If the target thread is currently making a foreign call, then the
exception will not be raised (and hence 'throwTo' will not return)
until the call has completed. This is the case regardless of whether
-the call is inside a 'mask' or not.
+the call is inside a 'mask' or not. However, in GHC a foreign call
+can be annotated as @interruptible@, in which case a 'throwTo' will
+cause the RTS to attempt to cause the call to return; see the GHC
+documentation for more details.
Important note: the behaviour of 'throwTo' differs from that described in
the paper \"Asynchronous exceptions in Haskell\"