Subject: [PATCH 2/2] powerpc/pseries: Wait for completion of hotplug events during PRRN handling

From: John Allen <[email-masked]>
Date: Fri, 13 Jul 2018 09:22:24 -0500

While handling PRRN events, the time to handle the actual hotplug events
dwarfs the time it takes to perform the device tree updates and queue the
hotplug events. In the case that PRRN events are being queued continuously,
hotplug events have been observed to be queued faster than the kernel can
actually handle them. This patch avoids the problem by waiting for a
hotplug request to complete before queueing more hotplug events.

Signed-off-by: John Allen <[email-masked]>
---
 arch/powerpc/platforms/pseries/mobility.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
index 8a8033a249c7..49930848fa78 100644
--- a/arch/powerpc/platforms/pseries/mobility.c
+++ b/arch/powerpc/platforms/pseries/mobility.c
@@ -242,6 +242,7 @@ static int add_dt_node(__be32 parent_phandle, __be32 drc_index)
 static void prrn_update_node(__be32 phandle)
 {
 	struct pseries_hp_errorlog *hp_elog;
+	struct completion hotplug_done;
 	struct device_node *dn;
 
 	/*
@@ -263,7 +264,9 @@ static void prrn_update_node(__be32 phandle)
 	hp_elog->id_type = PSERIES_HP_ELOG_ID_DRC_INDEX;
 	hp_elog->_drc_u.drc_index = phandle;
 
-	queue_hotplug_event(hp_elog, NULL, NULL);
+	init_completion(&hotplug_done);
+	queue_hotplug_event(hp_elog, &hotplug_done, NULL);
+	wait_for_completion(&hotplug_done);
 
 	kfree(hp_elog);
 }
-- 
2.17.1