auto merge of #11187 : alexcrichton/rust/once, r=brson

Rationale can be found in the first commit, but this is basically the same thing as `pthread_once`

1 files changed, 4 insertions, 9 deletions

diff --git a/src/libnative/io/net.rs b/src/libnative/io/net.rs
index 674f02d4a22..6736641c858 100644
--- a/src/libnative/io/net.rs
+++ b/src/libnative/io/net.rs
@@ -205,19 +205,14 @@ pub fn init() {
     }
 
     unsafe {
-        use std::unstable::mutex::{Mutex, MUTEX_INIT};
-        static mut LOCK: Mutex = MUTEX_INIT;
-        static mut INITIALIZED: bool = false;
-        if INITIALIZED { return }
-        LOCK.lock();
-        if !INITIALIZED {
+        use std::unstable::mutex::{Once, ONCE_INIT};
+        static mut INIT: Once = ONCE_INIT;
+        INIT.doit(|| {
             let mut data: WSADATA = intrinsics::init();
             let ret = WSAStartup(0x202,      // version 2.2
                                  &mut data);
             assert_eq!(ret, 0);
-            INITIALIZED = true;
-        }
-        LOCK.unlock();
+        });
     }
 }