1 /* ---------------------------------------------------------------------------
3 * (c) The GHC Team, 1998-2006
5 * Asynchronous exceptions
7 * --------------------------------------------------------------------------*/
9 #include "PosixSource.h"
12 #include "sm/Storage.h"
15 #include "RaiseAsync.h"
19 #include "sm/Sanity.h"
20 #include "Profiling.h"
22 #if defined(mingw32_HOST_OS)
23 #include "win32/IOManager.h"
26 static void raiseAsync (Capability *cap,
28 StgClosure *exception,
29 rtsBool stop_at_atomically,
30 StgUpdateFrame *stop_here);
32 static void removeFromQueues(Capability *cap, StgTSO *tso);
34 static void removeFromMVarBlockedQueue (StgTSO *tso);
36 static void blockedThrowTo (Capability *cap,
37 StgTSO *target, MessageThrowTo *msg);
39 static void throwToSendMsg (Capability *cap USED_IF_THREADS,
40 Capability *target_cap USED_IF_THREADS,
41 MessageThrowTo *msg USED_IF_THREADS);
43 /* -----------------------------------------------------------------------------
46 This version of throwTo is safe to use if and only if one of the
51 - all the other threads in the system are stopped (eg. during GC).
53 - we surely own the target TSO (eg. we just took it from the
54 run queue of the current capability, or we are running it).
56 It doesn't cater for blocking the source thread until the exception
58 -------------------------------------------------------------------------- */
61 throwToSingleThreaded(Capability *cap, StgTSO *tso, StgClosure *exception)
63 throwToSingleThreaded_(cap, tso, exception, rtsFalse);
67 throwToSingleThreaded_(Capability *cap, StgTSO *tso, StgClosure *exception,
68 rtsBool stop_at_atomically)
72 // Thread already dead?
73 if (tso->what_next == ThreadComplete || tso->what_next == ThreadKilled) {
77 // Remove it from any blocking queues
78 removeFromQueues(cap,tso);
80 raiseAsync(cap, tso, exception, stop_at_atomically, NULL);
84 suspendComputation(Capability *cap, StgTSO *tso, StgUpdateFrame *stop_here)
88 // Thread already dead?
89 if (tso->what_next == ThreadComplete || tso->what_next == ThreadKilled) {
93 // Remove it from any blocking queues
94 removeFromQueues(cap,tso);
96 raiseAsync(cap, tso, NULL, rtsFalse, stop_here);
99 /* -----------------------------------------------------------------------------
102 This function may be used to throw an exception from one thread to
103 another, during the course of normal execution. This is a tricky
104 task: the target thread might be running on another CPU, or it
105 may be blocked and could be woken up at any point by another CPU.
106 We have some delicate synchronisation to do.
108 The underlying scheme when multiple Capabilities are in use is
109 message passing: when the target of a throwTo is on another
110 Capability, we send a message (a MessageThrowTo closure) to that
113 If the throwTo needs to block because the target TSO is masking
114 exceptions (the TSO_BLOCKEX flag), then the message is placed on
115 the blocked_exceptions queue attached to the target TSO. When the
116 target TSO enters the unmasked state again, it must check the
117 queue. The blocked_exceptions queue is not locked; only the
118 Capability owning the TSO may modify it.
120 To make things simpler for throwTo, we always create the message
121 first before deciding what to do. The message may get sent, or it
122 may get attached to a TSO's blocked_exceptions queue, or the
123 exception may get thrown immediately and the message dropped,
124 depending on the current state of the target.
126 Currently we send a message if the target belongs to another
127 Capability, and it is
129 - NotBlocked, BlockedOnMsgThrowTo,
130 BlockedOnCCall_Interruptible
132 - or it is masking exceptions (TSO_BLOCKEX)
134 Currently, if the target is BlockedOnMVar, BlockedOnSTM, or
135 BlockedOnBlackHole then we acquire ownership of the TSO by locking
136 its parent container (e.g. the MVar) and then raise the exception.
137 We might change these cases to be more message-passing-like in the
142 NULL exception was raised, ok to continue
144 MessageThrowTo * exception was not raised; the source TSO
145 should now put itself in the state
146 BlockedOnMsgThrowTo, and when it is ready
147 it should unlock the mssage using
148 unlockClosure(msg, &stg_MSG_THROWTO_info);
149 If it decides not to raise the exception after
150 all, it can revoke it safely with
151 unlockClosure(msg, &stg_MSG_NULL_info);
153 -------------------------------------------------------------------------- */
156 throwTo (Capability *cap, // the Capability we hold
157 StgTSO *source, // the TSO sending the exception (or NULL)
158 StgTSO *target, // the TSO receiving the exception
159 StgClosure *exception) // the exception closure
163 msg = (MessageThrowTo *) allocate(cap, sizeofW(MessageThrowTo));
164 // message starts locked; the caller has to unlock it when it is
166 SET_HDR(msg, &stg_WHITEHOLE_info, CCS_SYSTEM);
167 msg->source = source;
168 msg->target = target;
169 msg->exception = exception;
171 switch (throwToMsg(cap, msg))
173 case THROWTO_SUCCESS:
175 case THROWTO_BLOCKED:
183 throwToMsg (Capability *cap, MessageThrowTo *msg)
186 StgTSO *target = msg->target;
187 Capability *target_cap;
193 debugTrace(DEBUG_sched, "throwTo: retrying...");
196 ASSERT(target != END_TSO_QUEUE);
198 // follow ThreadRelocated links in the target first
199 target = deRefTSO(target);
201 // Thread already dead?
202 if (target->what_next == ThreadComplete
203 || target->what_next == ThreadKilled) {
204 return THROWTO_SUCCESS;
207 debugTraceCap(DEBUG_sched, cap,
208 "throwTo: from thread %lu to thread %lu",
209 (unsigned long)msg->source->id,
210 (unsigned long)msg->target->id);
213 traceThreadStatus(DEBUG_sched, target);
216 target_cap = target->cap;
217 if (target->cap != cap) {
218 throwToSendMsg(cap, target_cap, msg);
219 return THROWTO_BLOCKED;
222 status = target->why_blocked;
227 if ((target->flags & TSO_BLOCKEX) == 0) {
228 // It's on our run queue and not blocking exceptions
229 raiseAsync(cap, target, msg->exception, rtsFalse, NULL);
230 return THROWTO_SUCCESS;
232 blockedThrowTo(cap,target,msg);
233 return THROWTO_BLOCKED;
237 case BlockedOnMsgThrowTo:
239 const StgInfoTable *i;
242 m = target->block_info.throwto;
244 // target is local to this cap, but has sent a throwto
245 // message to another cap.
247 // The source message is locked. We need to revoke the
248 // target's message so that we can raise the exception, so
249 // we attempt to lock it.
251 // There's a possibility of a deadlock if two threads are both
252 // trying to throwTo each other (or more generally, a cycle of
253 // threads). To break the symmetry we compare the addresses
254 // of the MessageThrowTo objects, and the one for which m <
255 // msg gets to spin, while the other can only try to lock
256 // once, but must then back off and unlock both before trying
259 i = lockClosure((StgClosure *)m);
261 i = tryLockClosure((StgClosure *)m);
263 // debugBelch("collision\n");
264 throwToSendMsg(cap, target->cap, msg);
265 return THROWTO_BLOCKED;
269 if (i == &stg_MSG_NULL_info) {
270 // we know there's a MSG_TRY_WAKEUP on the way, so we
271 // might as well just do it now. The message will
272 // be a no-op when it arrives.
273 unlockClosure((StgClosure*)m, i);
274 tryWakeupThread_(cap, target);
278 if (i != &stg_MSG_THROWTO_info) {
279 // if it's a MSG_NULL, this TSO has been woken up by another Cap
280 unlockClosure((StgClosure*)m, i);
284 if ((target->flags & TSO_BLOCKEX) &&
285 ((target->flags & TSO_INTERRUPTIBLE) == 0)) {
286 unlockClosure((StgClosure*)m, i);
287 blockedThrowTo(cap,target,msg);
288 return THROWTO_BLOCKED;
291 // nobody else can wake up this TSO after we claim the message
292 unlockClosure((StgClosure*)m, &stg_MSG_NULL_info);
294 raiseAsync(cap, target, msg->exception, rtsFalse, NULL);
295 return THROWTO_SUCCESS;
301 To establish ownership of this TSO, we need to acquire a
302 lock on the MVar that it is blocked on.
305 StgInfoTable *info USED_IF_THREADS;
307 mvar = (StgMVar *)target->block_info.closure;
309 // ASSUMPTION: tso->block_info must always point to a
310 // closure. In the threaded RTS it does.
311 switch (get_itbl(mvar)->type) {
319 info = lockClosure((StgClosure *)mvar);
321 if (target->what_next == ThreadRelocated) {
322 target = target->_link;
323 unlockClosure((StgClosure *)mvar,info);
326 // we have the MVar, let's check whether the thread
327 // is still blocked on the same MVar.
328 if (target->why_blocked != BlockedOnMVar
329 || (StgMVar *)target->block_info.closure != mvar) {
330 unlockClosure((StgClosure *)mvar, info);
334 if (target->_link == END_TSO_QUEUE) {
335 // the MVar operation has already completed. There is a
336 // MSG_TRY_WAKEUP on the way, but we can just wake up the
337 // thread now anyway and ignore the message when it
339 unlockClosure((StgClosure *)mvar, info);
340 tryWakeupThread_(cap, target);
344 if ((target->flags & TSO_BLOCKEX) &&
345 ((target->flags & TSO_INTERRUPTIBLE) == 0)) {
346 blockedThrowTo(cap,target,msg);
347 unlockClosure((StgClosure *)mvar, info);
348 return THROWTO_BLOCKED;
350 // revoke the MVar operation
351 removeFromMVarBlockedQueue(target);
352 raiseAsync(cap, target, msg->exception, rtsFalse, NULL);
353 unlockClosure((StgClosure *)mvar, info);
354 return THROWTO_SUCCESS;
358 case BlockedOnBlackHole:
360 if (target->flags & TSO_BLOCKEX) {
361 // BlockedOnBlackHole is not interruptible.
362 blockedThrowTo(cap,target,msg);
363 return THROWTO_BLOCKED;
365 // Revoke the message by replacing it with IND. We're not
366 // locking anything here, so we might still get a TRY_WAKEUP
367 // message from the owner of the blackhole some time in the
368 // future, but that doesn't matter.
369 ASSERT(target->block_info.bh->header.info == &stg_MSG_BLACKHOLE_info);
370 OVERWRITE_INFO(target->block_info.bh, &stg_IND_info);
371 raiseAsync(cap, target, msg->exception, rtsFalse, NULL);
372 return THROWTO_SUCCESS;
378 // Unblocking BlockedOnSTM threads requires the TSO to be
379 // locked; see STM.c:unpark_tso().
380 if (target->why_blocked != BlockedOnSTM) {
384 if ((target->flags & TSO_BLOCKEX) &&
385 ((target->flags & TSO_INTERRUPTIBLE) == 0)) {
386 blockedThrowTo(cap,target,msg);
388 return THROWTO_BLOCKED;
390 raiseAsync(cap, target, msg->exception, rtsFalse, NULL);
392 return THROWTO_SUCCESS;
395 case BlockedOnCCall_Interruptible:
399 // walk suspended_ccalls to find the correct worker thread
401 for (incall = cap->suspended_ccalls; incall != NULL; incall = incall->next) {
402 if (incall->suspended_tso == target) {
408 raiseAsync(cap, target, msg->exception, rtsFalse, NULL);
409 interruptWorkerTask(task);
410 return THROWTO_SUCCESS;
412 debugTraceCap(DEBUG_sched, cap, "throwTo: could not find worker thread to kill");
418 blockedThrowTo(cap,target,msg);
419 return THROWTO_BLOCKED;
421 #ifndef THREADEDED_RTS
425 #if defined(mingw32_HOST_OS)
426 case BlockedOnDoProc:
428 if ((target->flags & TSO_BLOCKEX) &&
429 ((target->flags & TSO_INTERRUPTIBLE) == 0)) {
430 blockedThrowTo(cap,target,msg);
431 return THROWTO_BLOCKED;
433 removeFromQueues(cap,target);
434 raiseAsync(cap, target, msg->exception, rtsFalse, NULL);
435 return THROWTO_SUCCESS;
440 barf("throwTo: unrecognised why_blocked value");
446 throwToSendMsg (Capability *cap STG_UNUSED,
447 Capability *target_cap USED_IF_THREADS,
448 MessageThrowTo *msg USED_IF_THREADS)
452 debugTraceCap(DEBUG_sched, cap, "throwTo: sending a throwto message to cap %lu", (unsigned long)target_cap->no);
454 sendMessage(cap, target_cap, (Message*)msg);
458 // Block a throwTo message on the target TSO's blocked_exceptions
459 // queue. The current Capability must own the target TSO in order to
460 // modify the blocked_exceptions queue.
462 blockedThrowTo (Capability *cap, StgTSO *target, MessageThrowTo *msg)
464 debugTraceCap(DEBUG_sched, cap, "throwTo: blocking on thread %lu",
465 (unsigned long)target->id);
467 ASSERT(target->cap == cap);
469 msg->link = target->blocked_exceptions;
470 target->blocked_exceptions = msg;
471 dirty_TSO(cap,target); // we modified the blocked_exceptions queue
474 /* -----------------------------------------------------------------------------
475 Waking up threads blocked in throwTo
477 There are two ways to do this: maybePerformBlockedException() will
478 perform the throwTo() for the thread at the head of the queue
479 immediately, and leave the other threads on the queue.
480 maybePerformBlockedException() also checks the TSO_BLOCKEX flag
481 before raising an exception.
483 awakenBlockedExceptionQueue() will wake up all the threads in the
484 queue, but not perform any throwTo() immediately. This might be
485 more appropriate when the target thread is the one actually running
488 Returns: non-zero if an exception was raised, zero otherwise.
489 -------------------------------------------------------------------------- */
492 maybePerformBlockedException (Capability *cap, StgTSO *tso)
495 const StgInfoTable *i;
497 if (tso->what_next == ThreadComplete || tso->what_next == ThreadFinished) {
498 if (tso->blocked_exceptions != END_BLOCKED_EXCEPTIONS_QUEUE) {
499 awakenBlockedExceptionQueue(cap,tso);
506 if (tso->blocked_exceptions != END_BLOCKED_EXCEPTIONS_QUEUE &&
507 (tso->flags & TSO_BLOCKEX) != 0) {
508 debugTraceCap(DEBUG_sched, cap, "throwTo: thread %lu has blocked exceptions but is inside block", (unsigned long)tso->id);
511 if (tso->blocked_exceptions != END_BLOCKED_EXCEPTIONS_QUEUE
512 && ((tso->flags & TSO_BLOCKEX) == 0
513 || ((tso->flags & TSO_INTERRUPTIBLE) && interruptible(tso)))) {
515 // We unblock just the first thread on the queue, and perform
516 // its throw immediately.
518 msg = tso->blocked_exceptions;
519 if (msg == END_BLOCKED_EXCEPTIONS_QUEUE) return 0;
520 i = lockClosure((StgClosure*)msg);
521 tso->blocked_exceptions = (MessageThrowTo*)msg->link;
522 if (i == &stg_MSG_NULL_info) {
523 unlockClosure((StgClosure*)msg,i);
527 throwToSingleThreaded(cap, msg->target, msg->exception);
528 unlockClosure((StgClosure*)msg,&stg_MSG_NULL_info);
529 tryWakeupThread(cap, msg->source);
535 // awakenBlockedExceptionQueue(): Just wake up the whole queue of
536 // blocked exceptions.
539 awakenBlockedExceptionQueue (Capability *cap, StgTSO *tso)
542 const StgInfoTable *i;
544 for (msg = tso->blocked_exceptions; msg != END_BLOCKED_EXCEPTIONS_QUEUE;
545 msg = (MessageThrowTo*)msg->link) {
546 i = lockClosure((StgClosure *)msg);
547 if (i != &stg_MSG_NULL_info) {
548 unlockClosure((StgClosure *)msg,&stg_MSG_NULL_info);
549 tryWakeupThread(cap, msg->source);
551 unlockClosure((StgClosure *)msg,i);
554 tso->blocked_exceptions = END_BLOCKED_EXCEPTIONS_QUEUE;
557 /* -----------------------------------------------------------------------------
558 Remove a thread from blocking queues.
560 This is for use when we raise an exception in another thread, which
563 Precondition: we have exclusive access to the TSO, via the same set
564 of conditions as throwToSingleThreaded() (c.f.).
565 -------------------------------------------------------------------------- */
568 removeFromMVarBlockedQueue (StgTSO *tso)
570 StgMVar *mvar = (StgMVar*)tso->block_info.closure;
571 StgMVarTSOQueue *q = (StgMVarTSOQueue*)tso->_link;
573 if (q == (StgMVarTSOQueue*)END_TSO_QUEUE) {
574 // already removed from this MVar
578 // Assume the MVar is locked. (not assertable; sometimes it isn't
579 // actually WHITEHOLE'd).
581 // We want to remove the MVAR_TSO_QUEUE object from the queue. It
582 // isn't doubly-linked so we can't actually remove it; instead we
583 // just overwrite it with an IND if possible and let the GC short
584 // it out. However, we have to be careful to maintain the deque
587 if (mvar->head == q) {
588 mvar->head = q->link;
589 q->header.info = &stg_IND_info;
590 if (mvar->tail == q) {
591 mvar->tail = (StgMVarTSOQueue*)END_TSO_QUEUE;
594 else if (mvar->tail == q) {
595 // we can't replace it with an IND in this case, because then
596 // we lose the tail pointer when the GC shorts out the IND.
597 // So we use MSG_NULL as a kind of non-dupable indirection;
598 // these are ignored by takeMVar/putMVar.
599 q->header.info = &stg_MSG_NULL_info;
602 q->header.info = &stg_IND_info;
605 // revoke the MVar operation
606 tso->_link = END_TSO_QUEUE;
610 removeFromQueues(Capability *cap, StgTSO *tso)
612 switch (tso->why_blocked) {
615 case ThreadMigrating:
619 // Be careful: nothing to do here! We tell the scheduler that the
620 // thread is runnable and we leave it to the stack-walking code to
621 // abort the transaction while unwinding the stack. We should
622 // perhaps have a debugging test to make sure that this really
623 // happens and that the 'zombie' transaction does not get
628 removeFromMVarBlockedQueue(tso);
631 case BlockedOnBlackHole:
635 case BlockedOnMsgThrowTo:
637 MessageThrowTo *m = tso->block_info.throwto;
638 // The message is locked by us, unless we got here via
639 // deleteAllThreads(), in which case we own all the
641 // ASSERT(m->header.info == &stg_WHITEHOLE_info);
643 // unlock and revoke it at the same time
644 unlockClosure((StgClosure*)m,&stg_MSG_NULL_info);
648 #if !defined(THREADED_RTS)
651 #if defined(mingw32_HOST_OS)
652 case BlockedOnDoProc:
654 removeThreadFromDeQueue(cap, &blocked_queue_hd, &blocked_queue_tl, tso);
655 #if defined(mingw32_HOST_OS)
656 /* (Cooperatively) signal that the worker thread should abort
659 abandonWorkRequest(tso->block_info.async_result->reqID);
664 removeThreadFromQueue(cap, &sleeping_queue, tso);
669 barf("removeFromQueues: %d", tso->why_blocked);
673 tso->why_blocked = NotBlocked;
674 appendToRunQueue(cap, tso);
677 /* -----------------------------------------------------------------------------
680 * The following function implements the magic for raising an
681 * asynchronous exception in an existing thread.
683 * We first remove the thread from any queue on which it might be
684 * blocked. The possible blockages are MVARs, BLOCKING_QUEUESs, and
685 * TSO blocked_exception queues.
687 * We strip the stack down to the innermost CATCH_FRAME, building
688 * thunks in the heap for all the active computations, so they can
689 * be restarted if necessary. When we reach a CATCH_FRAME, we build
690 * an application of the handler to the exception, and push it on
691 * the top of the stack.
693 * How exactly do we save all the active computations? We create an
694 * AP_STACK for every UpdateFrame on the stack. Entering one of these
695 * AP_STACKs pushes everything from the corresponding update frame
696 * upwards onto the stack. (Actually, it pushes everything up to the
697 * next update frame plus a pointer to the next AP_STACK object.
698 * Entering the next AP_STACK object pushes more onto the stack until we
699 * reach the last AP_STACK object - at which point the stack should look
700 * exactly as it did when we killed the TSO and we can continue
701 * execution by entering the closure on top of the stack.
703 * We can also kill a thread entirely - this happens if either (a) the
704 * exception passed to raiseAsync is NULL, or (b) there's no
705 * CATCH_FRAME on the stack. In either case, we strip the entire
706 * stack and replace the thread with a zombie.
708 * ToDo: in THREADED_RTS mode, this function is only safe if either
709 * (a) we hold all the Capabilities (eg. in GC, or if there is only
710 * one Capability), or (b) we own the Capability that the TSO is
711 * currently blocked on or on the run queue of.
713 * -------------------------------------------------------------------------- */
716 raiseAsync(Capability *cap, StgTSO *tso, StgClosure *exception,
717 rtsBool stop_at_atomically, StgUpdateFrame *stop_here)
719 StgRetInfoTable *info;
724 debugTraceCap(DEBUG_sched, cap,
725 "raising exception in thread %ld.", (long)tso->id);
727 #if defined(PROFILING)
729 * Debugging tool: on raising an exception, show where we are.
730 * See also Exception.cmm:stg_raisezh.
731 * This wasn't done for asynchronous exceptions originally; see #1450
733 if (RtsFlags.ProfFlags.showCCSOnException)
735 fprintCCS_stderr(tso->prof.CCCS);
738 // ASSUMES: the thread is not already complete or dead, or
739 // ThreadRelocated. Upper layers should deal with that.
740 ASSERT(tso->what_next != ThreadComplete &&
741 tso->what_next != ThreadKilled &&
742 tso->what_next != ThreadRelocated);
744 // only if we own this TSO (except that deleteThread() calls this
745 ASSERT(tso->cap == cap);
748 if (tso->why_blocked != NotBlocked) {
749 tso->why_blocked = NotBlocked;
750 appendToRunQueue(cap,tso);
753 // mark it dirty; we're about to change its stack.
758 if (stop_here != NULL) {
759 updatee = stop_here->updatee;
764 // The stack freezing code assumes there's a closure pointer on
765 // the top of the stack, so we have to arrange that this is the case...
767 if (sp[0] == (W_)&stg_enter_info) {
771 sp[0] = (W_)&stg_dummy_ret_closure;
775 while (stop_here == NULL || frame < (StgPtr)stop_here) {
777 // 1. Let the top of the stack be the "current closure"
779 // 2. Walk up the stack until we find either an UPDATE_FRAME or a
782 // 3. If it's an UPDATE_FRAME, then make an AP_STACK containing the
783 // current closure applied to the chunk of stack up to (but not
784 // including) the update frame. This closure becomes the "current
785 // closure". Go back to step 2.
787 // 4. If it's a CATCH_FRAME, then leave the exception handler on
788 // top of the stack applied to the exception.
790 // 5. If it's a STOP_FRAME, then kill the thread.
792 // NB: if we pass an ATOMICALLY_FRAME then abort the associated
795 info = get_ret_itbl((StgClosure *)frame);
797 switch (info->i.type) {
804 // First build an AP_STACK consisting of the stack chunk above the
805 // current update frame, with the top word on the stack as the
808 words = frame - sp - 1;
809 ap = (StgAP_STACK *)allocate(cap,AP_STACK_sizeW(words));
812 ap->fun = (StgClosure *)sp[0];
814 for(i=0; i < (nat)words; ++i) {
815 ap->payload[i] = (StgClosure *)*sp++;
818 SET_HDR(ap,&stg_AP_STACK_info,
819 ((StgClosure *)frame)->header.prof.ccs /* ToDo */);
820 TICK_ALLOC_UP_THK(words+1,0);
822 //IF_DEBUG(scheduler,
823 // debugBelch("sched: Updating ");
824 // printPtr((P_)((StgUpdateFrame *)frame)->updatee);
825 // debugBelch(" with ");
826 // printObj((StgClosure *)ap);
829 if (((StgUpdateFrame *)frame)->updatee == updatee) {
830 // If this update frame points to the same closure as
831 // the update frame further down the stack
832 // (stop_here), then don't perform the update. We
833 // want to keep the blackhole in this case, so we can
834 // detect and report the loop (#2783).
835 ap = (StgAP_STACK*)updatee;
837 // Perform the update
838 // TODO: this may waste some work, if the thunk has
839 // already been updated by another thread.
840 updateThunk(cap, tso,
841 ((StgUpdateFrame *)frame)->updatee, (StgClosure *)ap);
844 sp += sizeofW(StgUpdateFrame) - 1;
845 sp[0] = (W_)ap; // push onto stack
847 continue; //no need to bump frame
852 // We've stripped the entire stack, the thread is now dead.
853 tso->what_next = ThreadKilled;
854 tso->sp = frame + sizeofW(StgStopFrame);
859 // If we find a CATCH_FRAME, and we've got an exception to raise,
860 // then build the THUNK raise(exception), and leave it on
861 // top of the CATCH_FRAME ready to enter.
864 StgCatchFrame *cf = (StgCatchFrame *)frame;
867 if (exception == NULL) break;
869 // we've got an exception to raise, so let's pass it to the
870 // handler in this frame.
872 raise = (StgThunk *)allocate(cap,sizeofW(StgThunk)+1);
873 TICK_ALLOC_SE_THK(1,0);
874 SET_HDR(raise,&stg_raise_info,cf->header.prof.ccs);
875 raise->payload[0] = exception;
877 // throw away the stack from Sp up to the CATCH_FRAME.
881 /* Ensure that async excpetions are blocked now, so we don't get
882 * a surprise exception before we get around to executing the
885 tso->flags |= TSO_BLOCKEX;
886 if ((cf->exceptions_blocked & TSO_INTERRUPTIBLE) == 0) {
887 tso->flags &= ~TSO_INTERRUPTIBLE;
889 tso->flags |= TSO_INTERRUPTIBLE;
892 /* Put the newly-built THUNK on top of the stack, ready to execute
893 * when the thread restarts.
896 sp[-1] = (W_)&stg_enter_info;
898 tso->what_next = ThreadRunGHC;
899 IF_DEBUG(sanity, checkTSO(tso));
903 case ATOMICALLY_FRAME:
904 if (stop_at_atomically) {
905 ASSERT(tso->trec->enclosing_trec == NO_TREC);
906 stmCondemnTransaction(cap, tso -> trec);
908 // The ATOMICALLY_FRAME expects to be returned a
909 // result from the transaction, which it stores in the
910 // stack frame. Hence we arrange to return a dummy
911 // result, so that the GC doesn't get upset (#3578).
912 // Perhaps a better way would be to have a different
913 // ATOMICALLY_FRAME instance for condemned
914 // transactions, but I don't fully understand the
915 // interaction with STM invariants.
916 tso->sp[1] = (W_)&stg_NO_TREC_closure;
917 tso->sp[0] = (W_)&stg_gc_unpt_r1_info;
918 tso->what_next = ThreadRunGHC;
921 // Not stop_at_atomically... fall through and abort the
924 case CATCH_STM_FRAME:
925 case CATCH_RETRY_FRAME:
926 // IF we find an ATOMICALLY_FRAME then we abort the
927 // current transaction and propagate the exception. In
928 // this case (unlike ordinary exceptions) we do not care
929 // whether the transaction is valid or not because its
930 // possible validity cannot have caused the exception
931 // and will not be visible after the abort.
934 StgTRecHeader *trec = tso -> trec;
935 StgTRecHeader *outer = trec -> enclosing_trec;
936 debugTraceCap(DEBUG_stm, cap,
937 "found atomically block delivering async exception");
938 stmAbortTransaction(cap, trec);
939 stmFreeAbortedTRec(cap, trec);
948 // move on to the next stack frame
949 frame += stack_frame_sizeW((StgClosure *)frame);
952 // if we got here, then we stopped at stop_here
953 ASSERT(stop_here != NULL);