diff --git a/src/threads/CCLock.ml b/src/threads/CCLock.ml
index 1088c605..cd9aa456 100644
--- a/src/threads/CCLock.ml
+++ b/src/threads/CCLock.ml
@@ -1,28 +1,5 @@
-(*
-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.
-*)
 
+(* This file is free software, part of containers. See file "license" for more details. *)
 
 (** {1 Utils around Mutex} *)
 
@@ -162,7 +139,38 @@ let get_then_incr l =
   Mutex.unlock l.mutex;
   x
 
+let decr_then_get l =
+  Mutex.lock l.mutex;
+  l.content <- l.content - 1;
+  let x = l.content in
+  Mutex.unlock l.mutex;
+  x
+
+let get_then_decr l =
+  Mutex.lock l.mutex;
+  let x = l.content in
+  l.content <- l.content - 1;
+  Mutex.unlock l.mutex;
+  x
+
 (*$T
   let l = create 0 in 1 = incr_then_get l && 1 = get l
   let l = create 0 in 0 = get_then_incr l && 1 = get l
+  let l = create 10 in 9 = decr_then_get l && 9 = get l
+  let l = create 10 in 10 = get_then_decr l && 9 = get l
 *)
+
+let get_then_set l =
+  Mutex.lock l.mutex;
+  let x = l.content in
+  l.content <- true;
+  Mutex.unlock l.mutex;
+  x
+
+let get_then_clear l =
+  Mutex.lock l.mutex;
+  let x = l.content in
+  l.content <- false;
+  Mutex.unlock l.mutex;
+  x
+
diff --git a/src/threads/CCLock.mli b/src/threads/CCLock.mli
index e1982e8f..ce973086 100644
--- a/src/threads/CCLock.mli
+++ b/src/threads/CCLock.mli
@@ -1,32 +1,11 @@
-(*
-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.
-*)
 
+(* This file is free software, part of containers. See file "license" for more details. *)
 
 (** {1 Utils around Mutex}
 
-@since 0.8 *)
+    A value wrapped into a Mutex, for more safety.
+
+    @since 0.8 *)
 
 type 'a t
 (** A value surrounded with a lock *)
@@ -88,6 +67,21 @@ val incr_then_get : int t -> int
     @since NEXT_RELEASE *)
 
 val get_then_incr : int t -> int
-(** [incr_then_get x] increments [x], and return its previous value
+(** [get_then_incr x] increments [x], and return its previous value
     @since NEXT_RELEASE *)
 
+val decr_then_get : int t -> int
+(** [decr_then_get x] decrements [x], and return its new value
+    @since NEXT_RELEASE *)
+
+val get_then_decr : int t -> int
+(** [get_then_decr x] decrements [x], and return its previous value
+    @since NEXT_RELEASE *)
+
+val get_then_set : bool t -> bool
+(** [get_then_set b] sets [b] to [true], and return the old value
+    @since NEXT_RELEASE *)
+
+val get_then_clear : bool t -> bool
+(** [get_then_clear b] sets [b] to [false], and return the old value
+    @since NEXT_RELEASE *)