On 03/14/2013 03:51 AM, Paul Mackerras wrote: > On Fri, Mar 08, 2013 at 10:00:09PM -0600, Nathan Fontenot wrote: >> From: Jesse Larrew <jlar...@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 <nf...@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. >
We only allow for one event to be outstanding. When a PRRN Event is received we flush any work currently queued up and add the new event event to the workqueue (see prrn_schedule_work() from the patch). As I understand flush_work(), this would wait for any work in flight to complete, then remove all work before returning. I'll add a comment and update the patch description. -Nathan _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev