.sh? yes. I should probably give that script a more meaningful name, but by now I think it's too late for that. I also am running with paranoid set to "0" > > > The best I can tell things are getting wedged somehow in > > perf_cgroup_switch() while interrupts are disabled. Interrupts are never > > getting re-enabled, causing the RCU and NMI watchdogs to trigger (and more > > alarming things like the SATA bus resetting). > > > How do you get to perf_cgroup_switch() from the traces you provide below? It was my best guess after trying to trace through the code. It could in theory be anywhere but it definitely seems like it is happening after perf_cgroup_attach at some point when interrupts are disabled (possibly ftrace too?) It's difficult because some code gets inlined and then it's jumping to a function pointer. And then mid-debug the system finally had enough and started making threads hang forever while I was getting close. I've rebooted the machine I'll see if I can replicate. Vince