From: Scott Wood <swood@redhat.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org,
"Paul E . McKenney" <paulmck@linux.ibm.com>,
Joel Fernandes <joel@joelfernandes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Clark Williams <williams@redhat.com>
Subject: Re: [PATCH RT v3 1/5] rcu: Acquire RCU lock when disabling BHs
Date: Tue, 17 Sep 2019 11:12:48 -0500 [thread overview]
Message-ID: <ad29574b34aca9ab61d310508f4f21a35cac406e.camel@redhat.com> (raw)
In-Reply-To: <20190917144252.v34ina4z2ydchoit@linutronix.de>
On Tue, 2019-09-17 at 16:42 +0200, Sebastian Andrzej Siewior wrote:
> On 2019-09-17 09:06:28 [-0500], Scott Wood wrote:
> > Sorry, I missed that you were asking about rcu_read_lock_bh() as
> > well. I
> > did remove the change to rcu_read_lock_bh_held().
>
> Sorry for not being clear here.
>
> > With this patch, local_bh_disable() calls rcu_read_lock() on RT which
> > handles this debug stuff. Doing it twice shouldn't be explicitly
> > harmful,
> > but it's redundant, and debug kernels are slow enough as is.
>
> rcu_read_lock() does:
> > __rcu_read_lock();
> > __acquire(RCU);
> > rcu_lock_acquire(&rcu_lock_map);
> > RCU_LOCKDEP_WARN(!rcu_is_watching(),
> > "rcu_read_lock() used illegally while idle");
>
> __acquire() is removed removed by cpp.
> That RCU_LOCKDEP_WARN is doing the same thing as above and redundant.
> Am I right to assume that you consider
> rcu_lock_acquire(&rcu_bh_lock_map);
>
> redundant because the only user of that is also checking for
> rcu_lock_map?
Yes.
-Scott
next prev parent reply other threads:[~2019-09-17 16:13 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-11 16:57 [PATCH RT v3 0/5] RCU fixes Scott Wood
2019-09-11 16:57 ` [PATCH RT v3 1/5] rcu: Acquire RCU lock when disabling BHs Scott Wood
2019-09-12 22:09 ` Joel Fernandes
2019-09-17 7:44 ` Sebastian Andrzej Siewior
2019-09-17 14:06 ` Scott Wood
2019-09-17 14:42 ` Sebastian Andrzej Siewior
2019-09-17 16:12 ` Scott Wood [this message]
2019-09-23 16:41 ` Sebastian Andrzej Siewior
2019-09-11 16:57 ` [PATCH RT v3 2/5] sched: Rename sleeping_lock to rt_invol_sleep Scott Wood
2019-09-17 7:52 ` Sebastian Andrzej Siewior
2019-09-11 16:57 ` [PATCH RT v3 3/5] sched: migrate_dis/enable: Use rt_invol_sleep Scott Wood
2019-09-17 7:59 ` Sebastian Andrzej Siewior
2019-09-17 14:06 ` Scott Wood
2019-09-23 16:59 ` Scott Wood
2019-09-23 17:52 ` Sebastian Andrzej Siewior
2019-09-24 11:21 ` Sebastian Andrzej Siewior
2019-09-24 13:53 ` Scott Wood
2019-09-24 15:25 ` Sebastian Andrzej Siewior
2019-09-24 15:47 ` Scott Wood
2019-09-24 16:05 ` Sebastian Andrzej Siewior
2019-09-24 16:35 ` Scott Wood
2019-10-04 16:45 ` Sebastian Andrzej Siewior
2019-09-11 16:57 ` [PATCH RT v3 4/5] rcu: Disable use_softirq on PREEMPT_RT Scott Wood
2019-09-12 21:38 ` Joel Fernandes
2019-09-12 22:19 ` Joel Fernandes
2019-09-17 9:31 ` Sebastian Andrzej Siewior
2019-09-17 14:08 ` Scott Wood
2019-09-11 16:57 ` [PATCH RT v3 5/5] rcutorture: Avoid problematic critical section nesting on RT Scott Wood
2019-09-12 22:17 ` Joel Fernandes
2019-09-16 16:55 ` Scott Wood
2019-09-17 10:07 ` Sebastian Andrzej Siewior
2019-09-17 14:36 ` Scott Wood
2019-09-17 14:50 ` Sebastian Andrzej Siewior
2019-09-17 16:32 ` Scott Wood
2019-09-23 16:25 ` Sebastian Andrzej Siewior
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