concurrency.md

@@ -89,12 +89,7 @@ to avoid using the term.
 - No runnable process will be indefinitely delayed.
 - No thread can be blocked indefinitely on an MVar unless another thread holds the MVar indefinitely.
 
-**Non-blocking foreign call** as commonly used, actually means a foreign call that \*can\* block.  As a
-consequence of the fairness policy, one wishes to place the requirement on
-implementations that such a blocking foreign call _should_not_
-block progress of other Haskell threads.  The thread-nature of the
-foreign call is "blocking".  The Haskell-API nature is desired to be
-"non-blocking".
+**Concurrent foreign call** means a foreign call that should run concurrently with other Haskell threads.  It is a requirement of "fairness" (above) that a foreign call should not prevent other threads from making progress indefinitely.  Note that we used to use the term **non-blocking foreign call** here, but that lead to confusion with "foreign calls that block", which are foreign calls that may wait indefinitely for some resource, such as reading data from a socket.  "foreign calls that block" are the main reason for wanting support for concurrent foreign calls.
 
 **Scheduling.**
 All current (and likely future) implementations of