From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755094AbcC1R6P (ORCPT ); Mon, 28 Mar 2016 13:58:15 -0400 Received: from mail-qg0-f68.google.com ([209.85.192.68]:35754 "EHLO mail-qg0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751097AbcC1R6L convert rfc822-to-8bit (ORCPT ); Mon, 28 Mar 2016 13:58:11 -0400 MIME-Version: 1.0 In-Reply-To: <20160328173309.GA26086@dvhart-mobl5.amr.corp.intel.com> References: <1457740175-8327-1-git-send-email-gabriele.mzt@gmail.com> <1458341063-8753-1-git-send-email-gabriele.mzt@gmail.com> <20160321121736.GH8413@pali> <20160324093915.GZ8413@pali> <20160328173309.GA26086@dvhart-mobl5.amr.corp.intel.com> Date: Mon, 28 Mar 2016 19:58:09 +0200 Message-ID: Subject: Re: [PATCH v3] dell-rbtn: Ignore ACPI notifications if device is suspended From: Gabriele Mazzotta To: Darren Hart Cc: Rafael Wysocki , =?UTF-8?Q?Pali_Roh=C3=A1r?= , "D. Jared Dominguez" , "platform-driver-x86@vger.kernel.org" , Alex Hung , Andrei Borzenkov , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2016-03-28 19:33 GMT+02:00 Darren Hart : > On Thu, Mar 24, 2016 at 12:24:56PM +0100, Gabriele Mazzotta wrote: >> 2016-03-24 10:39 GMT+01:00 Pali Rohár : >> > On Monday 21 March 2016 16:13:34 Gabriele Mazzotta wrote: >> >> 2016-03-21 13:17 GMT+01:00 Pali Rohár : >> >> > On Friday 18 March 2016 23:44:23 Gabriele Mazzotta wrote: >> >> >> +#ifdef CONFIG_PM_SLEEP >> >> >> +static void ACPI_SYSTEM_XFACE rbtn_acpi_clear_flag(void *context) >> >> >> +{ >> >> >> + struct rbtn_data *rbtn_data = context; >> >> >> + >> >> >> + rbtn_data->suspended = false; >> >> >> +} >> >> >> + >> >> >> +static int rbtn_suspend(struct device *dev) >> >> >> +{ >> >> >> + struct acpi_device *device = to_acpi_device(dev); >> >> >> + struct rbtn_data *rbtn_data = acpi_driver_data(device); >> >> >> + >> >> >> + rbtn_data->suspended = true; >> >> >> + >> >> >> + return 0; >> >> >> +} >> >> >> + >> >> >> +static int rbtn_resume(struct device *dev) >> >> >> +{ >> >> >> + struct acpi_device *device = to_acpi_device(dev); >> >> >> + struct rbtn_data *rbtn_data = acpi_driver_data(device); >> >> >> + acpi_status status; >> >> >> + >> >> >> + /* >> >> >> + * Clear the flag only after we received the extra >> >> >> + * ACPI notification. >> >> >> + */ >> >> >> + status = acpi_os_execute(OSL_NOTIFY_HANDLER, >> >> >> + rbtn_acpi_clear_flag, rbtn_data); >> >> >> + if (ACPI_FAILURE(status)) >> >> >> + rbtn_data->suspended = false; >> >> > >> >> > I case when acpi_os_execute success it calls rbtn_acpi_clear_flag, >> >> > right? And that will set suspended to false. When acpi_os_execute fails, >> >> > then it set suspended too to false... Then whole acpi_os_execute doing >> >> > just "barrier" after which suspended flag can be set to false. So I >> >> > think rbtn_acpi_clear_flag function is not needed here. >> >> > >> >> > Cannot you pass NULL or empty function pointer as callback? Or what was >> >> > reason to do that flag clearing at "two places"? >> >> >> >> acpi_os_execute doesn't wait for the callback to be executed, so >> >> I can't clear the flag from rbtn_resume. >> > >> > acpi_os_execute calls callback asynchronously later? Or what exactly do it? >> >> In this case, it adds the callback to the kacpi_notify_wq workqueue >> for deferred execution. > > +Rafael for context/advice on the use of acpi_os_execute here. > > This is true, but a quick scan through that call path doesn't tell me why we > would need to call it here instead of just setting rbtn_data->suspended = false. > The comment suggests waiting for the event, but is that what this is doing? It > appears to me to be immediately scheduling the function to a work queue, not > waiting for the event notifier. > > Also, since there is no indication to the user that a failure occurs, this > function is basically equivalent in the success and failure case (the success > case is just slower). > > Am I missing something critical here? Maybe saying that we are waiting for the extra event is not really correct. Since the extra ACPI notification is processed by means of kacpi_notify_wq, or at least that's my understanding, our callback is likely going to be executed after we received the extra ACPI notification. This was suggested by Rafael [2]. The problem with setting the flag directly from the resume callback is that the extra notification might arrive after we cleared the flag, causing spurious input events [1]. [1] http://article.gmane.org/gmane.linux.drivers.platform.x86.devel/8001 [2] http://article.gmane.org/gmane.linux.drivers.platform.x86.devel/8201 > >> >> > -- >> > Pali Rohár >> > pali.rohar@gmail.com >> > > -- > Darren Hart > Intel Open Source Technology Center