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Subject[PATCH v2] drivers: base: cacheinfo: Ensure cpu hotplug work is done before Intel RDT
Date
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@vger.kernel.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: James Morse <james.morse@arm.com>
---
I haven't seen any problems because of this.

Changes since v1: lore.kernel.org/r/20190530161024.85637-1-james.morse@arm.com
* CC-list, added fixes/stable tags.

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

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index a7359535caf5..b444f89a2041 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -655,7 +655,8 @@ static int cacheinfo_cpu_pre_down(unsigned int cpu)

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);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 6a381594608c..50c893f03c21 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -175,6 +175,7 @@ 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,
--
2.20.1
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