From 94de821002f3378a59c2bf812ce73756f3ed0512 Mon Sep 17 00:00:00 2001
From: Aleksey Kladov <aleksey.kladov@gmail.com>
Date: Fri, 3 Aug 2018 14:18:06 +0300
Subject: [PATCH] Specify reentrancy gurantees of `Once::call_once`

---
 src/libstd/sync/once.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/libstd/sync/once.rs b/src/libstd/sync/once.rs
index 10282ecb65883..113fbbf1f616a 100644
--- a/src/libstd/sync/once.rs
+++ b/src/libstd/sync/once.rs
@@ -178,6 +178,10 @@ impl Once {
     /// happens-before relation between the closure and code executing after the
     /// return).
     ///
+    /// If the given closure recusively invokes `call_once` on the same `Once` 
+    /// instance the exact behavior is not specified, allowed outcomes are
+    /// a panic or a deadlock.
+    ///
     /// # Examples
     ///
     /// ```