Fix a bug in threadStackOverflow() (maybe #5214)
[ghc.git] / rts / Threads.c
1 /* ---------------------------------------------------------------------------
2 *
3 * (c) The GHC Team, 2006
4 *
5 * Thread-related functionality
6 *
7 * --------------------------------------------------------------------------*/
8
9 #include "PosixSource.h"
10 #include "Rts.h"
11
12 #include "Capability.h"
13 #include "Updates.h"
14 #include "Threads.h"
15 #include "STM.h"
16 #include "Schedule.h"
17 #include "Trace.h"
18 #include "ThreadLabels.h"
19 #include "Updates.h"
20 #include "Messages.h"
21 #include "RaiseAsync.h"
22 #include "Prelude.h"
23 #include "Printer.h"
24 #include "sm/Sanity.h"
25 #include "sm/Storage.h"
26
27 #include <string.h>
28
29 /* Next thread ID to allocate.
30 * LOCK: sched_mutex
31 */
32 static StgThreadID next_thread_id = 1;
33
34 /* The smallest stack size that makes any sense is:
35 * RESERVED_STACK_WORDS (so we can get back from the stack overflow)
36 * + sizeofW(StgStopFrame) (the stg_stop_thread_info frame)
37 * + 1 (the closure to enter)
38 * + 1 (stg_ap_v_ret)
39 * + 1 (spare slot req'd by stg_ap_v_ret)
40 *
41 * A thread with this stack will bomb immediately with a stack
42 * overflow, which will increase its stack size.
43 */
44 #define MIN_STACK_WORDS (RESERVED_STACK_WORDS + sizeofW(StgStopFrame) + 3)
45
46 /* ---------------------------------------------------------------------------
47 Create a new thread.
48
49 The new thread starts with the given stack size. Before the
50 scheduler can run, however, this thread needs to have a closure
51 (and possibly some arguments) pushed on its stack. See
52 pushClosure() in Schedule.h.
53
54 createGenThread() and createIOThread() (in SchedAPI.h) are
55 convenient packaged versions of this function.
56
57 currently pri (priority) is only used in a GRAN setup -- HWL
58 ------------------------------------------------------------------------ */
59 StgTSO *
60 createThread(Capability *cap, nat size)
61 {
62 StgTSO *tso;
63 StgStack *stack;
64 nat stack_size;
65
66 /* sched_mutex is *not* required */
67
68 /* catch ridiculously small stack sizes */
69 if (size < MIN_STACK_WORDS + sizeofW(StgStack)) {
70 size = MIN_STACK_WORDS + sizeofW(StgStack);
71 }
72
73 /* The size argument we are given includes all the per-thread
74 * overheads:
75 *
76 * - The TSO structure
77 * - The STACK header
78 *
79 * This is so that we can use a nice round power of 2 for the
80 * default stack size (e.g. 1k), and if we're allocating lots of
81 * threads back-to-back they'll fit nicely in a block. It's a bit
82 * of a benchmark hack, but it doesn't do any harm.
83 */
84 stack_size = round_to_mblocks(size - sizeofW(StgTSO));
85 stack = (StgStack *)allocate(cap, stack_size);
86 TICK_ALLOC_STACK(stack_size);
87 SET_HDR(stack, &stg_STACK_info, CCS_SYSTEM);
88 stack->stack_size = stack_size - sizeofW(StgStack);
89 stack->sp = stack->stack + stack->stack_size;
90 stack->dirty = 1;
91
92 tso = (StgTSO *)allocate(cap, sizeofW(StgTSO));
93 TICK_ALLOC_TSO();
94 SET_HDR(tso, &stg_TSO_info, CCS_SYSTEM);
95
96 // Always start with the compiled code evaluator
97 tso->what_next = ThreadRunGHC;
98 tso->why_blocked = NotBlocked;
99 tso->block_info.closure = (StgClosure *)END_TSO_QUEUE;
100 tso->blocked_exceptions = END_BLOCKED_EXCEPTIONS_QUEUE;
101 tso->bq = (StgBlockingQueue *)END_TSO_QUEUE;
102 tso->flags = 0;
103 tso->dirty = 1;
104 tso->_link = END_TSO_QUEUE;
105
106 tso->saved_errno = 0;
107 tso->bound = NULL;
108 tso->cap = cap;
109
110 tso->stackobj = stack;
111 tso->tot_stack_size = stack->stack_size;
112
113 tso->trec = NO_TREC;
114
115 #ifdef PROFILING
116 tso->prof.cccs = CCS_MAIN;
117 #endif
118
119 // put a stop frame on the stack
120 stack->sp -= sizeofW(StgStopFrame);
121 SET_HDR((StgClosure*)stack->sp,
122 (StgInfoTable *)&stg_stop_thread_info,CCS_SYSTEM);
123
124 /* Link the new thread on the global thread list.
125 */
126 ACQUIRE_LOCK(&sched_mutex);
127 tso->id = next_thread_id++; // while we have the mutex
128 tso->global_link = g0->threads;
129 g0->threads = tso;
130 RELEASE_LOCK(&sched_mutex);
131
132 // ToDo: report the stack size in the event?
133 traceEventCreateThread(cap, tso);
134
135 return tso;
136 }
137
138 /* ---------------------------------------------------------------------------
139 * Comparing Thread ids.
140 *
141 * This is used from STG land in the implementation of the
142 * instances of Eq/Ord for ThreadIds.
143 * ------------------------------------------------------------------------ */
144
145 int
146 cmp_thread(StgPtr tso1, StgPtr tso2)
147 {
148 StgThreadID id1 = ((StgTSO *)tso1)->id;
149 StgThreadID id2 = ((StgTSO *)tso2)->id;
150
151 if (id1 < id2) return (-1);
152 if (id1 > id2) return 1;
153 return 0;
154 }
155
156 /* ---------------------------------------------------------------------------
157 * Fetching the ThreadID from an StgTSO.
158 *
159 * This is used in the implementation of Show for ThreadIds.
160 * ------------------------------------------------------------------------ */
161 int
162 rts_getThreadId(StgPtr tso)
163 {
164 return ((StgTSO *)tso)->id;
165 }
166
167 /* -----------------------------------------------------------------------------
168 Remove a thread from a queue.
169 Fails fatally if the TSO is not on the queue.
170 -------------------------------------------------------------------------- */
171
172 rtsBool // returns True if we modified queue
173 removeThreadFromQueue (Capability *cap, StgTSO **queue, StgTSO *tso)
174 {
175 StgTSO *t, *prev;
176
177 prev = NULL;
178 for (t = *queue; t != END_TSO_QUEUE; prev = t, t = t->_link) {
179 if (t == tso) {
180 if (prev) {
181 setTSOLink(cap,prev,t->_link);
182 t->_link = END_TSO_QUEUE;
183 return rtsFalse;
184 } else {
185 *queue = t->_link;
186 t->_link = END_TSO_QUEUE;
187 return rtsTrue;
188 }
189 }
190 }
191 barf("removeThreadFromQueue: not found");
192 }
193
194 rtsBool // returns True if we modified head or tail
195 removeThreadFromDeQueue (Capability *cap,
196 StgTSO **head, StgTSO **tail, StgTSO *tso)
197 {
198 StgTSO *t, *prev;
199 rtsBool flag = rtsFalse;
200
201 prev = NULL;
202 for (t = *head; t != END_TSO_QUEUE; prev = t, t = t->_link) {
203 if (t == tso) {
204 if (prev) {
205 setTSOLink(cap,prev,t->_link);
206 flag = rtsFalse;
207 } else {
208 *head = t->_link;
209 flag = rtsTrue;
210 }
211 t->_link = END_TSO_QUEUE;
212 if (*tail == tso) {
213 if (prev) {
214 *tail = prev;
215 } else {
216 *tail = END_TSO_QUEUE;
217 }
218 return rtsTrue;
219 } else {
220 return flag;
221 }
222 }
223 }
224 barf("removeThreadFromMVarQueue: not found");
225 }
226
227 /* ----------------------------------------------------------------------------
228 tryWakeupThread()
229
230 Attempt to wake up a thread. tryWakeupThread is idempotent: it is
231 always safe to call it too many times, but it is not safe in
232 general to omit a call.
233
234 ------------------------------------------------------------------------- */
235
236 void
237 tryWakeupThread (Capability *cap, StgTSO *tso)
238 {
239 traceEventThreadWakeup (cap, tso, tso->cap->no);
240
241 #ifdef THREADED_RTS
242 if (tso->cap != cap)
243 {
244 MessageWakeup *msg;
245 msg = (MessageWakeup *)allocate(cap,sizeofW(MessageWakeup));
246 SET_HDR(msg, &stg_MSG_TRY_WAKEUP_info, CCS_SYSTEM);
247 msg->tso = tso;
248 sendMessage(cap, tso->cap, (Message*)msg);
249 debugTraceCap(DEBUG_sched, cap, "message: try wakeup thread %ld on cap %d",
250 (lnat)tso->id, tso->cap->no);
251 return;
252 }
253 #endif
254
255 switch (tso->why_blocked)
256 {
257 case BlockedOnMVar:
258 {
259 if (tso->_link == END_TSO_QUEUE) {
260 tso->block_info.closure = (StgClosure*)END_TSO_QUEUE;
261 goto unblock;
262 } else {
263 return;
264 }
265 }
266
267 case BlockedOnMsgThrowTo:
268 {
269 const StgInfoTable *i;
270
271 i = lockClosure(tso->block_info.closure);
272 unlockClosure(tso->block_info.closure, i);
273 if (i != &stg_MSG_NULL_info) {
274 debugTraceCap(DEBUG_sched, cap, "thread %ld still blocked on throwto (%p)",
275 (lnat)tso->id, tso->block_info.throwto->header.info);
276 return;
277 }
278
279 // remove the block frame from the stack
280 ASSERT(tso->stackobj->sp[0] == (StgWord)&stg_block_throwto_info);
281 tso->stackobj->sp += 3;
282 goto unblock;
283 }
284
285 case BlockedOnBlackHole:
286 case BlockedOnSTM:
287 case ThreadMigrating:
288 goto unblock;
289
290 default:
291 // otherwise, do nothing
292 return;
293 }
294
295 unblock:
296 // just run the thread now, if the BH is not really available,
297 // we'll block again.
298 tso->why_blocked = NotBlocked;
299 appendToRunQueue(cap,tso);
300
301 // We used to set the context switch flag here, which would
302 // trigger a context switch a short time in the future (at the end
303 // of the current nursery block). The idea is that we have just
304 // woken up a thread, so we may need to load-balance and migrate
305 // threads to other CPUs. On the other hand, setting the context
306 // switch flag here unfairly penalises the current thread by
307 // yielding its time slice too early.
308 //
309 // The synthetic benchmark nofib/smp/chan can be used to show the
310 // difference quite clearly.
311
312 // cap->context_switch = 1;
313 }
314
315 /* ----------------------------------------------------------------------------
316 migrateThread
317 ------------------------------------------------------------------------- */
318
319 void
320 migrateThread (Capability *from, StgTSO *tso, Capability *to)
321 {
322 traceEventMigrateThread (from, tso, to->no);
323 // ThreadMigrating tells the target cap that it needs to be added to
324 // the run queue when it receives the MSG_TRY_WAKEUP.
325 tso->why_blocked = ThreadMigrating;
326 tso->cap = to;
327 tryWakeupThread(from, tso);
328 }
329
330 /* ----------------------------------------------------------------------------
331 awakenBlockedQueue
332
333 wakes up all the threads on the specified queue.
334 ------------------------------------------------------------------------- */
335
336 void
337 wakeBlockingQueue(Capability *cap, StgBlockingQueue *bq)
338 {
339 MessageBlackHole *msg;
340 const StgInfoTable *i;
341
342 ASSERT(bq->header.info == &stg_BLOCKING_QUEUE_DIRTY_info ||
343 bq->header.info == &stg_BLOCKING_QUEUE_CLEAN_info );
344
345 for (msg = bq->queue; msg != (MessageBlackHole*)END_TSO_QUEUE;
346 msg = msg->link) {
347 i = msg->header.info;
348 if (i != &stg_IND_info) {
349 ASSERT(i == &stg_MSG_BLACKHOLE_info);
350 tryWakeupThread(cap,msg->tso);
351 }
352 }
353
354 // overwrite the BQ with an indirection so it will be
355 // collected at the next GC.
356 #if defined(DEBUG) && !defined(THREADED_RTS)
357 // XXX FILL_SLOP, but not if THREADED_RTS because in that case
358 // another thread might be looking at this BLOCKING_QUEUE and
359 // checking the owner field at the same time.
360 bq->bh = 0; bq->queue = 0; bq->owner = 0;
361 #endif
362 OVERWRITE_INFO(bq, &stg_IND_info);
363 }
364
365 // If we update a closure that we know we BLACKHOLE'd, and the closure
366 // no longer points to the current TSO as its owner, then there may be
367 // an orphaned BLOCKING_QUEUE closure with blocked threads attached to
368 // it. We therefore traverse the BLOCKING_QUEUEs attached to the
369 // current TSO to see if any can now be woken up.
370 void
371 checkBlockingQueues (Capability *cap, StgTSO *tso)
372 {
373 StgBlockingQueue *bq, *next;
374 StgClosure *p;
375
376 debugTraceCap(DEBUG_sched, cap,
377 "collision occurred; checking blocking queues for thread %ld",
378 (lnat)tso->id);
379
380 for (bq = tso->bq; bq != (StgBlockingQueue*)END_TSO_QUEUE; bq = next) {
381 next = bq->link;
382
383 if (bq->header.info == &stg_IND_info) {
384 // ToDo: could short it out right here, to avoid
385 // traversing this IND multiple times.
386 continue;
387 }
388
389 p = bq->bh;
390
391 if (p->header.info != &stg_BLACKHOLE_info ||
392 ((StgInd *)p)->indirectee != (StgClosure*)bq)
393 {
394 wakeBlockingQueue(cap,bq);
395 }
396 }
397 }
398
399 /* ----------------------------------------------------------------------------
400 updateThunk
401
402 Update a thunk with a value. In order to do this, we need to know
403 which TSO owns (or is evaluating) the thunk, in case we need to
404 awaken any threads that are blocked on it.
405 ------------------------------------------------------------------------- */
406
407 void
408 updateThunk (Capability *cap, StgTSO *tso, StgClosure *thunk, StgClosure *val)
409 {
410 StgClosure *v;
411 StgTSO *owner;
412 const StgInfoTable *i;
413
414 i = thunk->header.info;
415 if (i != &stg_BLACKHOLE_info &&
416 i != &stg_CAF_BLACKHOLE_info &&
417 i != &__stg_EAGER_BLACKHOLE_info &&
418 i != &stg_WHITEHOLE_info) {
419 updateWithIndirection(cap, thunk, val);
420 return;
421 }
422
423 v = ((StgInd*)thunk)->indirectee;
424
425 updateWithIndirection(cap, thunk, val);
426
427 i = v->header.info;
428 if (i == &stg_TSO_info) {
429 owner = (StgTSO*)v;
430 if (owner != tso) {
431 checkBlockingQueues(cap, tso);
432 }
433 return;
434 }
435
436 if (i != &stg_BLOCKING_QUEUE_CLEAN_info &&
437 i != &stg_BLOCKING_QUEUE_DIRTY_info) {
438 checkBlockingQueues(cap, tso);
439 return;
440 }
441
442 owner = ((StgBlockingQueue*)v)->owner;
443
444 if (owner != tso) {
445 checkBlockingQueues(cap, tso);
446 } else {
447 wakeBlockingQueue(cap, (StgBlockingQueue*)v);
448 }
449 }
450
451 /* ---------------------------------------------------------------------------
452 * rtsSupportsBoundThreads(): is the RTS built to support bound threads?
453 * used by Control.Concurrent for error checking.
454 * ------------------------------------------------------------------------- */
455
456 HsBool
457 rtsSupportsBoundThreads(void)
458 {
459 #if defined(THREADED_RTS)
460 return HS_BOOL_TRUE;
461 #else
462 return HS_BOOL_FALSE;
463 #endif
464 }
465
466 /* ---------------------------------------------------------------------------
467 * isThreadBound(tso): check whether tso is bound to an OS thread.
468 * ------------------------------------------------------------------------- */
469
470 StgBool
471 isThreadBound(StgTSO* tso USED_IF_THREADS)
472 {
473 #if defined(THREADED_RTS)
474 return (tso->bound != NULL);
475 #endif
476 return rtsFalse;
477 }
478
479 /* -----------------------------------------------------------------------------
480 Stack overflow
481
482 If the thread has reached its maximum stack size, then raise the
483 StackOverflow exception in the offending thread. Otherwise
484 relocate the TSO into a larger chunk of memory and adjust its stack
485 size appropriately.
486 -------------------------------------------------------------------------- */
487
488 void
489 threadStackOverflow (Capability *cap, StgTSO *tso)
490 {
491 StgStack *new_stack, *old_stack;
492 StgUnderflowFrame *frame;
493 lnat chunk_size;
494
495 IF_DEBUG(sanity,checkTSO(tso));
496
497 if (tso->tot_stack_size >= RtsFlags.GcFlags.maxStkSize
498 && !(tso->flags & TSO_BLOCKEX)) {
499 // NB. never raise a StackOverflow exception if the thread is
500 // inside Control.Exceptino.block. It is impractical to protect
501 // against stack overflow exceptions, since virtually anything
502 // can raise one (even 'catch'), so this is the only sensible
503 // thing to do here. See bug #767.
504 //
505
506 if (tso->flags & TSO_SQUEEZED) {
507 return;
508 }
509 // #3677: In a stack overflow situation, stack squeezing may
510 // reduce the stack size, but we don't know whether it has been
511 // reduced enough for the stack check to succeed if we try
512 // again. Fortunately stack squeezing is idempotent, so all we
513 // need to do is record whether *any* squeezing happened. If we
514 // are at the stack's absolute -K limit, and stack squeezing
515 // happened, then we try running the thread again. The
516 // TSO_SQUEEZED flag is set by threadPaused() to tell us whether
517 // squeezing happened or not.
518
519 debugTrace(DEBUG_gc,
520 "threadStackOverflow of TSO %ld (%p): stack too large (now %ld; max is %ld)",
521 (long)tso->id, tso, (long)tso->stackobj->stack_size,
522 RtsFlags.GcFlags.maxStkSize);
523 IF_DEBUG(gc,
524 /* If we're debugging, just print out the top of the stack */
525 printStackChunk(tso->stackobj->sp,
526 stg_min(tso->stackobj->stack + tso->stackobj->stack_size,
527 tso->stackobj->sp+64)));
528
529 // Send this thread the StackOverflow exception
530 throwToSingleThreaded(cap, tso, (StgClosure *)stackOverflow_closure);
531 }
532
533
534 // We also want to avoid enlarging the stack if squeezing has
535 // already released some of it. However, we don't want to get into
536 // a pathalogical situation where a thread has a nearly full stack
537 // (near its current limit, but not near the absolute -K limit),
538 // keeps allocating a little bit, squeezing removes a little bit,
539 // and then it runs again. So to avoid this, if we squeezed *and*
540 // there is still less than BLOCK_SIZE_W words free, then we enlarge
541 // the stack anyway.
542 if ((tso->flags & TSO_SQUEEZED) &&
543 ((W_)(tso->stackobj->sp - tso->stackobj->stack) >= BLOCK_SIZE_W)) {
544 return;
545 }
546
547 old_stack = tso->stackobj;
548
549 // If we used less than half of the previous stack chunk, then we
550 // must have failed a stack check for a large amount of stack. In
551 // this case we allocate a double-sized chunk to try to
552 // accommodate the large stack request. If that also fails, the
553 // next chunk will be 4x normal size, and so on.
554 //
555 // It would be better to have the mutator tell us how much stack
556 // was needed, as we do with heap allocations, but this works for
557 // now.
558 //
559 if (old_stack->sp > old_stack->stack + old_stack->stack_size / 2)
560 {
561 chunk_size = 2 * (old_stack->stack_size + sizeofW(StgStack));
562 }
563 else
564 {
565 chunk_size = RtsFlags.GcFlags.stkChunkSize;
566 }
567
568 debugTraceCap(DEBUG_sched, cap,
569 "allocating new stack chunk of size %d bytes",
570 chunk_size * sizeof(W_));
571
572 new_stack = (StgStack*) allocate(cap, chunk_size);
573 SET_HDR(new_stack, &stg_STACK_info, CCS_SYSTEM);
574 TICK_ALLOC_STACK(chunk_size);
575
576 new_stack->dirty = 0; // begin clean, we'll mark it dirty below
577 new_stack->stack_size = chunk_size - sizeofW(StgStack);
578 new_stack->sp = new_stack->stack + new_stack->stack_size;
579
580 tso->tot_stack_size += new_stack->stack_size;
581
582 {
583 StgWord *sp;
584 nat chunk_words, size;
585
586 // find the boundary of the chunk of old stack we're going to
587 // copy to the new stack. We skip over stack frames until we
588 // reach the smaller of
589 //
590 // * the chunk buffer size (+RTS -kb)
591 // * the end of the old stack
592 //
593 for (sp = old_stack->sp;
594 sp < stg_min(old_stack->sp + RtsFlags.GcFlags.stkChunkBufferSize,
595 old_stack->stack + old_stack->stack_size); )
596 {
597 size = stack_frame_sizeW((StgClosure*)sp);
598
599 // if including this frame would exceed the size of the
600 // new stack (taking into account the underflow frame),
601 // then stop at the previous frame.
602 if (sp + size > old_stack->stack + (new_stack->stack_size -
603 sizeofW(StgUnderflowFrame))) {
604 break;
605 }
606 sp += size;
607 }
608
609 if (sp == old_stack->stack + old_stack->stack_size) {
610 //
611 // the old stack chunk is now empty, so we do *not* insert
612 // an underflow frame pointing back to it. There are two
613 // cases: either the old stack chunk was the last one, in
614 // which case it ends with a STOP_FRAME, or it is not the
615 // last one, and it already ends with an UNDERFLOW_FRAME
616 // pointing to the previous chunk. In the latter case, we
617 // will copy the UNDERFLOW_FRAME into the new stack chunk.
618 // In both cases, the old chunk will be subsequently GC'd.
619 //
620 // With the default settings, -ki1k -kb1k, this means the
621 // first stack chunk will be discarded after the first
622 // overflow, being replaced by a non-moving 32k chunk.
623 //
624 } else {
625 new_stack->sp -= sizeofW(StgUnderflowFrame);
626 frame = (StgUnderflowFrame*)new_stack->sp;
627 frame->info = &stg_stack_underflow_frame_info;
628 frame->next_chunk = old_stack;
629 }
630
631 // copy the stack chunk between tso->sp and sp to
632 // new_tso->sp + (tso->sp - sp)
633 chunk_words = sp - old_stack->sp;
634
635 memcpy(/* dest */ new_stack->sp - chunk_words,
636 /* source */ old_stack->sp,
637 /* size */ chunk_words * sizeof(W_));
638
639 old_stack->sp += chunk_words;
640 new_stack->sp -= chunk_words;
641 }
642
643 tso->stackobj = new_stack;
644
645 // we're about to run it, better mark it dirty
646 dirty_STACK(cap, new_stack);
647
648 IF_DEBUG(sanity,checkTSO(tso));
649 // IF_DEBUG(scheduler,printTSO(new_tso));
650 }
651
652
653 /* ---------------------------------------------------------------------------
654 Stack underflow - called from the stg_stack_underflow_info frame
655 ------------------------------------------------------------------------ */
656
657 nat // returns offset to the return address
658 threadStackUnderflow (Capability *cap, StgTSO *tso)
659 {
660 StgStack *new_stack, *old_stack;
661 StgUnderflowFrame *frame;
662 nat retvals;
663
664 debugTraceCap(DEBUG_sched, cap, "stack underflow");
665
666 old_stack = tso->stackobj;
667
668 frame = (StgUnderflowFrame*)(old_stack->stack + old_stack->stack_size
669 - sizeofW(StgUnderflowFrame));
670 ASSERT(frame->info == &stg_stack_underflow_frame_info);
671
672 new_stack = (StgStack*)frame->next_chunk;
673 tso->stackobj = new_stack;
674
675 retvals = (P_)frame - old_stack->sp;
676 if (retvals != 0)
677 {
678 // we have some return values to copy to the old stack
679 if ((nat)(new_stack->sp - new_stack->stack) < retvals)
680 {
681 barf("threadStackUnderflow: not enough space for return values");
682 }
683
684 new_stack->sp -= retvals;
685
686 memcpy(/* dest */ new_stack->sp,
687 /* src */ old_stack->sp,
688 /* size */ retvals * sizeof(W_));
689 }
690
691 // empty the old stack. The GC may still visit this object
692 // because it is on the mutable list.
693 old_stack->sp = old_stack->stack + old_stack->stack_size;
694
695 // restore the stack parameters, and update tot_stack_size
696 tso->tot_stack_size -= old_stack->stack_size;
697
698 // we're about to run it, better mark it dirty
699 dirty_STACK(cap, new_stack);
700
701 return retvals;
702 }
703
704 /* ----------------------------------------------------------------------------
705 * Debugging: why is a thread blocked
706 * ------------------------------------------------------------------------- */
707
708 #if DEBUG
709 void
710 printThreadBlockage(StgTSO *tso)
711 {
712 switch (tso->why_blocked) {
713 #if defined(mingw32_HOST_OS)
714 case BlockedOnDoProc:
715 debugBelch("is blocked on proc (request: %u)", tso->block_info.async_result->reqID);
716 break;
717 #endif
718 #if !defined(THREADED_RTS)
719 case BlockedOnRead:
720 debugBelch("is blocked on read from fd %d", (int)(tso->block_info.fd));
721 break;
722 case BlockedOnWrite:
723 debugBelch("is blocked on write to fd %d", (int)(tso->block_info.fd));
724 break;
725 case BlockedOnDelay:
726 debugBelch("is blocked until %ld", (long)(tso->block_info.target));
727 break;
728 #endif
729 case BlockedOnMVar:
730 debugBelch("is blocked on an MVar @ %p", tso->block_info.closure);
731 break;
732 case BlockedOnBlackHole:
733 debugBelch("is blocked on a black hole %p",
734 ((StgBlockingQueue*)tso->block_info.bh->bh));
735 break;
736 case BlockedOnMsgThrowTo:
737 debugBelch("is blocked on a throwto message");
738 break;
739 case NotBlocked:
740 debugBelch("is not blocked");
741 break;
742 case ThreadMigrating:
743 debugBelch("is runnable, but not on the run queue");
744 break;
745 case BlockedOnCCall:
746 debugBelch("is blocked on an external call");
747 break;
748 case BlockedOnCCall_Interruptible:
749 debugBelch("is blocked on an external call (but may be interrupted)");
750 break;
751 case BlockedOnSTM:
752 debugBelch("is blocked on an STM operation");
753 break;
754 default:
755 barf("printThreadBlockage: strange tso->why_blocked: %d for TSO %d (%d)",
756 tso->why_blocked, tso->id, tso);
757 }
758 }
759
760
761 void
762 printThreadStatus(StgTSO *t)
763 {
764 debugBelch("\tthread %4lu @ %p ", (unsigned long)t->id, (void *)t);
765 {
766 void *label = lookupThreadLabel(t->id);
767 if (label) debugBelch("[\"%s\"] ",(char *)label);
768 }
769 switch (t->what_next) {
770 case ThreadKilled:
771 debugBelch("has been killed");
772 break;
773 case ThreadComplete:
774 debugBelch("has completed");
775 break;
776 default:
777 printThreadBlockage(t);
778 }
779 if (t->dirty) {
780 debugBelch(" (TSO_DIRTY)");
781 }
782 debugBelch("\n");
783 }
784
785 void
786 printAllThreads(void)
787 {
788 StgTSO *t, *next;
789 nat i, g;
790 Capability *cap;
791
792 debugBelch("all threads:\n");
793
794 for (i = 0; i < n_capabilities; i++) {
795 cap = &capabilities[i];
796 debugBelch("threads on capability %d:\n", cap->no);
797 for (t = cap->run_queue_hd; t != END_TSO_QUEUE; t = t->_link) {
798 printThreadStatus(t);
799 }
800 }
801
802 debugBelch("other threads:\n");
803 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
804 for (t = generations[g].threads; t != END_TSO_QUEUE; t = next) {
805 if (t->why_blocked != NotBlocked) {
806 printThreadStatus(t);
807 }
808 next = t->global_link;
809 }
810 }
811 }
812
813 // useful from gdb
814 void
815 printThreadQueue(StgTSO *t)
816 {
817 nat i = 0;
818 for (; t != END_TSO_QUEUE; t = t->_link) {
819 printThreadStatus(t);
820 i++;
821 }
822 debugBelch("%d threads on queue\n", i);
823 }
824
825 #endif /* DEBUG */