X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=rts%2FSTM.c;h=9d93972e94d057ece5407151d87428e5a03bb444;hb=77b7c34fa24860c91f56250defa91b2d1a7a1c00;hp=c271a25d3cf6bbfe0c2ccd6729a7e7956bf1fe76;hpb=067ec969bb0bdc4c88582e53b040fa2925cbcc56;p=ghc-hetmet.git

diff --git a/rts/STM.c b/rts/STM.c
index c271a25..9d93972 100644
--- a/rts/STM.c
+++ b/rts/STM.c
@@ -388,10 +388,18 @@ static void unpark_tso(Capability *cap, StgTSO *tso) {
 
 static void unpark_waiters_on(Capability *cap, StgTVar *s) {
   StgTVarWatchQueue *q;
+  StgTVarWatchQueue *trail;
   TRACE("unpark_waiters_on tvar=%p", s);
-  for (q = s -> first_watch_queue_entry; 
-       q != END_STM_WATCH_QUEUE; 
+  // unblock TSOs in reverse order, to be a bit fairer (#2319)
+  for (q = s -> first_watch_queue_entry, trail = q;
+       q != END_STM_WATCH_QUEUE;
        q = q -> next_queue_entry) {
+    trail = q;
+  }
+  q = trail;
+  for (;
+       q != END_STM_WATCH_QUEUE; 
+       q = q -> prev_queue_entry) {
     if (watcher_is_tso(q)) {
       unpark_tso(cap, (StgTSO *)(q -> closure));
     }