[PATCH 5.2 05/21] drivers: base: cacheinfo: Ensure cpu hotplug work is done before Intel RDT

[Greg Kroah-Hartman]

From: James Morse <james.morse@xxxxxxx>

commit 83b44fe343b5abfcb1b2261289bd0cfcfcfd60a8 upstream.

The cacheinfo structures are alloced/freed by cpu online/offline
callbacks. Originally these were only used by sysfs to expose the
cache topology to user space. Without any in-kernel dependencies
CPUHP_AP_ONLINE_DYN was an appropriate choice.

resctrl has started using these structures to identify CPUs that
share a cache. It updates its 'domain' structures from cpu
online/offline callbacks. These depend on the cacheinfo structures
(resctrl_online_cpu()->domain_add_cpu()->get_cache_id()->
 get_cpu_cacheinfo()).
These also run as CPUHP_AP_ONLINE_DYN.

Now that there is an in-kernel dependency, move the cacheinfo
work earlier so we know its done before resctrl's CPUHP_AP_ONLINE_DYN
work runs.

Fixes: 2264d9c74dda1 ("x86/intel_rdt: Build structures for each resource based on cache topology")
Cc: <stable@xxxxxxxxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Signed-off-by: James Morse <james.morse@xxxxxxx>
Link: https://lore.kernel.org/r/20190624173656.202407-1-james.morse@xxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/base/cacheinfo.c   |    3 ++-
 include/linux/cpuhotplug.h |    1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -655,7 +655,8 @@ static int cacheinfo_cpu_pre_down(unsign
 
 static int __init cacheinfo_sysfs_init(void)
 {
-	return cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "base/cacheinfo:online",
+	return cpuhp_setup_state(CPUHP_AP_BASE_CACHEINFO_ONLINE,
+				 "base/cacheinfo:online",
 				 cacheinfo_cpu_online, cacheinfo_cpu_pre_down);
 }
 device_initcall(cacheinfo_sysfs_init);
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -176,6 +176,7 @@ enum cpuhp_state {
 	CPUHP_AP_WATCHDOG_ONLINE,
 	CPUHP_AP_WORKQUEUE_ONLINE,
 	CPUHP_AP_RCUTREE_ONLINE,
+	CPUHP_AP_BASE_CACHEINFO_ONLINE,
 	CPUHP_AP_ONLINE_DYN,
 	CPUHP_AP_ONLINE_DYN_END		= CPUHP_AP_ONLINE_DYN + 30,
 	CPUHP_AP_X86_HPET_ONLINE,