1 files changed, 35 insertions, 0 deletions
diff --git a/docs/nspr/reference/pr_callonce.rst b/docs/nspr/reference/pr_callonce.rst
new file mode 100644
index 0000000000..912f1a3ac3
--- /dev/null
+++ b/docs/nspr/reference/pr_callonce.rst
@@ -0,0 +1,35 @@
+PR_CallOnce
+===========
+
+Ensures that subsystem initialization occurs only once.
+
+
+Syntax
+------
+
+.. code::
+
+   PRStatus PR_CallOnce(
+     PRCallOnceType *once,
+     PRCallOnceFN func);
+
+
+Parameters
+~~~~~~~~~~
+
+:ref:`PR_CallOnce` has these parameters:
+
+``once``
+   A pointer to an object of type :ref:`PRCallOnceType`. Initially (before
+   any threading issues exist), the object must be initialized to all
+   zeros. From that time on, the client should consider the object
+   read-only (or even opaque) and allow the runtime to manipulate its
+   content appropriately.
+``func``
+   A pointer to the function the calling client has designed to perform
+   the subsystem initialization. The function will be called once, at
+   most, for each subsystem to be initialized. It should return a
+   :ref:`PRStatus` indicating the result of the initialization process.
+   While the first thread executes this function, other threads
+   attempting the same initialization will be blocked until it has been
+   completed.