netdev - Re: [PATCH] remove CONFIG

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Date:   Wed, 29 Jun 2022 12:05:23 -0700
From:   Kalesh Singh <kaleshsingh@...gle.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     Christoph Hellwig <hch@....de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Christian Brauner <brauner@...nel.org>,
        Hridya Valsaraju <hridya@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Theodore Ts'o <tytso@....edu>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "Alex Xu (Hello71)" <alex_y_xu@...oo.ca>,
        Paolo Abeni <pabeni@...hat.com>, Rob Herring <robh@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
        wireguard@...ts.zx2c4.com, netdev@...r.kernel.org,
        rcu@...r.kernel.org, linux-kselftest@...r.kernel.org,
        sultan@...neltoast.com
Subject: Re: [PATCH] remove CONFIG_ANDROID

On Wed, Jun 29, 2022 at 07:34:58PM +0200, Jason A. Donenfeld wrote:
> On Wed, Jun 29, 2022 at 06:38:09PM +0200, Jason A. Donenfeld wrote:
> > On the technical topic, an Android developer friend following this
> > thread just pointed out to me that Android doesn't use PM_AUTOSLEEP and
> > just has userspace causing suspend frequently. So by his rough
> > estimation your patch actually *will* break Android devices. Zoinks.
> > Maybe he's right, maybe he's not -- I don't know -- but you should
> > probably look into this if you want this patch to land without breakage.
> 
> More details: https://cs.android.com/android/platform/superproject/+/master:system/core/libsuspend/autosuspend_wakeup_count.cpp;bpv=1;bpt=1;l=52?q=%22%2Fsys%2Fpower%2Fstate%22&start=51&gsn=sys_power_state&gs=kythe%3A%2F%2Fandroid.googlesource.com%2Fplatform%2Fsuperproject%3Flang%3Dc%252B%252B%3Fpath%3Dsystem%2Fcore%2Flibsuspend%2Fautosuspend_wakeup_count.cpp%23ftWlDJuOhS_2fn3Ri7rClxA30blj_idGgT12aoUHd1o
> 
> So indeed it looks like it's userspace controlled. If you want this to
> be a runtime, rather than a compiletime, switch, maybe
> autosuspend_init() of that file could write to a sysctl.
> 
> Who at Google "owns" that code? Can somebody CC them in?

Hi Jason,

Thanks for raising this.

Android no longer uses PM_AUTOSLEEP, is correct. libsuspend is
also now deprecated. Android autosuspend is initiatiated from the
userspace system suspend service [1].

A runtime config sounds more reasonable since in the !PM_AUTOSLEEP
case, it is userspace which decides the suspend policy.

[1] https://cs.android.com/android/platform/superproject/+/bf3906ecb33c98ff8edd96c852b884dbccb73295:system/hardware/interfaces/suspend/1.0/default/SystemSuspend.cpp;l=265

--Kalesh

> 
> Jason
>