linux-kernel - Re: [PATCH 2/2] add rcu_assign

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Message-ID: <20080214170803.GB8910@linux.vnet.ibm.com>
Date:	Thu, 14 Feb 2008 09:08:03 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Gautham R Shenoy <ego@...ibm.com>
Cc:	linux-kernel@...r.kernel.org, shemminger@...tta.com,
	davem@...emloft.net, netdev@...r.kernel.org, dipankar@...ibm.com,
	herbert@...dor.apana.org.au, akpm@...ux-foundation.org
Subject: Re: [PATCH 2/2] add rcu_assign_index() if ever needed

On Thu, Feb 14, 2008 at 09:02:09AM +0530, Gautham R Shenoy wrote:
> On Wed, Feb 13, 2008 at 02:05:15PM -0800, Paul E. McKenney wrote:
> > Hello again!
> > 
> > This is a speculative patch that as far as I can tell is not yet required.
> > If anyone applies RCU to a data structure allocated out of an array, using
> > array indexes in place of pointers to link the array elements together,
> > then the rcu_assign_index() function in this patch will be needed to
> > assign a given element's array index to the RCU-traversed index.  The
> > implementation is exactly that of the old rcu_assign_pointer(), so is
> > extremely well tested.
> > 
> > The existing rcu_assign_pointer() will emit a compiler warning in cases
> > where rcu_assign_index() is required.
> > 
> > Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> > ---
> > 
> >  rcupdate.h |   18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> > 
> > diff -urpNa -X dontdiff linux-2.6.24-rap/include/linux/rcupdate.h linux-2.6.24-rai/include/linux/rcupdate.h
> > --- linux-2.6.24-rap/include/linux/rcupdate.h	2008-02-13 13:36:47.000000000 -0800
> > +++ linux-2.6.24-rai/include/linux/rcupdate.h	2008-02-13 10:55:40.000000000 -0800
> > @@ -286,6 +286,24 @@ extern struct lockdep_map rcu_lock_map;
> >  	})
> > 
> >  /**
> > + * rcu_assign_index - assign (publicize) a index of a newly
> > + * initialized array elementg that will be dereferenced by RCU
> 			^^^^^^^^ 
> 
> I hope Andrew got that one while porting against the latest -mm :)
> 
> Looks good otherwise.

Good catch!!!

							Thanx, Paul
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