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Date: Thu, 14 Mar 2013 19:51:55 +1100
From: Paul Mackerras <paulus@samba.org>
To: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Subject: Re: [PATCH2/11] Add PRRN Event Handler
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On Fri, Mar 08, 2013 at 10:00:09PM -0600, Nathan Fontenot wrote:
> From: Jesse Larrew <jlarrew@linux.vnet.ibm.com>
> 
> A PRRN event is signaled via the RTAS event-scan mechanism, which
> returns a Hot Plug Event message "fixed part" indicating "Platform
> Resource Reassignment". In response to the Hot Plug Event message,
> we must call ibm,update-nodes to determine which resources were
> reassigned and then ibm,update-properties to obtain the new affinity
> information about those resources.
> 
> The PRRN event-scan RTAS message contains only the "fixed part" with
> the "Type" field set to the value 160 and no Extended Event Log. The
> four-byte Extended Event Log Length field is repurposed (since no
> Extended Event Log message is included) to pass the "scope" parameter
> that causes the ibm,update-nodes to return the nodes affected by the
> specific resource reassignment.
> 
> This patch adds a handler in rtasd for PRRN RTAS events. The function
> pseries_devicetree_update() (from mobility.c) is used to make the
> ibm,update-nodes/ibm,update-properties RTAS calls. Updating the NUMA maps
> (handled by a subsequent patch) will require significant processing,
> so pseries_devicetree_update() is called from an asynchronous workqueue
> to allow rtasd to continue processing events.
> 
> Signed-off-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>

[snip]

> +static s32 update_scope;

Do we have a guarantee that there can only be one of these events
outstanding at a time?  If so it would be nice to document that in a
comment next to this declaration, so we know in future that this is
why this is safe.

Paul.