From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754494AbdKMN0d (ORCPT ); Mon, 13 Nov 2017 08:26:33 -0500 Received: from mail-it0-f67.google.com ([209.85.214.67]:38947 "EHLO mail-it0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751521AbdKMN0a (ORCPT ); Mon, 13 Nov 2017 08:26:30 -0500 X-Google-Smtp-Source: AGs4zMbaLBgy8UVT270UMppqBEGCJcyx1zgZlUK6wx8WV8H4OWpsC6c5AsRXuA5/jGi756r6quyk3H2wCQeI5fUnfOg= MIME-Version: 1.0 In-Reply-To: <1713438.irjm9MTSvo@aspire.rjw.lan> References: <1713438.irjm9MTSvo@aspire.rjw.lan> From: Ulf Hansson Date: Mon, 13 Nov 2017 14:26:28 +0100 Message-ID: Subject: Re: [PATCH] PM / runtime: Drop children check from __pm_runtime_set_status() To: "Rafael J. Wysocki" Cc: Linux PM , LKML , Greg Kroah-Hartman , Alan Stern Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12 November 2017 at 01:27, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki > > The check for "active" children in __pm_runtime_set_status(), when > trying to set the parent device status to "suspended", doesn't > really make sense, because in fact it is not invalid to set the > status of a device with runtime PM disabled to "suspended" in any > case. It is invalid to enable runtime PM for a device with its > status set to "suspended" while its child_count reference counter > is nonzero, but the check in __pm_runtime_set_status() doesn't > really cover that situation. The reason to why I changed this in commit a8636c89648a ("PM / Runtime: Don't allow to suspend a device with an active child") was because to get a consistent behavior. Because, setting the device's status to active (RPM_ACTIVE) via __pm_runtime_set_status(), requires its parent to also be active (in case the parent has runtime PM enabled). I would prefer to try maintain this consistency, but I also I realize that commit a8636c89648a, should also have been checking if the parent has runtime PM enabled (again for consistency), which it doesn't. What about fixing that instead? Kind regards Uffe > > For this reason, drop the children check from __pm_runtime_set_status() > and add a check against child_count reference counters of "suspended" > devices to pm_runtime_enable(). > > Signed-off-by: Rafael J. Wysocki > --- > drivers/base/power/runtime.c | 30 ++++++++++-------------------- > 1 file changed, 10 insertions(+), 20 deletions(-) > > Index: linux-pm/drivers/base/power/runtime.c > =================================================================== > --- linux-pm.orig/drivers/base/power/runtime.c > +++ linux-pm/drivers/base/power/runtime.c > @@ -1101,29 +1101,13 @@ int __pm_runtime_set_status(struct devic > goto out; > } > > - if (dev->power.runtime_status == status) > + if (dev->power.runtime_status == status || !parent) > goto out_set; > > if (status == RPM_SUSPENDED) { > - /* > - * It is invalid to suspend a device with an active child, > - * unless it has been set to ignore its children. > - */ > - if (!dev->power.ignore_children && > - atomic_read(&dev->power.child_count)) { > - dev_err(dev, "runtime PM trying to suspend device but active child\n"); > - error = -EBUSY; > - goto out; > - } > - > - if (parent) { > - atomic_add_unless(&parent->power.child_count, -1, 0); > - notify_parent = !parent->power.ignore_children; > - } > - goto out_set; > - } > - > - if (parent) { > + atomic_add_unless(&parent->power.child_count, -1, 0); > + notify_parent = !parent->power.ignore_children; > + } else { > spin_lock_nested(&parent->power.lock, SINGLE_DEPTH_NESTING); > > /* > @@ -1307,6 +1291,12 @@ void pm_runtime_enable(struct device *de > else > dev_warn(dev, "Unbalanced %s!\n", __func__); > > + WARN(dev->power.runtime_status == RPM_SUSPENDED && > + !dev->power.ignore_children && > + atomic_read(&dev->power.child_count) > 0, > + "Enabling runtime PM for inactive device (%s) with active children\n", > + dev_name(dev)); > + > spin_unlock_irqrestore(&dev->power.lock, flags); > } > EXPORT_SYMBOL_GPL(pm_runtime_enable); >