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 6B93BC4360F for ; Thu, 4 Apr 2019 13:33:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 39D48206B7 for ; Thu, 4 Apr 2019 13:33:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="CHWYozrF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729896AbfDDNdc (ORCPT ); Thu, 4 Apr 2019 09:33:32 -0400 Received: from mail-lj1-f177.google.com ([209.85.208.177]:42853 "EHLO mail-lj1-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725914AbfDDNdc (ORCPT ); Thu, 4 Apr 2019 09:33:32 -0400 Received: by mail-lj1-f177.google.com with SMTP id v22so2093349lje.9 for ; Thu, 04 Apr 2019 06:33:31 -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=4ElSO3JilSrfvBpkYt7Xj0vpQkyxBUWJQkAMjQGNyec=; b=CHWYozrF9IRqOrTqfnTnQYzVZYbl1py9ORPjBudktMS1Y9AaMORPwrF1l5xvHbMah2 nhN6uwQeoi8/9OmN8pYeL/AaFe8KQYhJiemQgesoJVME6t5JFe5ZTYg+41AzwZvtRoj8 JcgdyCBAVIMTPLC0Rk7Xfoionlleu1T1KnZZjWL6FA/n4rleoz+nZcIzey4U/ZsIq/k2 c1QOwunGj4Tg87vzIDIU+5Tj3CoZNpWjtNIgm7xLvFqQdOQ4bDrUA3N7C5P6rljHcN2G dzUYNB/u+Ufyv+22O7qOMEZxLG+y2DkMyhDnaQT/9omw1fO/DzIowByScHeTuLoAB89p rRSA== 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=4ElSO3JilSrfvBpkYt7Xj0vpQkyxBUWJQkAMjQGNyec=; b=pKT16tV7ZpmRaNGASMwkfdaiNUZyTFDPVQCnYjfLUc+48OSpBKmIRQdjkHXmpqghxT Ceht96Jy6LvFTYbiOMX/NqnOqhRSHVjf11PlpEwvrZdLrKtJ3vhEqMJ8gWSGqK3TEXOZ PddsMZKWdf+U496tG6eI334mqUqqpBhR7U4fKMcECD59BqmQJPdBIcZ4uiAkDUzTxa3R w30ZkUxiF4Ww8V5duZkJOpm4ugURaUO26BSSc/ioLuCQMgsEPqwJ0jHV6tLBWta5YY2F I80tsfVYLakkGHYhdgOc8+HYEYs51+7xxdftgp3dnXRJVqp5AwCZe7jjGYmtU+oTs+HO Edhw== X-Gm-Message-State: APjAAAV67WB5k22eQjFJ/So9jBLQcwFRjlg4xjC46BtKFy4xXzBt+q61 DP41WmvK5Afx3G8l5EDBPJD4BiEo X-Google-Smtp-Source: APXvYqxy6WwFn3GV945cGGEvPdcKZhpcsUO3hoUaliFErAtYuGblWl8luc1eQ+SP1wPjsAm+7JA6TA== X-Received: by 2002:a2e:9a91:: with SMTP id p17mr3428781lji.127.1554384810285; Thu, 04 Apr 2019 06:33:30 -0700 (PDT) Received: from uranus.localdomain ([5.18.103.226]) by smtp.gmail.com with ESMTPSA id m1sm3645571lfb.78.2019.04.04.06.33.28 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 04 Apr 2019 06:33:29 -0700 (PDT) Received: by uranus.localdomain (Postfix, from userid 1000) id 57272460438; Thu, 4 Apr 2019 16:33:27 +0300 (MSK) Date: Thu, 4 Apr 2019 16:33:27 +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: <20190404133327.GP1421@uranus.lan> References: <20190403191944.GH1421@uranus.lan> <20190403203144.GI1421@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 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. > Seems so. I've spent plenty of time yesterday trying to figure out how we even reach the case when event = nil but without much luck. > Just ran with your patch applied and it hit the hard lockup case. > > I'll have to see if things are reproducible and I can try to see if I can > get a reproducible value for what even caused the issue. perf_fuzzer has > some infrastructure for determining that but it's hit or miss if you can > get anything useful from it. At least the sequence of events migh give us some ideas, maybe not indeed. Thanks a huge, Vince! > I'll keep running things, but I'm a bit busy at work here the next few > days so there might be some delay in the results. Sure, take your time. I think this problem with p4 is not urgent. I'll ping you if I get some more ideas.