diff --git a/src/threads/CCLock.ml b/src/threads/CCLock.ml
new file mode 100644
index 00000000..cdd03239
--- /dev/null
+++ b/src/threads/CCLock.ml
@@ -0,0 +1,61 @@
+
+(*
+copyright (c) 2013-2014, simon cruanes
+all rights reserved.
+
+redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+redistributions of source code must retain the above copyright notice, this
+list of conditions and the following disclaimer.  redistributions in binary
+form must reproduce the above copyright notice, this list of conditions and the
+following disclaimer in the documentation and/or other materials provided with
+the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*)
+
+
+(** {1 Utils around Mutex} *)
+
+type 'a t = {
+  mutex : Mutex.t;
+  mutable content : 'a;
+}
+
+let create content = {
+  mutex = Mutex.create();
+  content;
+}
+
+let with_lock l f =
+  Mutex.lock l.mutex;
+  try
+    let x = f l.content in
+    Mutex.unlock l.mutex;
+    x
+  with e ->
+    Mutex.unlock l.mutex;
+    raise e
+
+let mutex l = l.mutex
+
+let update l f =
+  with_lock l (fun x -> l.content <- f x)
+
+let get l =
+  Mutex.lock l.mutex;
+  let x = l.content in
+  Mutex.unlock l.mutex;
+  x
+
+
diff --git a/src/threads/CCLock.mli b/src/threads/CCLock.mli
new file mode 100644
index 00000000..33840712
--- /dev/null
+++ b/src/threads/CCLock.mli
@@ -0,0 +1,51 @@
+
+(*
+copyright (c) 2013-2014, simon cruanes
+all rights reserved.
+
+redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+redistributions of source code must retain the above copyright notice, this
+list of conditions and the following disclaimer.  redistributions in binary
+form must reproduce the above copyright notice, this list of conditions and the
+following disclaimer in the documentation and/or other materials provided with
+the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*)
+
+
+(** {1 Utils around Mutex}
+
+@since NEXT_RELEASE *)
+
+type 'a t
+(** A value surrounded with a lock *)
+
+val create : 'a -> 'a t
+(** Create a new protected value *)
+
+val with_lock : 'a t -> ('a -> 'b) -> 'b
+(** [with_lock l f] runs [f x] where [x] is the value protected with
+    the lock [l], in a critical section. If [f x] fails, [with_lock l f]
+    fails too but the lock is released *)
+
+val update : 'a t -> ('a -> 'a) -> unit
+(** [update l f] replaces the content [x] of [l] with [f x], atomically *)
+
+val mutex : _ t -> Mutex.t
+(** Underlying mutex *)
+
+val get : 'a t -> 'a
+(** Get the value in the lock. The value that is returned isn't protected! *)
+