percpu-refcount: add __must_check to percpu_ref_init() and don't use ACCESS_ONCE() in percpu_ref_kill_rcu()
Two small changes.
* Unlike most init functions, percpu_ref_init() allocates memory and
may fail. Let's mark it with __must_check in case the caller
forgets.
* percpu_ref_kill_rcu() is unnecessarily using ACCESS_ONCE() to
dereference @ref->pcpu_count, which can be misleading. The pointer
is guaranteed to be valid and visible and can't change underneath
the function. Drop ACCESS_ONCE().
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
index b61bd6f..8146aa9 100644
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -66,7 +66,8 @@
struct rcu_head rcu;
};
-int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release);
+int __must_check percpu_ref_init(struct percpu_ref *ref,
+ percpu_ref_func_t *release);
void percpu_ref_kill(struct percpu_ref *ref);
#define PCPU_STATUS_BITS 2
diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
index 9a78e55..b35eaac 100644
--- a/lib/percpu-refcount.c
+++ b/lib/percpu-refcount.c
@@ -57,12 +57,10 @@
static void percpu_ref_kill_rcu(struct rcu_head *rcu)
{
struct percpu_ref *ref = container_of(rcu, struct percpu_ref, rcu);
- unsigned __percpu *pcpu_count;
+ unsigned __percpu *pcpu_count = ref->pcpu_count;
unsigned count = 0;
int cpu;
- pcpu_count = ACCESS_ONCE(ref->pcpu_count);
-
/* Mask out PCPU_REF_DEAD */
pcpu_count = (unsigned __percpu *)
(((unsigned long) pcpu_count) & ~PCPU_STATUS_MASK);