From: Frederic Weisbecker <fweisbec@gmail.com>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
linux-kernel@vger.kernel.org,
Dipankar Sarma <dipankar@in.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Lai Jiangshan <laijs@cn.fujitsu.com>
Subject: Re: linux-next-20110923: warning kernel/rcutree.c:1833
Date: Mon, 3 Oct 2011 15:03:48 +0200 [thread overview]
Message-ID: <20111003130335.GD1835@somewhere> (raw)
In-Reply-To: <20111003003247.GD2539@linux.vnet.ibm.com>
On Sun, Oct 02, 2011 at 05:32:47PM -0700, Paul E. McKenney wrote:
> > > -void rcu_irq_enter(void)
> > > +int rcu_is_cpu_idle(void)
> > > {
> > > - rcu_exit_nohz();
> > > + return (atomic_read(&__get_cpu_var(rcu_dynticks).dynticks) & 0x1) == 0;
> > > }
> >
> > So that's not used in this patch but it's interesting for me
> > to backport "rcu: Detect illegal rcu dereference in extended quiescent state".
>
> Yep, that is why it is there.
Ok.
>
> > The above should be read from a preempt disabled section though
> > (remember "rcu: Fix preempt-unsafe debug check of rcu extended quiescent state")
>
> Yes, and that is why the last line of the header comment reads "The
> caller must have at least disabled preemption." Disabling preemption
> is not necessary in Tiny RCU because there is no other CPU for the task
> to go to. (Right?)
Right.
> > Those functions should probably lay in a separate patch. But I don't mind
> > much keeping the things as is and use these APIs in my next patches though.
> > I'll just fix the preempt enabled thing above.
>
> Or were you saying that you wish to make calls to rcu_is_cpu_idle()
> that have preemption enabled?
Yeah. That's going to be called from places like rcu_read_lock_held()
and things like this that don't need to disable preemption themselves.
Would be better to disable preemption from that function.
> And I can split the patch easily enough while keeping the diff the same,
> so you should be able to do your porting on top of the existing code.
No I'm actually pretty fine with the current state. Whether that's defined
in this patch or a following one is actually not important.
Thanks!
next prev parent reply other threads:[~2011-10-03 13:04 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-25 0:24 linux-next-20110923: warning kernel/rcutree.c:1833 Kirill A. Shutemov
2011-09-25 5:08 ` Paul E. McKenney
2011-09-25 11:26 ` Kirill A. Shutemov
2011-09-25 13:06 ` Frederic Weisbecker
2011-09-25 14:19 ` Kirill A. Shutemov
2011-09-25 16:48 ` Paul E. McKenney
2011-09-26 1:04 ` Frederic Weisbecker
2011-09-26 1:10 ` Frederic Weisbecker
2011-09-26 1:26 ` Paul E. McKenney
2011-09-26 1:41 ` Paul E. McKenney
2011-09-26 9:39 ` Frederic Weisbecker
2011-09-26 22:34 ` Paul E. McKenney
2011-09-27 12:07 ` Frederic Weisbecker
2011-09-26 9:42 ` Frederic Weisbecker
2011-09-26 22:35 ` Paul E. McKenney
2011-09-26 9:20 ` Frederic Weisbecker
2011-09-26 22:50 ` Paul E. McKenney
2011-09-27 12:16 ` Frederic Weisbecker
2011-09-27 18:01 ` Paul E. McKenney
2011-09-28 12:31 ` Frederic Weisbecker
2011-09-28 18:40 ` Paul E. McKenney
2011-09-28 23:46 ` Frederic Weisbecker
2011-09-29 0:55 ` Paul E. McKenney
2011-09-29 4:49 ` Paul E. McKenney
2011-09-29 12:30 ` Frederic Weisbecker
2011-09-29 17:12 ` Paul E. McKenney
2011-09-29 17:19 ` Paul E. McKenney
2011-09-29 23:18 ` Paul E. McKenney
2011-09-30 13:11 ` Frederic Weisbecker
2011-09-30 15:29 ` Paul E. McKenney
2011-09-30 19:24 ` Paul E. McKenney
2011-10-01 4:34 ` Paul E. McKenney
2011-10-01 12:24 ` Frederic Weisbecker
2011-10-01 12:28 ` Frederic Weisbecker
2011-10-01 16:35 ` Paul E. McKenney
2011-10-01 17:07 ` Paul E. McKenney
2011-10-02 3:23 ` Paul E. McKenney
2011-10-02 11:45 ` Frederic Weisbecker
2011-10-02 22:50 ` Frederic Weisbecker
2011-10-03 0:28 ` Paul E. McKenney
2011-10-03 12:59 ` Frederic Weisbecker
2011-10-03 16:22 ` Paul E. McKenney
2011-10-03 17:11 ` Frederic Weisbecker
2011-10-02 23:07 ` Frederic Weisbecker
2011-10-03 0:32 ` Paul E. McKenney
2011-10-03 13:03 ` Frederic Weisbecker [this message]
2011-10-03 16:30 ` Paul E. McKenney
2011-10-06 0:58 ` Paul E. McKenney
2011-10-06 1:59 ` Paul E. McKenney
2011-10-06 12:11 ` Frederic Weisbecker
2011-10-06 18:44 ` Paul E. McKenney
2011-10-06 23:44 ` Paul E. McKenney
2011-09-26 1:25 ` Paul E. McKenney
2011-09-26 8:48 ` Frederic Weisbecker
2011-09-26 8:49 ` Frederic Weisbecker
2011-09-26 22:30 ` Paul E. McKenney
2011-09-27 11:55 ` Frederic Weisbecker
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