linux-kernel - Re: [Bridge] [PATCH v3 tip/core/rcu 0/14] Sparse-related updates for 3.13

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Message-ID: <20131013111716.GG5790@linux.vnet.ibm.com>
Date:	Sun, 13 Oct 2013 04:17:16 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Josh Triplett <josh@...htriplett.org>, peterz@...radead.org,
	fweisbec@...il.com, dhowells@...hat.com, edumazet@...gle.com,
	gaofeng@...fujitsu.com, mingo@...nel.org,
	bridge@...ts.linux-foundation.org, jmorris@...ei.org,
	dipankar@...ibm.com, darren@...art.com, rostedt@...dmis.org,
	niv@...ibm.com, mathieu.desnoyers@...icios.com,
	kuznet@....inr.ac.ru, tglx@...utronix.de,
	johannes@...solutions.net, laijs@...fujitsu.com,
	yoshfuji@...ux-ipv6.org, netdev@...r.kernel.org,
	linux-decnet-user@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, kaber@...sh.net,
	stephen@...workplumber.org, sbw@....edu, tgraf@...g.ch,
	akpm@...ux-foundation.org, fengguang.wu@...el.com,
	davem@...emloft.net
Subject: Re: [Bridge] [PATCH v3 tip/core/rcu 0/14] Sparse-related updates for
 3.13

On Sat, Oct 12, 2013 at 07:43:54PM +0200, Hannes Frederic Sowa wrote:
> On Sat, Oct 12, 2013 at 07:39:30PM +0200, Hannes Frederic Sowa wrote:
> > On Sat, Oct 12, 2013 at 10:13:45AM -0700, Paul E. McKenney wrote:
> > > On Fri, Oct 11, 2013 at 11:53:27PM -0700, Josh Triplett wrote:
> > > > On Fri, Oct 11, 2013 at 04:16:59PM -0700, Paul E. McKenney wrote:
> > > > > Changes from v2:
> > > > > 
> > > > > o	Switch from rcu_assign_pointer() to ACCESS_ONCE() given that
> > > > > 	the pointers are all --rcu and already visible to readers,
> > > > > 	as suggested by Eric Dumazet and Josh Triplett.
> > > > 
> > > > Hang on a moment.  Do *none* of these cases need write memory barriers?
> > > 
> > > Sigh.  Some afternoons it doesn't pay to touch the keyboard.
> > > 
> > > Thank you for catching this.  I will fix, but at this point, I am thinking
> > > in terms of 3.14 rather than 3.13 for this series.
> > 
> > Some of them looked safe. You could also replace --rcu with __rcu in the
> > comments while at it.
> 
> Most of them deal with management, maybe a rtnl_assign_pointer with lockdep
> check for rtnl lock could help to not clean up the wrong bits.
> 
> I don't know if rtnl_assign_pointer is that a could name as it does not really
> explain why the barrier is not needed there. :/

Beyond a certain point, I need to let people who know more about Linux's
networking implementation handle this sort of thing.

							Thanx, Paul

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