[project @ 1999-11-15 14:14:43 by simonmar]

Fix queue corruption bug in unblocking of threads blocked on I/O.

diff --git a/ghc/rts/Schedule.c b/ghc/rts/Schedule.c
index c35d098..32e18b4 100644 (file)
--- a/ghc/rts/Schedule.c
+++ b/ghc/rts/Schedule.c
@@ -1,5 +1,5 @@
 /* -----------------------------------------------------------------------------
- * $Id: Schedule.c,v 1.32 1999/11/11 17:19:15 simonmar Exp $
+ * $Id: Schedule.c,v 1.33 1999/11/15 14:14:43 simonmar Exp $
  *
  * (c) The GHC Team, 1998-1999
  *
@@ -1246,13 +1246,20 @@ unblockThread(StgTSO *tso)
   case BlockedOnRead:
   case BlockedOnWrite:
     {
-      last = &blocked_queue_hd;
+      StgTSO *prev = NULL;
       for (t = blocked_queue_hd; t != END_TSO_QUEUE; 
-          last = &t->link, t = t->link) {
+          prev = t, t = t->link) {
        if (t == tso) {
-         *last = tso->link;
-         if (blocked_queue_tl == t) {
-           blocked_queue_tl = tso->link;
+         if (prev == NULL) {
+           blocked_queue_hd = t->link;
+           if (blocked_queue_tl == t) {
+             blocked_queue_tl = END_TSO_QUEUE;
+           }
+         } else {
+           prev->link = t->link;
+           if (blocked_queue_tl == t) {
+             blocked_queue_tl = prev;
+           }
          }
          goto done;
        }