[commit: ghc] master: comments (c1ae31f)

[Simon Marlow]

Repository : ssh://darcs.haskell.org//srv/darcs/ghc

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/c1ae31f65b740e6d65c3553dfbf8d849f2c59b6f

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

commit c1ae31f65b740e6d65c3553dfbf8d849f2c59b6f
Author: Simon Marlow <marlowsd at gmail.com>
Date:   Thu Feb 7 10:00:09 2013 +0000

    comments

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

 rts/win32/IOManager.c |   12 +++++++++++-
 1 files changed, 11 insertions(+), 1 deletions(-)

diff --git a/rts/win32/IOManager.c b/rts/win32/IOManager.c
index 65f5d4c..0091f23 100644
--- a/rts/win32/IOManager.c
+++ b/rts/win32/IOManager.c
@@ -199,7 +199,17 @@ IOWorkerProc(PVOID param)
 		    /* Approximate implementation of threadDelay;
 		     * 
 		     * Note: Sleep() is in milliseconds, not micros.
-		     */
+                     *
+                     * MSDN says of Sleep:
+                     *   If dwMilliseconds is greater than one tick
+                     *   but less than two, the wait can be anywhere
+                     *   between one and two ticks, and so on.
+                     *
+                     * so we need to add (milliseconds-per-tick - 1)
+                     * to the amount of time we sleep for.
+                     *
+                     * test ThreadDelay001 fails if we get this wrong.
+                     */
 		    Sleep(((work->workData.delayData.usecs + 999) / 1000) + iom->sleepResolution - 1);
 		    len = work->workData.delayData.usecs;
 		    complData = NULL;