From: "Paul E. McKenney" <paulmck@linux.ibm.com>
To: Scott Wood <swood@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
Juri Lelli <juri.lelli@redhat.com>,
Clark Williams <williams@redhat.com>,
linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH RT 1/4] rcu: Acquire RCU lock when disabling BHs
Date: Thu, 20 Jun 2019 14:20:35 -0700 [thread overview]
Message-ID: <20190620212035.GY26519@linux.ibm.com> (raw)
In-Reply-To: <1b6dfc95bba69aa53e4e84eebf6af60f0b9ed95c.camel@redhat.com>
On Thu, Jun 20, 2019 at 04:06:02PM -0500, Scott Wood wrote:
> On Thu, 2019-06-20 at 13:53 -0700, Paul E. McKenney wrote:
> > On Tue, Jun 18, 2019 at 08:19:05PM -0500, Scott Wood wrote:
> > > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> > > index fb267bc04fdf..aca4e5e25ace 100644
> > > --- a/include/linux/rcupdate.h
> > > +++ b/include/linux/rcupdate.h
> > > @@ -637,10 +637,12 @@ static inline void rcu_read_unlock(void)
> > > static inline void rcu_read_lock_bh(void)
> > > {
> > > local_bh_disable();
> > > +#ifndef CONFIG_PREEMPT_RT_FULL
> >
> > How about this instead?
> >
> > if (IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
> > return;
>
> OK.
>
> > > @@ -189,8 +193,10 @@ 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);
> > > + }
> > >
> > > preempt_check_resched();
> > > }
> >
> > And I have to ask...
> >
> > What did you do to test this change to kernel/softirq.c? My past attempts
> > to do this sort of thing have always run afoul of open-coded BH
> > transitions.
>
> Mostly rcutorture and loads such as kernel builds, on a debug kernel. By
> "open-coded BH transition" do you mean directly manipulating the preempt
> count? That would already be broken on RT.
OK, then maybe you guys have already done the needed cleanup work. Cool!
But don't the additions of rcu_read_lock() and rcu_read_unlock() want
to be protected by "!IS_ENABLED(CONFIG_PREEMPT_RT_FULL)" or similar?
Thanx, Paul
next prev parent reply other threads:[~2019-06-20 21:20 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-19 1:19 [PATCH RT 0/4] Address rcutorture issues Scott Wood
2019-06-19 1:19 ` [PATCH RT 1/4] rcu: Acquire RCU lock when disabling BHs Scott Wood
2019-06-20 20:53 ` Paul E. McKenney
2019-06-20 21:06 ` Scott Wood
2019-06-20 21:20 ` Paul E. McKenney [this message]
2019-06-20 21:38 ` Scott Wood
2019-06-20 22:16 ` Paul E. McKenney
2019-06-19 1:19 ` [PATCH RT 2/4] sched: migrate_enable: Use sleeping_lock to indicate involuntary sleep Scott Wood
2019-06-19 1:19 ` [RFC PATCH RT 3/4] rcu: unlock special: Treat irq and preempt disabled the same Scott Wood
2019-06-20 21:10 ` Paul E. McKenney
2019-06-20 21:59 ` Scott Wood
2019-06-20 22:25 ` Paul E. McKenney
2019-06-20 23:08 ` Scott Wood
2019-06-22 0:26 ` Paul E. McKenney
2019-06-22 19:13 ` Paul E. McKenney
2019-06-24 17:40 ` Scott Wood
2019-06-19 1:19 ` [RFC PATCH RT 4/4] rcutorture: Avoid problematic critical section nesting Scott Wood
2019-06-20 21:18 ` Paul E. McKenney
2019-06-20 21:43 ` Scott Wood
2019-06-21 16:38 ` Sebastian Andrzej Siewior
2019-06-21 23:59 ` Paul E. McKenney
2019-06-26 15:08 ` Steven Rostedt
2019-06-26 16:49 ` Scott Wood
2019-06-27 18:00 ` Paul E. McKenney
2019-06-27 20:16 ` Scott Wood
2019-06-27 20:50 ` Paul E. McKenney
2019-06-27 22:46 ` Scott Wood
2019-06-28 0:52 ` Paul E. McKenney
2019-06-28 19:37 ` Scott Wood
2019-06-28 20:24 ` Paul E. McKenney
2019-06-20 19:12 ` [PATCH RT 0/4] Address rcutorture issues Paul E. McKenney
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