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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 12FFCC33CAF for ; Mon, 13 Jan 2020 11:29:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E859A2081E for ; Mon, 13 Jan 2020 11:29:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726127AbgAML3h convert rfc822-to-8bit (ORCPT ); Mon, 13 Jan 2020 06:29:37 -0500 Received: from cloudserver094114.home.pl ([79.96.170.134]:56307 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725992AbgAML3h (ORCPT ); Mon, 13 Jan 2020 06:29:37 -0500 Received: from 79.184.255.90.ipv4.supernova.orange.pl (79.184.255.90) (HELO kreacher.localnet) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83.320) id 9ab51728271c6d21; Mon, 13 Jan 2020 12:29:34 +0100 From: "Rafael J. Wysocki" To: =?utf-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= Cc: Greg Kroah-Hartman , Len Brown , Pavel Machek , Steven Rostedt , Ingo Molnar , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] PM-runtime: add tracepoints for usage_count changes Date: Mon, 13 Jan 2020 12:29:33 +0100 Message-ID: <12840272.KYWuQ3LjJR@kreacher> In-Reply-To: <20200106100004.GA10946@qmqm.qmqm.pl> References: <20200104182123.GA1485543@kroah.com> <20200106100004.GA10946@qmqm.qmqm.pl> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset="UTF-8" Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Monday, January 6, 2020 11:00:04 AM CET Michał Mirosław wrote: > On Sat, Jan 04, 2020 at 07:21:23PM +0100, Greg Kroah-Hartman wrote: > > On Sat, Jan 04, 2020 at 05:27:57PM +0100, Michał Mirosław wrote: > > > Add tracepoints to remaining places where device's power.usage_count > > > is changed. This helps debugging where and why autosuspend is prevented. > > > > > > Signed-off-by: Michał Mirosław > > > --- > > > drivers/base/power/runtime.c | 13 +++++++++++-- > > > include/trace/events/rpm.h | 6 ++++++ > > > 2 files changed, 17 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c > > > index 48616f358854..16134a69bf6f 100644 > > > --- a/drivers/base/power/runtime.c > > > +++ b/drivers/base/power/runtime.c > > > @@ -1006,8 +1006,10 @@ int __pm_runtime_idle(struct device *dev, int rpmflags) > > > int retval; > > > > > > if (rpmflags & RPM_GET_PUT) { > > > - if (!atomic_dec_and_test(&dev->power.usage_count)) > > > + if (!atomic_dec_and_test(&dev->power.usage_count)) { > > > + trace_rpm_usage_rcuidle(dev, rpmflags); > > > > Who and what is really going to use these tracepoints? > > > > And putting them in these if statements seems odd, are you sure that's > > the correct place? What do these show to userspace? > > > > > return 0; > > > + } > > > } > > > > > > might_sleep_if(!(rpmflags & RPM_ASYNC) && !dev->power.irq_safe); > > > @@ -1038,8 +1040,10 @@ int __pm_runtime_suspend(struct device *dev, int rpmflags) > > > int retval; > > > > > > if (rpmflags & RPM_GET_PUT) { > > > - if (!atomic_dec_and_test(&dev->power.usage_count)) > > > + if (!atomic_dec_and_test(&dev->power.usage_count)) { > > > + trace_rpm_usage_rcuidle(dev, rpmflags); > > > return 0; > > > + } > > > } > > > > > > might_sleep_if(!(rpmflags & RPM_ASYNC) && !dev->power.irq_safe); > > > @@ -1101,6 +1105,7 @@ int pm_runtime_get_if_in_use(struct device *dev) > > > retval = dev->power.disable_depth > 0 ? -EINVAL : > > > dev->power.runtime_status == RPM_ACTIVE > > > && atomic_inc_not_zero(&dev->power.usage_count); > > > + trace_rpm_usage_rcuidle(dev, 0); > > > > Why this one? > > > > > > > spin_unlock_irqrestore(&dev->power.lock, flags); > > > return retval; > > > } > > > @@ -1434,6 +1439,8 @@ void pm_runtime_allow(struct device *dev) > > > dev->power.runtime_auto = true; > > > if (atomic_dec_and_test(&dev->power.usage_count)) > > > rpm_idle(dev, RPM_AUTO | RPM_ASYNC); > > > + else > > > + trace_rpm_usage_rcuidle(dev, RPM_AUTO | RPM_ASYNC); > > > > Are you sure this is correct? > > > > These feel odd... > > This covers all places where power.usage_count might have changed. > If atomic_dec_and_test() decrements usage_count but not to zero, > the new value will be traced in rpm_idle(). But if the value drops to > zero, then we need to trace it explicitly to be able to have all changes > accounted for in the trace. > > I actually used this patch to track down why USB storage device was > not autosuspending correctly. Fair enough, and the patch makes sense to me, so I'm queuing it up as 5.6 material. Thanks!