From: Scott Wood <swood@redhat.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Joel Fernandes <joel@joelfernandes.org>,
"Paul E. McKenney" <paulmck@linux.ibm.com>,
linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.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: Mon, 26 Aug 2019 18:21:46 -0500 [thread overview]
Message-ID: <b948ec6cccda31925ed8dc123bd0f55423fff3d4.camel@redhat.com> (raw)
In-Reply-To: <20190826155943.zvghokdn3iu2sipx@linutronix.de>
On Mon, 2019-08-26 at 17:59 +0200, Sebastian Andrzej Siewior wrote:
> On 2019-08-23 14:46:39 [-0500], Scott Wood wrote:
> > > > Before consolidation, RT mapped rcu_read_lock_bh_held() to
> > > > rcu_read_lock_bh() and called rcu_read_lock() from
> > > > rcu_read_lock_bh(). This
> > > > somehow got lost when rebasing on top of 5.0.
> > >
> > > so now rcu_read_lock_bh_held() is untouched and in_softirq() reports
> > > 1.
> > > So the problem is that we never hold RCU but report 1 like we do?
> >
> > Yes.
>
> I understand the part where "rcu_read_lock() becomes part of
> local_bh_disable()". But why do you modify rcu_read_lock_bh_held() and
> rcu_read_lock_bh()? Couldn't they remain as-is?
Yes, it looks like they can. I recall having problems with
rcu_read_lock_bh_held() in an earlier version which is what prompted the
change, but looking back I don't see what the problem was.
-Scott
next prev parent reply other threads:[~2019-08-26 23:21 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 [this message]
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
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