From patchwork Wed Jun 27 22:06:56 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Javier Martinez Canillas X-Patchwork-Id: 10492767 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 5E410601A0 for ; Wed, 27 Jun 2018 22:15:56 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 59BEB29F22 for ; Wed, 27 Jun 2018 22:15:56 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 4CC5429FE7; Wed, 27 Jun 2018 22:15:56 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI autolearn=unavailable version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 829D829F22 for ; Wed, 27 Jun 2018 22:15:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:Message-Id:Date: Subject:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To: References:List-Owner; bh=s3PdMz53Ez4CQrLRIjCr7QD62WQVjjuyHnGNj16RFe8=; b=Yja DISARACoV5T2Ymu6lmltSpl+aOGkUgaC8tuQjqYVOmSzK35fJHANLpDV2LX9fQTT/fVEZIHWNtLR6 Groa4esNE4qpE8e5g97hOiaJRxMKr00P/Hr3zNLWElzX0juSSj/Jh7zGlUnJA1XOuGJ9WCYgxfKYb jUbc3oLehqRhk3edRQ+gq5yrVJevr5+uNXUvHJcHmhBRHv+mbnnyt6g17wChUrdYFj4K9qHurcgBg 82aWWgVXjZ0WXXoIT18wJg60h15swH4ADh/UeL+e+BFA8K7yQsPGpsdzh/xteuwm1D1KIi5uXY0qV 8i93rx6ZXKjCMxFOlnZy4qxWRAE1PTw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1fYIj6-0004Cl-8W; Wed, 27 Jun 2018 22:15:48 +0000 Received: from mail-wm0-f67.google.com ([74.125.82.67]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1fYIj2-0004BG-So for linux-arm-kernel@lists.infradead.org; Wed, 27 Jun 2018 22:15:46 +0000 Received: by mail-wm0-f67.google.com with SMTP id z137-v6so7022628wmc.0 for ; Wed, 27 Jun 2018 15:15:31 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=/jlTPwjC2QOSC70OfROrsR01Fp2ChvkKkYQSli8f+FI=; b=fshuo1LRUYkUOd5Vy+e2GPcEhKc50E3GT7ovsLd6U2SwaSOCb4eHqsbiZFljCt6T6H 9SQBN/0o8J6yS74msFnzV3oLCfbZa24a3e0cGwjJ4synF8FpH/pLdNHSvPcsvvVWkff2 3ud4KEKpJtsUiQJ8KdI1UMciHEclColsXAXBqLC877OhrPEBtE+4YJopLERpKPVyDLca 7b0rDMo33fLvJHm2nmCk7qpIhtst/ZfJD9kZQR8wknkHyC6WO+/ijjKri+/fHKy/guLH YiFterWtHh3R4HK1y1c8NcCYxtO5kjOsp6uY3If6i95SqKRcMHepPfEtVaONSYLc0ZOK +8Gg== X-Gm-Message-State: APt69E2yJET4I1Dx0gdTynxk9t+x3OQgDlcG7MghZhVhI7+d6+jFoQo2 pzHQNAVEVELGIHZWlNXI5N3Qpw== X-Google-Smtp-Source: AAOMgpd9TZG38+FppRgNg8pcZUeMhehZkJEIiBs0cPnp2zKMsp2JaFoR3THvkMzz1PAtTP3P8rpGiQ== X-Received: by 2002:a1c:1414:: with SMTP id 20-v6mr5939866wmu.119.1530137234448; Wed, 27 Jun 2018 15:07:14 -0700 (PDT) Received: from minerva.home ([90.77.100.34]) by smtp.gmail.com with ESMTPSA id d4-v6sm7735767wrp.51.2018.06.27.15.07.13 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 27 Jun 2018 15:07:13 -0700 (PDT) From: Javier Martinez Canillas To: linux-kernel@vger.kernel.org Subject: [PATCH v2] driver core: add a debugfs entry to show deferred devices Date: Thu, 28 Jun 2018 00:06:56 +0200 Message-Id: <20180627220656.19298-1-javierm@redhat.com> X-Mailer: git-send-email 2.17.1 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20180627_151544_939157_ADBEE4A5 X-CRM114-Status: GOOD ( 18.67 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Rob Herring , Tomeu Vizoso , Greg Kroah-Hartman , Javier Martinez Canillas , Andy Shevchenko , Mark Brown , Peter Robinson , linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP 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 --- Andy, I didn't carry your Reviewed-by tag because it wasn't clear to me if you had agreed with the patch or not from your last email. 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. drivers/base/dd.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/drivers/base/dd.c b/drivers/base/dd.c index 1435d7281c6..489c484301b 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 +54,7 @@ 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; /* @@ -224,6 +226,24 @@ void device_unblock_probing(void) driver_deferred_probe_trigger(); } +/* + * deferred_devs_show() - Show the devices in the deferred probe pending list. + */ +static int deferred_devs_show(struct seq_file *s, void *data) +{ + struct device_private *curr; + + mutex_lock(&deferred_probe_mutex); + + list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe) + seq_printf(s, "%s\n", dev_name(curr->device)); + + mutex_unlock(&deferred_probe_mutex); + + return 0; +} +DEFINE_SHOW_ATTRIBUTE(deferred_devs); + /** * deferred_probe_initcall() - Enable probing of deferred devices * @@ -233,6 +253,9 @@ void device_unblock_probing(void) */ static int deferred_probe_initcall(void) { + deferred_devices = debugfs_create_file("devices_deferred", 0444, NULL, + NULL, &deferred_devs_fops); + driver_deferred_probe_enable = true; driver_deferred_probe_trigger(); /* Sort as many dependencies as possible before exiting initcalls */ @@ -242,6 +265,12 @@ static int deferred_probe_initcall(void) } late_initcall(deferred_probe_initcall); +static void __exit deferred_probe_exit(void) +{ + debugfs_remove_recursive(deferred_devices); +} +__exitcall(deferred_probe_exit); + /** * device_is_bound() - Check if device is bound to a driver * @dev: device to check