From patchwork Wed Nov 13 23:21:30 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Leonard Crestez X-Patchwork-Id: 11242853 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id AF974138C for ; Wed, 13 Nov 2019 23:21:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A6FE7206D3 for ; Wed, 13 Nov 2019 23:21:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727063AbfKMXVl (ORCPT ); Wed, 13 Nov 2019 18:21:41 -0500 Received: from inva021.nxp.com ([92.121.34.21]:58126 "EHLO inva021.nxp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726251AbfKMXVl (ORCPT ); Wed, 13 Nov 2019 18:21:41 -0500 Received: from inva021.nxp.com (localhost [127.0.0.1]) by inva021.eu-rdc02.nxp.com (Postfix) with ESMTP id 8CBD8200199; Thu, 14 Nov 2019 00:21:38 +0100 (CET) Received: from inva024.eu-rdc02.nxp.com (inva024.eu-rdc02.nxp.com [134.27.226.22]) by inva021.eu-rdc02.nxp.com (Postfix) with ESMTP id 7F2F5200139; Thu, 14 Nov 2019 00:21:38 +0100 (CET) Received: from fsr-ub1864-112.ea.freescale.net (fsr-ub1864-112.ea.freescale.net [10.171.82.98]) by inva024.eu-rdc02.nxp.com (Postfix) with ESMTP id 0F83B205D5; Thu, 14 Nov 2019 00:21:38 +0100 (CET) From: Leonard Crestez To: Chanwoo Choi , MyungJoo Ham Cc: Kyungmin Park , "Rafael J. Wysocki" , Matthias Kaehlcke , =?utf-8?b?QXJ0dXIgxZp3aWdvxYQ=?= , Georgi Djakov , Viresh Kumar , linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-imx@nxp.com Subject: [PATCH 0/5] PM / devfreq: Don't take lock in devfreq_add_device Date: Thu, 14 Nov 2019 01:21:30 +0200 Message-Id: X-Mailer: git-send-email 2.17.1 X-Virus-Scanned: ClamAV using ClamSMTP Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Right now the devfreq_add_device takes devfreq->lock as soon as the device is allocated, this is awkward and unnecessary. In general an object should be initialized in isolation and only be made available to the system when it's in a consistent state. Locking the device during initialization causes problems (lockdep warnings) when interacting with other subsystems that also use heavy locking. There are also a few fields (such as trans_table) which are initialized after device_register even through they're readable from sysfs, these are now allocated earlier. This was spawned by the attempt to add dev_pm_qos support. I split this series here because it might benefit from separate discussion. Notifiers from pm_qos are executed under a single global dev_pm_qos_mtx and need to take devfreq->lock, this means that in order to prevent possible deadlocks all initialization of dev_pm_qos must be performed outside the devfreq->lock. PM QoS requests from sysfs should be initialized before the device is registered (because they're touched from sysfs) but all of that is currently done with devfreq->lock held! This series makes some tricky changes but the end results is easier to understand and maintain. For example it removes a scary unlock/lock pair around set_freq_table, maybe this also caused problems in the past? Alternative solutions exist: all PM QoS setup could be done after device_add just like governor setup and the min/max_freq_store could return an error if the qos request is not yet properly initialized. It might even be possible to modify dev_pm_qos to call notifiers without holding internal locks? That is generally a good idea for all notifiers. Changes since split from PM_QOS: * Add a patch which moves devm from devfreq->dev->parent to devfreq->dev. See: https://patchwork.kernel.org/project/linux-arm-kernel/list/?series=196443 Leonard Crestez (5): PM / devfreq: Don't fail devfreq_dev_release if not in list PM / devfreq: Split device_register usage PM / devfreq: Move more initialization before registration PM / devfreq: Don't use devm on parent device PM / devfreq: Don't take lock in devfreq_add_device drivers/devfreq/devfreq.c | 41 ++++++++++++--------------------------- 1 file changed, 12 insertions(+), 29 deletions(-)