From: Scott Wood <swood@redhat.com>
To: paulmck@linux.ibm.com
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org,
Joel Fernandes <joel@joelfernandes.org>,
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 1/3] rcu: Acquire RCU lock when disabling BHs
Date: Thu, 22 Aug 2019 21:36:21 -0500 [thread overview]
Message-ID: <2981acb99554a80211118350975577ab8faa3a2d.camel@redhat.com> (raw)
In-Reply-To: <20190821233358.GU28441@linux.ibm.com>
On Wed, 2019-08-21 at 16:33 -0700, Paul E. McKenney wrote:
> On Wed, Aug 21, 2019 at 06:19:04PM -0500, Scott Wood wrote:
> > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> > index 388ace315f32..d6e357378732 100644
> > --- a/include/linux/rcupdate.h
> > +++ b/include/linux/rcupdate.h
> > @@ -615,10 +615,12 @@ static inline void rcu_read_unlock(void)
> > static inline void rcu_read_lock_bh(void)
> > {
> > local_bh_disable();
> > +#ifndef CONFIG_PREEMPT_RT_FULL
> > __acquire(RCU_BH);
> > rcu_lock_acquire(&rcu_bh_lock_map);
> > RCU_LOCKDEP_WARN(!rcu_is_watching(),
> > "rcu_read_lock_bh() used illegally while idle");
> > +#endif
>
> Any chance of this using "if (!IS_ENABLED(CONFIG_PREEMPT_RT_FULL))"?
> We should be OK providing a do-nothing __maybe_unused rcu_bh_lock_map
> for lockdep-enabled -rt kernels, right?
OK.
> > @@ -185,8 +189,10 @@ void __local_bh_enable_ip(unsigned long ip,
> > > > unsigned int cnt)
> > WARN_ON_ONCE(count < 0);
> > local_irq_enable();
> >
> > - if (!in_atomic())
> > + if (!in_atomic()) {
> > + rcu_read_unlock();
> > local_unlock(bh_lock);
> > + }
>
> The return from in_atomic() is guaranteed to be the same at
> local_bh_enable() time as was at the call to the corresponding
> local_bh_disable()?
That's an existing requirement on RT (which rcutorture currently violates)
due to bh_lock.
> I could have sworn that I ran afoul of this last year. Might these
> added rcu_read_lock() and rcu_read_unlock() calls need to check for
> CONFIG_PREEMPT_RT_FULL?
This code is already under a PREEMPT_RT_FULL ifdef.
-Scott
next prev parent reply other threads:[~2019-08-23 2:36 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 [this message]
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
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