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=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL autolearn=unavailable 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 6A9D8C31E5D for ; Wed, 19 Jun 2019 10:33:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 44395208CB for ; Wed, 19 Jun 2019 10:33:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="p0Sz0EF5" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731560AbfFSKd0 (ORCPT ); Wed, 19 Jun 2019 06:33:26 -0400 Received: from mail-qt1-f194.google.com ([209.85.160.194]:40942 "EHLO mail-qt1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731134AbfFSKd0 (ORCPT ); Wed, 19 Jun 2019 06:33:26 -0400 Received: by mail-qt1-f194.google.com with SMTP id a15so19189094qtn.7 for ; Wed, 19 Jun 2019 03:33:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=A5r+fNs6piiH+aGROj+Wzs8FJ/AgXElJ3JaEl+QTwIo=; b=p0Sz0EF57FLawqG1VabOdKC+Bzkx1UdG2TqBFuTGofHL6o9iG0MRLdNfctgnNozh2f 6F8Mh9THCLq2XpLwTG7HOAWojfnYHMZN+2/aDw5bnfkdIYYrFBfaz9aLdcjqWmSfu8ZE VlQbGTn3du33tcn4jSQVpNBG+tHNQ5Bhoi156ScFhodZXXbrqwCrcAH3v1e3JUdcn9XX U7CGA6FdOtRrPimU4yrSNENfugRzIwMbgpGbn/TNF/NZLkviGFU2QXWBNV5e/Sa9CIJ4 QuxvwO4lDynAaiy9HaOwaLl3ut7ueE36ejJI53EkALbw+xzhHFg20VPeoriGxgaYIp2Y Xctw== 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=A5r+fNs6piiH+aGROj+Wzs8FJ/AgXElJ3JaEl+QTwIo=; b=F3YX1AFUPv25aZbwlUgpXLrUB41SK79kn+2HW5vKI5oSCBNhWR0Nu2CCiBC2EuyLv9 1TcqNH/YZPZgqd8n0LZAJcbWsO4Bnl/d7H7QF4LgBI9xcdrS0bjBs+BKKOBb6eQ+Jkea RNJLOwC1uJbIjtNrAR4iRbUJDLLlbtALR2hZRtZHAhWN8HH/8+So7JEmLKUiAXgxh/Tr eu8kEg1T0IWvm2OuAA9RxTM1j9jnlWyT1Sk2Wh+RolOu8PhKhG2D5/wjJHVzqs73WzF4 7NCnOj6s/1G2ueY9qXX4IwrCAXMc8EHVsvPFbDdWCh8LwOBKtgkwb6et84KfcWfW6sUg OWyg== X-Gm-Message-State: APjAAAWioivAy2e29k/ABAF3KARsl5rNjdG1bZu/hIivQnZLH3Fr7w7h 7X8MVqeR+OsTYhGQIE8AploXo930PoOZXmbTK1XvNw== X-Google-Smtp-Source: APXvYqzsT65B1Q6a584qTVdugWKlIu1yIZmyVh6lrG95htoJMyCqQWISMHXkLYv5iX+GmxabuYhjkdpTL/3YmtcKZeU= X-Received: by 2002:a0c:b999:: with SMTP id v25mr20736885qvf.36.1560940404444; Wed, 19 Jun 2019 03:33:24 -0700 (PDT) MIME-Version: 1.0 References: <20190618182502.GC203031@google.com> <4587569.x9DSL43cXO@kreacher> In-Reply-To: From: Joel Fernandes Date: Wed, 19 Jun 2019 06:33:12 -0400 Message-ID: Subject: Re: Alternatives to /sys/kernel/debug/wakeup_sources To: "Rafael J. Wysocki" Cc: Tri Vo , "Rafael J. Wysocki" , Sandeep Patil , Viresh Kumar , Hridya Valsaraju , Linux PM , "Cc: Android Kernel" , Greg Kroah-Hartman , LKML 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 Wed, Jun 19, 2019 at 4:35 AM Rafael J. Wysocki wrote: > > On Wed, Jun 19, 2019 at 1:52 AM Joel Fernandes wrote: > > > > On Tue, Jun 18, 2019 at 7:15 PM Tri Vo wrote: > > [snip] > > > > > > > > > > > > > > Android userspace reading wakeup_sources is not ideal because: > > > > > > > - Debugfs API is not stable, i.e. Android tools built on top of it are > > > > > > > not guaranteed to be backward/forward compatible. > > > > > > > - This file requires debugfs to be mounted, which itself is > > > > > > > undesirable for security reasons. > > > > > > > > > > > > > > To address these problems, we want to contribute a way to expose these > > > > > > > statistics that doesn't depend on debugfs. > > > > > > > > > > > > > > Some initial thoughts/questions: Should we expose the stats in sysfs? > > > > > > > Or maybe implement eBPF-based solution? What do you think? > > > > > > > > > > We are going through Android's out-of-tree kernel dependencies along with > > > > > userspace APIs that are not necessarily considered "stable and forever > > > > > supported" upstream. The debugfs dependencies showed up on our radar as a > > > > > result and so we are wondering if we should worry about changes in debugfs > > > > > interface and hence the question(s) below. > > > > > > > > > > So, can we rely on /d/wakeup_sources to be considered a userspace API and > > > > > hence maintained stable as we do for other /proc and /sys entries? > > > > > > > > > > If yes, then we will go ahead and add tests for this in LTP or > > > > > somewhere else suitable. > > > > > > > > No, debugfs is not ABI. > > > > > > > > > If no, then we would love to hear suggestions for any changes that need to be > > > > > made or we simply just move the debugfs entry into somewhere like > > > > > /sys/power/ ? > > > > > > > > No, moving that entire file from debugfs into sysfs is not an option either. > > > > > > > > The statistics for the wakeup sources associated with devices are already there > > > > under /sys/devices/.../power/ , but I guess you want all wakeup sources? > > > > > > > > That would require adding a kobject to struct wakeup_source and exposing > > > > all of the statistics as separate attributes under it. In which case it would be > > > > good to replace the existing wakeup statistics under /sys/devices/.../power/ > > > > with symbolic links to the attributes under the wakeup_source kobject. > > > > > > Thanks for your input, Rafael! Your suggestion makes sense. I'll work > > > on a patch for this. > > > > Does that entail making each wake up source, a new sysfs node under a > > particular device, and then adding stats under that new node? > > Not under a device, because there are wakeup source objects without > associated devices. > > It is conceivable to have a "wakeup_sources" directory under > /sys/power/ and sysfs nodes for all wakeup sources in there. > > Then, instead of exposing wakeup statistics directly under > /sys/devices/.../power/, there can be symbolic links from there to the > new wakeup source nodes under "wakeup_sources" (so as to avoid > exposing the same data in two different places in sysfs, which may be > confusing). Makes sense to me, thanks! - Joel