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=-3.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 BA4E4C3A59D for ; Fri, 16 Aug 2019 22:38:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 81E24206C1 for ; Fri, 16 Aug 2019 22:38:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=android.com header.i=@android.com header.b="a3cDSghN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727796AbfHPWiT (ORCPT ); Fri, 16 Aug 2019 18:38:19 -0400 Received: from mail-ot1-f68.google.com ([209.85.210.68]:42473 "EHLO mail-ot1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727747AbfHPWiT (ORCPT ); Fri, 16 Aug 2019 18:38:19 -0400 Received: by mail-ot1-f68.google.com with SMTP id j7so10992503ota.9 for ; Fri, 16 Aug 2019 15:38:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=android.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=n8CirlaHdh28gHLoP6h4JqrJrGvDIaVMTsL4o/hfB+Q=; b=a3cDSghN76lmTismZG0JY1fRaRl8s1zZgZTjxVK+xaaaaNNs90B2T83Rml4/QmQ5L7 yfLiWFwyVeKL+BQnCjYloJqOxGfu6F7R1bUiLxfbh5kZoEDY5d08QKizcXOGAKsiBOri Jeu1SafRJxBUH0jR/68px4blC5ni9fY6lFFNoVeOfnqD7DFsqZp9VMiawqCl8VgrSsFM RsvCefaLOLf9t973heAsMqOJaeSuBqM17B3cQACIIelOALYiS7paaVYQ9qItOM0m+G4u XfB4w/J44LUPWEnFS0Q2d5CruoJ5QqMkVVKH6ALvzzjvKm6+W1gCYeiWMX1HJFVfaxMP tr1Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=n8CirlaHdh28gHLoP6h4JqrJrGvDIaVMTsL4o/hfB+Q=; b=jcXhTTqZhaQSZj9wlYqeDbLGG+9y5RZySD4820bHFisuZsGqfkEmlBfTqYeDNDLRKy sxmWYa9uE5BaEyzNUg7LrlZq85tSTjrFRoAI0okYcPydGdmsHbz6EN+5barC6VshZ8UW 8Usj+6NyHf9jDy4KjqlklvBkmdyZqAqclgOLt0p5JZ7LW1tJTmj09cKYF83yingbvM5i quGCP/LoEvfNQPCjVlw4BKCWG8fmK+Xq1LfGRTW6C/28wMJmHri1CzCgxUwGAg+6nN2S Lb+JXCtNqNFJ1mgL7g9+9d7jgVdpIBwAf90iWDBeAN12a3rFzWeJeKzqALbwosr0ThyZ D2Fw== X-Gm-Message-State: APjAAAVdjcWxQ00TUmPkvUX/d5WsaaVCAnVTPKkxayqiV0sfyczW1j0z MQe9IdIWblaflDTS15YxYqiBrWhAP+BotRZzsvPK2g== X-Google-Smtp-Source: APXvYqyLof2LMIjakexWruidxXTOuja6QYEBN71Wz09dSSdidzjc076P0/NGpcQ8yXPJKdtCNEZZ3ZWNW8ha6hRJgHA= X-Received: by 2002:a9d:3466:: with SMTP id v93mr9635813otb.312.1565995098349; Fri, 16 Aug 2019 15:38:18 -0700 (PDT) MIME-Version: 1.0 References: <20190816145602.231163-1-swboyd@chromium.org> <5d57242c.1c69fb81.bba86.14f6@mx.google.com> In-Reply-To: <5d57242c.1c69fb81.bba86.14f6@mx.google.com> From: Tri Vo Date: Fri, 16 Aug 2019 15:38:07 -0700 Message-ID: Subject: Re: [PATCH] PM / wakeup: Register wakeup class kobj after device is added To: Stephen Boyd Cc: "Rafael J. Wysocki" , LKML , Linux PM , Qian Cai 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 Fri, Aug 16, 2019 at 2:46 PM Stephen Boyd wrote: > > Quoting Tri Vo (2019-08-16 14:27:35) > > On Fri, Aug 16, 2019 at 7:56 AM Stephen Boyd wrote: > > > diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c > > > index 1b9c281cbe41..27ee00f50bd7 100644 > > > --- a/drivers/base/power/sysfs.c > > > +++ b/drivers/base/power/sysfs.c > > > @@ -5,6 +5,7 @@ > > > #include > > > #include > > > #include > > > +#include > > > #include > > > #include > > > #include "power.h" > > > @@ -661,14 +662,21 @@ int dpm_sysfs_add(struct device *dev) > > > if (rc) > > > goto err_runtime; > > > } > > > + if (dev->power.wakeup) { > > > > This conditional checks for the situation when wakeup source > > registration have been previously attempted, but failed at > > wakeup_source_sysfs_add(). My concern is that it's not easy to > > understand what this check does without knowing exactly what > > device_wakeup_enable() does to dev->power.wakeup before we reach this > > point. > > Oh, actually this is wrong. It should be a check for > dev->power.wakeup->dev being non-NULL. That's the variable that's set by > wakeup_source_sysfs_add() upon success. So I should make it: > > if (dev->power.wakeup && !dev->power.wakeup->dev) Oh ok, this makes more sense now :) > > And there's the problem that CONFIG_PM_SLEEP could be unset. Let me fix > it up with a new inline function like device_has_wakeup_dev(). > > > > > > + rc = wakeup_source_sysfs_add(dev, dev->power.wakeup); > > > + if (rc) > > > + goto err_wakeup; > > > + } > > > if (dev->power.set_latency_tolerance) { > > > rc = sysfs_merge_group(&dev->kobj, > > > &pm_qos_latency_tolerance_attr_group); > > > if (rc) > > > - goto err_wakeup; > > > + goto err_wakeup_source; > > > } > > > return 0; > > > > > > + err_wakeup_source: > > > + wakeup_source_sysfs_remove(dev->power.wakeup); > > > err_wakeup: > > > sysfs_unmerge_group(&dev->kobj, &pm_wakeup_attr_group); > > > err_runtime: > > > diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c > > > index f7925820b5ca..5817b51d2b15 100644 > > > --- a/drivers/base/power/wakeup.c > > > +++ b/drivers/base/power/wakeup.c > > > @@ -220,10 +220,12 @@ struct wakeup_source *wakeup_source_register(struct device *dev, > > > > > > ws = wakeup_source_create(name); > > > if (ws) { > > > - ret = wakeup_source_sysfs_add(dev, ws); > > > - if (ret) { > > > - wakeup_source_free(ws); > > > - return NULL; > > > + if (!dev || device_is_registered(dev)) { > > > > Is there a possible race condition here? If dev->power.wakeup check in > > dpm_sysfs_add() is done at the same time as device_is_registered(dev) > > check here, then wakeup_source_sysfs_add() won't ever be called? > > The same race exists for device_set_wakeup_capable() so I didn't bother > to try to avoid it. I suppose wakeup_source_sysfs_add() could run > completely, allocate the device and set the name, etc., but not call > device_add() and then we can set ws->dev and call device_add() under a > mutex so that we keep a very small window where the wakeup class is > published to sysfs. Or just throw a big mutex around the whole wakeup > class creation path so that there isn't a chance of a race. But really, > is anyone going to call device_set_wakeup_*() on a device that is also > being added to the system? Seems unlikely. True. I don't have a strong opinion. > > > > > > + ret = wakeup_source_sysfs_add(dev, ws); > > > + if (ret) { > > > + wakeup_source_free(ws);