+
+ // Note [mvar-heap-check] We want to do the heap check in the
+ // branch here, to avoid the conditional in the common case.
+ // However, we've already locked the MVar above, so we better
+ // be careful to unlock it again if the the heap check fails.
+ // Unfortunately we don't have an easy way to inject any code
+ // into the heap check generated by the code generator, so we
+ // have to do it in stg_gc_gen (see HeapStackCheck.cmm).
+ HP_CHK_GEN_TICKY(SIZEOF_StgMVarTSOQueue, R1_PTR, stg_takeMVarzh);
+
+ q = Hp - SIZEOF_StgMVarTSOQueue + WDS(1);
+
+ SET_HDR(q, stg_MVAR_TSO_QUEUE_info, CCS_SYSTEM);
+ StgMVarTSOQueue_link(q) = END_TSO_QUEUE;
+ StgMVarTSOQueue_tso(q) = CurrentTSO;
+