linux-kernel - Re: [RFC][PATCH] module: Optimize __module

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Message-ID: <20150228233203.GL15405@linux.vnet.ibm.com>
Date:	Sat, 28 Feb 2015 15:32:03 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Andi Kleen <andi@...stfloor.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org, oleg@...hat.com,
	rusty@...tcorp.com.au, mingo@...nel.org
Subject: Re: [RFC][PATCH] module: Optimize __module_address() using a latched
 RB-tree

On Sat, Feb 28, 2015 at 05:56:54PM +0100, Peter Zijlstra wrote:
> On Sat, Feb 28, 2015 at 05:41:12PM +0100, Peter Zijlstra wrote:
> > > > > +	rb_link_node(&mn->node, parent, link);
> > > > 
> > > > This makes the new module visible to readers, if I understand correctly.
> > > 
> > > You do.
> > 
> > I think I have reconsidered; this does not in fact make it visible.
> 
> Ah; never mind, it is. An iterator could have started in data[0], gone
> on holiday while the modification took place, and resumed once it is
> done and magically see the element appear.
> 
> Therefore we do indeed need the atomic publishing and I think this also
> settles my question about Alpha.

Whew!

Though otherwise whatever you were doing would have been pretty cool
and fun to learn about.  ;-)

							Thanx, Paul

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