[commit: ghc] master: base: Note platform dependence of registerFd (fd63ea5)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/fd63ea5686fe5b856c3ebdc5f28bf7a2547bd96f/ghc

>---------------------------------------------------------------

commit fd63ea5686fe5b856c3ebdc5f28bf7a2547bd96f
Author: Ben Gamari <ben at smart-cactus.org>
Date:   Fri Oct 23 17:09:31 2015 +0200

    base: Note platform dependence of registerFd
    
    Just a documentation change. Fixes #10736.


>---------------------------------------------------------------

fd63ea5686fe5b856c3ebdc5f28bf7a2547bd96f
 libraries/base/GHC/Event/Manager.hs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libraries/base/GHC/Event/Manager.hs b/libraries/base/GHC/Event/Manager.hs
index b674866..a94f8e8 100644
--- a/libraries/base/GHC/Event/Manager.hs
+++ b/libraries/base/GHC/Event/Manager.hs
@@ -305,6 +305,11 @@ step mgr at EventManager{..} = do
 -- | Register interest in the given events, without waking the event
 -- manager thread.  The 'Bool' return value indicates whether the
 -- event manager ought to be woken.
+--
+-- Note that the event manager is generally implemented in terms of the
+-- platform's @selectg@ or @epoll@ system call, which tend to vary in
+-- what sort of fds are permitted. For instance, waiting on regular files
+-- is not allowed on many platforms.
 registerFd_ :: EventManager -> IOCallback -> Fd -> Event -> Lifetime
             -> IO (FdKey, Bool)
 registerFd_ mgr@(EventManager{..}) cb fd evs lt = do