[PATCH v07 6/9] pmt/numa: Disable arch_update_cpu_topology during CPU readd

[Michael Bringmann]

pmt/numa: Disable arch_update_cpu_topology during post migration
CPU readd updates when evaluating device-tree changes after LPM
to avoid thread deadlocks trying to update node assignments.
System timing between all of the threads and timers restarted in
a migrated system overlapped frequently allowing tasks to start
acquiring resources (get_online_cpus) needed by rebuild_sched_domains.
Defer the operation of that function until after the CPU readd has
completed.

Signed-off-by: Michael Bringmann <mwb at linux.vnet.ibm.com>
---
 arch/powerpc/platforms/pseries/hotplug-cpu.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
index 1906ee57..df1791b 100644
--- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
+++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -26,6 +26,7 @@
 #include <linux/sched.h>	/* for idle_task_exit */
 #include <linux/sched/hotplug.h>
 #include <linux/cpu.h>
+#include <linux/cpuset.h>
 #include <linux/of.h>
 #include <linux/slab.h>
 #include <asm/prom.h>
@@ -684,9 +685,15 @@ static int dlpar_cpu_readd_by_index(u32 drc_index)
 
 	pr_info("Attempting to re-add CPU, drc index %x\n", drc_index);
 
+	arch_update_cpu_topology_suspend();
 	rc = dlpar_cpu_remove_by_index(drc_index, false);
-	if (!rc)
+	arch_update_cpu_topology_resume();
+
+	if (!rc) {
+		arch_update_cpu_topology_suspend();
 		rc = dlpar_cpu_add(drc_index, false);
+		arch_update_cpu_topology_resume();
+	}
 
 	if (rc)
 		pr_info("Failed to update cpu at drc_index %lx\n",