[PATCH 1/1] powerpc/pseries: Enable RAS hotplug events late

[Sam Bobroff]

Currently if the kernel receives a memory hot-unplug event early
enough, it may get stuck in an infinite loop in
dissolve_free_huge_pages(). This appears as a stall just after:

pseries-hotplug-mem: Attempting to hot-remove XX LMB(s) at YYYYYYYY

It appears to be caused by "minimum_order" being uninitialized, due to
init_ras_IRQ() executing before hugetlb_init().

To correct this, extract the part of init_ras_IRQ() that enables
hotplug event processing and place it in the machine_late_initcall
phase, which is guaranteed to be after hugetlb_init() is called.

Signed-off-by: Sam Bobroff <sam.bobroff at au1.ibm.com>
---
 arch/powerpc/platforms/pseries/ras.c | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c
index 81d8614e7379..ba284949af06 100644
--- a/arch/powerpc/platforms/pseries/ras.c
+++ b/arch/powerpc/platforms/pseries/ras.c
@@ -66,6 +66,26 @@ static int __init init_ras_IRQ(void)
 		of_node_put(np);
 	}
 
+	/* EPOW Events */
+	np = of_find_node_by_path("/event-sources/epow-events");
+	if (np != NULL) {
+		request_event_sources_irqs(np, ras_epow_interrupt, "RAS_EPOW");
+		of_node_put(np);
+	}
+
+	return 0;
+}
+machine_subsys_initcall(pseries, init_ras_IRQ);
+
+/*
+ * Enable the hotplug interrupt late because processing them may touch other
+ * devices or systems (e.g. hugepages) that have not been initialized at the
+ * subsys stage.
+ */
+int __init init_ras_hotplug_IRQ(void)
+{
+	struct device_node *np;
+
 	/* Hotplug Events */
 	np = of_find_node_by_path("/event-sources/hot-plug-events");
 	if (np != NULL) {
@@ -75,16 +95,9 @@ static int __init init_ras_IRQ(void)
 		of_node_put(np);
 	}
 
-	/* EPOW Events */
-	np = of_find_node_by_path("/event-sources/epow-events");
-	if (np != NULL) {
-		request_event_sources_irqs(np, ras_epow_interrupt, "RAS_EPOW");
-		of_node_put(np);
-	}
-
 	return 0;
 }
-machine_subsys_initcall(pseries, init_ras_IRQ);
+machine_late_initcall(pseries, init_ras_hotplug_IRQ);
 
 #define EPOW_SHUTDOWN_NORMAL				1
 #define EPOW_SHUTDOWN_ON_UPS				2
-- 
2.16.1.74.g9b0b1f47b