linux-kernel - [PATCH percpu/for-3.19 2/2] percpu_ref: implement percpu_ref_is

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Message-ID: <20141113220453.GE2598@htj.dyndns.org>
Date:	Thu, 13 Nov 2014 17:04:53 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Kent Overstreet <kmo@...erainc.com>
Cc:	linux-kernel@...r.kernel.org
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@...nel.org>
Cc: Kent Overstreet <kmo@...erainc.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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