Scale columns in cost-centre-stack report to their contents
[ghc.git] / rts / Schedule.c
1 /* ---------------------------------------------------------------------------
2 *
3 * (c) The GHC Team, 1998-2006
4 *
5 * The scheduler and thread-related functionality
6 *
7 * --------------------------------------------------------------------------*/
8
9 #include "PosixSource.h"
10 #define KEEP_LOCKCLOSURE
11 #include "Rts.h"
12
13 #include "sm/Storage.h"
14 #include "RtsUtils.h"
15 #include "StgRun.h"
16 #include "Schedule.h"
17 #include "Interpreter.h"
18 #include "Printer.h"
19 #include "RtsSignals.h"
20 #include "sm/Sanity.h"
21 #include "Stats.h"
22 #include "STM.h"
23 #include "Prelude.h"
24 #include "ThreadLabels.h"
25 #include "Updates.h"
26 #include "Proftimer.h"
27 #include "ProfHeap.h"
28 #include "Weak.h"
29 #include "sm/GC.h" // waitForGcThreads, releaseGCThreads, N
30 #include "Sparks.h"
31 #include "Capability.h"
32 #include "Task.h"
33 #include "AwaitEvent.h"
34 #if defined(mingw32_HOST_OS)
35 #include "win32/IOManager.h"
36 #endif
37 #include "Trace.h"
38 #include "RaiseAsync.h"
39 #include "Threads.h"
40 #include "Timer.h"
41 #include "ThreadPaused.h"
42 #include "Messages.h"
43
44 #ifdef HAVE_SYS_TYPES_H
45 #include <sys/types.h>
46 #endif
47 #ifdef HAVE_UNISTD_H
48 #include <unistd.h>
49 #endif
50
51 #include <string.h>
52 #include <stdlib.h>
53 #include <stdarg.h>
54
55 #ifdef HAVE_ERRNO_H
56 #include <errno.h>
57 #endif
58
59 #ifdef TRACING
60 #include "eventlog/EventLog.h"
61 #endif
62 /* -----------------------------------------------------------------------------
63 * Global variables
64 * -------------------------------------------------------------------------- */
65
66 #if !defined(THREADED_RTS)
67 // Blocked/sleeping thrads
68 StgTSO *blocked_queue_hd = NULL;
69 StgTSO *blocked_queue_tl = NULL;
70 StgTSO *sleeping_queue = NULL; // perhaps replace with a hash table?
71 #endif
72
73 /* Set to true when the latest garbage collection failed to reclaim
74 * enough space, and the runtime should proceed to shut itself down in
75 * an orderly fashion (emitting profiling info etc.)
76 */
77 rtsBool heap_overflow = rtsFalse;
78
79 /* flag that tracks whether we have done any execution in this time slice.
80 * LOCK: currently none, perhaps we should lock (but needs to be
81 * updated in the fast path of the scheduler).
82 *
83 * NB. must be StgWord, we do xchg() on it.
84 */
85 volatile StgWord recent_activity = ACTIVITY_YES;
86
87 /* if this flag is set as well, give up execution
88 * LOCK: none (changes monotonically)
89 */
90 volatile StgWord sched_state = SCHED_RUNNING;
91
92 /* This is used in `TSO.h' and gcc 2.96 insists that this variable actually
93 * exists - earlier gccs apparently didn't.
94 * -= chak
95 */
96 StgTSO dummy_tso;
97
98 /*
99 * Set to TRUE when entering a shutdown state (via shutdownHaskellAndExit()) --
100 * in an MT setting, needed to signal that a worker thread shouldn't hang around
101 * in the scheduler when it is out of work.
102 */
103 rtsBool shutting_down_scheduler = rtsFalse;
104
105 /*
106 * This mutex protects most of the global scheduler data in
107 * the THREADED_RTS runtime.
108 */
109 #if defined(THREADED_RTS)
110 Mutex sched_mutex;
111 #endif
112
113 #if !defined(mingw32_HOST_OS)
114 #define FORKPROCESS_PRIMOP_SUPPORTED
115 #endif
116
117 /* -----------------------------------------------------------------------------
118 * static function prototypes
119 * -------------------------------------------------------------------------- */
120
121 static Capability *schedule (Capability *initialCapability, Task *task);
122
123 //
124 // These function all encapsulate parts of the scheduler loop, and are
125 // abstracted only to make the structure and control flow of the
126 // scheduler clearer.
127 //
128 static void schedulePreLoop (void);
129 static void scheduleFindWork (Capability *cap);
130 #if defined(THREADED_RTS)
131 static void scheduleYield (Capability **pcap, Task *task);
132 #endif
133 static void scheduleStartSignalHandlers (Capability *cap);
134 static void scheduleCheckBlockedThreads (Capability *cap);
135 static void scheduleProcessInbox(Capability *cap);
136 static void scheduleDetectDeadlock (Capability *cap, Task *task);
137 static void schedulePushWork(Capability *cap, Task *task);
138 #if defined(THREADED_RTS)
139 static void scheduleActivateSpark(Capability *cap);
140 #endif
141 static void schedulePostRunThread(Capability *cap, StgTSO *t);
142 static rtsBool scheduleHandleHeapOverflow( Capability *cap, StgTSO *t );
143 static rtsBool scheduleHandleYield( Capability *cap, StgTSO *t,
144 nat prev_what_next );
145 static void scheduleHandleThreadBlocked( StgTSO *t );
146 static rtsBool scheduleHandleThreadFinished( Capability *cap, Task *task,
147 StgTSO *t );
148 static rtsBool scheduleNeedHeapProfile(rtsBool ready_to_gc);
149 static Capability *scheduleDoGC(Capability *cap, Task *task,
150 rtsBool force_major);
151
152 static void deleteThread (Capability *cap, StgTSO *tso);
153 static void deleteAllThreads (Capability *cap);
154
155 #ifdef FORKPROCESS_PRIMOP_SUPPORTED
156 static void deleteThread_(Capability *cap, StgTSO *tso);
157 #endif
158
159 /* ---------------------------------------------------------------------------
160 Main scheduling loop.
161
162 We use round-robin scheduling, each thread returning to the
163 scheduler loop when one of these conditions is detected:
164
165 * out of heap space
166 * timer expires (thread yields)
167 * thread blocks
168 * thread ends
169 * stack overflow
170
171 GRAN version:
172 In a GranSim setup this loop iterates over the global event queue.
173 This revolves around the global event queue, which determines what
174 to do next. Therefore, it's more complicated than either the
175 concurrent or the parallel (GUM) setup.
176 This version has been entirely removed (JB 2008/08).
177
178 GUM version:
179 GUM iterates over incoming messages.
180 It starts with nothing to do (thus CurrentTSO == END_TSO_QUEUE),
181 and sends out a fish whenever it has nothing to do; in-between
182 doing the actual reductions (shared code below) it processes the
183 incoming messages and deals with delayed operations
184 (see PendingFetches).
185 This is not the ugliest code you could imagine, but it's bloody close.
186
187 (JB 2008/08) This version was formerly indicated by a PP-Flag PAR,
188 now by PP-flag PARALLEL_HASKELL. The Eden RTS (in GHC-6.x) uses it,
189 as well as future GUM versions. This file has been refurbished to
190 only contain valid code, which is however incomplete, refers to
191 invalid includes etc.
192
193 ------------------------------------------------------------------------ */
194
195 static Capability *
196 schedule (Capability *initialCapability, Task *task)
197 {
198 StgTSO *t;
199 Capability *cap;
200 StgThreadReturnCode ret;
201 nat prev_what_next;
202 rtsBool ready_to_gc;
203 #if defined(THREADED_RTS)
204 rtsBool first = rtsTrue;
205 #endif
206
207 cap = initialCapability;
208
209 // Pre-condition: this task owns initialCapability.
210 // The sched_mutex is *NOT* held
211 // NB. on return, we still hold a capability.
212
213 debugTrace (DEBUG_sched, "cap %d: schedule()", initialCapability->no);
214
215 schedulePreLoop();
216
217 // -----------------------------------------------------------
218 // Scheduler loop starts here:
219
220 while (1) {
221
222 // Check whether we have re-entered the RTS from Haskell without
223 // going via suspendThread()/resumeThread (i.e. a 'safe' foreign
224 // call).
225 if (cap->in_haskell) {
226 errorBelch("schedule: re-entered unsafely.\n"
227 " Perhaps a 'foreign import unsafe' should be 'safe'?");
228 stg_exit(EXIT_FAILURE);
229 }
230
231 // The interruption / shutdown sequence.
232 //
233 // In order to cleanly shut down the runtime, we want to:
234 // * make sure that all main threads return to their callers
235 // with the state 'Interrupted'.
236 // * clean up all OS threads assocated with the runtime
237 // * free all memory etc.
238 //
239 // So the sequence for ^C goes like this:
240 //
241 // * ^C handler sets sched_state := SCHED_INTERRUPTING and
242 // arranges for some Capability to wake up
243 //
244 // * all threads in the system are halted, and the zombies are
245 // placed on the run queue for cleaning up. We acquire all
246 // the capabilities in order to delete the threads, this is
247 // done by scheduleDoGC() for convenience (because GC already
248 // needs to acquire all the capabilities). We can't kill
249 // threads involved in foreign calls.
250 //
251 // * somebody calls shutdownHaskell(), which calls exitScheduler()
252 //
253 // * sched_state := SCHED_SHUTTING_DOWN
254 //
255 // * all workers exit when the run queue on their capability
256 // drains. All main threads will also exit when their TSO
257 // reaches the head of the run queue and they can return.
258 //
259 // * eventually all Capabilities will shut down, and the RTS can
260 // exit.
261 //
262 // * We might be left with threads blocked in foreign calls,
263 // we should really attempt to kill these somehow (TODO);
264
265 switch (sched_state) {
266 case SCHED_RUNNING:
267 break;
268 case SCHED_INTERRUPTING:
269 debugTrace(DEBUG_sched, "SCHED_INTERRUPTING");
270 #if defined(THREADED_RTS)
271 discardSparksCap(cap);
272 #endif
273 /* scheduleDoGC() deletes all the threads */
274 cap = scheduleDoGC(cap,task,rtsFalse);
275
276 // after scheduleDoGC(), we must be shutting down. Either some
277 // other Capability did the final GC, or we did it above,
278 // either way we can fall through to the SCHED_SHUTTING_DOWN
279 // case now.
280 ASSERT(sched_state == SCHED_SHUTTING_DOWN);
281 // fall through
282
283 case SCHED_SHUTTING_DOWN:
284 debugTrace(DEBUG_sched, "SCHED_SHUTTING_DOWN");
285 // If we are a worker, just exit. If we're a bound thread
286 // then we will exit below when we've removed our TSO from
287 // the run queue.
288 if (!isBoundTask(task) && emptyRunQueue(cap)) {
289 return cap;
290 }
291 break;
292 default:
293 barf("sched_state: %d", sched_state);
294 }
295
296 scheduleFindWork(cap);
297
298 /* work pushing, currently relevant only for THREADED_RTS:
299 (pushes threads, wakes up idle capabilities for stealing) */
300 schedulePushWork(cap,task);
301
302 scheduleDetectDeadlock(cap,task);
303
304 #if defined(THREADED_RTS)
305 cap = task->cap; // reload cap, it might have changed
306 #endif
307
308 // Normally, the only way we can get here with no threads to
309 // run is if a keyboard interrupt received during
310 // scheduleCheckBlockedThreads() or scheduleDetectDeadlock().
311 // Additionally, it is not fatal for the
312 // threaded RTS to reach here with no threads to run.
313 //
314 // win32: might be here due to awaitEvent() being abandoned
315 // as a result of a console event having been delivered.
316
317 #if defined(THREADED_RTS)
318 if (first)
319 {
320 // XXX: ToDo
321 // // don't yield the first time, we want a chance to run this
322 // // thread for a bit, even if there are others banging at the
323 // // door.
324 // first = rtsFalse;
325 // ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
326 }
327
328 scheduleYield(&cap,task);
329
330 if (emptyRunQueue(cap)) continue; // look for work again
331 #endif
332
333 #if !defined(THREADED_RTS) && !defined(mingw32_HOST_OS)
334 if ( emptyRunQueue(cap) ) {
335 ASSERT(sched_state >= SCHED_INTERRUPTING);
336 }
337 #endif
338
339 //
340 // Get a thread to run
341 //
342 t = popRunQueue(cap);
343
344 // Sanity check the thread we're about to run. This can be
345 // expensive if there is lots of thread switching going on...
346 IF_DEBUG(sanity,checkTSO(t));
347
348 #if defined(THREADED_RTS)
349 // Check whether we can run this thread in the current task.
350 // If not, we have to pass our capability to the right task.
351 {
352 InCall *bound = t->bound;
353
354 if (bound) {
355 if (bound->task == task) {
356 // yes, the Haskell thread is bound to the current native thread
357 } else {
358 debugTrace(DEBUG_sched,
359 "thread %lu bound to another OS thread",
360 (unsigned long)t->id);
361 // no, bound to a different Haskell thread: pass to that thread
362 pushOnRunQueue(cap,t);
363 continue;
364 }
365 } else {
366 // The thread we want to run is unbound.
367 if (task->incall->tso) {
368 debugTrace(DEBUG_sched,
369 "this OS thread cannot run thread %lu",
370 (unsigned long)t->id);
371 // no, the current native thread is bound to a different
372 // Haskell thread, so pass it to any worker thread
373 pushOnRunQueue(cap,t);
374 continue;
375 }
376 }
377 }
378 #endif
379
380 // If we're shutting down, and this thread has not yet been
381 // killed, kill it now. This sometimes happens when a finalizer
382 // thread is created by the final GC, or a thread previously
383 // in a foreign call returns.
384 if (sched_state >= SCHED_INTERRUPTING &&
385 !(t->what_next == ThreadComplete || t->what_next == ThreadKilled)) {
386 deleteThread(cap,t);
387 }
388
389 /* context switches are initiated by the timer signal, unless
390 * the user specified "context switch as often as possible", with
391 * +RTS -C0
392 */
393 if (RtsFlags.ConcFlags.ctxtSwitchTicks == 0
394 && !emptyThreadQueues(cap)) {
395 cap->context_switch = 1;
396 }
397
398 run_thread:
399
400 // CurrentTSO is the thread to run. t might be different if we
401 // loop back to run_thread, so make sure to set CurrentTSO after
402 // that.
403 cap->r.rCurrentTSO = t;
404
405 startHeapProfTimer();
406
407 // ----------------------------------------------------------------------
408 // Run the current thread
409
410 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
411 ASSERT(t->cap == cap);
412 ASSERT(t->bound ? t->bound->task->cap == cap : 1);
413
414 prev_what_next = t->what_next;
415
416 errno = t->saved_errno;
417 #if mingw32_HOST_OS
418 SetLastError(t->saved_winerror);
419 #endif
420
421 cap->in_haskell = rtsTrue;
422
423 dirty_TSO(cap,t);
424 dirty_STACK(cap,t->stackobj);
425
426 #if defined(THREADED_RTS)
427 if (recent_activity == ACTIVITY_DONE_GC) {
428 // ACTIVITY_DONE_GC means we turned off the timer signal to
429 // conserve power (see #1623). Re-enable it here.
430 nat prev;
431 prev = xchg((P_)&recent_activity, ACTIVITY_YES);
432 if (prev == ACTIVITY_DONE_GC) {
433 startTimer();
434 }
435 } else if (recent_activity != ACTIVITY_INACTIVE) {
436 // If we reached ACTIVITY_INACTIVE, then don't reset it until
437 // we've done the GC. The thread running here might just be
438 // the IO manager thread that handle_tick() woke up via
439 // wakeUpRts().
440 recent_activity = ACTIVITY_YES;
441 }
442 #endif
443
444 traceEventRunThread(cap, t);
445
446 switch (prev_what_next) {
447
448 case ThreadKilled:
449 case ThreadComplete:
450 /* Thread already finished, return to scheduler. */
451 ret = ThreadFinished;
452 break;
453
454 case ThreadRunGHC:
455 {
456 StgRegTable *r;
457 r = StgRun((StgFunPtr) stg_returnToStackTop, &cap->r);
458 cap = regTableToCapability(r);
459 ret = r->rRet;
460 break;
461 }
462
463 case ThreadInterpret:
464 cap = interpretBCO(cap);
465 ret = cap->r.rRet;
466 break;
467
468 default:
469 barf("schedule: invalid what_next field");
470 }
471
472 cap->in_haskell = rtsFalse;
473
474 // The TSO might have moved, eg. if it re-entered the RTS and a GC
475 // happened. So find the new location:
476 t = cap->r.rCurrentTSO;
477
478 // And save the current errno in this thread.
479 // XXX: possibly bogus for SMP because this thread might already
480 // be running again, see code below.
481 t->saved_errno = errno;
482 #if mingw32_HOST_OS
483 // Similarly for Windows error code
484 t->saved_winerror = GetLastError();
485 #endif
486
487 if (ret == ThreadBlocked) {
488 if (t->why_blocked == BlockedOnBlackHole) {
489 StgTSO *owner = blackHoleOwner(t->block_info.bh->bh);
490 traceEventStopThread(cap, t, t->why_blocked + 6,
491 owner != NULL ? owner->id : 0);
492 } else {
493 traceEventStopThread(cap, t, t->why_blocked + 6, 0);
494 }
495 } else {
496 traceEventStopThread(cap, t, ret, 0);
497 }
498
499 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
500 ASSERT(t->cap == cap);
501
502 // ----------------------------------------------------------------------
503
504 // Costs for the scheduler are assigned to CCS_SYSTEM
505 stopHeapProfTimer();
506 #if defined(PROFILING)
507 CCCS = CCS_SYSTEM;
508 #endif
509
510 schedulePostRunThread(cap,t);
511
512 ready_to_gc = rtsFalse;
513
514 switch (ret) {
515 case HeapOverflow:
516 ready_to_gc = scheduleHandleHeapOverflow(cap,t);
517 break;
518
519 case StackOverflow:
520 // just adjust the stack for this thread, then pop it back
521 // on the run queue.
522 threadStackOverflow(cap, t);
523 pushOnRunQueue(cap,t);
524 break;
525
526 case ThreadYielding:
527 if (scheduleHandleYield(cap, t, prev_what_next)) {
528 // shortcut for switching between compiler/interpreter:
529 goto run_thread;
530 }
531 break;
532
533 case ThreadBlocked:
534 scheduleHandleThreadBlocked(t);
535 break;
536
537 case ThreadFinished:
538 if (scheduleHandleThreadFinished(cap, task, t)) return cap;
539 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
540 break;
541
542 default:
543 barf("schedule: invalid thread return code %d", (int)ret);
544 }
545
546 if (ready_to_gc || scheduleNeedHeapProfile(ready_to_gc)) {
547 cap = scheduleDoGC(cap,task,rtsFalse);
548 }
549 } /* end of while() */
550 }
551
552 /* -----------------------------------------------------------------------------
553 * Run queue operations
554 * -------------------------------------------------------------------------- */
555
556 void
557 removeFromRunQueue (Capability *cap, StgTSO *tso)
558 {
559 if (tso->block_info.prev == END_TSO_QUEUE) {
560 ASSERT(cap->run_queue_hd == tso);
561 cap->run_queue_hd = tso->_link;
562 } else {
563 setTSOLink(cap, tso->block_info.prev, tso->_link);
564 }
565 if (tso->_link == END_TSO_QUEUE) {
566 ASSERT(cap->run_queue_tl == tso);
567 cap->run_queue_tl = tso->block_info.prev;
568 } else {
569 setTSOPrev(cap, tso->_link, tso->block_info.prev);
570 }
571 tso->_link = tso->block_info.prev = END_TSO_QUEUE;
572
573 IF_DEBUG(sanity, checkRunQueue(cap));
574 }
575
576 /* ----------------------------------------------------------------------------
577 * Setting up the scheduler loop
578 * ------------------------------------------------------------------------- */
579
580 static void
581 schedulePreLoop(void)
582 {
583 // initialisation for scheduler - what cannot go into initScheduler()
584 }
585
586 /* -----------------------------------------------------------------------------
587 * scheduleFindWork()
588 *
589 * Search for work to do, and handle messages from elsewhere.
590 * -------------------------------------------------------------------------- */
591
592 static void
593 scheduleFindWork (Capability *cap)
594 {
595 scheduleStartSignalHandlers(cap);
596
597 scheduleProcessInbox(cap);
598
599 scheduleCheckBlockedThreads(cap);
600
601 #if defined(THREADED_RTS)
602 if (emptyRunQueue(cap)) { scheduleActivateSpark(cap); }
603 #endif
604 }
605
606 #if defined(THREADED_RTS)
607 STATIC_INLINE rtsBool
608 shouldYieldCapability (Capability *cap, Task *task)
609 {
610 // we need to yield this capability to someone else if..
611 // - another thread is initiating a GC
612 // - another Task is returning from a foreign call
613 // - the thread at the head of the run queue cannot be run
614 // by this Task (it is bound to another Task, or it is unbound
615 // and this task it bound).
616 return (waiting_for_gc ||
617 cap->returning_tasks_hd != NULL ||
618 (!emptyRunQueue(cap) && (task->incall->tso == NULL
619 ? cap->run_queue_hd->bound != NULL
620 : cap->run_queue_hd->bound != task->incall)));
621 }
622
623 // This is the single place where a Task goes to sleep. There are
624 // two reasons it might need to sleep:
625 // - there are no threads to run
626 // - we need to yield this Capability to someone else
627 // (see shouldYieldCapability())
628 //
629 // Careful: the scheduler loop is quite delicate. Make sure you run
630 // the tests in testsuite/concurrent (all ways) after modifying this,
631 // and also check the benchmarks in nofib/parallel for regressions.
632
633 static void
634 scheduleYield (Capability **pcap, Task *task)
635 {
636 Capability *cap = *pcap;
637
638 // if we have work, and we don't need to give up the Capability, continue.
639 //
640 if (!shouldYieldCapability(cap,task) &&
641 (!emptyRunQueue(cap) ||
642 !emptyInbox(cap) ||
643 sched_state >= SCHED_INTERRUPTING))
644 return;
645
646 // otherwise yield (sleep), and keep yielding if necessary.
647 do {
648 yieldCapability(&cap,task);
649 }
650 while (shouldYieldCapability(cap,task));
651
652 // note there may still be no threads on the run queue at this
653 // point, the caller has to check.
654
655 *pcap = cap;
656 return;
657 }
658 #endif
659
660 /* -----------------------------------------------------------------------------
661 * schedulePushWork()
662 *
663 * Push work to other Capabilities if we have some.
664 * -------------------------------------------------------------------------- */
665
666 static void
667 schedulePushWork(Capability *cap USED_IF_THREADS,
668 Task *task USED_IF_THREADS)
669 {
670 /* following code not for PARALLEL_HASKELL. I kept the call general,
671 future GUM versions might use pushing in a distributed setup */
672 #if defined(THREADED_RTS)
673
674 Capability *free_caps[n_capabilities], *cap0;
675 nat i, n_free_caps;
676
677 // migration can be turned off with +RTS -qm
678 if (!RtsFlags.ParFlags.migrate) return;
679
680 // Check whether we have more threads on our run queue, or sparks
681 // in our pool, that we could hand to another Capability.
682 if (cap->run_queue_hd == END_TSO_QUEUE) {
683 if (sparkPoolSizeCap(cap) < 2) return;
684 } else {
685 if (cap->run_queue_hd->_link == END_TSO_QUEUE &&
686 sparkPoolSizeCap(cap) < 1) return;
687 }
688
689 // First grab as many free Capabilities as we can.
690 for (i=0, n_free_caps=0; i < n_capabilities; i++) {
691 cap0 = &capabilities[i];
692 if (cap != cap0 && tryGrabCapability(cap0,task)) {
693 if (!emptyRunQueue(cap0)
694 || cap->returning_tasks_hd != NULL
695 || cap->inbox != (Message*)END_TSO_QUEUE) {
696 // it already has some work, we just grabbed it at
697 // the wrong moment. Or maybe it's deadlocked!
698 releaseCapability(cap0);
699 } else {
700 free_caps[n_free_caps++] = cap0;
701 }
702 }
703 }
704
705 // we now have n_free_caps free capabilities stashed in
706 // free_caps[]. Share our run queue equally with them. This is
707 // probably the simplest thing we could do; improvements we might
708 // want to do include:
709 //
710 // - giving high priority to moving relatively new threads, on
711 // the gournds that they haven't had time to build up a
712 // working set in the cache on this CPU/Capability.
713 //
714 // - giving low priority to moving long-lived threads
715
716 if (n_free_caps > 0) {
717 StgTSO *prev, *t, *next;
718 rtsBool pushed_to_all;
719
720 debugTrace(DEBUG_sched,
721 "cap %d: %s and %d free capabilities, sharing...",
722 cap->no,
723 (!emptyRunQueue(cap) && cap->run_queue_hd->_link != END_TSO_QUEUE)?
724 "excess threads on run queue":"sparks to share (>=2)",
725 n_free_caps);
726
727 i = 0;
728 pushed_to_all = rtsFalse;
729
730 if (cap->run_queue_hd != END_TSO_QUEUE) {
731 prev = cap->run_queue_hd;
732 t = prev->_link;
733 prev->_link = END_TSO_QUEUE;
734 for (; t != END_TSO_QUEUE; t = next) {
735 next = t->_link;
736 t->_link = END_TSO_QUEUE;
737 if (t->bound == task->incall // don't move my bound thread
738 || tsoLocked(t)) { // don't move a locked thread
739 setTSOLink(cap, prev, t);
740 setTSOPrev(cap, t, prev);
741 prev = t;
742 } else if (i == n_free_caps) {
743 pushed_to_all = rtsTrue;
744 i = 0;
745 // keep one for us
746 setTSOLink(cap, prev, t);
747 setTSOPrev(cap, t, prev);
748 prev = t;
749 } else {
750 appendToRunQueue(free_caps[i],t);
751
752 traceEventMigrateThread (cap, t, free_caps[i]->no);
753
754 if (t->bound) { t->bound->task->cap = free_caps[i]; }
755 t->cap = free_caps[i];
756 i++;
757 }
758 }
759 cap->run_queue_tl = prev;
760
761 IF_DEBUG(sanity, checkRunQueue(cap));
762 }
763
764 #ifdef SPARK_PUSHING
765 /* JB I left this code in place, it would work but is not necessary */
766
767 // If there are some free capabilities that we didn't push any
768 // threads to, then try to push a spark to each one.
769 if (!pushed_to_all) {
770 StgClosure *spark;
771 // i is the next free capability to push to
772 for (; i < n_free_caps; i++) {
773 if (emptySparkPoolCap(free_caps[i])) {
774 spark = tryStealSpark(cap->sparks);
775 if (spark != NULL) {
776 debugTrace(DEBUG_sched, "pushing spark %p to capability %d", spark, free_caps[i]->no);
777
778 traceEventStealSpark(free_caps[i], t, cap->no);
779
780 newSpark(&(free_caps[i]->r), spark);
781 }
782 }
783 }
784 }
785 #endif /* SPARK_PUSHING */
786
787 // release the capabilities
788 for (i = 0; i < n_free_caps; i++) {
789 task->cap = free_caps[i];
790 releaseAndWakeupCapability(free_caps[i]);
791 }
792 }
793 task->cap = cap; // reset to point to our Capability.
794
795 #endif /* THREADED_RTS */
796
797 }
798
799 /* ----------------------------------------------------------------------------
800 * Start any pending signal handlers
801 * ------------------------------------------------------------------------- */
802
803 #if defined(RTS_USER_SIGNALS) && !defined(THREADED_RTS)
804 static void
805 scheduleStartSignalHandlers(Capability *cap)
806 {
807 if (RtsFlags.MiscFlags.install_signal_handlers && signals_pending()) {
808 // safe outside the lock
809 startSignalHandlers(cap);
810 }
811 }
812 #else
813 static void
814 scheduleStartSignalHandlers(Capability *cap STG_UNUSED)
815 {
816 }
817 #endif
818
819 /* ----------------------------------------------------------------------------
820 * Check for blocked threads that can be woken up.
821 * ------------------------------------------------------------------------- */
822
823 static void
824 scheduleCheckBlockedThreads(Capability *cap USED_IF_NOT_THREADS)
825 {
826 #if !defined(THREADED_RTS)
827 //
828 // Check whether any waiting threads need to be woken up. If the
829 // run queue is empty, and there are no other tasks running, we
830 // can wait indefinitely for something to happen.
831 //
832 if ( !emptyQueue(blocked_queue_hd) || !emptyQueue(sleeping_queue) )
833 {
834 awaitEvent (emptyRunQueue(cap));
835 }
836 #endif
837 }
838
839 /* ----------------------------------------------------------------------------
840 * Detect deadlock conditions and attempt to resolve them.
841 * ------------------------------------------------------------------------- */
842
843 static void
844 scheduleDetectDeadlock (Capability *cap, Task *task)
845 {
846 /*
847 * Detect deadlock: when we have no threads to run, there are no
848 * threads blocked, waiting for I/O, or sleeping, and all the
849 * other tasks are waiting for work, we must have a deadlock of
850 * some description.
851 */
852 if ( emptyThreadQueues(cap) )
853 {
854 #if defined(THREADED_RTS)
855 /*
856 * In the threaded RTS, we only check for deadlock if there
857 * has been no activity in a complete timeslice. This means
858 * we won't eagerly start a full GC just because we don't have
859 * any threads to run currently.
860 */
861 if (recent_activity != ACTIVITY_INACTIVE) return;
862 #endif
863
864 debugTrace(DEBUG_sched, "deadlocked, forcing major GC...");
865
866 // Garbage collection can release some new threads due to
867 // either (a) finalizers or (b) threads resurrected because
868 // they are unreachable and will therefore be sent an
869 // exception. Any threads thus released will be immediately
870 // runnable.
871 cap = scheduleDoGC (cap, task, rtsTrue/*force major GC*/);
872 // when force_major == rtsTrue. scheduleDoGC sets
873 // recent_activity to ACTIVITY_DONE_GC and turns off the timer
874 // signal.
875
876 if ( !emptyRunQueue(cap) ) return;
877
878 #if defined(RTS_USER_SIGNALS) && !defined(THREADED_RTS)
879 /* If we have user-installed signal handlers, then wait
880 * for signals to arrive rather then bombing out with a
881 * deadlock.
882 */
883 if ( RtsFlags.MiscFlags.install_signal_handlers && anyUserHandlers() ) {
884 debugTrace(DEBUG_sched,
885 "still deadlocked, waiting for signals...");
886
887 awaitUserSignals();
888
889 if (signals_pending()) {
890 startSignalHandlers(cap);
891 }
892
893 // either we have threads to run, or we were interrupted:
894 ASSERT(!emptyRunQueue(cap) || sched_state >= SCHED_INTERRUPTING);
895
896 return;
897 }
898 #endif
899
900 #if !defined(THREADED_RTS)
901 /* Probably a real deadlock. Send the current main thread the
902 * Deadlock exception.
903 */
904 if (task->incall->tso) {
905 switch (task->incall->tso->why_blocked) {
906 case BlockedOnSTM:
907 case BlockedOnBlackHole:
908 case BlockedOnMsgThrowTo:
909 case BlockedOnMVar:
910 throwToSingleThreaded(cap, task->incall->tso,
911 (StgClosure *)nonTermination_closure);
912 return;
913 default:
914 barf("deadlock: main thread blocked in a strange way");
915 }
916 }
917 return;
918 #endif
919 }
920 }
921
922
923 /* ----------------------------------------------------------------------------
924 * Send pending messages (PARALLEL_HASKELL only)
925 * ------------------------------------------------------------------------- */
926
927 #if defined(PARALLEL_HASKELL)
928 static void
929 scheduleSendPendingMessages(void)
930 {
931
932 # if defined(PAR) // global Mem.Mgmt., omit for now
933 if (PendingFetches != END_BF_QUEUE) {
934 processFetches();
935 }
936 # endif
937
938 if (RtsFlags.ParFlags.BufferTime) {
939 // if we use message buffering, we must send away all message
940 // packets which have become too old...
941 sendOldBuffers();
942 }
943 }
944 #endif
945
946 /* ----------------------------------------------------------------------------
947 * Process message in the current Capability's inbox
948 * ------------------------------------------------------------------------- */
949
950 static void
951 scheduleProcessInbox (Capability *cap USED_IF_THREADS)
952 {
953 #if defined(THREADED_RTS)
954 Message *m, *next;
955 int r;
956
957 while (!emptyInbox(cap)) {
958 if (cap->r.rCurrentNursery->link == NULL ||
959 g0->n_new_large_words >= large_alloc_lim) {
960 scheduleDoGC(cap, cap->running_task, rtsFalse);
961 }
962
963 // don't use a blocking acquire; if the lock is held by
964 // another thread then just carry on. This seems to avoid
965 // getting stuck in a message ping-pong situation with other
966 // processors. We'll check the inbox again later anyway.
967 //
968 // We should really use a more efficient queue data structure
969 // here. The trickiness is that we must ensure a Capability
970 // never goes idle if the inbox is non-empty, which is why we
971 // use cap->lock (cap->lock is released as the last thing
972 // before going idle; see Capability.c:releaseCapability()).
973 r = TRY_ACQUIRE_LOCK(&cap->lock);
974 if (r != 0) return;
975
976 m = cap->inbox;
977 cap->inbox = (Message*)END_TSO_QUEUE;
978
979 RELEASE_LOCK(&cap->lock);
980
981 while (m != (Message*)END_TSO_QUEUE) {
982 next = m->link;
983 executeMessage(cap, m);
984 m = next;
985 }
986 }
987 #endif
988 }
989
990 /* ----------------------------------------------------------------------------
991 * Activate spark threads (PARALLEL_HASKELL and THREADED_RTS)
992 * ------------------------------------------------------------------------- */
993
994 #if defined(THREADED_RTS)
995 static void
996 scheduleActivateSpark(Capability *cap)
997 {
998 if (anySparks())
999 {
1000 createSparkThread(cap);
1001 debugTrace(DEBUG_sched, "creating a spark thread");
1002 }
1003 }
1004 #endif // PARALLEL_HASKELL || THREADED_RTS
1005
1006 /* ----------------------------------------------------------------------------
1007 * After running a thread...
1008 * ------------------------------------------------------------------------- */
1009
1010 static void
1011 schedulePostRunThread (Capability *cap, StgTSO *t)
1012 {
1013 // We have to be able to catch transactions that are in an
1014 // infinite loop as a result of seeing an inconsistent view of
1015 // memory, e.g.
1016 //
1017 // atomically $ do
1018 // [a,b] <- mapM readTVar [ta,tb]
1019 // when (a == b) loop
1020 //
1021 // and a is never equal to b given a consistent view of memory.
1022 //
1023 if (t -> trec != NO_TREC && t -> why_blocked == NotBlocked) {
1024 if (!stmValidateNestOfTransactions (t -> trec)) {
1025 debugTrace(DEBUG_sched | DEBUG_stm,
1026 "trec %p found wasting its time", t);
1027
1028 // strip the stack back to the
1029 // ATOMICALLY_FRAME, aborting the (nested)
1030 // transaction, and saving the stack of any
1031 // partially-evaluated thunks on the heap.
1032 throwToSingleThreaded_(cap, t, NULL, rtsTrue);
1033
1034 // ASSERT(get_itbl((StgClosure *)t->sp)->type == ATOMICALLY_FRAME);
1035 }
1036 }
1037
1038 /* some statistics gathering in the parallel case */
1039 }
1040
1041 /* -----------------------------------------------------------------------------
1042 * Handle a thread that returned to the scheduler with ThreadHeepOverflow
1043 * -------------------------------------------------------------------------- */
1044
1045 static rtsBool
1046 scheduleHandleHeapOverflow( Capability *cap, StgTSO *t )
1047 {
1048 // did the task ask for a large block?
1049 if (cap->r.rHpAlloc > BLOCK_SIZE) {
1050 // if so, get one and push it on the front of the nursery.
1051 bdescr *bd;
1052 lnat blocks;
1053
1054 blocks = (lnat)BLOCK_ROUND_UP(cap->r.rHpAlloc) / BLOCK_SIZE;
1055
1056 if (blocks > BLOCKS_PER_MBLOCK) {
1057 barf("allocation of %ld bytes too large (GHC should have complained at compile-time)", (long)cap->r.rHpAlloc);
1058 }
1059
1060 debugTrace(DEBUG_sched,
1061 "--<< thread %ld (%s) stopped: requesting a large block (size %ld)\n",
1062 (long)t->id, what_next_strs[t->what_next], blocks);
1063
1064 // don't do this if the nursery is (nearly) full, we'll GC first.
1065 if (cap->r.rCurrentNursery->link != NULL ||
1066 cap->r.rNursery->n_blocks == 1) { // paranoia to prevent infinite loop
1067 // if the nursery has only one block.
1068
1069 bd = allocGroup_lock(blocks);
1070 cap->r.rNursery->n_blocks += blocks;
1071
1072 // link the new group into the list
1073 bd->link = cap->r.rCurrentNursery;
1074 bd->u.back = cap->r.rCurrentNursery->u.back;
1075 if (cap->r.rCurrentNursery->u.back != NULL) {
1076 cap->r.rCurrentNursery->u.back->link = bd;
1077 } else {
1078 cap->r.rNursery->blocks = bd;
1079 }
1080 cap->r.rCurrentNursery->u.back = bd;
1081
1082 // initialise it as a nursery block. We initialise the
1083 // step, gen_no, and flags field of *every* sub-block in
1084 // this large block, because this is easier than making
1085 // sure that we always find the block head of a large
1086 // block whenever we call Bdescr() (eg. evacuate() and
1087 // isAlive() in the GC would both have to do this, at
1088 // least).
1089 {
1090 bdescr *x;
1091 for (x = bd; x < bd + blocks; x++) {
1092 initBdescr(x,g0,g0);
1093 x->free = x->start;
1094 x->flags = 0;
1095 }
1096 }
1097
1098 // This assert can be a killer if the app is doing lots
1099 // of large block allocations.
1100 IF_DEBUG(sanity, checkNurserySanity(cap->r.rNursery));
1101
1102 // now update the nursery to point to the new block
1103 cap->r.rCurrentNursery = bd;
1104
1105 // we might be unlucky and have another thread get on the
1106 // run queue before us and steal the large block, but in that
1107 // case the thread will just end up requesting another large
1108 // block.
1109 pushOnRunQueue(cap,t);
1110 return rtsFalse; /* not actually GC'ing */
1111 }
1112 }
1113
1114 if (cap->r.rHpLim == NULL || cap->context_switch) {
1115 // Sometimes we miss a context switch, e.g. when calling
1116 // primitives in a tight loop, MAYBE_GC() doesn't check the
1117 // context switch flag, and we end up waiting for a GC.
1118 // See #1984, and concurrent/should_run/1984
1119 cap->context_switch = 0;
1120 appendToRunQueue(cap,t);
1121 } else {
1122 pushOnRunQueue(cap,t);
1123 }
1124 return rtsTrue;
1125 /* actual GC is done at the end of the while loop in schedule() */
1126 }
1127
1128 /* -----------------------------------------------------------------------------
1129 * Handle a thread that returned to the scheduler with ThreadYielding
1130 * -------------------------------------------------------------------------- */
1131
1132 static rtsBool
1133 scheduleHandleYield( Capability *cap, StgTSO *t, nat prev_what_next )
1134 {
1135 /* put the thread back on the run queue. Then, if we're ready to
1136 * GC, check whether this is the last task to stop. If so, wake
1137 * up the GC thread. getThread will block during a GC until the
1138 * GC is finished.
1139 */
1140
1141 ASSERT(t->_link == END_TSO_QUEUE);
1142
1143 // Shortcut if we're just switching evaluators: don't bother
1144 // doing stack squeezing (which can be expensive), just run the
1145 // thread.
1146 if (cap->context_switch == 0 && t->what_next != prev_what_next) {
1147 debugTrace(DEBUG_sched,
1148 "--<< thread %ld (%s) stopped to switch evaluators",
1149 (long)t->id, what_next_strs[t->what_next]);
1150 return rtsTrue;
1151 }
1152
1153 // Reset the context switch flag. We don't do this just before
1154 // running the thread, because that would mean we would lose ticks
1155 // during GC, which can lead to unfair scheduling (a thread hogs
1156 // the CPU because the tick always arrives during GC). This way
1157 // penalises threads that do a lot of allocation, but that seems
1158 // better than the alternative.
1159 cap->context_switch = 0;
1160
1161 IF_DEBUG(sanity,
1162 //debugBelch("&& Doing sanity check on yielding TSO %ld.", t->id);
1163 checkTSO(t));
1164
1165 appendToRunQueue(cap,t);
1166
1167 return rtsFalse;
1168 }
1169
1170 /* -----------------------------------------------------------------------------
1171 * Handle a thread that returned to the scheduler with ThreadBlocked
1172 * -------------------------------------------------------------------------- */
1173
1174 static void
1175 scheduleHandleThreadBlocked( StgTSO *t
1176 #if !defined(DEBUG)
1177 STG_UNUSED
1178 #endif
1179 )
1180 {
1181
1182 // We don't need to do anything. The thread is blocked, and it
1183 // has tidied up its stack and placed itself on whatever queue
1184 // it needs to be on.
1185
1186 // ASSERT(t->why_blocked != NotBlocked);
1187 // Not true: for example,
1188 // - the thread may have woken itself up already, because
1189 // threadPaused() might have raised a blocked throwTo
1190 // exception, see maybePerformBlockedException().
1191
1192 #ifdef DEBUG
1193 traceThreadStatus(DEBUG_sched, t);
1194 #endif
1195 }
1196
1197 /* -----------------------------------------------------------------------------
1198 * Handle a thread that returned to the scheduler with ThreadFinished
1199 * -------------------------------------------------------------------------- */
1200
1201 static rtsBool
1202 scheduleHandleThreadFinished (Capability *cap STG_UNUSED, Task *task, StgTSO *t)
1203 {
1204 /* Need to check whether this was a main thread, and if so,
1205 * return with the return value.
1206 *
1207 * We also end up here if the thread kills itself with an
1208 * uncaught exception, see Exception.cmm.
1209 */
1210
1211 // blocked exceptions can now complete, even if the thread was in
1212 // blocked mode (see #2910).
1213 awakenBlockedExceptionQueue (cap, t);
1214
1215 //
1216 // Check whether the thread that just completed was a bound
1217 // thread, and if so return with the result.
1218 //
1219 // There is an assumption here that all thread completion goes
1220 // through this point; we need to make sure that if a thread
1221 // ends up in the ThreadKilled state, that it stays on the run
1222 // queue so it can be dealt with here.
1223 //
1224
1225 if (t->bound) {
1226
1227 if (t->bound != task->incall) {
1228 #if !defined(THREADED_RTS)
1229 // Must be a bound thread that is not the topmost one. Leave
1230 // it on the run queue until the stack has unwound to the
1231 // point where we can deal with this. Leaving it on the run
1232 // queue also ensures that the garbage collector knows about
1233 // this thread and its return value (it gets dropped from the
1234 // step->threads list so there's no other way to find it).
1235 appendToRunQueue(cap,t);
1236 return rtsFalse;
1237 #else
1238 // this cannot happen in the threaded RTS, because a
1239 // bound thread can only be run by the appropriate Task.
1240 barf("finished bound thread that isn't mine");
1241 #endif
1242 }
1243
1244 ASSERT(task->incall->tso == t);
1245
1246 if (t->what_next == ThreadComplete) {
1247 if (task->incall->ret) {
1248 // NOTE: return val is stack->sp[1] (see StgStartup.hc)
1249 *(task->incall->ret) = (StgClosure *)task->incall->tso->stackobj->sp[1];
1250 }
1251 task->incall->stat = Success;
1252 } else {
1253 if (task->incall->ret) {
1254 *(task->incall->ret) = NULL;
1255 }
1256 if (sched_state >= SCHED_INTERRUPTING) {
1257 if (heap_overflow) {
1258 task->incall->stat = HeapExhausted;
1259 } else {
1260 task->incall->stat = Interrupted;
1261 }
1262 } else {
1263 task->incall->stat = Killed;
1264 }
1265 }
1266 #ifdef DEBUG
1267 removeThreadLabel((StgWord)task->incall->tso->id);
1268 #endif
1269
1270 // We no longer consider this thread and task to be bound to
1271 // each other. The TSO lives on until it is GC'd, but the
1272 // task is about to be released by the caller, and we don't
1273 // want anyone following the pointer from the TSO to the
1274 // defunct task (which might have already been
1275 // re-used). This was a real bug: the GC updated
1276 // tso->bound->tso which lead to a deadlock.
1277 t->bound = NULL;
1278 task->incall->tso = NULL;
1279
1280 return rtsTrue; // tells schedule() to return
1281 }
1282
1283 return rtsFalse;
1284 }
1285
1286 /* -----------------------------------------------------------------------------
1287 * Perform a heap census
1288 * -------------------------------------------------------------------------- */
1289
1290 static rtsBool
1291 scheduleNeedHeapProfile( rtsBool ready_to_gc STG_UNUSED )
1292 {
1293 // When we have +RTS -i0 and we're heap profiling, do a census at
1294 // every GC. This lets us get repeatable runs for debugging.
1295 if (performHeapProfile ||
1296 (RtsFlags.ProfFlags.profileInterval==0 &&
1297 RtsFlags.ProfFlags.doHeapProfile && ready_to_gc)) {
1298 return rtsTrue;
1299 } else {
1300 return rtsFalse;
1301 }
1302 }
1303
1304 /* -----------------------------------------------------------------------------
1305 * Perform a garbage collection if necessary
1306 * -------------------------------------------------------------------------- */
1307
1308 static Capability *
1309 scheduleDoGC (Capability *cap, Task *task USED_IF_THREADS, rtsBool force_major)
1310 {
1311 rtsBool heap_census;
1312 #ifdef THREADED_RTS
1313 /* extern static volatile StgWord waiting_for_gc;
1314 lives inside capability.c */
1315 rtsBool gc_type, prev_pending_gc;
1316 nat i;
1317 #endif
1318
1319 if (sched_state == SCHED_SHUTTING_DOWN) {
1320 // The final GC has already been done, and the system is
1321 // shutting down. We'll probably deadlock if we try to GC
1322 // now.
1323 return cap;
1324 }
1325
1326 #ifdef THREADED_RTS
1327 if (sched_state < SCHED_INTERRUPTING
1328 && RtsFlags.ParFlags.parGcEnabled
1329 && N >= RtsFlags.ParFlags.parGcGen
1330 && ! oldest_gen->mark)
1331 {
1332 gc_type = PENDING_GC_PAR;
1333 } else {
1334 gc_type = PENDING_GC_SEQ;
1335 }
1336
1337 // In order to GC, there must be no threads running Haskell code.
1338 // Therefore, the GC thread needs to hold *all* the capabilities,
1339 // and release them after the GC has completed.
1340 //
1341 // This seems to be the simplest way: previous attempts involved
1342 // making all the threads with capabilities give up their
1343 // capabilities and sleep except for the *last* one, which
1344 // actually did the GC. But it's quite hard to arrange for all
1345 // the other tasks to sleep and stay asleep.
1346 //
1347
1348 /* Other capabilities are prevented from running yet more Haskell
1349 threads if waiting_for_gc is set. Tested inside
1350 yieldCapability() and releaseCapability() in Capability.c */
1351
1352 prev_pending_gc = cas(&waiting_for_gc, 0, gc_type);
1353 if (prev_pending_gc) {
1354 do {
1355 debugTrace(DEBUG_sched, "someone else is trying to GC (%d)...",
1356 prev_pending_gc);
1357 ASSERT(cap);
1358 yieldCapability(&cap,task);
1359 } while (waiting_for_gc);
1360 return cap; // NOTE: task->cap might have changed here
1361 }
1362
1363 setContextSwitches();
1364
1365 // The final shutdown GC is always single-threaded, because it's
1366 // possible that some of the Capabilities have no worker threads.
1367
1368 if (gc_type == PENDING_GC_SEQ)
1369 {
1370 traceEventRequestSeqGc(cap);
1371 }
1372 else
1373 {
1374 traceEventRequestParGc(cap);
1375 debugTrace(DEBUG_sched, "ready_to_gc, grabbing GC threads");
1376 }
1377
1378 if (gc_type == PENDING_GC_SEQ)
1379 {
1380 // single-threaded GC: grab all the capabilities
1381 for (i=0; i < n_capabilities; i++) {
1382 debugTrace(DEBUG_sched, "ready_to_gc, grabbing all the capabilies (%d/%d)", i, n_capabilities);
1383 if (cap != &capabilities[i]) {
1384 Capability *pcap = &capabilities[i];
1385 // we better hope this task doesn't get migrated to
1386 // another Capability while we're waiting for this one.
1387 // It won't, because load balancing happens while we have
1388 // all the Capabilities, but even so it's a slightly
1389 // unsavoury invariant.
1390 task->cap = pcap;
1391 waitForReturnCapability(&pcap, task);
1392 if (pcap != &capabilities[i]) {
1393 barf("scheduleDoGC: got the wrong capability");
1394 }
1395 }
1396 }
1397 }
1398 else
1399 {
1400 // multi-threaded GC: make sure all the Capabilities donate one
1401 // GC thread each.
1402 waitForGcThreads(cap);
1403 }
1404
1405 #endif
1406
1407 IF_DEBUG(scheduler, printAllThreads());
1408
1409 delete_threads_and_gc:
1410 /*
1411 * We now have all the capabilities; if we're in an interrupting
1412 * state, then we should take the opportunity to delete all the
1413 * threads in the system.
1414 */
1415 if (sched_state == SCHED_INTERRUPTING) {
1416 deleteAllThreads(cap);
1417 sched_state = SCHED_SHUTTING_DOWN;
1418 }
1419
1420 heap_census = scheduleNeedHeapProfile(rtsTrue);
1421
1422 traceEventGcStart(cap);
1423 #if defined(THREADED_RTS)
1424 // reset waiting_for_gc *before* GC, so that when the GC threads
1425 // emerge they don't immediately re-enter the GC.
1426 waiting_for_gc = 0;
1427 GarbageCollect(force_major || heap_census, gc_type, cap);
1428 #else
1429 GarbageCollect(force_major || heap_census, 0, cap);
1430 #endif
1431 traceEventGcEnd(cap);
1432
1433 if (recent_activity == ACTIVITY_INACTIVE && force_major)
1434 {
1435 // We are doing a GC because the system has been idle for a
1436 // timeslice and we need to check for deadlock. Record the
1437 // fact that we've done a GC and turn off the timer signal;
1438 // it will get re-enabled if we run any threads after the GC.
1439 recent_activity = ACTIVITY_DONE_GC;
1440 stopTimer();
1441 }
1442 else
1443 {
1444 // the GC might have taken long enough for the timer to set
1445 // recent_activity = ACTIVITY_INACTIVE, but we aren't
1446 // necessarily deadlocked:
1447 recent_activity = ACTIVITY_YES;
1448 }
1449
1450 #if defined(THREADED_RTS)
1451 if (gc_type == PENDING_GC_PAR)
1452 {
1453 releaseGCThreads(cap);
1454 }
1455 #endif
1456
1457 if (heap_census) {
1458 debugTrace(DEBUG_sched, "performing heap census");
1459 heapCensus();
1460 performHeapProfile = rtsFalse;
1461 }
1462
1463 if (heap_overflow && sched_state < SCHED_INTERRUPTING) {
1464 // GC set the heap_overflow flag, so we should proceed with
1465 // an orderly shutdown now. Ultimately we want the main
1466 // thread to return to its caller with HeapExhausted, at which
1467 // point the caller should call hs_exit(). The first step is
1468 // to delete all the threads.
1469 //
1470 // Another way to do this would be to raise an exception in
1471 // the main thread, which we really should do because it gives
1472 // the program a chance to clean up. But how do we find the
1473 // main thread? It should presumably be the same one that
1474 // gets ^C exceptions, but that's all done on the Haskell side
1475 // (GHC.TopHandler).
1476 sched_state = SCHED_INTERRUPTING;
1477 goto delete_threads_and_gc;
1478 }
1479
1480 #ifdef SPARKBALANCE
1481 /* JB
1482 Once we are all together... this would be the place to balance all
1483 spark pools. No concurrent stealing or adding of new sparks can
1484 occur. Should be defined in Sparks.c. */
1485 balanceSparkPoolsCaps(n_capabilities, capabilities);
1486 #endif
1487
1488 #if defined(THREADED_RTS)
1489 if (gc_type == PENDING_GC_SEQ) {
1490 // release our stash of capabilities.
1491 for (i = 0; i < n_capabilities; i++) {
1492 if (cap != &capabilities[i]) {
1493 task->cap = &capabilities[i];
1494 releaseCapability(&capabilities[i]);
1495 }
1496 }
1497 }
1498 if (cap) {
1499 task->cap = cap;
1500 } else {
1501 task->cap = NULL;
1502 }
1503 #endif
1504
1505 return cap;
1506 }
1507
1508 /* ---------------------------------------------------------------------------
1509 * Singleton fork(). Do not copy any running threads.
1510 * ------------------------------------------------------------------------- */
1511
1512 pid_t
1513 forkProcess(HsStablePtr *entry
1514 #ifndef FORKPROCESS_PRIMOP_SUPPORTED
1515 STG_UNUSED
1516 #endif
1517 )
1518 {
1519 #ifdef FORKPROCESS_PRIMOP_SUPPORTED
1520 pid_t pid;
1521 StgTSO* t,*next;
1522 Capability *cap;
1523 nat g;
1524
1525 #if defined(THREADED_RTS)
1526 if (RtsFlags.ParFlags.nNodes > 1) {
1527 errorBelch("forking not supported with +RTS -N<n> greater than 1");
1528 stg_exit(EXIT_FAILURE);
1529 }
1530 #endif
1531
1532 debugTrace(DEBUG_sched, "forking!");
1533
1534 // ToDo: for SMP, we should probably acquire *all* the capabilities
1535 cap = rts_lock();
1536
1537 // no funny business: hold locks while we fork, otherwise if some
1538 // other thread is holding a lock when the fork happens, the data
1539 // structure protected by the lock will forever be in an
1540 // inconsistent state in the child. See also #1391.
1541 ACQUIRE_LOCK(&sched_mutex);
1542 ACQUIRE_LOCK(&cap->lock);
1543 ACQUIRE_LOCK(&cap->running_task->lock);
1544
1545 stopTimer(); // See #4074
1546
1547 #if defined(TRACING)
1548 flushEventLog(); // so that child won't inherit dirty file buffers
1549 #endif
1550
1551 pid = fork();
1552
1553 if (pid) { // parent
1554
1555 startTimer(); // #4074
1556
1557 RELEASE_LOCK(&sched_mutex);
1558 RELEASE_LOCK(&cap->lock);
1559 RELEASE_LOCK(&cap->running_task->lock);
1560
1561 // just return the pid
1562 rts_unlock(cap);
1563 return pid;
1564
1565 } else { // child
1566
1567 #if defined(THREADED_RTS)
1568 initMutex(&sched_mutex);
1569 initMutex(&cap->lock);
1570 initMutex(&cap->running_task->lock);
1571 #endif
1572
1573 #ifdef TRACING
1574 resetTracing();
1575 #endif
1576
1577 // Now, all OS threads except the thread that forked are
1578 // stopped. We need to stop all Haskell threads, including
1579 // those involved in foreign calls. Also we need to delete
1580 // all Tasks, because they correspond to OS threads that are
1581 // now gone.
1582
1583 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
1584 for (t = generations[g].threads; t != END_TSO_QUEUE; t = next) {
1585 next = t->global_link;
1586 // don't allow threads to catch the ThreadKilled
1587 // exception, but we do want to raiseAsync() because these
1588 // threads may be evaluating thunks that we need later.
1589 deleteThread_(cap,t);
1590
1591 // stop the GC from updating the InCall to point to
1592 // the TSO. This is only necessary because the
1593 // OSThread bound to the TSO has been killed, and
1594 // won't get a chance to exit in the usual way (see
1595 // also scheduleHandleThreadFinished).
1596 t->bound = NULL;
1597 }
1598 }
1599
1600 // Empty the run queue. It seems tempting to let all the
1601 // killed threads stay on the run queue as zombies to be
1602 // cleaned up later, but some of them correspond to bound
1603 // threads for which the corresponding Task does not exist.
1604 cap->run_queue_hd = END_TSO_QUEUE;
1605 cap->run_queue_tl = END_TSO_QUEUE;
1606
1607 // Any suspended C-calling Tasks are no more, their OS threads
1608 // don't exist now:
1609 cap->suspended_ccalls = NULL;
1610
1611 // Empty the threads lists. Otherwise, the garbage
1612 // collector may attempt to resurrect some of these threads.
1613 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
1614 generations[g].threads = END_TSO_QUEUE;
1615 }
1616
1617 discardTasksExcept(cap->running_task);
1618
1619 #if defined(THREADED_RTS)
1620 // Wipe our spare workers list, they no longer exist. New
1621 // workers will be created if necessary.
1622 cap->spare_workers = NULL;
1623 cap->n_spare_workers = 0;
1624 cap->returning_tasks_hd = NULL;
1625 cap->returning_tasks_tl = NULL;
1626 #endif
1627
1628 // On Unix, all timers are reset in the child, so we need to start
1629 // the timer again.
1630 initTimer();
1631 startTimer();
1632
1633 #if defined(THREADED_RTS)
1634 cap = ioManagerStartCap(cap);
1635 #endif
1636
1637 cap = rts_evalStableIO(cap, entry, NULL); // run the action
1638 rts_checkSchedStatus("forkProcess",cap);
1639
1640 rts_unlock(cap);
1641 hs_exit(); // clean up and exit
1642 stg_exit(EXIT_SUCCESS);
1643 }
1644 #else /* !FORKPROCESS_PRIMOP_SUPPORTED */
1645 barf("forkProcess#: primop not supported on this platform, sorry!\n");
1646 #endif
1647 }
1648
1649 /* ---------------------------------------------------------------------------
1650 * Delete all the threads in the system
1651 * ------------------------------------------------------------------------- */
1652
1653 static void
1654 deleteAllThreads ( Capability *cap )
1655 {
1656 // NOTE: only safe to call if we own all capabilities.
1657
1658 StgTSO* t, *next;
1659 nat g;
1660
1661 debugTrace(DEBUG_sched,"deleting all threads");
1662 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
1663 for (t = generations[g].threads; t != END_TSO_QUEUE; t = next) {
1664 next = t->global_link;
1665 deleteThread(cap,t);
1666 }
1667 }
1668
1669 // The run queue now contains a bunch of ThreadKilled threads. We
1670 // must not throw these away: the main thread(s) will be in there
1671 // somewhere, and the main scheduler loop has to deal with it.
1672 // Also, the run queue is the only thing keeping these threads from
1673 // being GC'd, and we don't want the "main thread has been GC'd" panic.
1674
1675 #if !defined(THREADED_RTS)
1676 ASSERT(blocked_queue_hd == END_TSO_QUEUE);
1677 ASSERT(sleeping_queue == END_TSO_QUEUE);
1678 #endif
1679 }
1680
1681 /* -----------------------------------------------------------------------------
1682 Managing the suspended_ccalls list.
1683 Locks required: sched_mutex
1684 -------------------------------------------------------------------------- */
1685
1686 STATIC_INLINE void
1687 suspendTask (Capability *cap, Task *task)
1688 {
1689 InCall *incall;
1690
1691 incall = task->incall;
1692 ASSERT(incall->next == NULL && incall->prev == NULL);
1693 incall->next = cap->suspended_ccalls;
1694 incall->prev = NULL;
1695 if (cap->suspended_ccalls) {
1696 cap->suspended_ccalls->prev = incall;
1697 }
1698 cap->suspended_ccalls = incall;
1699 }
1700
1701 STATIC_INLINE void
1702 recoverSuspendedTask (Capability *cap, Task *task)
1703 {
1704 InCall *incall;
1705
1706 incall = task->incall;
1707 if (incall->prev) {
1708 incall->prev->next = incall->next;
1709 } else {
1710 ASSERT(cap->suspended_ccalls == incall);
1711 cap->suspended_ccalls = incall->next;
1712 }
1713 if (incall->next) {
1714 incall->next->prev = incall->prev;
1715 }
1716 incall->next = incall->prev = NULL;
1717 }
1718
1719 /* ---------------------------------------------------------------------------
1720 * Suspending & resuming Haskell threads.
1721 *
1722 * When making a "safe" call to C (aka _ccall_GC), the task gives back
1723 * its capability before calling the C function. This allows another
1724 * task to pick up the capability and carry on running Haskell
1725 * threads. It also means that if the C call blocks, it won't lock
1726 * the whole system.
1727 *
1728 * The Haskell thread making the C call is put to sleep for the
1729 * duration of the call, on the suspended_ccalling_threads queue. We
1730 * give out a token to the task, which it can use to resume the thread
1731 * on return from the C function.
1732 *
1733 * If this is an interruptible C call, this means that the FFI call may be
1734 * unceremoniously terminated and should be scheduled on an
1735 * unbound worker thread.
1736 * ------------------------------------------------------------------------- */
1737
1738 void *
1739 suspendThread (StgRegTable *reg, rtsBool interruptible)
1740 {
1741 Capability *cap;
1742 int saved_errno;
1743 StgTSO *tso;
1744 Task *task;
1745 #if mingw32_HOST_OS
1746 StgWord32 saved_winerror;
1747 #endif
1748
1749 saved_errno = errno;
1750 #if mingw32_HOST_OS
1751 saved_winerror = GetLastError();
1752 #endif
1753
1754 /* assume that *reg is a pointer to the StgRegTable part of a Capability.
1755 */
1756 cap = regTableToCapability(reg);
1757
1758 task = cap->running_task;
1759 tso = cap->r.rCurrentTSO;
1760
1761 traceEventStopThread(cap, tso, THREAD_SUSPENDED_FOREIGN_CALL, 0);
1762
1763 // XXX this might not be necessary --SDM
1764 tso->what_next = ThreadRunGHC;
1765
1766 threadPaused(cap,tso);
1767
1768 if (interruptible) {
1769 tso->why_blocked = BlockedOnCCall_Interruptible;
1770 } else {
1771 tso->why_blocked = BlockedOnCCall;
1772 }
1773
1774 // Hand back capability
1775 task->incall->suspended_tso = tso;
1776 task->incall->suspended_cap = cap;
1777
1778 ACQUIRE_LOCK(&cap->lock);
1779
1780 suspendTask(cap,task);
1781 cap->in_haskell = rtsFalse;
1782 releaseCapability_(cap,rtsFalse);
1783
1784 RELEASE_LOCK(&cap->lock);
1785
1786 errno = saved_errno;
1787 #if mingw32_HOST_OS
1788 SetLastError(saved_winerror);
1789 #endif
1790 return task;
1791 }
1792
1793 StgRegTable *
1794 resumeThread (void *task_)
1795 {
1796 StgTSO *tso;
1797 InCall *incall;
1798 Capability *cap;
1799 Task *task = task_;
1800 int saved_errno;
1801 #if mingw32_HOST_OS
1802 StgWord32 saved_winerror;
1803 #endif
1804
1805 saved_errno = errno;
1806 #if mingw32_HOST_OS
1807 saved_winerror = GetLastError();
1808 #endif
1809
1810 incall = task->incall;
1811 cap = incall->suspended_cap;
1812 task->cap = cap;
1813
1814 // Wait for permission to re-enter the RTS with the result.
1815 waitForReturnCapability(&cap,task);
1816 // we might be on a different capability now... but if so, our
1817 // entry on the suspended_ccalls list will also have been
1818 // migrated.
1819
1820 // Remove the thread from the suspended list
1821 recoverSuspendedTask(cap,task);
1822
1823 tso = incall->suspended_tso;
1824 incall->suspended_tso = NULL;
1825 incall->suspended_cap = NULL;
1826 tso->_link = END_TSO_QUEUE; // no write barrier reqd
1827
1828 traceEventRunThread(cap, tso);
1829
1830 /* Reset blocking status */
1831 tso->why_blocked = NotBlocked;
1832
1833 if ((tso->flags & TSO_BLOCKEX) == 0) {
1834 // avoid locking the TSO if we don't have to
1835 if (tso->blocked_exceptions != END_BLOCKED_EXCEPTIONS_QUEUE) {
1836 maybePerformBlockedException(cap,tso);
1837 }
1838 }
1839
1840 cap->r.rCurrentTSO = tso;
1841 cap->in_haskell = rtsTrue;
1842 errno = saved_errno;
1843 #if mingw32_HOST_OS
1844 SetLastError(saved_winerror);
1845 #endif
1846
1847 /* We might have GC'd, mark the TSO dirty again */
1848 dirty_TSO(cap,tso);
1849 dirty_STACK(cap,tso->stackobj);
1850
1851 IF_DEBUG(sanity, checkTSO(tso));
1852
1853 return &cap->r;
1854 }
1855
1856 /* ---------------------------------------------------------------------------
1857 * scheduleThread()
1858 *
1859 * scheduleThread puts a thread on the end of the runnable queue.
1860 * This will usually be done immediately after a thread is created.
1861 * The caller of scheduleThread must create the thread using e.g.
1862 * createThread and push an appropriate closure
1863 * on this thread's stack before the scheduler is invoked.
1864 * ------------------------------------------------------------------------ */
1865
1866 void
1867 scheduleThread(Capability *cap, StgTSO *tso)
1868 {
1869 // The thread goes at the *end* of the run-queue, to avoid possible
1870 // starvation of any threads already on the queue.
1871 appendToRunQueue(cap,tso);
1872 }
1873
1874 void
1875 scheduleThreadOn(Capability *cap, StgWord cpu USED_IF_THREADS, StgTSO *tso)
1876 {
1877 #if defined(THREADED_RTS)
1878 tso->flags |= TSO_LOCKED; // we requested explicit affinity; don't
1879 // move this thread from now on.
1880 cpu %= RtsFlags.ParFlags.nNodes;
1881 if (cpu == cap->no) {
1882 appendToRunQueue(cap,tso);
1883 } else {
1884 migrateThread(cap, tso, &capabilities[cpu]);
1885 }
1886 #else
1887 appendToRunQueue(cap,tso);
1888 #endif
1889 }
1890
1891 Capability *
1892 scheduleWaitThread (StgTSO* tso, /*[out]*/HaskellObj* ret, Capability *cap)
1893 {
1894 Task *task;
1895 StgThreadID id;
1896
1897 // We already created/initialised the Task
1898 task = cap->running_task;
1899
1900 // This TSO is now a bound thread; make the Task and TSO
1901 // point to each other.
1902 tso->bound = task->incall;
1903 tso->cap = cap;
1904
1905 task->incall->tso = tso;
1906 task->incall->ret = ret;
1907 task->incall->stat = NoStatus;
1908
1909 appendToRunQueue(cap,tso);
1910
1911 id = tso->id;
1912 debugTrace(DEBUG_sched, "new bound thread (%lu)", (unsigned long)id);
1913
1914 cap = schedule(cap,task);
1915
1916 ASSERT(task->incall->stat != NoStatus);
1917 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
1918
1919 debugTrace(DEBUG_sched, "bound thread (%lu) finished", (unsigned long)id);
1920 return cap;
1921 }
1922
1923 /* ----------------------------------------------------------------------------
1924 * Starting Tasks
1925 * ------------------------------------------------------------------------- */
1926
1927 #if defined(THREADED_RTS)
1928 void scheduleWorker (Capability *cap, Task *task)
1929 {
1930 // schedule() runs without a lock.
1931 cap = schedule(cap,task);
1932
1933 // On exit from schedule(), we have a Capability, but possibly not
1934 // the same one we started with.
1935
1936 // During shutdown, the requirement is that after all the
1937 // Capabilities are shut down, all workers that are shutting down
1938 // have finished workerTaskStop(). This is why we hold on to
1939 // cap->lock until we've finished workerTaskStop() below.
1940 //
1941 // There may be workers still involved in foreign calls; those
1942 // will just block in waitForReturnCapability() because the
1943 // Capability has been shut down.
1944 //
1945 ACQUIRE_LOCK(&cap->lock);
1946 releaseCapability_(cap,rtsFalse);
1947 workerTaskStop(task);
1948 RELEASE_LOCK(&cap->lock);
1949 }
1950 #endif
1951
1952 /* ---------------------------------------------------------------------------
1953 * initScheduler()
1954 *
1955 * Initialise the scheduler. This resets all the queues - if the
1956 * queues contained any threads, they'll be garbage collected at the
1957 * next pass.
1958 *
1959 * ------------------------------------------------------------------------ */
1960
1961 void
1962 initScheduler(void)
1963 {
1964 #if !defined(THREADED_RTS)
1965 blocked_queue_hd = END_TSO_QUEUE;
1966 blocked_queue_tl = END_TSO_QUEUE;
1967 sleeping_queue = END_TSO_QUEUE;
1968 #endif
1969
1970 sched_state = SCHED_RUNNING;
1971 recent_activity = ACTIVITY_YES;
1972
1973 #if defined(THREADED_RTS)
1974 /* Initialise the mutex and condition variables used by
1975 * the scheduler. */
1976 initMutex(&sched_mutex);
1977 #endif
1978
1979 ACQUIRE_LOCK(&sched_mutex);
1980
1981 /* A capability holds the state a native thread needs in
1982 * order to execute STG code. At least one capability is
1983 * floating around (only THREADED_RTS builds have more than one).
1984 */
1985 initCapabilities();
1986
1987 initTaskManager();
1988
1989 #if defined(THREADED_RTS)
1990 initSparkPools();
1991 #endif
1992
1993 RELEASE_LOCK(&sched_mutex);
1994
1995 #if defined(THREADED_RTS)
1996 /*
1997 * Eagerly start one worker to run each Capability, except for
1998 * Capability 0. The idea is that we're probably going to start a
1999 * bound thread on Capability 0 pretty soon, so we don't want a
2000 * worker task hogging it.
2001 */
2002 {
2003 nat i;
2004 Capability *cap;
2005 for (i = 1; i < n_capabilities; i++) {
2006 cap = &capabilities[i];
2007 ACQUIRE_LOCK(&cap->lock);
2008 startWorkerTask(cap);
2009 RELEASE_LOCK(&cap->lock);
2010 }
2011 }
2012 #endif
2013 }
2014
2015 void
2016 exitScheduler (rtsBool wait_foreign USED_IF_THREADS)
2017 /* see Capability.c, shutdownCapability() */
2018 {
2019 Task *task = NULL;
2020
2021 task = newBoundTask();
2022
2023 // If we haven't killed all the threads yet, do it now.
2024 if (sched_state < SCHED_SHUTTING_DOWN) {
2025 sched_state = SCHED_INTERRUPTING;
2026 waitForReturnCapability(&task->cap,task);
2027 scheduleDoGC(task->cap,task,rtsFalse);
2028 ASSERT(task->incall->tso == NULL);
2029 releaseCapability(task->cap);
2030 }
2031 sched_state = SCHED_SHUTTING_DOWN;
2032
2033 #if defined(THREADED_RTS)
2034 {
2035 nat i;
2036
2037 for (i = 0; i < n_capabilities; i++) {
2038 ASSERT(task->incall->tso == NULL);
2039 shutdownCapability(&capabilities[i], task, wait_foreign);
2040 }
2041 }
2042 #endif
2043
2044 boundTaskExiting(task);
2045 }
2046
2047 void
2048 freeScheduler( void )
2049 {
2050 nat still_running;
2051
2052 ACQUIRE_LOCK(&sched_mutex);
2053 still_running = freeTaskManager();
2054 // We can only free the Capabilities if there are no Tasks still
2055 // running. We might have a Task about to return from a foreign
2056 // call into waitForReturnCapability(), for example (actually,
2057 // this should be the *only* thing that a still-running Task can
2058 // do at this point, and it will block waiting for the
2059 // Capability).
2060 if (still_running == 0) {
2061 freeCapabilities();
2062 if (n_capabilities != 1) {
2063 stgFree(capabilities);
2064 }
2065 }
2066 RELEASE_LOCK(&sched_mutex);
2067 #if defined(THREADED_RTS)
2068 closeMutex(&sched_mutex);
2069 #endif
2070 }
2071
2072 /* -----------------------------------------------------------------------------
2073 performGC
2074
2075 This is the interface to the garbage collector from Haskell land.
2076 We provide this so that external C code can allocate and garbage
2077 collect when called from Haskell via _ccall_GC.
2078 -------------------------------------------------------------------------- */
2079
2080 static void
2081 performGC_(rtsBool force_major)
2082 {
2083 Task *task;
2084
2085 // We must grab a new Task here, because the existing Task may be
2086 // associated with a particular Capability, and chained onto the
2087 // suspended_ccalls queue.
2088 task = newBoundTask();
2089
2090 waitForReturnCapability(&task->cap,task);
2091 scheduleDoGC(task->cap,task,force_major);
2092 releaseCapability(task->cap);
2093 boundTaskExiting(task);
2094 }
2095
2096 void
2097 performGC(void)
2098 {
2099 performGC_(rtsFalse);
2100 }
2101
2102 void
2103 performMajorGC(void)
2104 {
2105 performGC_(rtsTrue);
2106 }
2107
2108 /* ---------------------------------------------------------------------------
2109 Interrupt execution
2110 - usually called inside a signal handler so it mustn't do anything fancy.
2111 ------------------------------------------------------------------------ */
2112
2113 void
2114 interruptStgRts(void)
2115 {
2116 sched_state = SCHED_INTERRUPTING;
2117 setContextSwitches();
2118 #if defined(THREADED_RTS)
2119 wakeUpRts();
2120 #endif
2121 }
2122
2123 /* -----------------------------------------------------------------------------
2124 Wake up the RTS
2125
2126 This function causes at least one OS thread to wake up and run the
2127 scheduler loop. It is invoked when the RTS might be deadlocked, or
2128 an external event has arrived that may need servicing (eg. a
2129 keyboard interrupt).
2130
2131 In the single-threaded RTS we don't do anything here; we only have
2132 one thread anyway, and the event that caused us to want to wake up
2133 will have interrupted any blocking system call in progress anyway.
2134 -------------------------------------------------------------------------- */
2135
2136 #if defined(THREADED_RTS)
2137 void wakeUpRts(void)
2138 {
2139 // This forces the IO Manager thread to wakeup, which will
2140 // in turn ensure that some OS thread wakes up and runs the
2141 // scheduler loop, which will cause a GC and deadlock check.
2142 ioManagerWakeup();
2143 }
2144 #endif
2145
2146 /* -----------------------------------------------------------------------------
2147 Deleting threads
2148
2149 This is used for interruption (^C) and forking, and corresponds to
2150 raising an exception but without letting the thread catch the
2151 exception.
2152 -------------------------------------------------------------------------- */
2153
2154 static void
2155 deleteThread (Capability *cap STG_UNUSED, StgTSO *tso)
2156 {
2157 // NOTE: must only be called on a TSO that we have exclusive
2158 // access to, because we will call throwToSingleThreaded() below.
2159 // The TSO must be on the run queue of the Capability we own, or
2160 // we must own all Capabilities.
2161
2162 if (tso->why_blocked != BlockedOnCCall &&
2163 tso->why_blocked != BlockedOnCCall_Interruptible) {
2164 throwToSingleThreaded(tso->cap,tso,NULL);
2165 }
2166 }
2167
2168 #ifdef FORKPROCESS_PRIMOP_SUPPORTED
2169 static void
2170 deleteThread_(Capability *cap, StgTSO *tso)
2171 { // for forkProcess only:
2172 // like deleteThread(), but we delete threads in foreign calls, too.
2173
2174 if (tso->why_blocked == BlockedOnCCall ||
2175 tso->why_blocked == BlockedOnCCall_Interruptible) {
2176 tso->what_next = ThreadKilled;
2177 appendToRunQueue(tso->cap, tso);
2178 } else {
2179 deleteThread(cap,tso);
2180 }
2181 }
2182 #endif
2183
2184 /* -----------------------------------------------------------------------------
2185 raiseExceptionHelper
2186
2187 This function is called by the raise# primitve, just so that we can
2188 move some of the tricky bits of raising an exception from C-- into
2189 C. Who knows, it might be a useful re-useable thing here too.
2190 -------------------------------------------------------------------------- */
2191
2192 StgWord
2193 raiseExceptionHelper (StgRegTable *reg, StgTSO *tso, StgClosure *exception)
2194 {
2195 Capability *cap = regTableToCapability(reg);
2196 StgThunk *raise_closure = NULL;
2197 StgPtr p, next;
2198 StgRetInfoTable *info;
2199 //
2200 // This closure represents the expression 'raise# E' where E
2201 // is the exception raise. It is used to overwrite all the
2202 // thunks which are currently under evaluataion.
2203 //
2204
2205 // OLD COMMENT (we don't have MIN_UPD_SIZE now):
2206 // LDV profiling: stg_raise_info has THUNK as its closure
2207 // type. Since a THUNK takes at least MIN_UPD_SIZE words in its
2208 // payload, MIN_UPD_SIZE is more approprate than 1. It seems that
2209 // 1 does not cause any problem unless profiling is performed.
2210 // However, when LDV profiling goes on, we need to linearly scan
2211 // small object pool, where raise_closure is stored, so we should
2212 // use MIN_UPD_SIZE.
2213 //
2214 // raise_closure = (StgClosure *)RET_STGCALL1(P_,allocate,
2215 // sizeofW(StgClosure)+1);
2216 //
2217
2218 //
2219 // Walk up the stack, looking for the catch frame. On the way,
2220 // we update any closures pointed to from update frames with the
2221 // raise closure that we just built.
2222 //
2223 p = tso->stackobj->sp;
2224 while(1) {
2225 info = get_ret_itbl((StgClosure *)p);
2226 next = p + stack_frame_sizeW((StgClosure *)p);
2227 switch (info->i.type) {
2228
2229 case UPDATE_FRAME:
2230 // Only create raise_closure if we need to.
2231 if (raise_closure == NULL) {
2232 raise_closure =
2233 (StgThunk *)allocate(cap,sizeofW(StgThunk)+1);
2234 SET_HDR(raise_closure, &stg_raise_info, CCCS);
2235 raise_closure->payload[0] = exception;
2236 }
2237 updateThunk(cap, tso, ((StgUpdateFrame *)p)->updatee,
2238 (StgClosure *)raise_closure);
2239 p = next;
2240 continue;
2241
2242 case ATOMICALLY_FRAME:
2243 debugTrace(DEBUG_stm, "found ATOMICALLY_FRAME at %p", p);
2244 tso->stackobj->sp = p;
2245 return ATOMICALLY_FRAME;
2246
2247 case CATCH_FRAME:
2248 tso->stackobj->sp = p;
2249 return CATCH_FRAME;
2250
2251 case CATCH_STM_FRAME:
2252 debugTrace(DEBUG_stm, "found CATCH_STM_FRAME at %p", p);
2253 tso->stackobj->sp = p;
2254 return CATCH_STM_FRAME;
2255
2256 case UNDERFLOW_FRAME:
2257 tso->stackobj->sp = p;
2258 threadStackUnderflow(cap,tso);
2259 p = tso->stackobj->sp;
2260 continue;
2261
2262 case STOP_FRAME:
2263 tso->stackobj->sp = p;
2264 return STOP_FRAME;
2265
2266 case CATCH_RETRY_FRAME:
2267 default:
2268 p = next;
2269 continue;
2270 }
2271 }
2272 }
2273
2274
2275 /* -----------------------------------------------------------------------------
2276 findRetryFrameHelper
2277
2278 This function is called by the retry# primitive. It traverses the stack
2279 leaving tso->sp referring to the frame which should handle the retry.
2280
2281 This should either be a CATCH_RETRY_FRAME (if the retry# is within an orElse#)
2282 or should be a ATOMICALLY_FRAME (if the retry# reaches the top level).
2283
2284 We skip CATCH_STM_FRAMEs (aborting and rolling back the nested tx that they
2285 create) because retries are not considered to be exceptions, despite the
2286 similar implementation.
2287
2288 We should not expect to see CATCH_FRAME or STOP_FRAME because those should
2289 not be created within memory transactions.
2290 -------------------------------------------------------------------------- */
2291
2292 StgWord
2293 findRetryFrameHelper (Capability *cap, StgTSO *tso)
2294 {
2295 StgPtr p, next;
2296 StgRetInfoTable *info;
2297
2298 p = tso->stackobj->sp;
2299 while (1) {
2300 info = get_ret_itbl((StgClosure *)p);
2301 next = p + stack_frame_sizeW((StgClosure *)p);
2302 switch (info->i.type) {
2303
2304 case ATOMICALLY_FRAME:
2305 debugTrace(DEBUG_stm,
2306 "found ATOMICALLY_FRAME at %p during retry", p);
2307 tso->stackobj->sp = p;
2308 return ATOMICALLY_FRAME;
2309
2310 case CATCH_RETRY_FRAME:
2311 debugTrace(DEBUG_stm,
2312 "found CATCH_RETRY_FRAME at %p during retrry", p);
2313 tso->stackobj->sp = p;
2314 return CATCH_RETRY_FRAME;
2315
2316 case CATCH_STM_FRAME: {
2317 StgTRecHeader *trec = tso -> trec;
2318 StgTRecHeader *outer = trec -> enclosing_trec;
2319 debugTrace(DEBUG_stm,
2320 "found CATCH_STM_FRAME at %p during retry", p);
2321 debugTrace(DEBUG_stm, "trec=%p outer=%p", trec, outer);
2322 stmAbortTransaction(cap, trec);
2323 stmFreeAbortedTRec(cap, trec);
2324 tso -> trec = outer;
2325 p = next;
2326 continue;
2327 }
2328
2329 case UNDERFLOW_FRAME:
2330 threadStackUnderflow(cap,tso);
2331 p = tso->stackobj->sp;
2332 continue;
2333
2334 default:
2335 ASSERT(info->i.type != CATCH_FRAME);
2336 ASSERT(info->i.type != STOP_FRAME);
2337 p = next;
2338 continue;
2339 }
2340 }
2341 }
2342
2343 /* -----------------------------------------------------------------------------
2344 resurrectThreads is called after garbage collection on the list of
2345 threads found to be garbage. Each of these threads will be woken
2346 up and sent a signal: BlockedOnDeadMVar if the thread was blocked
2347 on an MVar, or NonTermination if the thread was blocked on a Black
2348 Hole.
2349
2350 Locks: assumes we hold *all* the capabilities.
2351 -------------------------------------------------------------------------- */
2352
2353 void
2354 resurrectThreads (StgTSO *threads)
2355 {
2356 StgTSO *tso, *next;
2357 Capability *cap;
2358 generation *gen;
2359
2360 for (tso = threads; tso != END_TSO_QUEUE; tso = next) {
2361 next = tso->global_link;
2362
2363 gen = Bdescr((P_)tso)->gen;
2364 tso->global_link = gen->threads;
2365 gen->threads = tso;
2366
2367 debugTrace(DEBUG_sched, "resurrecting thread %lu", (unsigned long)tso->id);
2368
2369 // Wake up the thread on the Capability it was last on
2370 cap = tso->cap;
2371
2372 switch (tso->why_blocked) {
2373 case BlockedOnMVar:
2374 /* Called by GC - sched_mutex lock is currently held. */
2375 throwToSingleThreaded(cap, tso,
2376 (StgClosure *)blockedIndefinitelyOnMVar_closure);
2377 break;
2378 case BlockedOnBlackHole:
2379 throwToSingleThreaded(cap, tso,
2380 (StgClosure *)nonTermination_closure);
2381 break;
2382 case BlockedOnSTM:
2383 throwToSingleThreaded(cap, tso,
2384 (StgClosure *)blockedIndefinitelyOnSTM_closure);
2385 break;
2386 case NotBlocked:
2387 /* This might happen if the thread was blocked on a black hole
2388 * belonging to a thread that we've just woken up (raiseAsync
2389 * can wake up threads, remember...).
2390 */
2391 continue;
2392 case BlockedOnMsgThrowTo:
2393 // This can happen if the target is masking, blocks on a
2394 // black hole, and then is found to be unreachable. In
2395 // this case, we want to let the target wake up and carry
2396 // on, and do nothing to this thread.
2397 continue;
2398 default:
2399 barf("resurrectThreads: thread blocked in a strange way: %d",
2400 tso->why_blocked);
2401 }
2402 }
2403 }