rcu: Document unique-name limitation for DEFINE_STATIC_SRCU()

[linux-2.6-block.git] / include / linux / srcu.h

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index f5f80c5643ac5669abbb1e3e736ded2f49b5f3a0..dc8eb63c6568a8b0d2b9a2d793f80f255f3fc570 100644 (file)
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -99,8 +99,23 @@ void process_srcu(struct work_struct *work);
        }
 
 /*
- * define and init a srcu struct at build time.
- * dont't call init_srcu_struct() nor cleanup_srcu_struct() on it.
+ * Define and initialize a srcu struct at build time.
+ * Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it.
+ *
+ * Note that although DEFINE_STATIC_SRCU() hides the name from other
+ * files, the per-CPU variable rules nevertheless require that the
+ * chosen name be globally unique.  These rules also prohibit use of
+ * DEFINE_STATIC_SRCU() within a function.  If these rules are too
+ * restrictive, declare the srcu_struct manually.  For example, in
+ * each file:
+ *
+ *     static struct srcu_struct my_srcu;
+ *
+ * Then, before the first use of each my_srcu, manually initialize it:
+ *
+ *     init_srcu_struct(&my_srcu);
+ *
+ * See include/linux/percpu-defs.h for the rules on per-CPU variables.
  */
 #define __DEFINE_SRCU(name, is_static)                                 \
        static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\