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From: "Paul E. McKenney" <paulmck@kernel.org>
To: Davidlohr Bueso <dave@stgolabs.net>
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 12:56:28 -0700	[thread overview]
Message-ID: <20200904195628.GL29330@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20200904172432.wgxn6x5tpnt4lcln@linux-p48b>

On Fri, Sep 04, 2020 at 10:24:32AM -0700, Davidlohr Bueso wrote:
> 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>

Applied, thank you!

							Thanx, Paul

  reply	other threads:[~2020-09-04 19:56 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-31 22:49 Question on task_blocks_on_rt_mutex() 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
2020-09-04 19:56               ` Paul E. McKenney [this message]
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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