need locking around use of weak_ptr_list in mkWeak#

diff --git a/rts/PrimOps.cmm b/rts/PrimOps.cmm
index 5e762b1..b88ca7a 100644 (file)
--- a/rts/PrimOps.cmm
+++ b/rts/PrimOps.cmm
@@ -321,8 +321,10 @@ stg_mkWeakzh
   StgWeak_finalizer(w)  = R3;
   StgWeak_cfinalizer(w) = stg_NO_FINALIZER_closure;
 
+  ACQUIRE_LOCK(sm_mutex);
   StgWeak_link(w)      = W_[weak_ptr_list];
   W_[weak_ptr_list]    = w;
+  RELEASE_LOCK(sm_mutex);
 
   IF_DEBUG(weak, foreign "C" debugBelch(stg_weak_msg,w) []);