From: Davidlohr Bueso <dave@stgolabs.net>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: peterz@infradead.org, mingo@redhat.com, will@kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: Question on task_blocks_on_rt_mutex()
Date: Fri, 4 Sep 2020 10:24:32 -0700 [thread overview]
Message-ID: <20200904172432.wgxn6x5tpnt4lcln@linux-p48b> (raw)
In-Reply-To: <20200903200639.GA8956@paulmck-ThinkPad-P72>
On Thu, 03 Sep 2020, Paul E. McKenney wrote:
>commit d93a64389f4d544ded241d0ba30b2586497f5dc0
>Author: Paul E. McKenney <paulmck@kernel.org>
>Date: Tue Sep 1 16:58:41 2020 -0700
>
> torture: Periodically pause in stutter_wait()
>
> Running locktorture scenario LOCK05 results in hangs:
>
> tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --torture lock --duration 3 --configs LOCK05
>
> The lock_torture_writer() kthreads set themselves to MAX_NICE while
> running SCHED_OTHER. Other locktorture kthreads run at default niceness,
> also SCHED_OTHER. This results in these other locktorture kthreads
> indefinitely preempting the lock_torture_writer() kthreads. Note that
> the cond_resched() in the stutter_wait() function's loop is ineffective
> because this scenario is built with CONFIG_PREEMPT=y.
>
> It is not clear that such indefinite preemption is supposed to happen, but
> in the meantime this commit prevents kthreads running in stutter_wait()
> from being completely CPU-bound, thus allowing the other threads to get
> some CPU in a timely fashion. This commit also uses hrtimers to provide
> very short sleeps to avoid degrading the sudden-on testing that stutter
> is supposed to provide.
>
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviwed-by: Davidlohr Bueso <dbueso@suse.de>
next prev parent reply other threads:[~2020-09-04 18:10 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-31 22:49 Paul E. McKenney
2020-08-31 23:21 ` Paul E. McKenney
2020-09-01 17:49 ` Paul E. McKenney
2020-09-01 23:58 ` Paul E. McKenney
2020-09-02 1:51 ` Davidlohr Bueso
2020-09-02 15:54 ` Paul E. McKenney
2020-09-03 20:06 ` Paul E. McKenney
2020-09-04 17:24 ` Davidlohr Bueso [this message]
2020-09-04 19:56 ` Paul E. McKenney
2020-09-05 21:24 ` Joel Fernandes
2020-09-05 21:45 ` Joel Fernandes
2020-09-06 4:14 ` Paul E. McKenney
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