[PATCH v8 6/7] apei/ghes: Use unrcu_pointer for cmpxchg

Jia He
2022-10-10T02:37:27Z

ghes_estatus_caches should be add rcu annotation to avoid sparse warnings.
drivers/acpi/apei/ghes.c:733:25: sparse: sparse: incompatible types in comparison expression (different address spaces):
drivers/acpi/apei/ghes.c:733:25: sparse: struct ghes_estatus_cache [noderef] __rcu *
drivers/acpi/apei/ghes.c:733:25: sparse: struct ghes_estatus_cache *
drivers/acpi/apei/ghes.c:813:25: sparse: sparse: incompatible types in comparison expression (different address spaces):
drivers/acpi/apei/ghes.c:813:25: sparse: struct ghes_estatus_cache [noderef] __rcu *
drivers/acpi/apei/ghes.c:813:25: sparse: struct ghes_estatus_cache *

unrcu_pointer is to strip the __rcu in cmpxchg.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Jia He <justin.he@arm.com>
---
drivers/acpi/apei/ghes.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index 27c72b175e4b..c2fc0dd05bf7 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -150,7 +150,7 @@ struct ghes_vendor_record_entry {
static struct gen_pool *ghes_estatus_pool;
static unsigned long ghes_estatus_pool_size_request;

-static struct ghes_estatus_cache *ghes_estatus_caches[GHES_ESTATUS_CACHES_SIZE];
+static struct ghes_estatus_cache __rcu *ghes_estatus_caches[GHES_ESTATUS_CACHES_SIZE];
static atomic_t ghes_estatus_cache_alloced;

static int ghes_panic_timeout __read_mostly = 30;
@@ -840,8 +840,9 @@ static void ghes_estatus_cache_add(
}
/* new_cache must be put into array after its contents are written */
smp_wmb();
- if (slot != -1 && cmpxchg(ghes_estatus_caches + slot,
- slot_cache, new_cache) == slot_cache) {
+ if (slot != -1 && unrcu_pointer(cmpxchg(ghes_estatus_caches + slot,
+ RCU_INITIALIZER(slot_cache),
+ RCU_INITIALIZER(new_cache))) == slot_cache) {
if (slot_cache)
call_rcu(&slot_cache->rcu, ghes_estatus_cache_rcu_free);
} else
--
2.25.1