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

From: "Paul E. McKenney" <paulmck@kernel.org>
To: "Christian König" <christian.koenig@amd.com>
Cc: "Uladzislau Rezki" <urezki@gmail.com>,
	"Alex Xu (Hello71)" <alex_y_xu@yahoo.ca>,
	wireguard@lists.zx2c4.com, "Jason A. Donenfeld" <Jason@zx2c4.com>,
	"Joel Fernandes" <joel@joelfernandes.org>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	Xinhui.Pan@amd.com, linux-kernel@vger.kernel.org,
	amd-gfx@lists.freedesktop.org,
	"Suren Baghdasaryan" <surenb@google.com>,
	rcu@vger.kernel.org, "Hridya Valsaraju" <hridya@google.com>,
	"Arve Hjønnevåg" <arve@android.com>,
	"Theodore Ts'o" <tytso@mit.edu>,
	alexander.deucher@amd.com, "Todd Kjos" <tkjos@android.com>,
	uladzislau.rezki@sony.com, "Martijn Coenen" <maco@android.com>,
	"Christian Brauner" <christian@brauner.io>
Subject: Re: CONFIG_ANDROID (was: rcu_sched detected expedited stalls in amdgpu after suspend)
Date: Thu, 7 Jul 2022 06:29:21 -0700	[thread overview]
Message-ID: <20220707132921.GK1790663@paulmck-ThinkPad-P17-Gen-1> (raw)
In-Reply-To: <fbf83d60-67d3-698d-e2d2-02dc8d7e49c4@amd.com>

On Thu, Jul 07, 2022 at 09:30:39AM +0200, Christian König wrote:
> Am 06.07.22 um 22:42 schrieb Paul E. McKenney:
> > On Wed, Jul 06, 2022 at 08:09:49PM +0200, Uladzislau Rezki wrote:
> > > On Wed, Jul 06, 2022 at 10:58:36AM -0700, Paul E. McKenney wrote:
> > > > On Wed, Jul 06, 2022 at 07:48:20PM +0200, Uladzislau Rezki wrote:
> > > > > Hello.
> > > > > 
> > > > > On Mon, Jul 04, 2022 at 01:30:50PM +0200, Christian König wrote:
> > > > > > Hi guys,
> > > > > > 
> > > > > > Am 28.06.22 um 22:11 schrieb Uladzislau Rezki:
> > > > > > > > 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?
> > > > > > sorry for jumping in so later, I was on vacation for a week.
> > > > > > 
> > > > > > Well when any RCU period is longer than 20ms and amdgpu in the backtrace my
> > > > > > educated guess is that we messed up some timeout waiting for the hw.
> > > > > > 
> > > > > > We usually do wait a few us, but it can be that somebody is waiting for ms
> > > > > > instead.
> > > > > > 
> > > > > > So there are some todos here as far as I can see and It would be helpful to
> > > > > > get a cleaner backtrace if possible.
> > > > > > 
> > > > > Actually CONFIG_ANDROID looks like is going to be removed, so the CONFIG_RCU_EXP_CPU_STALL_TIMEOUT
> > > > > will not have any dependencies on the CONFIG_ANDROID anymore:
> > > > > 
> > > > > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flkml.org%2Flkml%2F2022%2F6%2F29%2F756&amp;data=05%7C01%7Cchristian.koenig%40amd.com%7C8b36bcb4fe61475c0eb708da5f8ffce8%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637927369274030797%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=eaK66spsbWVi2uRhcFK7eu4usgkHFZCSvErZxB%2F2npM%3D&amp;reserved=0
> > > > But you can set the RCU_EXP_CPU_STALL_TIMEOUT Kconfig option, if you
> > > > wish.  Setting this option to 20 will get you the behavior previously
> > > > obtained by setting the now-defunct ANDROID Kconfig option.
> > > > 
> > > Right. Or over boot parameter. So for us it is not a big issue :)
> > Specifically rcupdate.rcu_exp_cpu_stall_timeout, for those just now
> > tuning in.  ;-)
> 
> I was just about to write a response asking for that :)
> 
> Thanks, I will suggest to our QA to add this parameter while doing some
> tests.

Very good!  Please let me know how it goes.

							Thanx, Paul