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=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 251A4C3279B for ; Sun, 8 Jul 2018 13:21:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DB0A020881 for ; Sun, 8 Jul 2018 13:21:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DB0A020881 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org 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 S932953AbeGHNVK (ORCPT ); Sun, 8 Jul 2018 09:21:10 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:44428 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932680AbeGHNVJ (ORCPT ); Sun, 8 Jul 2018 09:21:09 -0400 Received: from localhost (unknown [46.44.180.42]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 50D7DCA8; Sun, 8 Jul 2018 13:21:09 +0000 (UTC) Date: Sun, 8 Jul 2018 15:21:07 +0200 From: Greg Kroah-Hartman To: Javier Martinez Canillas Cc: linux-kernel@vger.kernel.org, Tomeu Vizoso , Rob Herring , Mark Brown , Andy Shevchenko , Peter Robinson , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v3] driver core: add a debugfs entry to show deferred devices Message-ID: <20180708132107.GA25491@kroah.com> References: <20180708003256.15655-1-javierm@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180708003256.15655-1-javierm@redhat.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jul 08, 2018 at 02:32:56AM +0200, Javier Martinez Canillas wrote: > With Device Trees (DT), the dependencies of the devices are defined in the > DT, then the drivers parse that information to lookup the needed resources > that have as dependencies. > > Since drivers and devices are registered in a non-deterministic way, it is > possible that a device that is a dependency has not been registered yet by > the time that is looked up. > > In this case the driver that requires this dependency cannot probe and has > to defer it. So the driver core adds it to a list of deferred devices that > is iterated again every time that a new driver is probed successfully. > > For debugging purposes it may be useful to know what are the devices whose > probe function was deferred. Add a debugfs entry showing that information. > > $ cat /sys/kernel/debug/devices_deferred > 48070000.i2c:twl@48:bci > musb-hdrc.0.auto > omapdrm.0 > > This information could be obtained partially by enabling debugging, but it > means that the kernel log has to be parsed and the probe deferral balanced > with the successes. This can be error probe and has to be done in a ad-hoc > manner by everyone who needs to debug these kind of issues. > > Since the information is already known by the kernel, just show it to make > it easier to debug. > > Signed-off-by: Javier Martinez Canillas > Reviewed-by: Andy Shevchenko > Reviewed-by: Mark Brown > > --- > > Changes since RFC v1: > - Remove unneeded ret variable from deferred_devs_show() > > Changes since RFC v2: > - Use DEFINE_SHOW_ATTRIBUTE() macro. > - Don't propagate debugfs_create_file() error. > - Remove IS_ENABLED(CONFIG_DEBUG_FS) guards. > - Drop RFC prefix. > > Changes since v1: > - Better explain in the commit message why this patch is useful. > - Rename deferred_devices entry to devices_deferred. > - Add an exit function and remove the debugfs entry. > > Changes since v2: > - Add Andy Shevchenko and Mark Brown Reviewed-by tag. > - Rebase on top of Greg's driver-core-next branch. > > > drivers/base/dd.c | 30 ++++++++++++++++++++++++++++++ > 1 file changed, 30 insertions(+) > > diff --git a/drivers/base/dd.c b/drivers/base/dd.c > index 6ea9c5cece7..140f534ee9c 100644 > --- a/drivers/base/dd.c > +++ b/drivers/base/dd.c > @@ -16,6 +16,7 @@ > * Copyright (c) 2007-2009 Novell Inc. > */ > > +#include > #include > #include > #include > @@ -53,6 +54,8 @@ static DEFINE_MUTEX(deferred_probe_mutex); > static LIST_HEAD(deferred_probe_pending_list); > static LIST_HEAD(deferred_probe_active_list); > static atomic_t deferred_trigger_count = ATOMIC_INIT(0); > +static struct dentry *deferred_devices; > +static bool initcalls_done; Wait, why add this variable? No one uses it that I can see in this patch, doesn't it create a build warning? You did test-build this, right? greg k-h