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=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 2F6D8C2D0D1 for ; Mon, 6 Jan 2020 10:00:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C5ECE24673 for ; Mon, 6 Jan 2020 10:00:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=rere.qmqm.pl header.i=@rere.qmqm.pl header.b="SQSRAtim" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725821AbgAFKAL (ORCPT ); Mon, 6 Jan 2020 05:00:11 -0500 Received: from rere.qmqm.pl ([91.227.64.183]:58440 "EHLO rere.qmqm.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725446AbgAFKAL (ORCPT ); Mon, 6 Jan 2020 05:00:11 -0500 Received: from remote.user (localhost [127.0.0.1]) by rere.qmqm.pl (Postfix) with ESMTPSA id 47rrbW64m1zV6; Mon, 6 Jan 2020 11:00:07 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=rere.qmqm.pl; s=1; t=1578304808; bh=cL4mF1jHUeGe0pKz/0D4gMOsnENC81lNvvo2kdmArbw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=SQSRAtimoT4S5oqIEhtwVHIDIIABk1PQ+gDFywwA12mVBxFRczNTPkaAVOfE3ufl9 L3RIGEGymoOXMqIelWI+HgGTlo1tSmjBaF6zL8sBarb/8EqOcqC3c4Ek45kH9eEo0V zvLNihcBDd0dE7h0G/k7j1iFKP9Vc2Hbt3GKqjUt0CeZypoxOnm+HVbPS0r5y2XSwm YdmfgMAK+ZclPu0b52QY6ekXCCopqoKk0jPQl6AsgRtxQELwtc31nTeXpQujcCOR6a ExD7P1+Ri/LBqJCZ9U5sGe1Nh8jdFaat+iG86csKydya9ziBgCzYXal0U9ndRyUjQS jmKoMoJwdhxtw== X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.101.4 at mail Date: Mon, 6 Jan 2020 11:00:04 +0100 From: =?iso-8859-2?Q?Micha=B3_Miros=B3aw?= To: Greg Kroah-Hartman Cc: "Rafael J. Wysocki" , 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 Message-ID: <20200106100004.GA10946@qmqm.qmqm.pl> References: <20200104182123.GA1485543@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-2 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200104182123.GA1485543@kroah.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org 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. Best Regards, Michał Mirosław