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From: Joel Fernandes <joel@joelfernandes.org>
To: Scott Wood <swood@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org,
	"Paul E . McKenney" <paulmck@linux.ibm.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Clark Williams <williams@redhat.com>
Subject: Re: [PATCH RT v2 3/3] rcu: Disable use_softirq on PREEMPT_RT
Date: Thu, 22 Aug 2019 20:52:18 -0400	[thread overview]
Message-ID: <20190823005218.GA36261@google.com> (raw)
In-Reply-To: <c44d6ab34f2f4e4a5d36036cc8b356a3f4f3519b.camel@redhat.com>

On Thu, Aug 22, 2019 at 02:31:17PM -0500, Scott Wood wrote:
> On Thu, 2019-08-22 at 09:59 -0400, Joel Fernandes wrote:
> > On Wed, Aug 21, 2019 at 06:19:06PM -0500, Scott Wood wrote:
> > > I think the prohibition on use_softirq can be dropped once RT gets the
> > > latest RCU code, but the question of what use_softirq should default
> > > to on PREEMPT_RT remains.
> > 
> > Independent of the question of what use_softirq should default to, could
> > we
> > test RT with latest RCU code now to check if the deadlock goes away?  That
> > way, maybe we can find any issues in current RCU that cause scheduler
> > deadlocks in the situation you pointed. The reason I am asking is because
> > recently additional commits [1] try to prevent deadlock and it'd be nice
> > to
> > ensure that other conditions are not lingering (I don't think they are but
> > it'd be nice to be sure).
> > 
> > I am happy to do such testing myself if you want, however what does it
> > take
> > to apply the RT patchset to the latest mainline? Is it an achievable feat?
> 
> I did run such a test (cherry picking all RCU patches that aren't already in
> RT, plus your RFC patch to rcu_read_unlock_special, rather than applying RT
> to current mainline) with rcutorture plus a looping kernel build overnight,
> and didn't see any splats with or without use_softirq.

Cool, that's good to know you didn't see splats!

thanks,

 - Joel


      reply	other threads:[~2019-08-23  0:52 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-21 23:19 [PATCH RT v2 0/3] RCU fixes Scott Wood
2019-08-21 23:19 ` [PATCH RT v2 1/3] rcu: Acquire RCU lock when disabling BHs Scott Wood
2019-08-21 23:33   ` Paul E. McKenney
2019-08-22 13:39     ` Joel Fernandes
2019-08-22 15:27       ` Paul E. McKenney
2019-08-23  1:50         ` Joel Fernandes
2019-08-23  2:11           ` Paul E. McKenney
2019-08-23  3:23       ` Scott Wood
2019-08-23 12:30         ` Paul E. McKenney
2019-08-23 16:17         ` Sebastian Andrzej Siewior
2019-08-23 19:46           ` Scott Wood
2019-08-26 15:59             ` Sebastian Andrzej Siewior
2019-08-26 23:21               ` Scott Wood
2019-08-23  2:36     ` Scott Wood
2019-08-23  2:54       ` Paul E. McKenney
2019-08-21 23:19 ` [PATCH RT v2 2/3] sched: migrate_enable: Use sleeping_lock to indicate involuntary sleep Scott Wood
2019-08-21 23:35   ` Paul E. McKenney
2019-08-23  1:21     ` Scott Wood
2019-08-23 16:20   ` Sebastian Andrzej Siewior
2019-08-23 19:28     ` Scott Wood
2019-08-24  3:10       ` Joel Fernandes
2019-08-26 15:25         ` Sebastian Andrzej Siewior
2019-08-26 16:29           ` Paul E. McKenney
2019-08-26 17:49             ` Scott Wood
2019-08-26 18:12               ` Paul E. McKenney
2019-08-27  9:23             ` Sebastian Andrzej Siewior
2019-08-27 13:08               ` Joel Fernandes
2019-08-27 15:58                 ` Paul E. McKenney
2019-08-27 16:06                   ` Joel Fernandes
2019-08-27 15:53               ` Paul E. McKenney
2019-08-28  9:27                 ` Sebastian Andrzej Siewior
2019-08-28 12:54                   ` Paul E. McKenney
2019-08-28 13:14                     ` Sebastian Andrzej Siewior
2019-08-28 13:59                       ` Joel Fernandes
2019-08-28 15:51                         ` Paul E. McKenney
2019-08-28 15:50                       ` Paul E. McKenney
2019-08-21 23:19 ` [PATCH RT v2 3/3] rcu: Disable use_softirq on PREEMPT_RT Scott Wood
2019-08-21 23:40   ` Paul E. McKenney
2019-08-23 16:32     ` Sebastian Andrzej Siewior
2019-08-22 13:59   ` Joel Fernandes
2019-08-22 15:29     ` Paul E. McKenney
2019-08-22 19:31     ` Scott Wood
2019-08-23  0:52       ` Joel Fernandes [this message]

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