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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Scott Wood <swood@redhat.com>
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 17:59:43 +0200	[thread overview]
Message-ID: <20190826155943.zvghokdn3iu2sipx@linutronix.de> (raw)
In-Reply-To: <40dd3a7e37ed9b3d03c50221dafc7aa137827ce8.camel@redhat.com>

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?

> -Scott

Sebastian

  reply	other threads:[~2019-08-26 15:59 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 [this message]
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

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