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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 39111C43613 for ; Mon, 24 Jun 2019 01:48:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0E1CB2063F for ; Mon, 24 Jun 2019 01:48:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=android.com header.i=@android.com header.b="aYkg+TE3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726341AbfFXBs4 (ORCPT ); Sun, 23 Jun 2019 21:48:56 -0400 Received: from mail-ot1-f65.google.com ([209.85.210.65]:35452 "EHLO mail-ot1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726312AbfFXBs4 (ORCPT ); Sun, 23 Jun 2019 21:48:56 -0400 Received: by mail-ot1-f65.google.com with SMTP id j19so11930289otq.2 for ; Sun, 23 Jun 2019 18:48:55 -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=KoQYiQrMBAoPwcouH5zLkPtiukwZNYdGgxBPjr/sF88=; b=aYkg+TE39brESepUpYvudC15qXREldRUSMU/512F+I3btn18W+Xyfqt6LgqaLTPCkh vCiVE2NlKC1hkzVZQPazcAnCKBWcQ56W8WagWpEk5ys8BlKUE8Tti5E4ZaCMNNgKYpGM MsJCrSidc4ZdUr0WbczMxSGC8q3qfuxN9gHvUsNU/IRlKcdg7NcG/cBP9kWp0ZZM4AQd 4ix6Wuk06EKbD7SsXf7AWQrjeWS/JMdohdjDev0BJ5XI/c1gmGhRnKg2GmyCbWj0FLzb 02XeKxEDDNRRW0+Xg44AIg6KcDbGzWU1YaXJnupcpQ18Kg5Ez8NhzflUYscbN98fUctm UGOw== 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=KoQYiQrMBAoPwcouH5zLkPtiukwZNYdGgxBPjr/sF88=; b=DTg1mlfBCBeVffPyLo5o1EPR4TTN3XurOLIilcqleXIFQWbJeM//BsySIJIoCRsd6a PyjcnEig63HhFkm4SR/9YSoQw6ISYbRqmH0cGlIDzL1Q87LgPy1rmsIrlqptz/hL7yd3 BWlD0gD8w2R9cSbl8R1WtjaGbxytJ9gmvjGgZN9diZm3OsVf30AKE3W2kQBciODLzkcm aB4KQC9i7Z+pqfakfZIAlKUaKukYwA7nc6eC0ZvchTV5xcL9yJrHQsPiB04qNcO0cFhb x9Vm6zaTTli/EgscP/TbC8JJCILF9oqwDNZ6K7eHLbhBBKlmQRPicMPNP4yejIy8riHU X1jQ== X-Gm-Message-State: APjAAAWVbdf6eR0EYcQqMa7VRmkKgooAiDVUuxnBf5VrodHGC2ORurEL RRH4jiP0mYjWzJfrxtaBMPcmVzYKyWd7rqazbOmiWw== X-Google-Smtp-Source: APXvYqyu3RIcWBRJLSScwP9CuXO3dOu2zHqFIr87b56yxDl/RFshM7fhRGX07M5Ok8/ypr/fYnAwbIpE31qvkI24V9g= X-Received: by 2002:a9d:450a:: with SMTP id w10mr43913762ote.148.1561340935025; Sun, 23 Jun 2019 18:48:55 -0700 (PDT) MIME-Version: 1.0 References: <20190618182502.GC203031@google.com> <4587569.x9DSL43cXO@kreacher> In-Reply-To: From: Tri Vo Date: Sun, 23 Jun 2019 18:48:43 -0700 Message-ID: Subject: Re: Alternatives to /sys/kernel/debug/wakeup_sources To: "Rafael J. Wysocki" Cc: Joel Fernandes , "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 1:35 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). This may be a dumb question. Is it appropriate to make symbolic links in sysfs from one attribute to another attribute? For example, /sys/devices/.../power/wakeup_count -> /sys/power/wakeup_sources/.../wakeup_count. I only see kobject to kobject symlinks around. And I don't think we can make /sys/devices/.../power/ directory a symlink to where our new wakeup stats will be, since the former contains attributes other than wakeup ones. Thanks!