linux-kernel - Re: [PATCH 2/2][RT] powerpc - Make the irq reverse mapping radix tree lockless

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Message-Id: <1216962819.11188.82.camel@pasglop>
Date:	Fri, 25 Jul 2008 15:13:39 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Sebastien Dugue <sebastien.dugue@...l.net>,
	Linux-rt <linux-rt-users@...r.kernel.org>,
	linux-ppc <linuxppc-dev@...abs.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <michael@...erman.id.au>,
	Tim Chavez <tinytim@...ibm.com>,
	Jean Pierre Dion <jean-pierre.dion@...l.net>,
	Gilles Carry <Gilles.Carry@....bull.net>
Subject: Re: [PATCH 2/2][RT] powerpc - Make the irq reverse mapping radix
	tree lockless


> >   Concurrency between readers and writers are handled by the intrinsic
> > properties of the concurrent radix tree. Concurrency between the tree
> > initialization which is done asynchronously with readers and writers access
> > is handled via an atomic variable (revmap_trees_allocated) set when the
> > tree has been initialized and checked before any reader or writer access
> > just like we used to check for tree.gfp_mask != 0 before.
> 
> Hmm, RCU radix tree is in mainline too for quite a while. I thought
> Ben had already converted this code over ages ago...
> 
> Nothing against the -rt patch, but mainline should probably be updated
> to use RCU as well?

No, I haven't updated that code yet, and yes, we should do it :-)

Cheers,
Ben.


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