From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga06.intel.com ([134.134.136.31]:42438 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726956AbeIDSjz (ORCPT ); Tue, 4 Sep 2018 14:39:55 -0400 Date: Tue, 4 Sep 2018 08:16:02 -0600 From: Keith Busch To: Lukas Wunner Cc: Linux PCI , Bjorn Helgaas , Benjamin Herrenschmidt , Sinan Kaya , Thomas Tai , poza@codeaurora.org Subject: Re: [PATCH 14/16] pciehp: Ignore link events during DPC event Message-ID: <20180904141602.GG9677@localhost.localdomain> References: <20180831212639.10196-1-keith.busch@intel.com> <20180831212639.10196-15-keith.busch@intel.com> <20180902142714.wsqi4rfggundjli7@wunner.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20180902142714.wsqi4rfggundjli7@wunner.de> Sender: linux-pci-owner@vger.kernel.org List-ID: On Sun, Sep 02, 2018 at 04:27:14PM +0200, Lukas Wunner wrote: > On Fri, Aug 31, 2018 at 03:26:37PM -0600, Keith Busch wrote: > > This patch adds a channel state to a subordinate bus. When a DPC event is > > triggered, the DPC driver will set the channel state to frozen, and the > > pciehp driver will ignore link events if the subordinate bus is being > > managed by DPC error handling. > > > > This is safe because the pciehp and DPC drivers share the same > > interrupt. The DPC driver sets the bus state in the top-half interrupt > > context, and the pciehp driver checks and masks off link events in its > > bottom-half error handler. > > I really liked Sinan's approach of checking in pciehp whether a fatal > error is pending and waiting for it to be handled: > https://patchwork.ozlabs.org/patch/959464/ > > This seemed to avoid any races with DPC and is small and simple. > Can we pursue a solution along those lines? That introduces a completely different race between the error handling and hotplug threads. We don't control which interrupt fires first or any way ensure they're even the same event.