const StgInfoTable *info;
StgClosure *p;
StgBlockingQueue *bq;
- StgClosure *bh = msg->bh;
+ StgClosure *bh = UNTAG_CLOSURE(msg->bh);
StgTSO *owner;
debugTraceCap(DEBUG_sched, cap, "message: thread %d blocking on blackhole %p",
return 0;
}
- // we know at this point that the closure
+ // The blackhole must indirect to a TSO, a BLOCKING_QUEUE, an IND,
+ // or a value.
loop:
- p = ((StgInd*)bh)->indirectee;
+ // NB. VOLATILE_LOAD(), because otherwise gcc hoists the load
+ // and turns this into an infinite loop.
+ p = UNTAG_CLOSURE((StgClosure*)VOLATILE_LOAD(&((StgInd*)bh)->indirectee));
info = p->header.info;
if (info == &stg_IND_info)