From: Michael Ellerman <mpe@ellerman•id.au>
To: Zhouyi Zhou <zhouzhouyi@gmail•com>,
"Paul E. McKenney" <paulmck@kernel•org>
Cc: rcu <rcu@vger•kernel.org>,
Miguel Ojeda <miguel.ojeda.sandonis@gmail•com>,
linuxppc-dev <linuxppc-dev@lists•ozlabs.org>,
Nicholas Piggin <npiggin@gmail•com>
Subject: Re: rcu_sched self-detected stall on CPU
Date: Sun, 10 Apr 2022 21:33:43 +1000 [thread overview]
Message-ID: <871qy56ulk.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <CAABZP2zEU8eULq30ZLcUeqxjXuLTKO4b3wm_Jo458Nq_JJ7pEw@mail.gmail.com>
Zhouyi Zhou <zhouzhouyi@gmail•com> writes:
> On Fri, Apr 8, 2022 at 10:07 PM Paul E. McKenney <paulmck@kernel•org> wrote:
>> On Fri, Apr 08, 2022 at 06:02:19PM +0800, Zhouyi Zhou wrote:
>> > On Fri, Apr 8, 2022 at 3:23 PM Michael Ellerman <mpe@ellerman•id.au> wrote:
...
>> > > I haven't seen it in my testing. But using Miguel's config I can
>> > > reproduce it seemingly on every boot.
>> > >
>> > > For me it bisects to:
>> > >
>> > > 35de589cb879 ("powerpc/time: improve decrementer clockevent processing")
>> > >
>> > > Which seems plausible.
>> > I also bisect to 35de589cb879 ("powerpc/time: improve decrementer
>> > clockevent processing")
...
>>
>> > > Reverting that on mainline makes the bug go away.
>> > I also revert that on the mainline, and am currently doing a pressure
>> > test (by repeatedly invoking qemu and checking the console.log) on PPC
>> > VM in Oregon State University.
> After 306 rounds of stress test on mainline without triggering the bug
> (last for 4 hours and 27 minutes), I think the bug is indeed caused by
> 35de589cb879 ("powerpc/time: improve decrementer clockevent
> processing") and stop the test for now.
Thanks for testing, that's pretty conclusive.
I'm not inclined to actually revert it yet.
We need to understand if there's actually a bug in the patch, or if it's
just exposing some existing bug/bad behavior we have. The fact that it
only appears with CONFIG_HIGH_RES_TIMERS=n is suspicious.
Do we have some code that inadvertently relies on something enabled by
HIGH_RES_TIMERS=y, or do we have a bug that is hidden by HIGH_RES_TIMERS=y ?
cheers
next prev parent reply other threads:[~2022-04-10 11:34 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-05 21:41 rcu_sched self-detected stall on CPU Miguel Ojeda
2022-04-06 9:31 ` Zhouyi Zhou
2022-04-06 17:00 ` Paul E. McKenney
2022-04-06 18:25 ` Zhouyi Zhou
2022-04-06 19:50 ` Paul E. McKenney
2022-04-07 2:26 ` Zhouyi Zhou
2022-04-07 10:07 ` Miguel Ojeda
2022-04-07 15:15 ` Paul E. McKenney
2022-04-07 17:05 ` Miguel Ojeda
2022-04-07 17:55 ` Paul E. McKenney
2022-04-07 23:14 ` Zhouyi Zhou
2022-04-08 1:43 ` Paul E. McKenney
2022-04-08 7:23 ` Michael Ellerman
2022-04-08 10:02 ` Zhouyi Zhou
2022-04-08 14:07 ` Paul E. McKenney
2022-04-08 14:25 ` Zhouyi Zhou
2022-04-10 11:33 ` Michael Ellerman [this message]
2022-04-11 3:05 ` Paul E. McKenney
2022-04-12 6:53 ` Michael Ellerman
2022-04-12 13:36 ` Paul E. McKenney
2022-04-08 13:52 ` Miguel Ojeda
2022-04-08 14:06 ` Paul E. McKenney
2022-04-08 14:42 ` Michael Ellerman
2022-04-08 15:52 ` Paul E. McKenney
2022-04-08 17:02 ` Miguel Ojeda
2022-04-13 5:11 ` Nicholas Piggin
2022-04-13 6:10 ` Low-res tick handler device not going to ONESHOT_STOPPED when tick is stopped (was: rcu_sched self-detected stall on CPU) Nicholas Piggin
2022-04-14 17:15 ` Paul E. McKenney
2022-04-22 15:53 ` Thomas Gleixner
2022-04-23 2:29 ` Re: Nicholas Piggin
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