1 files changed, 19 insertions, 0 deletions

diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
index 0ddd2839ca84..3dfbf237cd8f 100644
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -67,6 +67,7 @@ struct percpu_ref {
 
 int __must_check percpu_ref_init(struct percpu_ref *ref,
                                  percpu_ref_func_t *release);
+void percpu_ref_reinit(struct percpu_ref *ref);
 void percpu_ref_exit(struct percpu_ref *ref);
 void percpu_ref_kill_and_confirm(struct percpu_ref *ref,
                                  percpu_ref_func_t *confirm_kill);
@@ -99,6 +100,9 @@ static inline bool __pcpu_ref_alive(struct percpu_ref *ref,
 {
         unsigned long pcpu_ptr = ACCESS_ONCE(ref->pcpu_count_ptr);
 
+        /* paired with smp_store_release() in percpu_ref_reinit() */
+        smp_read_barrier_depends();
+
         if (unlikely(pcpu_ptr & PCPU_REF_DEAD))
                 return false;
 
@@ -206,4 +210,19 @@ static inline void percpu_ref_put(struct percpu_ref *ref)
         rcu_read_unlock_sched();
 }
 
+/**
+ * percpu_ref_is_zero - test whether a percpu refcount reached zero
+ * @ref: percpu_ref to test
+ *
+ * Returns %true if @ref reached zero.
+ */
+static inline bool percpu_ref_is_zero(struct percpu_ref *ref)
+{
+        unsigned __percpu *pcpu_count;
+
+        if (__pcpu_ref_alive(ref, &pcpu_count))
+                return false;
+        return !atomic_read(&ref->count);
+}
+
 #endif