1 /* ---------------------------------------------------------------------------
3 * (c) The GHC Team, 1998-2006
5 * The scheduler and thread-related functionality
7 * --------------------------------------------------------------------------*/
9 #include "PosixSource.h"
10 #define KEEP_LOCKCLOSURE
15 #include "OSThreads.h"
20 #include "StgMiscClosures.h"
21 #include "Interpreter.h"
23 #include "RtsSignals.h"
29 #include "ThreadLabels.h"
30 #include "LdvProfile.h"
32 #include "Proftimer.h"
35 /* PARALLEL_HASKELL includes go here */
38 #include "Capability.h"
40 #include "AwaitEvent.h"
41 #if defined(mingw32_HOST_OS)
42 #include "win32/IOManager.h"
45 #include "RaiseAsync.h"
47 #include "ThrIOManager.h"
49 #ifdef HAVE_SYS_TYPES_H
50 #include <sys/types.h>
64 // Turn off inlining when debugging - it obfuscates things
67 # define STATIC_INLINE static
70 /* -----------------------------------------------------------------------------
72 * -------------------------------------------------------------------------- */
74 #if !defined(THREADED_RTS)
75 // Blocked/sleeping thrads
76 StgTSO *blocked_queue_hd = NULL;
77 StgTSO *blocked_queue_tl = NULL;
78 StgTSO *sleeping_queue = NULL; // perhaps replace with a hash table?
81 /* Threads blocked on blackholes.
82 * LOCK: sched_mutex+capability, or all capabilities
84 StgTSO *blackhole_queue = NULL;
86 /* The blackhole_queue should be checked for threads to wake up. See
87 * Schedule.h for more thorough comment.
88 * LOCK: none (doesn't matter if we miss an update)
90 rtsBool blackholes_need_checking = rtsFalse;
92 /* flag that tracks whether we have done any execution in this time slice.
93 * LOCK: currently none, perhaps we should lock (but needs to be
94 * updated in the fast path of the scheduler).
96 * NB. must be StgWord, we do xchg() on it.
98 volatile StgWord recent_activity = ACTIVITY_YES;
100 /* if this flag is set as well, give up execution
101 * LOCK: none (changes monotonically)
103 volatile StgWord sched_state = SCHED_RUNNING;
105 /* This is used in `TSO.h' and gcc 2.96 insists that this variable actually
106 * exists - earlier gccs apparently didn't.
112 * Set to TRUE when entering a shutdown state (via shutdownHaskellAndExit()) --
113 * in an MT setting, needed to signal that a worker thread shouldn't hang around
114 * in the scheduler when it is out of work.
116 rtsBool shutting_down_scheduler = rtsFalse;
119 * This mutex protects most of the global scheduler data in
120 * the THREADED_RTS runtime.
122 #if defined(THREADED_RTS)
126 #if !defined(mingw32_HOST_OS)
127 #define FORKPROCESS_PRIMOP_SUPPORTED
130 /* -----------------------------------------------------------------------------
131 * static function prototypes
132 * -------------------------------------------------------------------------- */
134 static Capability *schedule (Capability *initialCapability, Task *task);
137 // These function all encapsulate parts of the scheduler loop, and are
138 // abstracted only to make the structure and control flow of the
139 // scheduler clearer.
141 static void schedulePreLoop (void);
142 static void scheduleFindWork (Capability *cap);
143 #if defined(THREADED_RTS)
144 static void scheduleYield (Capability **pcap, Task *task);
146 static void scheduleStartSignalHandlers (Capability *cap);
147 static void scheduleCheckBlockedThreads (Capability *cap);
148 static void scheduleCheckWakeupThreads(Capability *cap USED_IF_NOT_THREADS);
149 static void scheduleCheckBlackHoles (Capability *cap);
150 static void scheduleDetectDeadlock (Capability *cap, Task *task);
151 static void schedulePushWork(Capability *cap, Task *task);
152 #if defined(PARALLEL_HASKELL)
153 static rtsBool scheduleGetRemoteWork(Capability *cap);
154 static void scheduleSendPendingMessages(void);
156 #if defined(PARALLEL_HASKELL) || defined(THREADED_RTS)
157 static void scheduleActivateSpark(Capability *cap);
159 static void schedulePostRunThread(Capability *cap, StgTSO *t);
160 static rtsBool scheduleHandleHeapOverflow( Capability *cap, StgTSO *t );
161 static void scheduleHandleStackOverflow( Capability *cap, Task *task,
163 static rtsBool scheduleHandleYield( Capability *cap, StgTSO *t,
164 nat prev_what_next );
165 static void scheduleHandleThreadBlocked( StgTSO *t );
166 static rtsBool scheduleHandleThreadFinished( Capability *cap, Task *task,
168 static rtsBool scheduleNeedHeapProfile(rtsBool ready_to_gc);
169 static Capability *scheduleDoGC(Capability *cap, Task *task,
170 rtsBool force_major);
172 static rtsBool checkBlackHoles(Capability *cap);
174 static StgTSO *threadStackOverflow(Capability *cap, StgTSO *tso);
175 static StgTSO *threadStackUnderflow(Task *task, StgTSO *tso);
177 static void deleteThread (Capability *cap, StgTSO *tso);
178 static void deleteAllThreads (Capability *cap);
180 #ifdef FORKPROCESS_PRIMOP_SUPPORTED
181 static void deleteThread_(Capability *cap, StgTSO *tso);
185 static char *whatNext_strs[] = {
195 /* -----------------------------------------------------------------------------
196 * Putting a thread on the run queue: different scheduling policies
197 * -------------------------------------------------------------------------- */
200 addToRunQueue( Capability *cap, StgTSO *t )
202 #if defined(PARALLEL_HASKELL)
203 if (RtsFlags.ParFlags.doFairScheduling) {
204 // this does round-robin scheduling; good for concurrency
205 appendToRunQueue(cap,t);
207 // this does unfair scheduling; good for parallelism
208 pushOnRunQueue(cap,t);
211 // this does round-robin scheduling; good for concurrency
212 appendToRunQueue(cap,t);
216 /* ---------------------------------------------------------------------------
217 Main scheduling loop.
219 We use round-robin scheduling, each thread returning to the
220 scheduler loop when one of these conditions is detected:
223 * timer expires (thread yields)
229 In a GranSim setup this loop iterates over the global event queue.
230 This revolves around the global event queue, which determines what
231 to do next. Therefore, it's more complicated than either the
232 concurrent or the parallel (GUM) setup.
233 This version has been entirely removed (JB 2008/08).
236 GUM iterates over incoming messages.
237 It starts with nothing to do (thus CurrentTSO == END_TSO_QUEUE),
238 and sends out a fish whenever it has nothing to do; in-between
239 doing the actual reductions (shared code below) it processes the
240 incoming messages and deals with delayed operations
241 (see PendingFetches).
242 This is not the ugliest code you could imagine, but it's bloody close.
244 (JB 2008/08) This version was formerly indicated by a PP-Flag PAR,
245 now by PP-flag PARALLEL_HASKELL. The Eden RTS (in GHC-6.x) uses it,
246 as well as future GUM versions. This file has been refurbished to
247 only contain valid code, which is however incomplete, refers to
248 invalid includes etc.
250 ------------------------------------------------------------------------ */
253 schedule (Capability *initialCapability, Task *task)
257 StgThreadReturnCode ret;
258 #if defined(PARALLEL_HASKELL)
259 rtsBool receivedFinish = rtsFalse;
263 #if defined(THREADED_RTS)
264 rtsBool first = rtsTrue;
267 cap = initialCapability;
269 // Pre-condition: this task owns initialCapability.
270 // The sched_mutex is *NOT* held
271 // NB. on return, we still hold a capability.
273 debugTrace (DEBUG_sched,
274 "### NEW SCHEDULER LOOP (task: %p, cap: %p)",
275 task, initialCapability);
279 // -----------------------------------------------------------
280 // Scheduler loop starts here:
282 #if defined(PARALLEL_HASKELL)
283 #define TERMINATION_CONDITION (!receivedFinish)
285 #define TERMINATION_CONDITION rtsTrue
288 while (TERMINATION_CONDITION) {
290 // Check whether we have re-entered the RTS from Haskell without
291 // going via suspendThread()/resumeThread (i.e. a 'safe' foreign
293 if (cap->in_haskell) {
294 errorBelch("schedule: re-entered unsafely.\n"
295 " Perhaps a 'foreign import unsafe' should be 'safe'?");
296 stg_exit(EXIT_FAILURE);
299 // The interruption / shutdown sequence.
301 // In order to cleanly shut down the runtime, we want to:
302 // * make sure that all main threads return to their callers
303 // with the state 'Interrupted'.
304 // * clean up all OS threads assocated with the runtime
305 // * free all memory etc.
307 // So the sequence for ^C goes like this:
309 // * ^C handler sets sched_state := SCHED_INTERRUPTING and
310 // arranges for some Capability to wake up
312 // * all threads in the system are halted, and the zombies are
313 // placed on the run queue for cleaning up. We acquire all
314 // the capabilities in order to delete the threads, this is
315 // done by scheduleDoGC() for convenience (because GC already
316 // needs to acquire all the capabilities). We can't kill
317 // threads involved in foreign calls.
319 // * somebody calls shutdownHaskell(), which calls exitScheduler()
321 // * sched_state := SCHED_SHUTTING_DOWN
323 // * all workers exit when the run queue on their capability
324 // drains. All main threads will also exit when their TSO
325 // reaches the head of the run queue and they can return.
327 // * eventually all Capabilities will shut down, and the RTS can
330 // * We might be left with threads blocked in foreign calls,
331 // we should really attempt to kill these somehow (TODO);
333 switch (sched_state) {
336 case SCHED_INTERRUPTING:
337 debugTrace(DEBUG_sched, "SCHED_INTERRUPTING");
338 #if defined(THREADED_RTS)
339 discardSparksCap(cap);
341 /* scheduleDoGC() deletes all the threads */
342 cap = scheduleDoGC(cap,task,rtsFalse);
344 // after scheduleDoGC(), we must be shutting down. Either some
345 // other Capability did the final GC, or we did it above,
346 // either way we can fall through to the SCHED_SHUTTING_DOWN
348 ASSERT(sched_state == SCHED_SHUTTING_DOWN);
351 case SCHED_SHUTTING_DOWN:
352 debugTrace(DEBUG_sched, "SCHED_SHUTTING_DOWN");
353 // If we are a worker, just exit. If we're a bound thread
354 // then we will exit below when we've removed our TSO from
356 if (task->tso == NULL && emptyRunQueue(cap)) {
361 barf("sched_state: %d", sched_state);
364 scheduleFindWork(cap);
366 /* work pushing, currently relevant only for THREADED_RTS:
367 (pushes threads, wakes up idle capabilities for stealing) */
368 schedulePushWork(cap,task);
370 #if defined(PARALLEL_HASKELL)
371 /* since we perform a blocking receive and continue otherwise,
372 either we never reach here or we definitely have work! */
373 // from here: non-empty run queue
374 ASSERT(!emptyRunQueue(cap));
376 if (PacketsWaiting()) { /* now process incoming messages, if any
379 CAUTION: scheduleGetRemoteWork called
380 above, waits for messages as well! */
381 processMessages(cap, &receivedFinish);
383 #endif // PARALLEL_HASKELL: non-empty run queue!
385 scheduleDetectDeadlock(cap,task);
387 #if defined(THREADED_RTS)
388 cap = task->cap; // reload cap, it might have changed
391 // Normally, the only way we can get here with no threads to
392 // run is if a keyboard interrupt received during
393 // scheduleCheckBlockedThreads() or scheduleDetectDeadlock().
394 // Additionally, it is not fatal for the
395 // threaded RTS to reach here with no threads to run.
397 // win32: might be here due to awaitEvent() being abandoned
398 // as a result of a console event having been delivered.
400 #if defined(THREADED_RTS)
404 // // don't yield the first time, we want a chance to run this
405 // // thread for a bit, even if there are others banging at the
408 // ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
412 scheduleYield(&cap,task);
413 if (emptyRunQueue(cap)) continue; // look for work again
416 #if !defined(THREADED_RTS) && !defined(mingw32_HOST_OS)
417 if ( emptyRunQueue(cap) ) {
418 ASSERT(sched_state >= SCHED_INTERRUPTING);
423 // Get a thread to run
425 t = popRunQueue(cap);
427 // Sanity check the thread we're about to run. This can be
428 // expensive if there is lots of thread switching going on...
429 IF_DEBUG(sanity,checkTSO(t));
431 #if defined(THREADED_RTS)
432 // Check whether we can run this thread in the current task.
433 // If not, we have to pass our capability to the right task.
435 Task *bound = t->bound;
439 debugTrace(DEBUG_sched,
440 "### Running thread %lu in bound thread", (unsigned long)t->id);
441 // yes, the Haskell thread is bound to the current native thread
443 debugTrace(DEBUG_sched,
444 "### thread %lu bound to another OS thread", (unsigned long)t->id);
445 // no, bound to a different Haskell thread: pass to that thread
446 pushOnRunQueue(cap,t);
450 // The thread we want to run is unbound.
452 debugTrace(DEBUG_sched,
453 "### this OS thread cannot run thread %lu", (unsigned long)t->id);
454 // no, the current native thread is bound to a different
455 // Haskell thread, so pass it to any worker thread
456 pushOnRunQueue(cap,t);
463 // If we're shutting down, and this thread has not yet been
464 // killed, kill it now. This sometimes happens when a finalizer
465 // thread is created by the final GC, or a thread previously
466 // in a foreign call returns.
467 if (sched_state >= SCHED_INTERRUPTING &&
468 !(t->what_next == ThreadComplete || t->what_next == ThreadKilled)) {
472 /* context switches are initiated by the timer signal, unless
473 * the user specified "context switch as often as possible", with
476 if (RtsFlags.ConcFlags.ctxtSwitchTicks == 0
477 && !emptyThreadQueues(cap)) {
478 cap->context_switch = 1;
483 // CurrentTSO is the thread to run. t might be different if we
484 // loop back to run_thread, so make sure to set CurrentTSO after
486 cap->r.rCurrentTSO = t;
488 debugTrace(DEBUG_sched, "-->> running thread %ld %s ...",
489 (long)t->id, whatNext_strs[t->what_next]);
491 startHeapProfTimer();
493 // Check for exceptions blocked on this thread
494 maybePerformBlockedException (cap, t);
496 // ----------------------------------------------------------------------
497 // Run the current thread
499 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
500 ASSERT(t->cap == cap);
501 ASSERT(t->bound ? t->bound->cap == cap : 1);
503 prev_what_next = t->what_next;
505 errno = t->saved_errno;
507 SetLastError(t->saved_winerror);
510 cap->in_haskell = rtsTrue;
514 #if defined(THREADED_RTS)
515 if (recent_activity == ACTIVITY_DONE_GC) {
516 // ACTIVITY_DONE_GC means we turned off the timer signal to
517 // conserve power (see #1623). Re-enable it here.
519 prev = xchg((P_)&recent_activity, ACTIVITY_YES);
520 if (prev == ACTIVITY_DONE_GC) {
524 recent_activity = ACTIVITY_YES;
528 switch (prev_what_next) {
532 /* Thread already finished, return to scheduler. */
533 ret = ThreadFinished;
539 r = StgRun((StgFunPtr) stg_returnToStackTop, &cap->r);
540 cap = regTableToCapability(r);
545 case ThreadInterpret:
546 cap = interpretBCO(cap);
551 barf("schedule: invalid what_next field");
554 cap->in_haskell = rtsFalse;
556 // The TSO might have moved, eg. if it re-entered the RTS and a GC
557 // happened. So find the new location:
558 t = cap->r.rCurrentTSO;
560 // We have run some Haskell code: there might be blackhole-blocked
561 // threads to wake up now.
562 // Lock-free test here should be ok, we're just setting a flag.
563 if ( blackhole_queue != END_TSO_QUEUE ) {
564 blackholes_need_checking = rtsTrue;
567 // And save the current errno in this thread.
568 // XXX: possibly bogus for SMP because this thread might already
569 // be running again, see code below.
570 t->saved_errno = errno;
572 // Similarly for Windows error code
573 t->saved_winerror = GetLastError();
576 #if defined(THREADED_RTS)
577 // If ret is ThreadBlocked, and this Task is bound to the TSO that
578 // blocked, we are in limbo - the TSO is now owned by whatever it
579 // is blocked on, and may in fact already have been woken up,
580 // perhaps even on a different Capability. It may be the case
581 // that task->cap != cap. We better yield this Capability
582 // immediately and return to normaility.
583 if (ret == ThreadBlocked) {
584 debugTrace(DEBUG_sched,
585 "--<< thread %lu (%s) stopped: blocked",
586 (unsigned long)t->id, whatNext_strs[t->what_next]);
591 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
592 ASSERT(t->cap == cap);
594 // ----------------------------------------------------------------------
596 // Costs for the scheduler are assigned to CCS_SYSTEM
598 #if defined(PROFILING)
602 schedulePostRunThread(cap,t);
604 t = threadStackUnderflow(task,t);
606 ready_to_gc = rtsFalse;
610 ready_to_gc = scheduleHandleHeapOverflow(cap,t);
614 scheduleHandleStackOverflow(cap,task,t);
618 if (scheduleHandleYield(cap, t, prev_what_next)) {
619 // shortcut for switching between compiler/interpreter:
625 scheduleHandleThreadBlocked(t);
629 if (scheduleHandleThreadFinished(cap, task, t)) return cap;
630 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
634 barf("schedule: invalid thread return code %d", (int)ret);
637 if (ready_to_gc || scheduleNeedHeapProfile(ready_to_gc)) {
638 cap = scheduleDoGC(cap,task,rtsFalse);
640 } /* end of while() */
643 /* ----------------------------------------------------------------------------
644 * Setting up the scheduler loop
645 * ------------------------------------------------------------------------- */
648 schedulePreLoop(void)
650 // initialisation for scheduler - what cannot go into initScheduler()
653 /* -----------------------------------------------------------------------------
656 * Search for work to do, and handle messages from elsewhere.
657 * -------------------------------------------------------------------------- */
660 scheduleFindWork (Capability *cap)
662 scheduleStartSignalHandlers(cap);
664 // Only check the black holes here if we've nothing else to do.
665 // During normal execution, the black hole list only gets checked
666 // at GC time, to avoid repeatedly traversing this possibly long
667 // list each time around the scheduler.
668 if (emptyRunQueue(cap)) { scheduleCheckBlackHoles(cap); }
670 scheduleCheckWakeupThreads(cap);
672 scheduleCheckBlockedThreads(cap);
674 #if defined(THREADED_RTS) || defined(PARALLEL_HASKELL)
675 if (emptyRunQueue(cap)) { scheduleActivateSpark(cap); }
678 #if defined(PARALLEL_HASKELL)
679 // if messages have been buffered...
680 scheduleSendPendingMessages();
683 #if defined(PARALLEL_HASKELL)
684 if (emptyRunQueue(cap)) {
685 receivedFinish = scheduleGetRemoteWork(cap);
686 continue; // a new round, (hopefully) with new work
688 in GUM, this a) sends out a FISH and returns IF no fish is
690 b) (blocking) awaits and receives messages
692 in Eden, this is only the blocking receive, as b) in GUM.
698 #if defined(THREADED_RTS)
699 STATIC_INLINE rtsBool
700 shouldYieldCapability (Capability *cap, Task *task)
702 // we need to yield this capability to someone else if..
703 // - another thread is initiating a GC
704 // - another Task is returning from a foreign call
705 // - the thread at the head of the run queue cannot be run
706 // by this Task (it is bound to another Task, or it is unbound
707 // and this task it bound).
708 return (waiting_for_gc ||
709 cap->returning_tasks_hd != NULL ||
710 (!emptyRunQueue(cap) && (task->tso == NULL
711 ? cap->run_queue_hd->bound != NULL
712 : cap->run_queue_hd->bound != task)));
715 // This is the single place where a Task goes to sleep. There are
716 // two reasons it might need to sleep:
717 // - there are no threads to run
718 // - we need to yield this Capability to someone else
719 // (see shouldYieldCapability())
721 // Careful: the scheduler loop is quite delicate. Make sure you run
722 // the tests in testsuite/concurrent (all ways) after modifying this,
723 // and also check the benchmarks in nofib/parallel for regressions.
726 scheduleYield (Capability **pcap, Task *task)
728 Capability *cap = *pcap;
730 // if we have work, and we don't need to give up the Capability, continue.
731 if (!shouldYieldCapability(cap,task) &&
732 (!emptyRunQueue(cap) ||
733 blackholes_need_checking ||
734 sched_state >= SCHED_INTERRUPTING))
737 // otherwise yield (sleep), and keep yielding if necessary.
739 yieldCapability(&cap,task);
741 while (shouldYieldCapability(cap,task));
743 // note there may still be no threads on the run queue at this
744 // point, the caller has to check.
751 /* -----------------------------------------------------------------------------
754 * Push work to other Capabilities if we have some.
755 * -------------------------------------------------------------------------- */
758 schedulePushWork(Capability *cap USED_IF_THREADS,
759 Task *task USED_IF_THREADS)
761 /* following code not for PARALLEL_HASKELL. I kept the call general,
762 future GUM versions might use pushing in a distributed setup */
763 #if defined(THREADED_RTS)
765 Capability *free_caps[n_capabilities], *cap0;
768 // migration can be turned off with +RTS -qg
769 if (!RtsFlags.ParFlags.migrate) return;
771 // Check whether we have more threads on our run queue, or sparks
772 // in our pool, that we could hand to another Capability.
773 if ((emptyRunQueue(cap) || cap->run_queue_hd->_link == END_TSO_QUEUE)
774 && sparkPoolSizeCap(cap) < 2) {
778 // First grab as many free Capabilities as we can.
779 for (i=0, n_free_caps=0; i < n_capabilities; i++) {
780 cap0 = &capabilities[i];
781 if (cap != cap0 && tryGrabCapability(cap0,task)) {
782 if (!emptyRunQueue(cap0) || cap->returning_tasks_hd != NULL) {
783 // it already has some work, we just grabbed it at
784 // the wrong moment. Or maybe it's deadlocked!
785 releaseCapability(cap0);
787 free_caps[n_free_caps++] = cap0;
792 // we now have n_free_caps free capabilities stashed in
793 // free_caps[]. Share our run queue equally with them. This is
794 // probably the simplest thing we could do; improvements we might
795 // want to do include:
797 // - giving high priority to moving relatively new threads, on
798 // the gournds that they haven't had time to build up a
799 // working set in the cache on this CPU/Capability.
801 // - giving low priority to moving long-lived threads
803 if (n_free_caps > 0) {
804 StgTSO *prev, *t, *next;
805 rtsBool pushed_to_all;
807 debugTrace(DEBUG_sched,
808 "cap %d: %s and %d free capabilities, sharing...",
810 (!emptyRunQueue(cap) && cap->run_queue_hd->_link != END_TSO_QUEUE)?
811 "excess threads on run queue":"sparks to share (>=2)",
815 pushed_to_all = rtsFalse;
817 if (cap->run_queue_hd != END_TSO_QUEUE) {
818 prev = cap->run_queue_hd;
820 prev->_link = END_TSO_QUEUE;
821 for (; t != END_TSO_QUEUE; t = next) {
823 t->_link = END_TSO_QUEUE;
824 if (t->what_next == ThreadRelocated
825 || t->bound == task // don't move my bound thread
826 || tsoLocked(t)) { // don't move a locked thread
827 setTSOLink(cap, prev, t);
829 } else if (i == n_free_caps) {
830 pushed_to_all = rtsTrue;
833 setTSOLink(cap, prev, t);
836 debugTrace(DEBUG_sched, "pushing thread %lu to capability %d", (unsigned long)t->id, free_caps[i]->no);
837 appendToRunQueue(free_caps[i],t);
838 if (t->bound) { t->bound->cap = free_caps[i]; }
839 t->cap = free_caps[i];
843 cap->run_queue_tl = prev;
847 /* JB I left this code in place, it would work but is not necessary */
849 // If there are some free capabilities that we didn't push any
850 // threads to, then try to push a spark to each one.
851 if (!pushed_to_all) {
853 // i is the next free capability to push to
854 for (; i < n_free_caps; i++) {
855 if (emptySparkPoolCap(free_caps[i])) {
856 spark = tryStealSpark(cap->sparks);
858 debugTrace(DEBUG_sched, "pushing spark %p to capability %d", spark, free_caps[i]->no);
859 newSpark(&(free_caps[i]->r), spark);
864 #endif /* SPARK_PUSHING */
866 // release the capabilities
867 for (i = 0; i < n_free_caps; i++) {
868 task->cap = free_caps[i];
869 releaseAndWakeupCapability(free_caps[i]);
872 task->cap = cap; // reset to point to our Capability.
874 #endif /* THREADED_RTS */
878 /* ----------------------------------------------------------------------------
879 * Start any pending signal handlers
880 * ------------------------------------------------------------------------- */
882 #if defined(RTS_USER_SIGNALS) && !defined(THREADED_RTS)
884 scheduleStartSignalHandlers(Capability *cap)
886 if (RtsFlags.MiscFlags.install_signal_handlers && signals_pending()) {
887 // safe outside the lock
888 startSignalHandlers(cap);
893 scheduleStartSignalHandlers(Capability *cap STG_UNUSED)
898 /* ----------------------------------------------------------------------------
899 * Check for blocked threads that can be woken up.
900 * ------------------------------------------------------------------------- */
903 scheduleCheckBlockedThreads(Capability *cap USED_IF_NOT_THREADS)
905 #if !defined(THREADED_RTS)
907 // Check whether any waiting threads need to be woken up. If the
908 // run queue is empty, and there are no other tasks running, we
909 // can wait indefinitely for something to happen.
911 if ( !emptyQueue(blocked_queue_hd) || !emptyQueue(sleeping_queue) )
913 awaitEvent( emptyRunQueue(cap) && !blackholes_need_checking );
919 /* ----------------------------------------------------------------------------
920 * Check for threads woken up by other Capabilities
921 * ------------------------------------------------------------------------- */
924 scheduleCheckWakeupThreads(Capability *cap USED_IF_THREADS)
926 #if defined(THREADED_RTS)
927 // Any threads that were woken up by other Capabilities get
928 // appended to our run queue.
929 if (!emptyWakeupQueue(cap)) {
930 ACQUIRE_LOCK(&cap->lock);
931 if (emptyRunQueue(cap)) {
932 cap->run_queue_hd = cap->wakeup_queue_hd;
933 cap->run_queue_tl = cap->wakeup_queue_tl;
935 setTSOLink(cap, cap->run_queue_tl, cap->wakeup_queue_hd);
936 cap->run_queue_tl = cap->wakeup_queue_tl;
938 cap->wakeup_queue_hd = cap->wakeup_queue_tl = END_TSO_QUEUE;
939 RELEASE_LOCK(&cap->lock);
944 /* ----------------------------------------------------------------------------
945 * Check for threads blocked on BLACKHOLEs that can be woken up
946 * ------------------------------------------------------------------------- */
948 scheduleCheckBlackHoles (Capability *cap)
950 if ( blackholes_need_checking ) // check without the lock first
952 ACQUIRE_LOCK(&sched_mutex);
953 if ( blackholes_need_checking ) {
954 blackholes_need_checking = rtsFalse;
955 // important that we reset the flag *before* checking the
956 // blackhole queue, otherwise we could get deadlock. This
957 // happens as follows: we wake up a thread that
958 // immediately runs on another Capability, blocks on a
959 // blackhole, and then we reset the blackholes_need_checking flag.
960 checkBlackHoles(cap);
962 RELEASE_LOCK(&sched_mutex);
966 /* ----------------------------------------------------------------------------
967 * Detect deadlock conditions and attempt to resolve them.
968 * ------------------------------------------------------------------------- */
971 scheduleDetectDeadlock (Capability *cap, Task *task)
974 #if defined(PARALLEL_HASKELL)
975 // ToDo: add deadlock detection in GUM (similar to THREADED_RTS) -- HWL
980 * Detect deadlock: when we have no threads to run, there are no
981 * threads blocked, waiting for I/O, or sleeping, and all the
982 * other tasks are waiting for work, we must have a deadlock of
985 if ( emptyThreadQueues(cap) )
987 #if defined(THREADED_RTS)
989 * In the threaded RTS, we only check for deadlock if there
990 * has been no activity in a complete timeslice. This means
991 * we won't eagerly start a full GC just because we don't have
992 * any threads to run currently.
994 if (recent_activity != ACTIVITY_INACTIVE) return;
997 debugTrace(DEBUG_sched, "deadlocked, forcing major GC...");
999 // Garbage collection can release some new threads due to
1000 // either (a) finalizers or (b) threads resurrected because
1001 // they are unreachable and will therefore be sent an
1002 // exception. Any threads thus released will be immediately
1004 cap = scheduleDoGC (cap, task, rtsTrue/*force major GC*/);
1005 // when force_major == rtsTrue. scheduleDoGC sets
1006 // recent_activity to ACTIVITY_DONE_GC and turns off the timer
1009 if ( !emptyRunQueue(cap) ) return;
1011 #if defined(RTS_USER_SIGNALS) && !defined(THREADED_RTS)
1012 /* If we have user-installed signal handlers, then wait
1013 * for signals to arrive rather then bombing out with a
1016 if ( RtsFlags.MiscFlags.install_signal_handlers && anyUserHandlers() ) {
1017 debugTrace(DEBUG_sched,
1018 "still deadlocked, waiting for signals...");
1022 if (signals_pending()) {
1023 startSignalHandlers(cap);
1026 // either we have threads to run, or we were interrupted:
1027 ASSERT(!emptyRunQueue(cap) || sched_state >= SCHED_INTERRUPTING);
1033 #if !defined(THREADED_RTS)
1034 /* Probably a real deadlock. Send the current main thread the
1035 * Deadlock exception.
1038 switch (task->tso->why_blocked) {
1040 case BlockedOnBlackHole:
1041 case BlockedOnException:
1043 throwToSingleThreaded(cap, task->tso,
1044 (StgClosure *)nonTermination_closure);
1047 barf("deadlock: main thread blocked in a strange way");
1056 /* ----------------------------------------------------------------------------
1057 * Send pending messages (PARALLEL_HASKELL only)
1058 * ------------------------------------------------------------------------- */
1060 #if defined(PARALLEL_HASKELL)
1062 scheduleSendPendingMessages(void)
1065 # if defined(PAR) // global Mem.Mgmt., omit for now
1066 if (PendingFetches != END_BF_QUEUE) {
1071 if (RtsFlags.ParFlags.BufferTime) {
1072 // if we use message buffering, we must send away all message
1073 // packets which have become too old...
1079 /* ----------------------------------------------------------------------------
1080 * Activate spark threads (PARALLEL_HASKELL and THREADED_RTS)
1081 * ------------------------------------------------------------------------- */
1083 #if defined(PARALLEL_HASKELL) || defined(THREADED_RTS)
1085 scheduleActivateSpark(Capability *cap)
1089 createSparkThread(cap);
1090 debugTrace(DEBUG_sched, "creating a spark thread");
1093 #endif // PARALLEL_HASKELL || THREADED_RTS
1095 /* ----------------------------------------------------------------------------
1096 * Get work from a remote node (PARALLEL_HASKELL only)
1097 * ------------------------------------------------------------------------- */
1099 #if defined(PARALLEL_HASKELL)
1100 static rtsBool /* return value used in PARALLEL_HASKELL only */
1101 scheduleGetRemoteWork (Capability *cap STG_UNUSED)
1103 #if defined(PARALLEL_HASKELL)
1104 rtsBool receivedFinish = rtsFalse;
1106 // idle() , i.e. send all buffers, wait for work
1107 if (RtsFlags.ParFlags.BufferTime) {
1108 IF_PAR_DEBUG(verbose,
1109 debugBelch("...send all pending data,"));
1112 for (i=1; i<=nPEs; i++)
1113 sendImmediately(i); // send all messages away immediately
1117 /* this would be the place for fishing in GUM...
1119 if (no-earlier-fish-around)
1120 sendFish(choosePe());
1123 // Eden:just look for incoming messages (blocking receive)
1124 IF_PAR_DEBUG(verbose,
1125 debugBelch("...wait for incoming messages...\n"));
1126 processMessages(cap, &receivedFinish); // blocking receive...
1129 return receivedFinish;
1130 // reenter scheduling look after having received something
1132 #else /* !PARALLEL_HASKELL, i.e. THREADED_RTS */
1134 return rtsFalse; /* return value unused in THREADED_RTS */
1136 #endif /* PARALLEL_HASKELL */
1138 #endif // PARALLEL_HASKELL || THREADED_RTS
1140 /* ----------------------------------------------------------------------------
1141 * After running a thread...
1142 * ------------------------------------------------------------------------- */
1145 schedulePostRunThread (Capability *cap, StgTSO *t)
1147 // We have to be able to catch transactions that are in an
1148 // infinite loop as a result of seeing an inconsistent view of
1152 // [a,b] <- mapM readTVar [ta,tb]
1153 // when (a == b) loop
1155 // and a is never equal to b given a consistent view of memory.
1157 if (t -> trec != NO_TREC && t -> why_blocked == NotBlocked) {
1158 if (!stmValidateNestOfTransactions (t -> trec)) {
1159 debugTrace(DEBUG_sched | DEBUG_stm,
1160 "trec %p found wasting its time", t);
1162 // strip the stack back to the
1163 // ATOMICALLY_FRAME, aborting the (nested)
1164 // transaction, and saving the stack of any
1165 // partially-evaluated thunks on the heap.
1166 throwToSingleThreaded_(cap, t, NULL, rtsTrue);
1168 ASSERT(get_itbl((StgClosure *)t->sp)->type == ATOMICALLY_FRAME);
1172 /* some statistics gathering in the parallel case */
1175 /* -----------------------------------------------------------------------------
1176 * Handle a thread that returned to the scheduler with ThreadHeepOverflow
1177 * -------------------------------------------------------------------------- */
1180 scheduleHandleHeapOverflow( Capability *cap, StgTSO *t )
1182 // did the task ask for a large block?
1183 if (cap->r.rHpAlloc > BLOCK_SIZE) {
1184 // if so, get one and push it on the front of the nursery.
1188 blocks = (lnat)BLOCK_ROUND_UP(cap->r.rHpAlloc) / BLOCK_SIZE;
1190 debugTrace(DEBUG_sched,
1191 "--<< thread %ld (%s) stopped: requesting a large block (size %ld)\n",
1192 (long)t->id, whatNext_strs[t->what_next], blocks);
1194 // don't do this if the nursery is (nearly) full, we'll GC first.
1195 if (cap->r.rCurrentNursery->link != NULL ||
1196 cap->r.rNursery->n_blocks == 1) { // paranoia to prevent infinite loop
1197 // if the nursery has only one block.
1200 bd = allocGroup( blocks );
1202 cap->r.rNursery->n_blocks += blocks;
1204 // link the new group into the list
1205 bd->link = cap->r.rCurrentNursery;
1206 bd->u.back = cap->r.rCurrentNursery->u.back;
1207 if (cap->r.rCurrentNursery->u.back != NULL) {
1208 cap->r.rCurrentNursery->u.back->link = bd;
1210 #if !defined(THREADED_RTS)
1211 ASSERT(g0s0->blocks == cap->r.rCurrentNursery &&
1212 g0s0 == cap->r.rNursery);
1214 cap->r.rNursery->blocks = bd;
1216 cap->r.rCurrentNursery->u.back = bd;
1218 // initialise it as a nursery block. We initialise the
1219 // step, gen_no, and flags field of *every* sub-block in
1220 // this large block, because this is easier than making
1221 // sure that we always find the block head of a large
1222 // block whenever we call Bdescr() (eg. evacuate() and
1223 // isAlive() in the GC would both have to do this, at
1227 for (x = bd; x < bd + blocks; x++) {
1228 x->step = cap->r.rNursery;
1234 // This assert can be a killer if the app is doing lots
1235 // of large block allocations.
1236 IF_DEBUG(sanity, checkNurserySanity(cap->r.rNursery));
1238 // now update the nursery to point to the new block
1239 cap->r.rCurrentNursery = bd;
1241 // we might be unlucky and have another thread get on the
1242 // run queue before us and steal the large block, but in that
1243 // case the thread will just end up requesting another large
1245 pushOnRunQueue(cap,t);
1246 return rtsFalse; /* not actually GC'ing */
1250 debugTrace(DEBUG_sched,
1251 "--<< thread %ld (%s) stopped: HeapOverflow",
1252 (long)t->id, whatNext_strs[t->what_next]);
1254 if (cap->context_switch) {
1255 // Sometimes we miss a context switch, e.g. when calling
1256 // primitives in a tight loop, MAYBE_GC() doesn't check the
1257 // context switch flag, and we end up waiting for a GC.
1258 // See #1984, and concurrent/should_run/1984
1259 cap->context_switch = 0;
1260 addToRunQueue(cap,t);
1262 pushOnRunQueue(cap,t);
1265 /* actual GC is done at the end of the while loop in schedule() */
1268 /* -----------------------------------------------------------------------------
1269 * Handle a thread that returned to the scheduler with ThreadStackOverflow
1270 * -------------------------------------------------------------------------- */
1273 scheduleHandleStackOverflow (Capability *cap, Task *task, StgTSO *t)
1275 debugTrace (DEBUG_sched,
1276 "--<< thread %ld (%s) stopped, StackOverflow",
1277 (long)t->id, whatNext_strs[t->what_next]);
1279 /* just adjust the stack for this thread, then pop it back
1283 /* enlarge the stack */
1284 StgTSO *new_t = threadStackOverflow(cap, t);
1286 /* The TSO attached to this Task may have moved, so update the
1289 if (task->tso == t) {
1292 pushOnRunQueue(cap,new_t);
1296 /* -----------------------------------------------------------------------------
1297 * Handle a thread that returned to the scheduler with ThreadYielding
1298 * -------------------------------------------------------------------------- */
1301 scheduleHandleYield( Capability *cap, StgTSO *t, nat prev_what_next )
1303 // Reset the context switch flag. We don't do this just before
1304 // running the thread, because that would mean we would lose ticks
1305 // during GC, which can lead to unfair scheduling (a thread hogs
1306 // the CPU because the tick always arrives during GC). This way
1307 // penalises threads that do a lot of allocation, but that seems
1308 // better than the alternative.
1309 cap->context_switch = 0;
1311 /* put the thread back on the run queue. Then, if we're ready to
1312 * GC, check whether this is the last task to stop. If so, wake
1313 * up the GC thread. getThread will block during a GC until the
1317 if (t->what_next != prev_what_next) {
1318 debugTrace(DEBUG_sched,
1319 "--<< thread %ld (%s) stopped to switch evaluators",
1320 (long)t->id, whatNext_strs[t->what_next]);
1322 debugTrace(DEBUG_sched,
1323 "--<< thread %ld (%s) stopped, yielding",
1324 (long)t->id, whatNext_strs[t->what_next]);
1329 //debugBelch("&& Doing sanity check on yielding TSO %ld.", t->id);
1331 ASSERT(t->_link == END_TSO_QUEUE);
1333 // Shortcut if we're just switching evaluators: don't bother
1334 // doing stack squeezing (which can be expensive), just run the
1336 if (t->what_next != prev_what_next) {
1340 addToRunQueue(cap,t);
1345 /* -----------------------------------------------------------------------------
1346 * Handle a thread that returned to the scheduler with ThreadBlocked
1347 * -------------------------------------------------------------------------- */
1350 scheduleHandleThreadBlocked( StgTSO *t
1351 #if !defined(GRAN) && !defined(DEBUG)
1357 // We don't need to do anything. The thread is blocked, and it
1358 // has tidied up its stack and placed itself on whatever queue
1359 // it needs to be on.
1361 // ASSERT(t->why_blocked != NotBlocked);
1362 // Not true: for example,
1363 // - in THREADED_RTS, the thread may already have been woken
1364 // up by another Capability. This actually happens: try
1365 // conc023 +RTS -N2.
1366 // - the thread may have woken itself up already, because
1367 // threadPaused() might have raised a blocked throwTo
1368 // exception, see maybePerformBlockedException().
1371 if (traceClass(DEBUG_sched)) {
1372 debugTraceBegin("--<< thread %lu (%s) stopped: ",
1373 (unsigned long)t->id, whatNext_strs[t->what_next]);
1374 printThreadBlockage(t);
1380 /* -----------------------------------------------------------------------------
1381 * Handle a thread that returned to the scheduler with ThreadFinished
1382 * -------------------------------------------------------------------------- */
1385 scheduleHandleThreadFinished (Capability *cap STG_UNUSED, Task *task, StgTSO *t)
1387 /* Need to check whether this was a main thread, and if so,
1388 * return with the return value.
1390 * We also end up here if the thread kills itself with an
1391 * uncaught exception, see Exception.cmm.
1393 debugTrace(DEBUG_sched, "--++ thread %lu (%s) finished",
1394 (unsigned long)t->id, whatNext_strs[t->what_next]);
1397 // Check whether the thread that just completed was a bound
1398 // thread, and if so return with the result.
1400 // There is an assumption here that all thread completion goes
1401 // through this point; we need to make sure that if a thread
1402 // ends up in the ThreadKilled state, that it stays on the run
1403 // queue so it can be dealt with here.
1408 if (t->bound != task) {
1409 #if !defined(THREADED_RTS)
1410 // Must be a bound thread that is not the topmost one. Leave
1411 // it on the run queue until the stack has unwound to the
1412 // point where we can deal with this. Leaving it on the run
1413 // queue also ensures that the garbage collector knows about
1414 // this thread and its return value (it gets dropped from the
1415 // step->threads list so there's no other way to find it).
1416 appendToRunQueue(cap,t);
1419 // this cannot happen in the threaded RTS, because a
1420 // bound thread can only be run by the appropriate Task.
1421 barf("finished bound thread that isn't mine");
1425 ASSERT(task->tso == t);
1427 if (t->what_next == ThreadComplete) {
1429 // NOTE: return val is tso->sp[1] (see StgStartup.hc)
1430 *(task->ret) = (StgClosure *)task->tso->sp[1];
1432 task->stat = Success;
1435 *(task->ret) = NULL;
1437 if (sched_state >= SCHED_INTERRUPTING) {
1438 task->stat = Interrupted;
1440 task->stat = Killed;
1444 removeThreadLabel((StgWord)task->tso->id);
1446 return rtsTrue; // tells schedule() to return
1452 /* -----------------------------------------------------------------------------
1453 * Perform a heap census
1454 * -------------------------------------------------------------------------- */
1457 scheduleNeedHeapProfile( rtsBool ready_to_gc STG_UNUSED )
1459 // When we have +RTS -i0 and we're heap profiling, do a census at
1460 // every GC. This lets us get repeatable runs for debugging.
1461 if (performHeapProfile ||
1462 (RtsFlags.ProfFlags.profileInterval==0 &&
1463 RtsFlags.ProfFlags.doHeapProfile && ready_to_gc)) {
1470 /* -----------------------------------------------------------------------------
1471 * Perform a garbage collection if necessary
1472 * -------------------------------------------------------------------------- */
1475 scheduleDoGC (Capability *cap, Task *task USED_IF_THREADS, rtsBool force_major)
1477 rtsBool heap_census;
1479 /* extern static volatile StgWord waiting_for_gc;
1480 lives inside capability.c */
1481 rtsBool was_waiting;
1485 if (sched_state == SCHED_SHUTTING_DOWN) {
1486 // The final GC has already been done, and the system is
1487 // shutting down. We'll probably deadlock if we try to GC
1493 // In order to GC, there must be no threads running Haskell code.
1494 // Therefore, the GC thread needs to hold *all* the capabilities,
1495 // and release them after the GC has completed.
1497 // This seems to be the simplest way: previous attempts involved
1498 // making all the threads with capabilities give up their
1499 // capabilities and sleep except for the *last* one, which
1500 // actually did the GC. But it's quite hard to arrange for all
1501 // the other tasks to sleep and stay asleep.
1504 /* Other capabilities are prevented from running yet more Haskell
1505 threads if waiting_for_gc is set. Tested inside
1506 yieldCapability() and releaseCapability() in Capability.c */
1508 was_waiting = cas(&waiting_for_gc, 0, 1);
1511 debugTrace(DEBUG_sched, "someone else is trying to GC...");
1512 if (cap) yieldCapability(&cap,task);
1513 } while (waiting_for_gc);
1514 return cap; // NOTE: task->cap might have changed here
1517 setContextSwitches();
1518 for (i=0; i < n_capabilities; i++) {
1519 debugTrace(DEBUG_sched, "ready_to_gc, grabbing all the capabilies (%d/%d)", i, n_capabilities);
1520 if (cap != &capabilities[i]) {
1521 Capability *pcap = &capabilities[i];
1522 // we better hope this task doesn't get migrated to
1523 // another Capability while we're waiting for this one.
1524 // It won't, because load balancing happens while we have
1525 // all the Capabilities, but even so it's a slightly
1526 // unsavoury invariant.
1528 waitForReturnCapability(&pcap, task);
1529 if (pcap != &capabilities[i]) {
1530 barf("scheduleDoGC: got the wrong capability");
1535 waiting_for_gc = rtsFalse;
1538 // so this happens periodically:
1539 if (cap) scheduleCheckBlackHoles(cap);
1541 IF_DEBUG(scheduler, printAllThreads());
1544 * We now have all the capabilities; if we're in an interrupting
1545 * state, then we should take the opportunity to delete all the
1546 * threads in the system.
1548 if (sched_state >= SCHED_INTERRUPTING) {
1549 deleteAllThreads(&capabilities[0]);
1550 sched_state = SCHED_SHUTTING_DOWN;
1553 heap_census = scheduleNeedHeapProfile(rtsTrue);
1555 /* everybody back, start the GC.
1556 * Could do it in this thread, or signal a condition var
1557 * to do it in another thread. Either way, we need to
1558 * broadcast on gc_pending_cond afterward.
1560 #if defined(THREADED_RTS)
1561 debugTrace(DEBUG_sched, "doing GC");
1563 GarbageCollect(force_major || heap_census);
1566 debugTrace(DEBUG_sched, "performing heap census");
1568 performHeapProfile = rtsFalse;
1573 Once we are all together... this would be the place to balance all
1574 spark pools. No concurrent stealing or adding of new sparks can
1575 occur. Should be defined in Sparks.c. */
1576 balanceSparkPoolsCaps(n_capabilities, capabilities);
1581 // We've just done a major GC and we don't need the timer
1582 // signal turned on any more (#1623).
1583 // NB. do this *before* releasing the Capabilities, to avoid
1585 recent_activity = ACTIVITY_DONE_GC;
1589 #if defined(THREADED_RTS)
1590 // release our stash of capabilities.
1591 for (i = 0; i < n_capabilities; i++) {
1592 if (cap != &capabilities[i]) {
1593 task->cap = &capabilities[i];
1594 releaseCapability(&capabilities[i]);
1607 /* ---------------------------------------------------------------------------
1608 * Singleton fork(). Do not copy any running threads.
1609 * ------------------------------------------------------------------------- */
1612 forkProcess(HsStablePtr *entry
1613 #ifndef FORKPROCESS_PRIMOP_SUPPORTED
1618 #ifdef FORKPROCESS_PRIMOP_SUPPORTED
1625 #if defined(THREADED_RTS)
1626 if (RtsFlags.ParFlags.nNodes > 1) {
1627 errorBelch("forking not supported with +RTS -N<n> greater than 1");
1628 stg_exit(EXIT_FAILURE);
1632 debugTrace(DEBUG_sched, "forking!");
1634 // ToDo: for SMP, we should probably acquire *all* the capabilities
1637 // no funny business: hold locks while we fork, otherwise if some
1638 // other thread is holding a lock when the fork happens, the data
1639 // structure protected by the lock will forever be in an
1640 // inconsistent state in the child. See also #1391.
1641 ACQUIRE_LOCK(&sched_mutex);
1642 ACQUIRE_LOCK(&cap->lock);
1643 ACQUIRE_LOCK(&cap->running_task->lock);
1647 if (pid) { // parent
1649 RELEASE_LOCK(&sched_mutex);
1650 RELEASE_LOCK(&cap->lock);
1651 RELEASE_LOCK(&cap->running_task->lock);
1653 // just return the pid
1659 #if defined(THREADED_RTS)
1660 initMutex(&sched_mutex);
1661 initMutex(&cap->lock);
1662 initMutex(&cap->running_task->lock);
1665 // Now, all OS threads except the thread that forked are
1666 // stopped. We need to stop all Haskell threads, including
1667 // those involved in foreign calls. Also we need to delete
1668 // all Tasks, because they correspond to OS threads that are
1671 for (s = 0; s < total_steps; s++) {
1672 for (t = all_steps[s].threads; t != END_TSO_QUEUE; t = next) {
1673 if (t->what_next == ThreadRelocated) {
1676 next = t->global_link;
1677 // don't allow threads to catch the ThreadKilled
1678 // exception, but we do want to raiseAsync() because these
1679 // threads may be evaluating thunks that we need later.
1680 deleteThread_(cap,t);
1685 // Empty the run queue. It seems tempting to let all the
1686 // killed threads stay on the run queue as zombies to be
1687 // cleaned up later, but some of them correspond to bound
1688 // threads for which the corresponding Task does not exist.
1689 cap->run_queue_hd = END_TSO_QUEUE;
1690 cap->run_queue_tl = END_TSO_QUEUE;
1692 // Any suspended C-calling Tasks are no more, their OS threads
1694 cap->suspended_ccalling_tasks = NULL;
1696 // Empty the threads lists. Otherwise, the garbage
1697 // collector may attempt to resurrect some of these threads.
1698 for (s = 0; s < total_steps; s++) {
1699 all_steps[s].threads = END_TSO_QUEUE;
1702 // Wipe the task list, except the current Task.
1703 ACQUIRE_LOCK(&sched_mutex);
1704 for (task = all_tasks; task != NULL; task=task->all_link) {
1705 if (task != cap->running_task) {
1706 #if defined(THREADED_RTS)
1707 initMutex(&task->lock); // see #1391
1712 RELEASE_LOCK(&sched_mutex);
1714 #if defined(THREADED_RTS)
1715 // Wipe our spare workers list, they no longer exist. New
1716 // workers will be created if necessary.
1717 cap->spare_workers = NULL;
1718 cap->returning_tasks_hd = NULL;
1719 cap->returning_tasks_tl = NULL;
1722 // On Unix, all timers are reset in the child, so we need to start
1727 cap = rts_evalStableIO(cap, entry, NULL); // run the action
1728 rts_checkSchedStatus("forkProcess",cap);
1731 hs_exit(); // clean up and exit
1732 stg_exit(EXIT_SUCCESS);
1734 #else /* !FORKPROCESS_PRIMOP_SUPPORTED */
1735 barf("forkProcess#: primop not supported on this platform, sorry!\n");
1740 /* ---------------------------------------------------------------------------
1741 * Delete all the threads in the system
1742 * ------------------------------------------------------------------------- */
1745 deleteAllThreads ( Capability *cap )
1747 // NOTE: only safe to call if we own all capabilities.
1752 debugTrace(DEBUG_sched,"deleting all threads");
1753 for (s = 0; s < total_steps; s++) {
1754 for (t = all_steps[s].threads; t != END_TSO_QUEUE; t = next) {
1755 if (t->what_next == ThreadRelocated) {
1758 next = t->global_link;
1759 deleteThread(cap,t);
1764 // The run queue now contains a bunch of ThreadKilled threads. We
1765 // must not throw these away: the main thread(s) will be in there
1766 // somewhere, and the main scheduler loop has to deal with it.
1767 // Also, the run queue is the only thing keeping these threads from
1768 // being GC'd, and we don't want the "main thread has been GC'd" panic.
1770 #if !defined(THREADED_RTS)
1771 ASSERT(blocked_queue_hd == END_TSO_QUEUE);
1772 ASSERT(sleeping_queue == END_TSO_QUEUE);
1776 /* -----------------------------------------------------------------------------
1777 Managing the suspended_ccalling_tasks list.
1778 Locks required: sched_mutex
1779 -------------------------------------------------------------------------- */
1782 suspendTask (Capability *cap, Task *task)
1784 ASSERT(task->next == NULL && task->prev == NULL);
1785 task->next = cap->suspended_ccalling_tasks;
1787 if (cap->suspended_ccalling_tasks) {
1788 cap->suspended_ccalling_tasks->prev = task;
1790 cap->suspended_ccalling_tasks = task;
1794 recoverSuspendedTask (Capability *cap, Task *task)
1797 task->prev->next = task->next;
1799 ASSERT(cap->suspended_ccalling_tasks == task);
1800 cap->suspended_ccalling_tasks = task->next;
1803 task->next->prev = task->prev;
1805 task->next = task->prev = NULL;
1808 /* ---------------------------------------------------------------------------
1809 * Suspending & resuming Haskell threads.
1811 * When making a "safe" call to C (aka _ccall_GC), the task gives back
1812 * its capability before calling the C function. This allows another
1813 * task to pick up the capability and carry on running Haskell
1814 * threads. It also means that if the C call blocks, it won't lock
1817 * The Haskell thread making the C call is put to sleep for the
1818 * duration of the call, on the susepended_ccalling_threads queue. We
1819 * give out a token to the task, which it can use to resume the thread
1820 * on return from the C function.
1821 * ------------------------------------------------------------------------- */
1824 suspendThread (StgRegTable *reg)
1831 StgWord32 saved_winerror;
1834 saved_errno = errno;
1836 saved_winerror = GetLastError();
1839 /* assume that *reg is a pointer to the StgRegTable part of a Capability.
1841 cap = regTableToCapability(reg);
1843 task = cap->running_task;
1844 tso = cap->r.rCurrentTSO;
1846 debugTrace(DEBUG_sched,
1847 "thread %lu did a safe foreign call",
1848 (unsigned long)cap->r.rCurrentTSO->id);
1850 // XXX this might not be necessary --SDM
1851 tso->what_next = ThreadRunGHC;
1853 threadPaused(cap,tso);
1855 if ((tso->flags & TSO_BLOCKEX) == 0) {
1856 tso->why_blocked = BlockedOnCCall;
1857 tso->flags |= TSO_BLOCKEX;
1858 tso->flags &= ~TSO_INTERRUPTIBLE;
1860 tso->why_blocked = BlockedOnCCall_NoUnblockExc;
1863 // Hand back capability
1864 task->suspended_tso = tso;
1866 ACQUIRE_LOCK(&cap->lock);
1868 suspendTask(cap,task);
1869 cap->in_haskell = rtsFalse;
1870 releaseCapability_(cap,rtsFalse);
1872 RELEASE_LOCK(&cap->lock);
1874 #if defined(THREADED_RTS)
1875 /* Preparing to leave the RTS, so ensure there's a native thread/task
1876 waiting to take over.
1878 debugTrace(DEBUG_sched, "thread %lu: leaving RTS", (unsigned long)tso->id);
1881 errno = saved_errno;
1883 SetLastError(saved_winerror);
1889 resumeThread (void *task_)
1896 StgWord32 saved_winerror;
1899 saved_errno = errno;
1901 saved_winerror = GetLastError();
1905 // Wait for permission to re-enter the RTS with the result.
1906 waitForReturnCapability(&cap,task);
1907 // we might be on a different capability now... but if so, our
1908 // entry on the suspended_ccalling_tasks list will also have been
1911 // Remove the thread from the suspended list
1912 recoverSuspendedTask(cap,task);
1914 tso = task->suspended_tso;
1915 task->suspended_tso = NULL;
1916 tso->_link = END_TSO_QUEUE; // no write barrier reqd
1917 debugTrace(DEBUG_sched, "thread %lu: re-entering RTS", (unsigned long)tso->id);
1919 if (tso->why_blocked == BlockedOnCCall) {
1920 awakenBlockedExceptionQueue(cap,tso);
1921 tso->flags &= ~(TSO_BLOCKEX | TSO_INTERRUPTIBLE);
1924 /* Reset blocking status */
1925 tso->why_blocked = NotBlocked;
1927 cap->r.rCurrentTSO = tso;
1928 cap->in_haskell = rtsTrue;
1929 errno = saved_errno;
1931 SetLastError(saved_winerror);
1934 /* We might have GC'd, mark the TSO dirty again */
1937 IF_DEBUG(sanity, checkTSO(tso));
1942 /* ---------------------------------------------------------------------------
1945 * scheduleThread puts a thread on the end of the runnable queue.
1946 * This will usually be done immediately after a thread is created.
1947 * The caller of scheduleThread must create the thread using e.g.
1948 * createThread and push an appropriate closure
1949 * on this thread's stack before the scheduler is invoked.
1950 * ------------------------------------------------------------------------ */
1953 scheduleThread(Capability *cap, StgTSO *tso)
1955 // The thread goes at the *end* of the run-queue, to avoid possible
1956 // starvation of any threads already on the queue.
1957 appendToRunQueue(cap,tso);
1961 scheduleThreadOn(Capability *cap, StgWord cpu USED_IF_THREADS, StgTSO *tso)
1963 #if defined(THREADED_RTS)
1964 tso->flags |= TSO_LOCKED; // we requested explicit affinity; don't
1965 // move this thread from now on.
1966 cpu %= RtsFlags.ParFlags.nNodes;
1967 if (cpu == cap->no) {
1968 appendToRunQueue(cap,tso);
1970 wakeupThreadOnCapability(cap, &capabilities[cpu], tso);
1973 appendToRunQueue(cap,tso);
1978 scheduleWaitThread (StgTSO* tso, /*[out]*/HaskellObj* ret, Capability *cap)
1982 // We already created/initialised the Task
1983 task = cap->running_task;
1985 // This TSO is now a bound thread; make the Task and TSO
1986 // point to each other.
1992 task->stat = NoStatus;
1994 appendToRunQueue(cap,tso);
1996 debugTrace(DEBUG_sched, "new bound thread (%lu)", (unsigned long)tso->id);
1998 cap = schedule(cap,task);
2000 ASSERT(task->stat != NoStatus);
2001 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
2003 debugTrace(DEBUG_sched, "bound thread (%lu) finished", (unsigned long)task->tso->id);
2007 /* ----------------------------------------------------------------------------
2009 * ------------------------------------------------------------------------- */
2011 #if defined(THREADED_RTS)
2012 void OSThreadProcAttr
2013 workerStart(Task *task)
2017 // See startWorkerTask().
2018 ACQUIRE_LOCK(&task->lock);
2020 RELEASE_LOCK(&task->lock);
2022 // set the thread-local pointer to the Task:
2025 // schedule() runs without a lock.
2026 cap = schedule(cap,task);
2028 // On exit from schedule(), we have a Capability, but possibly not
2029 // the same one we started with.
2031 // During shutdown, the requirement is that after all the
2032 // Capabilities are shut down, all workers that are shutting down
2033 // have finished workerTaskStop(). This is why we hold on to
2034 // cap->lock until we've finished workerTaskStop() below.
2036 // There may be workers still involved in foreign calls; those
2037 // will just block in waitForReturnCapability() because the
2038 // Capability has been shut down.
2040 ACQUIRE_LOCK(&cap->lock);
2041 releaseCapability_(cap,rtsFalse);
2042 workerTaskStop(task);
2043 RELEASE_LOCK(&cap->lock);
2047 /* ---------------------------------------------------------------------------
2050 * Initialise the scheduler. This resets all the queues - if the
2051 * queues contained any threads, they'll be garbage collected at the
2054 * ------------------------------------------------------------------------ */
2059 #if !defined(THREADED_RTS)
2060 blocked_queue_hd = END_TSO_QUEUE;
2061 blocked_queue_tl = END_TSO_QUEUE;
2062 sleeping_queue = END_TSO_QUEUE;
2065 blackhole_queue = END_TSO_QUEUE;
2067 sched_state = SCHED_RUNNING;
2068 recent_activity = ACTIVITY_YES;
2070 #if defined(THREADED_RTS)
2071 /* Initialise the mutex and condition variables used by
2073 initMutex(&sched_mutex);
2076 ACQUIRE_LOCK(&sched_mutex);
2078 /* A capability holds the state a native thread needs in
2079 * order to execute STG code. At least one capability is
2080 * floating around (only THREADED_RTS builds have more than one).
2086 #if defined(THREADED_RTS) || defined(PARALLEL_HASKELL)
2090 #if defined(THREADED_RTS)
2092 * Eagerly start one worker to run each Capability, except for
2093 * Capability 0. The idea is that we're probably going to start a
2094 * bound thread on Capability 0 pretty soon, so we don't want a
2095 * worker task hogging it.
2100 for (i = 1; i < n_capabilities; i++) {
2101 cap = &capabilities[i];
2102 ACQUIRE_LOCK(&cap->lock);
2103 startWorkerTask(cap, workerStart);
2104 RELEASE_LOCK(&cap->lock);
2109 trace(TRACE_sched, "start: %d capabilities", n_capabilities);
2111 RELEASE_LOCK(&sched_mutex);
2116 rtsBool wait_foreign
2117 #if !defined(THREADED_RTS)
2118 __attribute__((unused))
2121 /* see Capability.c, shutdownCapability() */
2125 #if defined(THREADED_RTS)
2126 ACQUIRE_LOCK(&sched_mutex);
2127 task = newBoundTask();
2128 RELEASE_LOCK(&sched_mutex);
2131 // If we haven't killed all the threads yet, do it now.
2132 if (sched_state < SCHED_SHUTTING_DOWN) {
2133 sched_state = SCHED_INTERRUPTING;
2134 scheduleDoGC(NULL,task,rtsFalse);
2136 sched_state = SCHED_SHUTTING_DOWN;
2138 #if defined(THREADED_RTS)
2142 for (i = 0; i < n_capabilities; i++) {
2143 shutdownCapability(&capabilities[i], task, wait_foreign);
2145 boundTaskExiting(task);
2151 freeScheduler( void )
2155 ACQUIRE_LOCK(&sched_mutex);
2156 still_running = freeTaskManager();
2157 // We can only free the Capabilities if there are no Tasks still
2158 // running. We might have a Task about to return from a foreign
2159 // call into waitForReturnCapability(), for example (actually,
2160 // this should be the *only* thing that a still-running Task can
2161 // do at this point, and it will block waiting for the
2163 if (still_running == 0) {
2165 if (n_capabilities != 1) {
2166 stgFree(capabilities);
2169 RELEASE_LOCK(&sched_mutex);
2170 #if defined(THREADED_RTS)
2171 closeMutex(&sched_mutex);
2175 /* -----------------------------------------------------------------------------
2178 This is the interface to the garbage collector from Haskell land.
2179 We provide this so that external C code can allocate and garbage
2180 collect when called from Haskell via _ccall_GC.
2181 -------------------------------------------------------------------------- */
2184 performGC_(rtsBool force_major)
2187 // We must grab a new Task here, because the existing Task may be
2188 // associated with a particular Capability, and chained onto the
2189 // suspended_ccalling_tasks queue.
2190 ACQUIRE_LOCK(&sched_mutex);
2191 task = newBoundTask();
2192 RELEASE_LOCK(&sched_mutex);
2193 scheduleDoGC(NULL,task,force_major);
2194 boundTaskExiting(task);
2200 performGC_(rtsFalse);
2204 performMajorGC(void)
2206 performGC_(rtsTrue);
2209 /* -----------------------------------------------------------------------------
2212 If the thread has reached its maximum stack size, then raise the
2213 StackOverflow exception in the offending thread. Otherwise
2214 relocate the TSO into a larger chunk of memory and adjust its stack
2216 -------------------------------------------------------------------------- */
2219 threadStackOverflow(Capability *cap, StgTSO *tso)
2221 nat new_stack_size, stack_words;
2226 IF_DEBUG(sanity,checkTSO(tso));
2228 // don't allow throwTo() to modify the blocked_exceptions queue
2229 // while we are moving the TSO:
2230 lockClosure((StgClosure *)tso);
2232 if (tso->stack_size >= tso->max_stack_size && !(tso->flags & TSO_BLOCKEX)) {
2233 // NB. never raise a StackOverflow exception if the thread is
2234 // inside Control.Exceptino.block. It is impractical to protect
2235 // against stack overflow exceptions, since virtually anything
2236 // can raise one (even 'catch'), so this is the only sensible
2237 // thing to do here. See bug #767.
2239 debugTrace(DEBUG_gc,
2240 "threadStackOverflow of TSO %ld (%p): stack too large (now %ld; max is %ld)",
2241 (long)tso->id, tso, (long)tso->stack_size, (long)tso->max_stack_size);
2243 /* If we're debugging, just print out the top of the stack */
2244 printStackChunk(tso->sp, stg_min(tso->stack+tso->stack_size,
2247 // Send this thread the StackOverflow exception
2249 throwToSingleThreaded(cap, tso, (StgClosure *)stackOverflow_closure);
2253 /* Try to double the current stack size. If that takes us over the
2254 * maximum stack size for this thread, then use the maximum instead
2255 * (that is, unless we're already at or over the max size and we
2256 * can't raise the StackOverflow exception (see above), in which
2257 * case just double the size). Finally round up so the TSO ends up as
2258 * a whole number of blocks.
2260 if (tso->stack_size >= tso->max_stack_size) {
2261 new_stack_size = tso->stack_size * 2;
2263 new_stack_size = stg_min(tso->stack_size * 2, tso->max_stack_size);
2265 new_tso_size = (lnat)BLOCK_ROUND_UP(new_stack_size * sizeof(W_) +
2266 TSO_STRUCT_SIZE)/sizeof(W_);
2267 new_tso_size = round_to_mblocks(new_tso_size); /* Be MBLOCK-friendly */
2268 new_stack_size = new_tso_size - TSO_STRUCT_SIZEW;
2270 debugTrace(DEBUG_sched,
2271 "increasing stack size from %ld words to %d.",
2272 (long)tso->stack_size, new_stack_size);
2274 dest = (StgTSO *)allocateLocal(cap,new_tso_size);
2275 TICK_ALLOC_TSO(new_stack_size,0);
2277 /* copy the TSO block and the old stack into the new area */
2278 memcpy(dest,tso,TSO_STRUCT_SIZE);
2279 stack_words = tso->stack + tso->stack_size - tso->sp;
2280 new_sp = (P_)dest + new_tso_size - stack_words;
2281 memcpy(new_sp, tso->sp, stack_words * sizeof(W_));
2283 /* relocate the stack pointers... */
2285 dest->stack_size = new_stack_size;
2287 /* Mark the old TSO as relocated. We have to check for relocated
2288 * TSOs in the garbage collector and any primops that deal with TSOs.
2290 * It's important to set the sp value to just beyond the end
2291 * of the stack, so we don't attempt to scavenge any part of the
2294 tso->what_next = ThreadRelocated;
2295 setTSOLink(cap,tso,dest);
2296 tso->sp = (P_)&(tso->stack[tso->stack_size]);
2297 tso->why_blocked = NotBlocked;
2299 IF_PAR_DEBUG(verbose,
2300 debugBelch("@@ threadStackOverflow of TSO %d (now at %p): stack size increased to %ld\n",
2301 tso->id, tso, tso->stack_size);
2302 /* If we're debugging, just print out the top of the stack */
2303 printStackChunk(tso->sp, stg_min(tso->stack+tso->stack_size,
2309 IF_DEBUG(sanity,checkTSO(dest));
2311 IF_DEBUG(scheduler,printTSO(dest));
2318 threadStackUnderflow (Task *task STG_UNUSED, StgTSO *tso)
2320 bdescr *bd, *new_bd;
2321 lnat free_w, tso_size_w;
2324 tso_size_w = tso_sizeW(tso);
2326 if (tso_size_w < MBLOCK_SIZE_W ||
2327 (nat)(tso->stack + tso->stack_size - tso->sp) > tso->stack_size / 4)
2332 // don't allow throwTo() to modify the blocked_exceptions queue
2333 // while we are moving the TSO:
2334 lockClosure((StgClosure *)tso);
2336 // this is the number of words we'll free
2337 free_w = round_to_mblocks(tso_size_w/2);
2339 bd = Bdescr((StgPtr)tso);
2340 new_bd = splitLargeBlock(bd, free_w / BLOCK_SIZE_W);
2341 bd->free = bd->start + TSO_STRUCT_SIZEW;
2343 new_tso = (StgTSO *)new_bd->start;
2344 memcpy(new_tso,tso,TSO_STRUCT_SIZE);
2345 new_tso->stack_size = new_bd->free - new_tso->stack;
2347 debugTrace(DEBUG_sched, "thread %ld: reducing TSO size from %lu words to %lu",
2348 (long)tso->id, tso_size_w, tso_sizeW(new_tso));
2350 tso->what_next = ThreadRelocated;
2351 tso->_link = new_tso; // no write barrier reqd: same generation
2353 // The TSO attached to this Task may have moved, so update the
2355 if (task->tso == tso) {
2356 task->tso = new_tso;
2362 IF_DEBUG(sanity,checkTSO(new_tso));
2367 /* ---------------------------------------------------------------------------
2369 - usually called inside a signal handler so it mustn't do anything fancy.
2370 ------------------------------------------------------------------------ */
2373 interruptStgRts(void)
2375 sched_state = SCHED_INTERRUPTING;
2376 setContextSwitches();
2380 /* -----------------------------------------------------------------------------
2383 This function causes at least one OS thread to wake up and run the
2384 scheduler loop. It is invoked when the RTS might be deadlocked, or
2385 an external event has arrived that may need servicing (eg. a
2386 keyboard interrupt).
2388 In the single-threaded RTS we don't do anything here; we only have
2389 one thread anyway, and the event that caused us to want to wake up
2390 will have interrupted any blocking system call in progress anyway.
2391 -------------------------------------------------------------------------- */
2396 #if defined(THREADED_RTS)
2397 // This forces the IO Manager thread to wakeup, which will
2398 // in turn ensure that some OS thread wakes up and runs the
2399 // scheduler loop, which will cause a GC and deadlock check.
2404 /* -----------------------------------------------------------------------------
2407 * Check the blackhole_queue for threads that can be woken up. We do
2408 * this periodically: before every GC, and whenever the run queue is
2411 * An elegant solution might be to just wake up all the blocked
2412 * threads with awakenBlockedQueue occasionally: they'll go back to
2413 * sleep again if the object is still a BLACKHOLE. Unfortunately this
2414 * doesn't give us a way to tell whether we've actually managed to
2415 * wake up any threads, so we would be busy-waiting.
2417 * -------------------------------------------------------------------------- */
2420 checkBlackHoles (Capability *cap)
2423 rtsBool any_woke_up = rtsFalse;
2426 // blackhole_queue is global:
2427 ASSERT_LOCK_HELD(&sched_mutex);
2429 debugTrace(DEBUG_sched, "checking threads blocked on black holes");
2431 // ASSUMES: sched_mutex
2432 prev = &blackhole_queue;
2433 t = blackhole_queue;
2434 while (t != END_TSO_QUEUE) {
2435 ASSERT(t->why_blocked == BlockedOnBlackHole);
2436 type = get_itbl(UNTAG_CLOSURE(t->block_info.closure))->type;
2437 if (type != BLACKHOLE && type != CAF_BLACKHOLE) {
2438 IF_DEBUG(sanity,checkTSO(t));
2439 t = unblockOne(cap, t);
2441 any_woke_up = rtsTrue;
2451 /* -----------------------------------------------------------------------------
2454 This is used for interruption (^C) and forking, and corresponds to
2455 raising an exception but without letting the thread catch the
2457 -------------------------------------------------------------------------- */
2460 deleteThread (Capability *cap, StgTSO *tso)
2462 // NOTE: must only be called on a TSO that we have exclusive
2463 // access to, because we will call throwToSingleThreaded() below.
2464 // The TSO must be on the run queue of the Capability we own, or
2465 // we must own all Capabilities.
2467 if (tso->why_blocked != BlockedOnCCall &&
2468 tso->why_blocked != BlockedOnCCall_NoUnblockExc) {
2469 throwToSingleThreaded(cap,tso,NULL);
2473 #ifdef FORKPROCESS_PRIMOP_SUPPORTED
2475 deleteThread_(Capability *cap, StgTSO *tso)
2476 { // for forkProcess only:
2477 // like deleteThread(), but we delete threads in foreign calls, too.
2479 if (tso->why_blocked == BlockedOnCCall ||
2480 tso->why_blocked == BlockedOnCCall_NoUnblockExc) {
2481 unblockOne(cap,tso);
2482 tso->what_next = ThreadKilled;
2484 deleteThread(cap,tso);
2489 /* -----------------------------------------------------------------------------
2490 raiseExceptionHelper
2492 This function is called by the raise# primitve, just so that we can
2493 move some of the tricky bits of raising an exception from C-- into
2494 C. Who knows, it might be a useful re-useable thing here too.
2495 -------------------------------------------------------------------------- */
2498 raiseExceptionHelper (StgRegTable *reg, StgTSO *tso, StgClosure *exception)
2500 Capability *cap = regTableToCapability(reg);
2501 StgThunk *raise_closure = NULL;
2503 StgRetInfoTable *info;
2505 // This closure represents the expression 'raise# E' where E
2506 // is the exception raise. It is used to overwrite all the
2507 // thunks which are currently under evaluataion.
2510 // OLD COMMENT (we don't have MIN_UPD_SIZE now):
2511 // LDV profiling: stg_raise_info has THUNK as its closure
2512 // type. Since a THUNK takes at least MIN_UPD_SIZE words in its
2513 // payload, MIN_UPD_SIZE is more approprate than 1. It seems that
2514 // 1 does not cause any problem unless profiling is performed.
2515 // However, when LDV profiling goes on, we need to linearly scan
2516 // small object pool, where raise_closure is stored, so we should
2517 // use MIN_UPD_SIZE.
2519 // raise_closure = (StgClosure *)RET_STGCALL1(P_,allocate,
2520 // sizeofW(StgClosure)+1);
2524 // Walk up the stack, looking for the catch frame. On the way,
2525 // we update any closures pointed to from update frames with the
2526 // raise closure that we just built.
2530 info = get_ret_itbl((StgClosure *)p);
2531 next = p + stack_frame_sizeW((StgClosure *)p);
2532 switch (info->i.type) {
2535 // Only create raise_closure if we need to.
2536 if (raise_closure == NULL) {
2538 (StgThunk *)allocateLocal(cap,sizeofW(StgThunk)+1);
2539 SET_HDR(raise_closure, &stg_raise_info, CCCS);
2540 raise_closure->payload[0] = exception;
2542 UPD_IND(((StgUpdateFrame *)p)->updatee,(StgClosure *)raise_closure);
2546 case ATOMICALLY_FRAME:
2547 debugTrace(DEBUG_stm, "found ATOMICALLY_FRAME at %p", p);
2549 return ATOMICALLY_FRAME;
2555 case CATCH_STM_FRAME:
2556 debugTrace(DEBUG_stm, "found CATCH_STM_FRAME at %p", p);
2558 return CATCH_STM_FRAME;
2564 case CATCH_RETRY_FRAME:
2573 /* -----------------------------------------------------------------------------
2574 findRetryFrameHelper
2576 This function is called by the retry# primitive. It traverses the stack
2577 leaving tso->sp referring to the frame which should handle the retry.
2579 This should either be a CATCH_RETRY_FRAME (if the retry# is within an orElse#)
2580 or should be a ATOMICALLY_FRAME (if the retry# reaches the top level).
2582 We skip CATCH_STM_FRAMEs (aborting and rolling back the nested tx that they
2583 create) because retries are not considered to be exceptions, despite the
2584 similar implementation.
2586 We should not expect to see CATCH_FRAME or STOP_FRAME because those should
2587 not be created within memory transactions.
2588 -------------------------------------------------------------------------- */
2591 findRetryFrameHelper (StgTSO *tso)
2594 StgRetInfoTable *info;
2598 info = get_ret_itbl((StgClosure *)p);
2599 next = p + stack_frame_sizeW((StgClosure *)p);
2600 switch (info->i.type) {
2602 case ATOMICALLY_FRAME:
2603 debugTrace(DEBUG_stm,
2604 "found ATOMICALLY_FRAME at %p during retry", p);
2606 return ATOMICALLY_FRAME;
2608 case CATCH_RETRY_FRAME:
2609 debugTrace(DEBUG_stm,
2610 "found CATCH_RETRY_FRAME at %p during retrry", p);
2612 return CATCH_RETRY_FRAME;
2614 case CATCH_STM_FRAME: {
2615 StgTRecHeader *trec = tso -> trec;
2616 StgTRecHeader *outer = stmGetEnclosingTRec(trec);
2617 debugTrace(DEBUG_stm,
2618 "found CATCH_STM_FRAME at %p during retry", p);
2619 debugTrace(DEBUG_stm, "trec=%p outer=%p", trec, outer);
2620 stmAbortTransaction(tso -> cap, trec);
2621 stmFreeAbortedTRec(tso -> cap, trec);
2622 tso -> trec = outer;
2629 ASSERT(info->i.type != CATCH_FRAME);
2630 ASSERT(info->i.type != STOP_FRAME);
2637 /* -----------------------------------------------------------------------------
2638 resurrectThreads is called after garbage collection on the list of
2639 threads found to be garbage. Each of these threads will be woken
2640 up and sent a signal: BlockedOnDeadMVar if the thread was blocked
2641 on an MVar, or NonTermination if the thread was blocked on a Black
2644 Locks: assumes we hold *all* the capabilities.
2645 -------------------------------------------------------------------------- */
2648 resurrectThreads (StgTSO *threads)
2654 for (tso = threads; tso != END_TSO_QUEUE; tso = next) {
2655 next = tso->global_link;
2657 step = Bdescr((P_)tso)->step;
2658 tso->global_link = step->threads;
2659 step->threads = tso;
2661 debugTrace(DEBUG_sched, "resurrecting thread %lu", (unsigned long)tso->id);
2663 // Wake up the thread on the Capability it was last on
2666 switch (tso->why_blocked) {
2668 case BlockedOnException:
2669 /* Called by GC - sched_mutex lock is currently held. */
2670 throwToSingleThreaded(cap, tso,
2671 (StgClosure *)blockedOnDeadMVar_closure);
2673 case BlockedOnBlackHole:
2674 throwToSingleThreaded(cap, tso,
2675 (StgClosure *)nonTermination_closure);
2678 throwToSingleThreaded(cap, tso,
2679 (StgClosure *)blockedIndefinitely_closure);
2682 /* This might happen if the thread was blocked on a black hole
2683 * belonging to a thread that we've just woken up (raiseAsync
2684 * can wake up threads, remember...).
2688 barf("resurrectThreads: thread blocked in a strange way");
2693 /* -----------------------------------------------------------------------------
2694 performPendingThrowTos is called after garbage collection, and
2695 passed a list of threads that were found to have pending throwTos
2696 (tso->blocked_exceptions was not empty), and were blocked.
2697 Normally this doesn't happen, because we would deliver the
2698 exception directly if the target thread is blocked, but there are
2699 small windows where it might occur on a multiprocessor (see
2702 NB. we must be holding all the capabilities at this point, just
2703 like resurrectThreads().
2704 -------------------------------------------------------------------------- */
2707 performPendingThrowTos (StgTSO *threads)
2713 for (tso = threads; tso != END_TSO_QUEUE; tso = next) {
2714 next = tso->global_link;
2716 step = Bdescr((P_)tso)->step;
2717 tso->global_link = step->threads;
2718 step->threads = tso;
2720 debugTrace(DEBUG_sched, "performing blocked throwTo to thread %lu", (unsigned long)tso->id);
2723 maybePerformBlockedException(cap, tso);