updateThunk: minor tweak to avoid an unnecessary call to checkBlockingQueues

1 files changed, 8 insertions, 4 deletions

diff --git a/rts/Threads.c b/rts/Threads.c
index 802a37c94c..997bcc8882 100644
--- a/rts/Threads.c
+++ b/rts/Threads.c
@@ -424,12 +424,16 @@ updateThunk (Capability *cap, StgTSO *tso, StgClosure *thunk, StgClosure *val)
 
     updateWithIndirection(cap, thunk, val);
 
+    // sometimes the TSO is locked when we reach here, so its header
+    // might be WHITEHOLE.  Hence check for the correct owner using
+    // pointer equality first.
+    if ((StgTSO*)v == tso) {
+        return;
+    }
+
     i = v->header.info;
     if (i == &stg_TSO_info) {
-        owner = (StgTSO*)v;
-        if (owner != tso) {
-            checkBlockingQueues(cap, tso);
-        }
+        checkBlockingQueues(cap, tso);
         return;
     }