1 files changed, 35 insertions, 0 deletions

diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
index ac4299120087..fe5a3342e960 100644
--- a/lib/percpu-refcount.c
+++ b/lib/percpu-refcount.c
@@ -61,6 +61,41 @@ int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release)
 EXPORT_SYMBOL_GPL(percpu_ref_init);
 
 /**
+ * percpu_ref_reinit - re-initialize a percpu refcount
+ * @ref: perpcu_ref to re-initialize
+ *
+ * Re-initialize @ref so that it's in the same state as when it finished
+ * percpu_ref_init().  @ref must have been initialized successfully, killed
+ * and reached 0 but not exited.
+ *
+ * Note that percpu_ref_tryget[_live]() are safe to perform on @ref while
+ * this function is in progress.
+ */
+void percpu_ref_reinit(struct percpu_ref *ref)
+{
+        unsigned __percpu *pcpu_count = pcpu_count_ptr(ref);
+        int cpu;
+
+        BUG_ON(!pcpu_count);
+        WARN_ON(!percpu_ref_is_zero(ref));
+
+        atomic_set(&ref->count, 1 + PCPU_COUNT_BIAS);
+
+        /*
+         * Restore per-cpu operation.  smp_store_release() is paired with
+         * smp_read_barrier_depends() in __pcpu_ref_alive() and guarantees
+         * that the zeroing is visible to all percpu accesses which can see
+         * the following PCPU_REF_DEAD clearing.
+         */
+        for_each_possible_cpu(cpu)
+                *per_cpu_ptr(pcpu_count, cpu) = 0;
+
+        smp_store_release(&ref->pcpu_count_ptr,
+                          ref->pcpu_count_ptr & ~PCPU_REF_DEAD);
+}
+EXPORT_SYMBOL_GPL(percpu_ref_reinit);
+
+/**
  * percpu_ref_exit - undo percpu_ref_init()
  * @ref: percpu_ref to exit
  *