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Subject[PATCH percpu/for-3.19 2/2] percpu_ref: implement percpu_ref_is_dying()
Implement percpu_ref_is_dying() which tests whether the ref is dying
or dead. This is useful to determine the current state when a
percpu_ref is used as a cyclic on/off switch via kill and reinit.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Kent Overstreet <kmo@daterainc.com>
---
include/linux/percpu-refcount.h | 14 ++++++++++++++
1 file changed, 14 insertions(+)

--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -258,6 +258,20 @@ static inline void percpu_ref_put(struct
}

/**
+ * percpu_ref_is_dying - test whether a percpu refcount is dying or dead
+ * @ref: percpu_ref to test
+ *
+ * Returns %true if @ref is dying or dead.
+ *
+ * This function is safe to call as long as @ref is between init and exit
+ * and the caller is responsible for synchronizing against state changes.
+ */
+static inline bool percpu_ref_is_dying(struct percpu_ref *ref)
+{
+ return ref->percpu_count_ptr & __PERCPU_REF_DEAD;
+}
+
+/**
* percpu_ref_is_zero - test whether a percpu refcount reached zero
* @ref: percpu_ref to test
*

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