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

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Message-ID: <YrtgeSmwLmpzN/zw@pc638>
Date:   Tue, 28 Jun 2022 22:11:37 +0200
From:   Uladzislau Rezki <urezki@...il.com>
To:     "Alex Xu (Hello71)" <alex_y_xu@...oo.ca>
Cc:     paulmck@...nel.org, 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".
> 
Sorry but we need to apply some assumption, i.e. to me the CONFIG_ANDROID
indicates that a kernel runs on the Android wise device. When you enable
this option on you specific box it is supposed that some Android related
code are activated also on your device which may lead to some side effect.

>
> 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.
> 
<snip>
diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug
index 9b64e55d4f61..ced0d1f7c675 100644
--- a/kernel/rcu/Kconfig.debug
+++ b/kernel/rcu/Kconfig.debug
@@ -94,7 +94,8 @@ config RCU_EXP_CPU_STALL_TIMEOUT
          If the RCU grace period persists, additional CPU stall warnings
          are printed at more widely spaced intervals.  A value of zero
          says to use the RCU_CPU_STALL_TIMEOUT value converted from
-         seconds to milliseconds.
+         seconds to milliseconds. If CONFIG_ANDROID is set for non-Android
+         platform and you unsure, set the RCU_EXP_CPU_STALL_TIMEOUT to zero.

 config RCU_TRACE
        bool "Enable tracing for RCU"
<snip>

Will it work for you?

--
Uladzislau Rezki