+ The SMP header
+
+ A thunk has a padding word to take the updated value. This is so
+ that the update doesn't overwrite the payload, so we can avoid
+ needing to lock the thunk during entry and update.
+
+ Note: this doesn't apply to THUNK_STATICs, which have no payload.
+
+ Note: we leave this padding word in all ways, rather than just SMP,
+ so that we don't have to recompile all our libraries for SMP.
+ -------------------------------------------------------------------------- */
+
+typedef struct {
+ StgWord pad;
+} StgSMPThunkHeader;
+
+/* -----------------------------------------------------------------------------