linux-kernel - Re: CONFIG_ANDROID (was: rcu_sched detected expedited stalls in amdgpu after suspend)

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Message-Id: <1656443915.mdjoauhqe0.none@localhost>
Date:   Tue, 28 Jun 2022 15:28:26 -0400
From:   "Alex Xu (Hello71)" <alex_y_xu@...oo.ca>
To:     paulmck@...nel.org
Cc:     alexander.deucher@....com, amd-gfx@...ts.freedesktop.org,
        Arve Hjønnevåg <arve@...roid.com>,
        Christian Brauner <christian@...uner.io>,
        christian.koenig@....com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hridya Valsaraju <hridya@...gle.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        linux-kernel@...r.kernel.org, Martijn Coenen <maco@...roid.com>,
        rcu@...r.kernel.org, Suren Baghdasaryan <surenb@...gle.com>,
        Todd Kjos <tkjos@...roid.com>, Theodore Ts'o <tytso@....edu>,
        uladzislau.rezki@...y.com, urezki@...il.com,
        wireguard@...ts.zx2c4.com, Xinhui.Pan@....com
Subject: Re: CONFIG_ANDROID (was: rcu_sched detected expedited stalls in
 amdgpu after suspend)

Excerpts from Paul E. McKenney's message of June 28, 2022 2:54 pm:
> All you need to do to get the previous behavior is to add something like
> this to your defconfig file:
> 
> CONFIG_RCU_EXP_CPU_STALL_TIMEOUT=21000
> 
> Any reason why this will not work for you?

As far as I know, I do not require any particular RCU debugging features 
intended for developers; as an individual user and distro maintainer, I 
would like to select the option corresponding to "emit errors for 
unexpected conditions which should be reported upstream", not "emit 
debugging information for development purposes".

Therefore, I think 0 is a suitable setting for me and most ordinary 
(not tightly controlled) distributions. My concern is that other users 
and distro maintainers will also have confusion about what value to set 
and whether the warnings are important, since the help text does not say 
anything about Android, and "make oldconfig" does not indicate that the 
default value is different for Android.

My suggestion is that the default be set to 0, and if a non-zero value 
is appropriate for Android, that should be communicated to the Android 
developers, not made conditional on CONFIG_ANDROID.

Thanks,
Alex.