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=-2.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 75E95C4360F for ; Thu, 4 Apr 2019 16:47:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3E2B020693 for ; Thu, 4 Apr 2019 16:47:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="vT41n3az" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729400AbfDDQrF (ORCPT ); Thu, 4 Apr 2019 12:47:05 -0400 Received: from mail-lj1-f195.google.com ([209.85.208.195]:36824 "EHLO mail-lj1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727212AbfDDQrE (ORCPT ); Thu, 4 Apr 2019 12:47:04 -0400 Received: by mail-lj1-f195.google.com with SMTP id r24so2720305ljg.3 for ; Thu, 04 Apr 2019 09:47:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=EuUJCkkF8EMeJhXuUWpVcEjJ3aQNWsOOW9Ft9o4wkUw=; b=vT41n3azLBzPxsjuLtHLjhEXyWSoRrYcY8AOY4/ad1KCN3DBKMX3gZK+X+yigUPKUo rx6foXla0O3fYtS+m9Dfa03GpjfFELLvkGaTC8d2TbzYfmisEP/k7saD8BfKPDLe8UZV jGC+sjzPxo6lCGNdoOrvdBWMyVebByL2ZlDU/rKQNvBCRwFYiEZFtI8TyBsYf4xeqH6p 4O/XHAIRuwNNKBvyc9jcBHf6KQgiIZAKelygbp3jnr6ECDqM/oD90VA9HKJCZwZUe7i1 pyXP5Te5qbzyoxx8NHtzWjL/1fqYfHDcIPwvacC344nkbCmdraQYfXhczaBsbUox1Qbd EvxQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=EuUJCkkF8EMeJhXuUWpVcEjJ3aQNWsOOW9Ft9o4wkUw=; b=NjYZbBsscexaoatQoqjHaGSDaO500jT9a3hosIm65SMpH7oB78UlMpN4kBnweKxfg8 gVZ9YM87Qh9bBK89B4u9tsYVwqrbsSjJ8lb31xkebJ3beZdW7jcR6MzlL+/axCjMpJDF uvHeLlEvKceoHmNwEknkJB/n3wHpL6mFOlWBLQ0VLSOMLyZ62oaRoZbHYpz2hzk9rphg nmuTxE0OJxd369GsjcbLu46iqAahaad5HLtzibyoxdSi0esS4HxlMTjWuoYhb5TgO4j9 oPvN3KGO0+JN/yOF7UlA3OicE9y/cKZ1M7WT785pFi6LU97Wg+dNSaSxkFwSgJBR6SHN JjJA== X-Gm-Message-State: APjAAAXuzA2LeTaSWD+vkU5B59LL6FllNlDGYehVutuiTVahFrGOQ7qT jBXYoRrc8BUGOU5hrC3qsrp6qcEh X-Google-Smtp-Source: APXvYqwIH35wa0aknRh53RHPK4HJD8UsM+ImzyK4tKGrlpokK5Qc0Lec99iRXt6HjV2MmKcjk1bgNw== X-Received: by 2002:a2e:8648:: with SMTP id i8mr4086539ljj.166.1554396422353; Thu, 04 Apr 2019 09:47:02 -0700 (PDT) Received: from uranus.localdomain ([5.18.103.226]) by smtp.gmail.com with ESMTPSA id i66sm4079357lji.43.2019.04.04.09.47.01 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 04 Apr 2019 09:47:01 -0700 (PDT) Received: by uranus.localdomain (Postfix, from userid 1000) id 73C21460438; Thu, 4 Apr 2019 19:47:00 +0300 (MSK) Date: Thu, 4 Apr 2019 19:47:00 +0300 From: Cyrill Gorcunov To: Vince Weaver Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, Arnaldo Carvalho de Melo , Alexander Shishkin , Ingo Molnar , Borislav Petkov , Namhyung Kim , Thomas Gleixner , Jiri Olsa , Stephane Eranian Subject: Re: perf: perf_fuzzer crashes on Pentium 4 systems Message-ID: <20190404164700.GR1421@uranus.lan> References: <20190403191944.GH1421@uranus.lan> <20190403203144.GI1421@uranus.lan> <20190404133327.GP1421@uranus.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 04, 2019 at 12:37:18PM -0400, Vince Weaver wrote: > On Thu, 4 Apr 2019, Cyrill Gorcunov wrote: > > > On Thu, Apr 04, 2019 at 09:25:47AM -0400, Vince Weaver wrote: > > > > > > It looks like there are at least two bugs here, one that's a full > > > hardlockup with nothing on serial console. The other is the NULL > > > dereference. > > OK, it turns out the hard-lock and the null pointer dereference might be > the same, I have a random seed for the fuzzer from a hard-lock crash that > reproduces and it generated the null pointer crash. (This is with your > patch applied). I see. My patch simply eliminates wrong event for unimplemented general events, but it definitely won't help with nil deref, so it mostly to eliminate some potential side effects. > I can try to see if I can bisect down to a specific event sequence that > triggers this, but that can be tricky sometimes if things lock up so fast > that the event log doesn't get written out before the crash. Oh, Vince, I suspect such kind of bisection might consume a lot of your time :( Maybe we could update perf fuzzer so that it would send events to some net-storage first then write them to the counters, iow to automatize this all stuff somehow?