Add capability sets to the tracing/events system
[ghc.git] / rts / Capability.c
1 /* ---------------------------------------------------------------------------
2 *
3 * (c) The GHC Team, 2003-2006
4 *
5 * Capabilities
6 *
7 * A Capability represent the token required to execute STG code,
8 * and all the state an OS thread/task needs to run Haskell code:
9 * its STG registers, a pointer to its TSO, a nursery etc. During
10 * STG execution, a pointer to the capabilitity is kept in a
11 * register (BaseReg; actually it is a pointer to cap->r).
12 *
13 * Only in an THREADED_RTS build will there be multiple capabilities,
14 * for non-threaded builds there is only one global capability, namely
15 * MainCapability.
16 *
17 * --------------------------------------------------------------------------*/
18
19 #include "PosixSource.h"
20 #include "Rts.h"
21
22 #include "Capability.h"
23 #include "Schedule.h"
24 #include "Sparks.h"
25 #include "Trace.h"
26 #include "sm/GC.h" // for gcWorkerThread()
27 #include "STM.h"
28 #include "RtsUtils.h"
29
30 // one global capability, this is the Capability for non-threaded
31 // builds, and for +RTS -N1
32 Capability MainCapability;
33
34 nat n_capabilities = 0;
35 Capability *capabilities = NULL;
36
37 // Holds the Capability which last became free. This is used so that
38 // an in-call has a chance of quickly finding a free Capability.
39 // Maintaining a global free list of Capabilities would require global
40 // locking, so we don't do that.
41 Capability *last_free_capability = NULL;
42
43 /* GC indicator, in scope for the scheduler, init'ed to false */
44 volatile StgWord waiting_for_gc = 0;
45
46 /* Let foreign code get the current Capability -- assuming there is one!
47 * This is useful for unsafe foreign calls because they are called with
48 * the current Capability held, but they are not passed it. For example,
49 * see see the integer-gmp package which calls allocateLocal() in its
50 * stgAllocForGMP() function (which gets called by gmp functions).
51 * */
52 Capability * rts_unsafeGetMyCapability (void)
53 {
54 #if defined(THREADED_RTS)
55 return myTask()->cap;
56 #else
57 return &MainCapability;
58 #endif
59 }
60
61 #if defined(THREADED_RTS)
62 STATIC_INLINE rtsBool
63 globalWorkToDo (void)
64 {
65 return sched_state >= SCHED_INTERRUPTING
66 || recent_activity == ACTIVITY_INACTIVE; // need to check for deadlock
67 }
68 #endif
69
70 #if defined(THREADED_RTS)
71 StgClosure *
72 findSpark (Capability *cap)
73 {
74 Capability *robbed;
75 StgClosurePtr spark;
76 rtsBool retry;
77 nat i = 0;
78
79 if (!emptyRunQueue(cap) || cap->returning_tasks_hd != NULL) {
80 // If there are other threads, don't try to run any new
81 // sparks: sparks might be speculative, we don't want to take
82 // resources away from the main computation.
83 return 0;
84 }
85
86 do {
87 retry = rtsFalse;
88
89 // first try to get a spark from our own pool.
90 // We should be using reclaimSpark(), because it works without
91 // needing any atomic instructions:
92 // spark = reclaimSpark(cap->sparks);
93 // However, measurements show that this makes at least one benchmark
94 // slower (prsa) and doesn't affect the others.
95 spark = tryStealSpark(cap);
96 if (spark != NULL) {
97 cap->sparks_converted++;
98
99 // Post event for running a spark from capability's own pool.
100 traceEventRunSpark(cap, cap->r.rCurrentTSO);
101
102 return spark;
103 }
104 if (!emptySparkPoolCap(cap)) {
105 retry = rtsTrue;
106 }
107
108 if (n_capabilities == 1) { return NULL; } // makes no sense...
109
110 debugTrace(DEBUG_sched,
111 "cap %d: Trying to steal work from other capabilities",
112 cap->no);
113
114 /* visit cap.s 0..n-1 in sequence until a theft succeeds. We could
115 start at a random place instead of 0 as well. */
116 for ( i=0 ; i < n_capabilities ; i++ ) {
117 robbed = &capabilities[i];
118 if (cap == robbed) // ourselves...
119 continue;
120
121 if (emptySparkPoolCap(robbed)) // nothing to steal here
122 continue;
123
124 spark = tryStealSpark(robbed);
125 if (spark == NULL && !emptySparkPoolCap(robbed)) {
126 // we conflicted with another thread while trying to steal;
127 // try again later.
128 retry = rtsTrue;
129 }
130
131 if (spark != NULL) {
132 cap->sparks_converted++;
133
134 traceEventStealSpark(cap, cap->r.rCurrentTSO, robbed->no);
135
136 return spark;
137 }
138 // otherwise: no success, try next one
139 }
140 } while (retry);
141
142 debugTrace(DEBUG_sched, "No sparks stolen");
143 return NULL;
144 }
145
146 // Returns True if any spark pool is non-empty at this moment in time
147 // The result is only valid for an instant, of course, so in a sense
148 // is immediately invalid, and should not be relied upon for
149 // correctness.
150 rtsBool
151 anySparks (void)
152 {
153 nat i;
154
155 for (i=0; i < n_capabilities; i++) {
156 if (!emptySparkPoolCap(&capabilities[i])) {
157 return rtsTrue;
158 }
159 }
160 return rtsFalse;
161 }
162 #endif
163
164 /* -----------------------------------------------------------------------------
165 * Manage the returning_tasks lists.
166 *
167 * These functions require cap->lock
168 * -------------------------------------------------------------------------- */
169
170 #if defined(THREADED_RTS)
171 STATIC_INLINE void
172 newReturningTask (Capability *cap, Task *task)
173 {
174 ASSERT_LOCK_HELD(&cap->lock);
175 ASSERT(task->next == NULL);
176 if (cap->returning_tasks_hd) {
177 ASSERT(cap->returning_tasks_tl->next == NULL);
178 cap->returning_tasks_tl->next = task;
179 } else {
180 cap->returning_tasks_hd = task;
181 }
182 cap->returning_tasks_tl = task;
183 }
184
185 STATIC_INLINE Task *
186 popReturningTask (Capability *cap)
187 {
188 ASSERT_LOCK_HELD(&cap->lock);
189 Task *task;
190 task = cap->returning_tasks_hd;
191 ASSERT(task);
192 cap->returning_tasks_hd = task->next;
193 if (!cap->returning_tasks_hd) {
194 cap->returning_tasks_tl = NULL;
195 }
196 task->next = NULL;
197 return task;
198 }
199 #endif
200
201 /* ----------------------------------------------------------------------------
202 * Initialisation
203 *
204 * The Capability is initially marked not free.
205 * ------------------------------------------------------------------------- */
206
207 static void
208 initCapability( Capability *cap, nat i )
209 {
210 nat g;
211
212 cap->no = i;
213 cap->in_haskell = rtsFalse;
214
215 cap->run_queue_hd = END_TSO_QUEUE;
216 cap->run_queue_tl = END_TSO_QUEUE;
217
218 #if defined(THREADED_RTS)
219 initMutex(&cap->lock);
220 cap->running_task = NULL; // indicates cap is free
221 cap->spare_workers = NULL;
222 cap->n_spare_workers = 0;
223 cap->suspended_ccalls = NULL;
224 cap->returning_tasks_hd = NULL;
225 cap->returning_tasks_tl = NULL;
226 cap->inbox = (Message*)END_TSO_QUEUE;
227 cap->sparks_created = 0;
228 cap->sparks_dud = 0;
229 cap->sparks_converted = 0;
230 cap->sparks_gcd = 0;
231 cap->sparks_fizzled = 0;
232 #endif
233
234 cap->f.stgEagerBlackholeInfo = (W_)&__stg_EAGER_BLACKHOLE_info;
235 cap->f.stgGCEnter1 = (StgFunPtr)__stg_gc_enter_1;
236 cap->f.stgGCFun = (StgFunPtr)__stg_gc_fun;
237
238 cap->mut_lists = stgMallocBytes(sizeof(bdescr *) *
239 RtsFlags.GcFlags.generations,
240 "initCapability");
241 cap->saved_mut_lists = stgMallocBytes(sizeof(bdescr *) *
242 RtsFlags.GcFlags.generations,
243 "initCapability");
244
245 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
246 cap->mut_lists[g] = NULL;
247 }
248
249 cap->free_tvar_watch_queues = END_STM_WATCH_QUEUE;
250 cap->free_invariant_check_queues = END_INVARIANT_CHECK_QUEUE;
251 cap->free_trec_chunks = END_STM_CHUNK_LIST;
252 cap->free_trec_headers = NO_TREC;
253 cap->transaction_tokens = 0;
254 cap->context_switch = 0;
255 cap->pinned_object_block = NULL;
256
257 traceCapsetAssignCap(CAPSET_OSPROCESS_DEFAULT, i);
258 }
259
260 /* ---------------------------------------------------------------------------
261 * Function: initCapabilities()
262 *
263 * Purpose: set up the Capability handling. For the THREADED_RTS build,
264 * we keep a table of them, the size of which is
265 * controlled by the user via the RTS flag -N.
266 *
267 * ------------------------------------------------------------------------- */
268 void
269 initCapabilities( void )
270 {
271 /* Declare a single capability set representing the process.
272 Each capability will get added to this capset. */
273 traceCapsetCreate(CAPSET_OSPROCESS_DEFAULT, CapsetTypeOsProcess);
274
275 #if defined(THREADED_RTS)
276 nat i;
277
278 #ifndef REG_Base
279 // We can't support multiple CPUs if BaseReg is not a register
280 if (RtsFlags.ParFlags.nNodes > 1) {
281 errorBelch("warning: multiple CPUs not supported in this build, reverting to 1");
282 RtsFlags.ParFlags.nNodes = 1;
283 }
284 #endif
285
286 n_capabilities = RtsFlags.ParFlags.nNodes;
287
288 if (n_capabilities == 1) {
289 capabilities = &MainCapability;
290 // THREADED_RTS must work on builds that don't have a mutable
291 // BaseReg (eg. unregisterised), so in this case
292 // capabilities[0] must coincide with &MainCapability.
293 } else {
294 capabilities = stgMallocBytes(n_capabilities * sizeof(Capability),
295 "initCapabilities");
296 }
297
298 for (i = 0; i < n_capabilities; i++) {
299 initCapability(&capabilities[i], i);
300 }
301
302 debugTrace(DEBUG_sched, "allocated %d capabilities", n_capabilities);
303
304 #else /* !THREADED_RTS */
305
306 n_capabilities = 1;
307 capabilities = &MainCapability;
308 initCapability(&MainCapability, 0);
309
310 #endif
311
312 // There are no free capabilities to begin with. We will start
313 // a worker Task to each Capability, which will quickly put the
314 // Capability on the free list when it finds nothing to do.
315 last_free_capability = &capabilities[0];
316 }
317
318 /* ----------------------------------------------------------------------------
319 * setContextSwitches: cause all capabilities to context switch as
320 * soon as possible.
321 * ------------------------------------------------------------------------- */
322
323 void setContextSwitches(void)
324 {
325 nat i;
326 for (i=0; i < n_capabilities; i++) {
327 contextSwitchCapability(&capabilities[i]);
328 }
329 }
330
331 /* ----------------------------------------------------------------------------
332 * Give a Capability to a Task. The task must currently be sleeping
333 * on its condition variable.
334 *
335 * Requires cap->lock (modifies cap->running_task).
336 *
337 * When migrating a Task, the migrater must take task->lock before
338 * modifying task->cap, to synchronise with the waking up Task.
339 * Additionally, the migrater should own the Capability (when
340 * migrating the run queue), or cap->lock (when migrating
341 * returning_workers).
342 *
343 * ------------------------------------------------------------------------- */
344
345 #if defined(THREADED_RTS)
346 STATIC_INLINE void
347 giveCapabilityToTask (Capability *cap USED_IF_DEBUG, Task *task)
348 {
349 ASSERT_LOCK_HELD(&cap->lock);
350 ASSERT(task->cap == cap);
351 debugTrace(DEBUG_sched, "passing capability %d to %s %p",
352 cap->no, task->incall->tso ? "bound task" : "worker",
353 (void *)task->id);
354 ACQUIRE_LOCK(&task->lock);
355 task->wakeup = rtsTrue;
356 // the wakeup flag is needed because signalCondition() doesn't
357 // flag the condition if the thread is already runniing, but we want
358 // it to be sticky.
359 signalCondition(&task->cond);
360 RELEASE_LOCK(&task->lock);
361 }
362 #endif
363
364 /* ----------------------------------------------------------------------------
365 * Function: releaseCapability(Capability*)
366 *
367 * Purpose: Letting go of a capability. Causes a
368 * 'returning worker' thread or a 'waiting worker'
369 * to wake up, in that order.
370 * ------------------------------------------------------------------------- */
371
372 #if defined(THREADED_RTS)
373 void
374 releaseCapability_ (Capability* cap,
375 rtsBool always_wakeup)
376 {
377 Task *task;
378
379 task = cap->running_task;
380
381 ASSERT_PARTIAL_CAPABILITY_INVARIANTS(cap,task);
382
383 cap->running_task = NULL;
384
385 // Check to see whether a worker thread can be given
386 // the go-ahead to return the result of an external call..
387 if (cap->returning_tasks_hd != NULL) {
388 giveCapabilityToTask(cap,cap->returning_tasks_hd);
389 // The Task pops itself from the queue (see waitForReturnCapability())
390 return;
391 }
392
393 if (waiting_for_gc == PENDING_GC_SEQ) {
394 last_free_capability = cap; // needed?
395 debugTrace(DEBUG_sched, "GC pending, set capability %d free", cap->no);
396 return;
397 }
398
399
400 // If the next thread on the run queue is a bound thread,
401 // give this Capability to the appropriate Task.
402 if (!emptyRunQueue(cap) && cap->run_queue_hd->bound) {
403 // Make sure we're not about to try to wake ourselves up
404 // ASSERT(task != cap->run_queue_hd->bound);
405 // assertion is false: in schedule() we force a yield after
406 // ThreadBlocked, but the thread may be back on the run queue
407 // by now.
408 task = cap->run_queue_hd->bound->task;
409 giveCapabilityToTask(cap,task);
410 return;
411 }
412
413 if (!cap->spare_workers) {
414 // Create a worker thread if we don't have one. If the system
415 // is interrupted, we only create a worker task if there
416 // are threads that need to be completed. If the system is
417 // shutting down, we never create a new worker.
418 if (sched_state < SCHED_SHUTTING_DOWN || !emptyRunQueue(cap)) {
419 debugTrace(DEBUG_sched,
420 "starting new worker on capability %d", cap->no);
421 startWorkerTask(cap);
422 return;
423 }
424 }
425
426 // If we have an unbound thread on the run queue, or if there's
427 // anything else to do, give the Capability to a worker thread.
428 if (always_wakeup ||
429 !emptyRunQueue(cap) || !emptyInbox(cap) ||
430 !emptySparkPoolCap(cap) || globalWorkToDo()) {
431 if (cap->spare_workers) {
432 giveCapabilityToTask(cap,cap->spare_workers);
433 // The worker Task pops itself from the queue;
434 return;
435 }
436 }
437
438 last_free_capability = cap;
439 debugTrace(DEBUG_sched, "freeing capability %d", cap->no);
440 }
441
442 void
443 releaseCapability (Capability* cap USED_IF_THREADS)
444 {
445 ACQUIRE_LOCK(&cap->lock);
446 releaseCapability_(cap, rtsFalse);
447 RELEASE_LOCK(&cap->lock);
448 }
449
450 void
451 releaseAndWakeupCapability (Capability* cap USED_IF_THREADS)
452 {
453 ACQUIRE_LOCK(&cap->lock);
454 releaseCapability_(cap, rtsTrue);
455 RELEASE_LOCK(&cap->lock);
456 }
457
458 static void
459 releaseCapabilityAndQueueWorker (Capability* cap USED_IF_THREADS)
460 {
461 Task *task;
462
463 ACQUIRE_LOCK(&cap->lock);
464
465 task = cap->running_task;
466
467 // If the Task is stopped, we shouldn't be yielding, we should
468 // be just exiting.
469 ASSERT(!task->stopped);
470
471 // If the current task is a worker, save it on the spare_workers
472 // list of this Capability. A worker can mark itself as stopped,
473 // in which case it is not replaced on the spare_worker queue.
474 // This happens when the system is shutting down (see
475 // Schedule.c:workerStart()).
476 if (!isBoundTask(task))
477 {
478 if (cap->n_spare_workers < MAX_SPARE_WORKERS)
479 {
480 task->next = cap->spare_workers;
481 cap->spare_workers = task;
482 cap->n_spare_workers++;
483 }
484 else
485 {
486 debugTrace(DEBUG_sched, "%d spare workers already, exiting",
487 cap->n_spare_workers);
488 releaseCapability_(cap,rtsFalse);
489 // hold the lock until after workerTaskStop; c.f. scheduleWorker()
490 workerTaskStop(task);
491 RELEASE_LOCK(&cap->lock);
492 shutdownThread();
493 }
494 }
495 // Bound tasks just float around attached to their TSOs.
496
497 releaseCapability_(cap,rtsFalse);
498
499 RELEASE_LOCK(&cap->lock);
500 }
501 #endif
502
503 /* ----------------------------------------------------------------------------
504 * waitForReturnCapability( Task *task )
505 *
506 * Purpose: when an OS thread returns from an external call,
507 * it calls waitForReturnCapability() (via Schedule.resumeThread())
508 * to wait for permission to enter the RTS & communicate the
509 * result of the external call back to the Haskell thread that
510 * made it.
511 *
512 * ------------------------------------------------------------------------- */
513 void
514 waitForReturnCapability (Capability **pCap, Task *task)
515 {
516 #if !defined(THREADED_RTS)
517
518 MainCapability.running_task = task;
519 task->cap = &MainCapability;
520 *pCap = &MainCapability;
521
522 #else
523 Capability *cap = *pCap;
524
525 if (cap == NULL) {
526 // Try last_free_capability first
527 cap = last_free_capability;
528 if (cap->running_task) {
529 nat i;
530 // otherwise, search for a free capability
531 cap = NULL;
532 for (i = 0; i < n_capabilities; i++) {
533 if (!capabilities[i].running_task) {
534 cap = &capabilities[i];
535 break;
536 }
537 }
538 if (cap == NULL) {
539 // Can't find a free one, use last_free_capability.
540 cap = last_free_capability;
541 }
542 }
543
544 // record the Capability as the one this Task is now assocated with.
545 task->cap = cap;
546
547 } else {
548 ASSERT(task->cap == cap);
549 }
550
551 ACQUIRE_LOCK(&cap->lock);
552
553 debugTrace(DEBUG_sched, "returning; I want capability %d", cap->no);
554
555 if (!cap->running_task) {
556 // It's free; just grab it
557 cap->running_task = task;
558 RELEASE_LOCK(&cap->lock);
559 } else {
560 newReturningTask(cap,task);
561 RELEASE_LOCK(&cap->lock);
562
563 for (;;) {
564 ACQUIRE_LOCK(&task->lock);
565 // task->lock held, cap->lock not held
566 if (!task->wakeup) waitCondition(&task->cond, &task->lock);
567 cap = task->cap;
568 task->wakeup = rtsFalse;
569 RELEASE_LOCK(&task->lock);
570
571 // now check whether we should wake up...
572 ACQUIRE_LOCK(&cap->lock);
573 if (cap->running_task == NULL) {
574 if (cap->returning_tasks_hd != task) {
575 giveCapabilityToTask(cap,cap->returning_tasks_hd);
576 RELEASE_LOCK(&cap->lock);
577 continue;
578 }
579 cap->running_task = task;
580 popReturningTask(cap);
581 RELEASE_LOCK(&cap->lock);
582 break;
583 }
584 RELEASE_LOCK(&cap->lock);
585 }
586
587 }
588
589 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
590
591 debugTrace(DEBUG_sched, "resuming capability %d", cap->no);
592
593 *pCap = cap;
594 #endif
595 }
596
597 #if defined(THREADED_RTS)
598 /* ----------------------------------------------------------------------------
599 * yieldCapability
600 * ------------------------------------------------------------------------- */
601
602 void
603 yieldCapability (Capability** pCap, Task *task)
604 {
605 Capability *cap = *pCap;
606
607 if (waiting_for_gc == PENDING_GC_PAR) {
608 traceEventGcStart(cap);
609 gcWorkerThread(cap);
610 traceEventGcEnd(cap);
611 return;
612 }
613
614 debugTrace(DEBUG_sched, "giving up capability %d", cap->no);
615
616 // We must now release the capability and wait to be woken up
617 // again.
618 task->wakeup = rtsFalse;
619 releaseCapabilityAndQueueWorker(cap);
620
621 for (;;) {
622 ACQUIRE_LOCK(&task->lock);
623 // task->lock held, cap->lock not held
624 if (!task->wakeup) waitCondition(&task->cond, &task->lock);
625 cap = task->cap;
626 task->wakeup = rtsFalse;
627 RELEASE_LOCK(&task->lock);
628
629 debugTrace(DEBUG_sched, "woken up on capability %d", cap->no);
630
631 ACQUIRE_LOCK(&cap->lock);
632 if (cap->running_task != NULL) {
633 debugTrace(DEBUG_sched,
634 "capability %d is owned by another task", cap->no);
635 RELEASE_LOCK(&cap->lock);
636 continue;
637 }
638
639 if (task->incall->tso == NULL) {
640 ASSERT(cap->spare_workers != NULL);
641 // if we're not at the front of the queue, release it
642 // again. This is unlikely to happen.
643 if (cap->spare_workers != task) {
644 giveCapabilityToTask(cap,cap->spare_workers);
645 RELEASE_LOCK(&cap->lock);
646 continue;
647 }
648 cap->spare_workers = task->next;
649 task->next = NULL;
650 cap->n_spare_workers--;
651 }
652 cap->running_task = task;
653 RELEASE_LOCK(&cap->lock);
654 break;
655 }
656
657 debugTrace(DEBUG_sched, "resuming capability %d", cap->no);
658 ASSERT(cap->running_task == task);
659
660 *pCap = cap;
661
662 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
663
664 return;
665 }
666
667 /* ----------------------------------------------------------------------------
668 * prodCapability
669 *
670 * If a Capability is currently idle, wake up a Task on it. Used to
671 * get every Capability into the GC.
672 * ------------------------------------------------------------------------- */
673
674 void
675 prodCapability (Capability *cap, Task *task)
676 {
677 ACQUIRE_LOCK(&cap->lock);
678 if (!cap->running_task) {
679 cap->running_task = task;
680 releaseCapability_(cap,rtsTrue);
681 }
682 RELEASE_LOCK(&cap->lock);
683 }
684
685 /* ----------------------------------------------------------------------------
686 * tryGrabCapability
687 *
688 * Attempt to gain control of a Capability if it is free.
689 *
690 * ------------------------------------------------------------------------- */
691
692 rtsBool
693 tryGrabCapability (Capability *cap, Task *task)
694 {
695 if (cap->running_task != NULL) return rtsFalse;
696 ACQUIRE_LOCK(&cap->lock);
697 if (cap->running_task != NULL) {
698 RELEASE_LOCK(&cap->lock);
699 return rtsFalse;
700 }
701 task->cap = cap;
702 cap->running_task = task;
703 RELEASE_LOCK(&cap->lock);
704 return rtsTrue;
705 }
706
707
708 #endif /* THREADED_RTS */
709
710 /* ----------------------------------------------------------------------------
711 * shutdownCapability
712 *
713 * At shutdown time, we want to let everything exit as cleanly as
714 * possible. For each capability, we let its run queue drain, and
715 * allow the workers to stop.
716 *
717 * This function should be called when interrupted and
718 * shutting_down_scheduler = rtsTrue, thus any worker that wakes up
719 * will exit the scheduler and call taskStop(), and any bound thread
720 * that wakes up will return to its caller. Runnable threads are
721 * killed.
722 *
723 * ------------------------------------------------------------------------- */
724
725 void
726 shutdownCapability (Capability *cap,
727 Task *task USED_IF_THREADS,
728 rtsBool safe USED_IF_THREADS)
729 {
730 #if defined(THREADED_RTS)
731 nat i;
732
733 task->cap = cap;
734
735 // Loop indefinitely until all the workers have exited and there
736 // are no Haskell threads left. We used to bail out after 50
737 // iterations of this loop, but that occasionally left a worker
738 // running which caused problems later (the closeMutex() below
739 // isn't safe, for one thing).
740
741 for (i = 0; /* i < 50 */; i++) {
742 ASSERT(sched_state == SCHED_SHUTTING_DOWN);
743
744 debugTrace(DEBUG_sched,
745 "shutting down capability %d, attempt %d", cap->no, i);
746 ACQUIRE_LOCK(&cap->lock);
747 if (cap->running_task) {
748 RELEASE_LOCK(&cap->lock);
749 debugTrace(DEBUG_sched, "not owner, yielding");
750 yieldThread();
751 continue;
752 }
753 cap->running_task = task;
754
755 if (cap->spare_workers) {
756 // Look for workers that have died without removing
757 // themselves from the list; this could happen if the OS
758 // summarily killed the thread, for example. This
759 // actually happens on Windows when the system is
760 // terminating the program, and the RTS is running in a
761 // DLL.
762 Task *t, *prev;
763 prev = NULL;
764 for (t = cap->spare_workers; t != NULL; t = t->next) {
765 if (!osThreadIsAlive(t->id)) {
766 debugTrace(DEBUG_sched,
767 "worker thread %p has died unexpectedly", (void *)t->id);
768 cap->n_spare_workers--;
769 if (!prev) {
770 cap->spare_workers = t->next;
771 } else {
772 prev->next = t->next;
773 }
774 prev = t;
775 }
776 }
777 }
778
779 if (!emptyRunQueue(cap) || cap->spare_workers) {
780 debugTrace(DEBUG_sched,
781 "runnable threads or workers still alive, yielding");
782 releaseCapability_(cap,rtsFalse); // this will wake up a worker
783 RELEASE_LOCK(&cap->lock);
784 yieldThread();
785 continue;
786 }
787
788 // If "safe", then busy-wait for any threads currently doing
789 // foreign calls. If we're about to unload this DLL, for
790 // example, we need to be sure that there are no OS threads
791 // that will try to return to code that has been unloaded.
792 // We can be a bit more relaxed when this is a standalone
793 // program that is about to terminate, and let safe=false.
794 if (cap->suspended_ccalls && safe) {
795 debugTrace(DEBUG_sched,
796 "thread(s) are involved in foreign calls, yielding");
797 cap->running_task = NULL;
798 RELEASE_LOCK(&cap->lock);
799 // The IO manager thread might have been slow to start up,
800 // so the first attempt to kill it might not have
801 // succeeded. Just in case, try again - the kill message
802 // will only be sent once.
803 //
804 // To reproduce this deadlock: run ffi002(threaded1)
805 // repeatedly on a loaded machine.
806 ioManagerDie();
807 yieldThread();
808 continue;
809 }
810
811 traceEventShutdown(cap);
812 RELEASE_LOCK(&cap->lock);
813 break;
814 }
815 // we now have the Capability, its run queue and spare workers
816 // list are both empty.
817
818 // ToDo: we can't drop this mutex, because there might still be
819 // threads performing foreign calls that will eventually try to
820 // return via resumeThread() and attempt to grab cap->lock.
821 // closeMutex(&cap->lock);
822
823 #endif /* THREADED_RTS */
824
825 traceCapsetRemoveCap(CAPSET_OSPROCESS_DEFAULT, cap->no);
826 }
827
828 void
829 shutdownCapabilities(Task *task, rtsBool safe)
830 {
831 nat i;
832 for (i=0; i < n_capabilities; i++) {
833 ASSERT(task->incall->tso == NULL);
834 shutdownCapability(&capabilities[i], task, safe);
835 }
836 traceCapsetDelete(CAPSET_OSPROCESS_DEFAULT);
837 }
838
839 static void
840 freeCapability (Capability *cap)
841 {
842 stgFree(cap->mut_lists);
843 stgFree(cap->saved_mut_lists);
844 #if defined(THREADED_RTS)
845 freeSparkPool(cap->sparks);
846 #endif
847 }
848
849 void
850 freeCapabilities (void)
851 {
852 #if defined(THREADED_RTS)
853 nat i;
854 for (i=0; i < n_capabilities; i++) {
855 freeCapability(&capabilities[i]);
856 }
857 #else
858 freeCapability(&MainCapability);
859 #endif
860 }
861
862 /* ---------------------------------------------------------------------------
863 Mark everything directly reachable from the Capabilities. When
864 using multiple GC threads, each GC thread marks all Capabilities
865 for which (c `mod` n == 0), for Capability c and thread n.
866 ------------------------------------------------------------------------ */
867
868 void
869 markCapability (evac_fn evac, void *user, Capability *cap,
870 rtsBool no_mark_sparks USED_IF_THREADS)
871 {
872 InCall *incall;
873
874 // Each GC thread is responsible for following roots from the
875 // Capability of the same number. There will usually be the same
876 // or fewer Capabilities as GC threads, but just in case there
877 // are more, we mark every Capability whose number is the GC
878 // thread's index plus a multiple of the number of GC threads.
879 evac(user, (StgClosure **)(void *)&cap->run_queue_hd);
880 evac(user, (StgClosure **)(void *)&cap->run_queue_tl);
881 #if defined(THREADED_RTS)
882 evac(user, (StgClosure **)(void *)&cap->inbox);
883 #endif
884 for (incall = cap->suspended_ccalls; incall != NULL;
885 incall=incall->next) {
886 evac(user, (StgClosure **)(void *)&incall->suspended_tso);
887 }
888
889 #if defined(THREADED_RTS)
890 if (!no_mark_sparks) {
891 traverseSparkQueue (evac, user, cap);
892 }
893 #endif
894
895 // Free STM structures for this Capability
896 stmPreGCHook(cap);
897 }
898
899 void
900 markCapabilities (evac_fn evac, void *user)
901 {
902 nat n;
903 for (n = 0; n < n_capabilities; n++) {
904 markCapability(evac, user, &capabilities[n], rtsFalse);
905 }
906 }