From patchwork Fri Jul 1 14:44:19 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Hilman X-Patchwork-Id: 935962 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter2.kernel.org (8.14.4/8.14.4) with ESMTP id p61EhaAA006893 for ; Fri, 1 Jul 2011 14:44:26 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756851Ab1GAOoZ (ORCPT ); Fri, 1 Jul 2011 10:44:25 -0400 Received: from na3sys009aog108.obsmtp.com ([74.125.149.199]:57782 "EHLO na3sys009aog108.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756621Ab1GAOoZ (ORCPT ); Fri, 1 Jul 2011 10:44:25 -0400 Received: from mail-iw0-f179.google.com ([209.85.214.179]) (using TLSv1) by na3sys009aob108.postini.com ([74.125.148.12]) with SMTP ID DSNKTg3dSAaMUhh0Dj7Gsy/mL1GpU3bCMsvu@postini.com; Fri, 01 Jul 2011 07:44:24 PDT Received: by iwl42 with SMTP id 42so3199985iwl.38 for ; Fri, 01 Jul 2011 07:44:22 -0700 (PDT) Received: by 10.231.48.208 with SMTP id s16mr2992764ibf.82.1309531462183; Fri, 01 Jul 2011 07:44:22 -0700 (PDT) Received: from localhost (c-24-19-7-36.hsd1.wa.comcast.net [24.19.7.36]) by mx.google.com with ESMTPS id v16sm1902031ibe.34.2011.07.01.07.44.20 (version=TLSv1/SSLv3 cipher=OTHER); Fri, 01 Jul 2011 07:44:21 -0700 (PDT) From: Kevin Hilman To: linux-pm@lists.linux-foundation.org Cc: "linux-omap\@vger.kernel.org" Subject: Re: runtime PM usage_count during driver_probe_device()? Organization: Texas Instruments, Inc. References: <87k4c3dktm.fsf@ti.com> Date: Fri, 01 Jul 2011 07:44:19 -0700 In-Reply-To: <87k4c3dktm.fsf@ti.com> (Kevin Hilman's message of "Thu, 30 Jun 2011 15:19:01 -0700") Message-ID: <87d3hu6oxo.fsf@ti.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1.50 (gnu/linux) MIME-Version: 1.0 Sender: linux-omap-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-omap@vger.kernel.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.6 (demeter2.kernel.org [140.211.167.43]); Fri, 01 Jul 2011 14:44:26 +0000 (UTC) Kevin Hilman writes: [...] > If the device bus type's or driver's ->probe() or ->remove() > callback runs pm_runtime_suspend() or pm_runtime_idle() or their > asynchronous counterparts, they will fail returning -EAGAIN, because > the device's usage counter is incremented by the core before > executing ->probe() and ->remove(). Still, it may be desirable to > suspend the device as soon as ->probe() or ->remove() has finished, > so the PM core uses pm_runtime_idle_sync() to invoke the > subsystem-level idle callback for the device at that time. [...] > Another curiosity is that, contrary to the above documentation, there is > no usage_count increment before the bus/driver ->remove() (although > there is a _get_sync/_put_sync around the sysfs_remove and notifier just > before the bus/driver->remove(). OK, so the ->probe() part has been explained and makes sense, but I would expect ->remove() to be similarily protected (as the documentation states.) But that is not the case. Is that a bug? If so, patch below makes the code match the documentation. Kevin From eef73ab2feb203bacb57dc35862f2a9969b61593 Mon Sep 17 00:00:00 2001 From: Kevin Hilman Date: Fri, 1 Jul 2011 07:37:47 -0700 Subject: [PATCH] driver core: prevent runtime PM races with ->remove() Runtime PM Documentation states that the runtime PM usage count is incremented during driver ->probe() and ->remove(). This is designed to prevent driver runtime PM races with subsystems which may initiate runtime PM transitions before during and after drivers are loaded. Current code increments the usage_count during ->probe() but not during ->remove(). This patch fixes the ->remove() part and makes the code match the documentation. Signed-off-by: Kevin Hilman Reviewed-by: Kevin Hilman --- drivers/base/dd.c | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/base/dd.c b/drivers/base/dd.c index 6658da7..47e079d 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c @@ -329,13 +329,13 @@ static void __device_release_driver(struct device *dev) blocking_notifier_call_chain(&dev->bus->p->bus_notifier, BUS_NOTIFY_UNBIND_DRIVER, dev); - - pm_runtime_put_sync(dev); - if (dev->bus && dev->bus->remove) dev->bus->remove(dev); else if (drv->remove) drv->remove(dev); + + pm_runtime_put_sync(dev); + devres_release_all(dev); dev->driver = NULL; klist_remove(&dev->p->knode_driver);