On Fri, 2013-04-05 at 13:22 -0500, Nathan Fontenot wrote:

Agreed, having to call stop_machine() for each cpu that gets updated is
pretty brutal. The plus side is that PRRN events should a rare occurrence 
and not cause too much pain.

So that doesn't happen on VPHN changes ?

The current design ties into the of notification chain so that we can do
the affinity update when the affinity property in the device tree is updated.
Switching to doing one stop and updating all of the cpus would require a
design change....and....

I went back and looked at the code again and there is another issue with
way this is done. Tying into the of notification chain is great for
being informed of when a property changes but the code (from patch 6/11)

+	case OF_RECONFIG_ADD_PROPERTY:
+	case OF_RECONFIG_UPDATE_PROPERTY:
+		update = (struct of_prop_reconfig *)data;
+		if (!of_prop_cmp(update->dn->type, "cpu")) {
+			u32 core_id;
+			of_property_read_u32(update->dn, "reg", &core_id);
+			stage_topology_update(core_id);
+			rc = NOTIFY_OK;
+		}
+		break;

Does not check to see which property is being updated and just assumes
the affinity is being updated. This code as is will do an affinity update
every time any property of a cpu is updated or added.

Since this needs an update I will also look at possibly doing this so
that we call stop_machine only once.

Any new patch set ?

Cheers,
Ben.