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Date: Wed, 24 Jul 2013 09:59:29 -0500
From: Robert Jennings <rcj@linux.vnet.ibm.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [PATCH] powerpc: VPHN topology change updates all siblings
Message-ID: <20130724145929.GA13737@linux.vnet.ibm.com>
References: <20130723123344.GA11611@linux.vnet.ibm.com>
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Cc: stable@vger.kernel.org, Paul Mackerras <paulus@samba.org>,
 Nathan Fontenot <nfont@linux.vnet.ibm.com>, linuxppc-dev@lists.ozlabs.org,
 Jan Stancek <jstancek@redhat.com>
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* Benjamin Herrenschmidt (benh@kernel.crashing.org) wrote:
> On Tue, 2013-07-23 at 07:33 -0500, Robert Jennings wrote:
> > When an associativity level change is found for one thread, the
> > siblings threads need to be updated as well.  This is done today
> > for PRRN in stage_topology_update() but is missing for VPHN in
> > update_cpu_associativity_changes_mask().
> > 
> > All threads should be updated to move to the new node.  Without this
> > patch, a single thread may be flagged for a topology change, leaving it
> > in a different node from its siblings, which is incorrect.  This causes
> > problems for the scheduler where overlapping scheduler groups are created
> > and a loop is formed in those groups.
> > 
> > Reported-by: Jan Stancek <jstancek@redhat.com>
> > Signed-off-by: Robert Jennings <rcj@linux.vnet.ibm.com>
> > Cc: <stable@vger.kernel.org>
> 
> Patch breaks the UP build ...
> 
> Cheers,
> Ben.

Very sorry about that, a fix is on the way.