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

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Message-ID: <20150228165654.GC24151@twins.programming.kicks-ass.net>
Date:	Sat, 28 Feb 2015 17:56:54 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
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 05:41:12PM +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.
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