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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 B7537C46464 for ; Tue, 6 Nov 2018 16:50:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 809522085B for ; Tue, 6 Nov 2018 16:50:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 809522085B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389408AbeKGCQE (ORCPT ); Tue, 6 Nov 2018 21:16:04 -0500 Received: from mga11.intel.com ([192.55.52.93]:55295 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389322AbeKGCQE (ORCPT ); Tue, 6 Nov 2018 21:16:04 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 Nov 2018 08:49:59 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,472,1534834800"; d="scan'208";a="83756664" Received: from unknown (HELO localhost.localdomain) ([10.232.112.69]) by fmsmga007.fm.intel.com with ESMTP; 06 Nov 2018 08:49:58 -0800 Date: Tue, 6 Nov 2018 09:47:52 -0700 From: Keith Busch To: Lorenzo Pieralisi Cc: Bjorn Helgaas , Linux PCI , Bjorn Helgaas , Benjamin Herrenschmidt , Sinan Kaya , Thomas Tai , poza@codeaurora.org, Lukas Wunner , Christoph Hellwig , Mika Westerberg , Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 00/12] error handling and pciehp maintenance Message-ID: <20181106164751.GA6217@localhost.localdomain> References: <20180918235848.26694-1-keith.busch@intel.com> <20181004214015.GK120535@bhelgaas-glaptop.roam.corp.google.com> <20181004221137.GB21834@localhost.localdomain> <20181005173145.GL120535@bhelgaas-glaptop.roam.corp.google.com> <20181008161847.GA30971@localhost.localdomain> <20181106163400.GA21193@e107981-ln.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181106163400.GA21193@e107981-ln.cambridge.arm.com> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 06, 2018 at 04:34:08PM +0000, Lorenzo Pieralisi wrote: > The question is whether we really need to dynamically patch the kernel > with ftrace to achieve what that patch does. > > Furthermore, it would also be good to report what bugs we are actually > fixing, from what you are writing falling back to the current method if > !DYNAMIC_FTRACE_WITH_REGS is broken in many ways and I would start with > fixing the current behaviour with something that does not depend on arch > features that may not even be implemented. There are two problems with the current method: 1. It may dereference pci_dev after it was freed 2. The pci_dev's children inherit its fake pci_bus's ops on enumeration Both result in kernel panic. The dynamic kernel patch just seemed like a cool way to inject errors without messing with the driver's structures. But if there's a more elegant way to do it, I'm all for it.