linux-kernel - Re: [PATCH RFC tip/core/rcu 24/41] rcu: Check for idle-loop entry while in RCU read-side critical section

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Date:	Thu, 2 Feb 2012 09:50:05 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Josh Triplett <josh@...htriplett.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
	dhowells@...hat.com, eric.dumazet@...il.com, darren@...art.com,
	fweisbec@...il.com, patches@...aro.org,
	"Paul E. McKenney" <paul.mckenney@...aro.org>
Subject: Re: [PATCH RFC tip/core/rcu 24/41] rcu: Check for idle-loop entry
 while in RCU read-side critical section

On Wed, Feb 01, 2012 at 09:13:37PM -0800, Josh Triplett wrote:
> On Wed, Feb 01, 2012 at 11:41:42AM -0800, Paul E. McKenney wrote:
> > --- a/kernel/rcutree.c
> > +++ b/kernel/rcutree.c
> > @@ -366,6 +366,20 @@ static void rcu_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval)
> >  	atomic_inc(&rdtp->dynticks);
> >  	smp_mb__after_atomic_inc();  /* Force ordering with next sojourn. */
> >  	WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
> > +
> > +	/*
> > +	 * The idle task is not permitted to enter the idle loop while
> > +	 * in an RCU read-side critical section.
> > +	 */
> > +	rcu_lockdep_assert(!lock_is_held(&rcu_lock_map),
> > +			   "Illegal idle entry in RCU read-side "
> > +			   "critical section.");
> > +	rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map),
> > +			   "Illegal idle entry in RCU-bh read-side "
> > +			   "critical section.");
> > +	rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map),
> > +			   "Illegal idle entry in RCU-sched read-side "
> > +			   "critical section.");
> 
> Quoting a paragraph I added to Documentation/CodingStyle:
> 
> > Statements longer than 80 columns will be broken into sensible chunks, unless
> > exceeding 80 columns significantly increases readability and does not hide
> > information. Descendants are always substantially shorter than the parent and
> > are placed substantially to the right. The same applies to function headers
> > with a long argument list. However, never break user-visible strings such as
> > printk messages, because that breaks the ability to grep for them.
> 
> So, please don't break those strings across multiple lines.  The same
> goes for the similar rcu_lockdep_assert strings added in a previous
> patch in this series.

Fixed!

Again, I leave it to you to get checkpatch.pl to complain about this.  ;-)

							Thanx, Paul

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