kref: add kref_test_and_get

Add kref_test_and_get() function, which atomically add a reference only if refcount is not zero. This prevent to add a reference to an object that is already being removed. Signed-off-by: Jerome Marchand <jmarchan@redhat.com> Cc: stable@kernel.org Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
git-mirror · Jan 5, 2011 · e4a683c · e4a683c
1 parent a6e8dc4
commit e4a683c
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diff --git a/include/linux/kref.h b/include/linux/kref.h
@@ -23,6 +23,7 @@ struct kref {
 
 void kref_init(struct kref *kref);
 void kref_get(struct kref *kref);
+int kref_test_and_get(struct kref *kref);
 int kref_put(struct kref *kref, void (*release) (struct kref *kref));
 
 #endif /* _KREF_H_ */
diff --git a/lib/kref.c b/lib/kref.c
@@ -36,6 +36,18 @@ void kref_get(struct kref *kref)
 	smp_mb__after_atomic_inc();
 }
 
+/**
+ * kref_test_and_get - increment refcount for object only if refcount is not
+ * zero.
+ * @kref: object.
+ *
+ * Return non-zero if the refcount was incremented, 0 otherwise
+ */
+int kref_test_and_get(struct kref *kref)
+{
+	return atomic_inc_not_zero(&kref->refcount);
+}
+
 /**
  * kref_put - decrement refcount for object.
  * @kref: object.