From: Simon Marlow <marlowsd@gmail.com>
Date: Thu, 19 May 2011 14:46:30 +0000 (+0100)
Subject: docs: note strict sequential ordering of MVar operations
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=8557ebbf1af0fa297db4bd3ee30d7c6e289fdca7;p=ghc-base.git

docs: note strict sequential ordering of MVar operations
---

diff --git a/Control/Concurrent/MVar.hs b/Control/Concurrent/MVar.hs
index 3a38294..2fda9f7 100644
--- a/Control/Concurrent/MVar.hs
+++ b/Control/Concurrent/MVar.hs
@@ -61,6 +61,13 @@
 -- in an 'MVar' to the appropriate normal form, or utilize a strict
 -- MVar provided by the strict-concurrency package.
 --
+-- * Ordering
+--
+-- 'MVar' operations are always observed to take place in the order
+-- they are written in the program, regardless of the memory model of
+-- the underlying machine.  This is in contrast to 'IORef' operations
+-- which may appear out-of-order to another thread in some cases.
+--
 -- * Example
 --
 -- Consider the following concurrent data structure, a skip channel.