MessageThrowTo *
throwTo (Capability *cap, // the Capability we hold
StgTSO *source, // the TSO sending the exception (or NULL)
StgTSO *target, // the TSO receiving the exception
StgClosure *exception) // the exception closure
{
MessageThrowTo *msg;
msg = (MessageThrowTo *) allocate(cap, sizeofW(MessageThrowTo));
// the message starts locked; see below
SET_HDR(msg, &stg_WHITEHOLE_info, CCS_SYSTEM);
msg->source = source;
msg->target = target;
msg->exception = exception;
switch (throwToMsg(cap, msg))
{
case THROWTO_SUCCESS:
// unlock the message now, otherwise we leave a WHITEHOLE in
// the heap (#6103)
SET_HDR(msg, &stg_MSG_THROWTO_info, CCS_SYSTEM);
return NULL;
case THROWTO_BLOCKED:
default:
// the caller will unlock the message when it is ready. We
// cannot unlock it yet, because the calling thread will need
// to tidy up its state first.
return msg;
}
}
void
executeMessage (Capability *cap, Message *m)
{
const StgInfoTable *i;
loop:
write_barrier(); // allow m->header to be modified by another thread
i = m->header.info;
if (i == &stg_MSG_TRY_WAKEUP_info)
{
StgTSO *tso = ((MessageWakeup *)m)->tso;
debugTraceCap(DEBUG_sched, cap, "message: try wakeup thread %ld",
(lnat)tso->id);
tryWakeupThread(cap, tso);
}
else if (i == &stg_MSG_THROWTO_info)
{
MessageThrowTo *t = (MessageThrowTo *)m;
nat r;
const StgInfoTable *i;
i = lockClosure((StgClosure*)m);
if (i != &stg_MSG_THROWTO_info) {
unlockClosure((StgClosure*)m, i);
goto loop;
}
debugTraceCap(DEBUG_sched, cap, "message: throwTo %ld -> %ld",
(lnat)t->source->id, (lnat)t->target->id);
ASSERT(t->source->why_blocked == BlockedOnMsgThrowTo);
ASSERT(t->source->block_info.closure == (StgClosure *)m);
r = throwToMsg(cap, t);
switch (r) {
case THROWTO_SUCCESS: {
// this message is done
StgTSO *source = t->source;
doneWithMsgThrowTo(t);
tryWakeupThread(cap, source);
break;
}
case THROWTO_BLOCKED:
// unlock the message
unlockClosure((StgClosure*)m, &stg_MSG_THROWTO_info);
break;
}
}
else if (i == &stg_MSG_BLACKHOLE_info)
{
nat r;
MessageBlackHole *b = (MessageBlackHole*)m;
r = messageBlackHole(cap, b);
if (r == 0) {
tryWakeupThread(cap, b->tso);
}
return;
}
else if (i == &stg_IND_info || i == &stg_MSG_NULL_info)
{
// message was revoked
return;
}
else if (i == &stg_WHITEHOLE_info)
{
goto loop;
}
else
{
barf("executeMessage: %p", i);
}
}
