linux-kernel - Re: [PATCH tip/core/rcu 09/15] rcu: Increasing rcu

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Message-ID: <20120616004931.GU2389@linux.vnet.ibm.com>
Date:	Fri, 15 Jun 2012 17:49:31 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Josh Triplett <josh@...htriplett.org>,
	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, 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 tip/core/rcu 09/15] rcu: Increasing rcu_barrier()
 concurrency

On Fri, Jun 15, 2012 at 08:21:20PM -0400, Steven Rostedt wrote:
> On Fri, 2012-06-15 at 16:31 -0700, Josh Triplett wrote:
> >   
> > > -	smp_mb();  /* Prevent any prior operations from leaking in. */
> > > +	/*
> > > +	 * Ensure tht all prior references, including to ->n_barrier_done,
> > > +	 * are ordered before the _rcu_barrier() machinery.
> > > +	 */
> > > +	smp_mb();  /* See above block comment. */
> > 
> > If checkpatch complains about the lack of a comment to the right of a
> > barrier even when the barrier has a comment directly above it, that
> > seems like a bug in checkpatch that needs fixing, to prevent developers
> > from having to add noise like "See above block comment.". :)
> 
> 
> Yuck yuck yuck yuck!!!
> 
> 
> Really, checkpatch is not the golden rule. I've copied an old checkpatch
> from something like 2.6.38 or so and use that today, where it was still
> reasonable. I've long abandoned the latest checkpatch, as it causes too
> many false positives. Or nazis like dictation.
> 
> My rule of thumb is this. If what checkpatch tells you to do makes the
> format either uglier, or look stupid, it's a good idea to ignore the
> checkpatch complaint.
> 
> I think in this case, you hit the latter.

Heh.  I have been doing this "/* See above block comment. */" thing for
quite some time.  ;-)

							Thanx, Paul

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