linux-kernel - Re: [PATCH tip/core/rcu 15/16] scripts: Make checkpatch.pl warn on expedited RCU grace periods

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Message-ID: <20150721012936.GQ3717@linux.vnet.ibm.com>
Date:	Mon, 20 Jul 2015 18:29:36 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
	mingo@...nel.org, laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
	dhowells@...hat.com, edumazet@...gle.com, dvhart@...ux.intel.com,
	fweisbec@...il.com, oleg@...hat.com, bobby.prani@...il.com,
	Andy Whitcroft <apw@...onical.com>
Subject: Re: [PATCH tip/core/rcu 15/16] scripts: Make checkpatch.pl warn on
 expedited RCU grace periods

On Mon, Jul 20, 2015 at 06:06:19PM -0700, Joe Perches wrote:
> On Mon, 2015-07-20 at 20:55 -0400, Steven Rostedt wrote:
> > On Fri, 17 Jul 2015 15:37:54 -0700
> > Joe Perches <joe@...ches.com> wrote:
> > 
> > > > +		if ($line =~ /\b(synchronize_rcu_expedited|synchronize_sched_expedited)\(/) {
> > > 
> > > It'd be faster perl without capture groups:
> > 
> > Is checkpatch such a critical code path that we could possibly notice
> > the difference in speed? Although the above may be few microseconds
> > slower, to me, the above looks a hell of a lot more readable.
> 
> Regardless, it's not as capable as it wouldn't find
> any miswritten form like
> 
> 	synchronize_<foo>_expedited ( args... )

Hmmm...  My current patch doesn't complain about this:

------------------------------------------------------------------------

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 77192953dee5..89577b8d3ba6 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -492,6 +492,8 @@ static void srcu_read_delay(struct torture_random_state *rrsp)
 	const long uspertick = 1000000 / HZ;
 	const long longdelay = 10;
 
+	synchronize_srcu_expedited(srcu_ctlp);
+
 	/* We want there to be long-running readers, but not all the time. */
 
 	delay = torture_random(rrsp) %

------------------------------------------------------------------------

But it does correctly complain when I add synchronize_rcu_expedited()
or synchronize_sched_expedited().

So what am I missing here?

							Thanx, Paul

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