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 case SCHED_SHUTTING_DOWN:
345 debugTrace(DEBUG_sched, "SCHED_SHUTTING_DOWN");
346 // If we are a worker, just exit. If we're a bound thread
347 // then we will exit below when we've removed our TSO from
349 if (task->tso == NULL && emptyRunQueue(cap)) {
354 barf("sched_state: %d", sched_state);
357 scheduleFindWork(cap);
359 /* work pushing, currently relevant only for THREADED_RTS:
360 (pushes threads, wakes up idle capabilities for stealing) */
361 schedulePushWork(cap,task);
363 #if defined(PARALLEL_HASKELL)
364 /* since we perform a blocking receive and continue otherwise,
365 either we never reach here or we definitely have work! */
366 // from here: non-empty run queue
367 ASSERT(!emptyRunQueue(cap));
369 if (PacketsWaiting()) { /* now process incoming messages, if any
372 CAUTION: scheduleGetRemoteWork called
373 above, waits for messages as well! */
374 processMessages(cap, &receivedFinish);
376 #endif // PARALLEL_HASKELL: non-empty run queue!
378 scheduleDetectDeadlock(cap,task);
380 #if defined(THREADED_RTS)
381 cap = task->cap; // reload cap, it might have changed
384 // Normally, the only way we can get here with no threads to
385 // run is if a keyboard interrupt received during
386 // scheduleCheckBlockedThreads() or scheduleDetectDeadlock().
387 // Additionally, it is not fatal for the
388 // threaded RTS to reach here with no threads to run.
390 // win32: might be here due to awaitEvent() being abandoned
391 // as a result of a console event having been delivered.
393 #if defined(THREADED_RTS)
397 // // don't yield the first time, we want a chance to run this
398 // // thread for a bit, even if there are others banging at the
401 // ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
405 scheduleYield(&cap,task);
406 if (emptyRunQueue(cap)) continue; // look for work again
409 #if !defined(THREADED_RTS) && !defined(mingw32_HOST_OS)
410 if ( emptyRunQueue(cap) ) {
411 ASSERT(sched_state >= SCHED_INTERRUPTING);
416 // Get a thread to run
418 t = popRunQueue(cap);
420 // Sanity check the thread we're about to run. This can be
421 // expensive if there is lots of thread switching going on...
422 IF_DEBUG(sanity,checkTSO(t));
424 #if defined(THREADED_RTS)
425 // Check whether we can run this thread in the current task.
426 // If not, we have to pass our capability to the right task.
428 Task *bound = t->bound;
432 debugTrace(DEBUG_sched,
433 "### Running thread %lu in bound thread", (unsigned long)t->id);
434 // yes, the Haskell thread is bound to the current native thread
436 debugTrace(DEBUG_sched,
437 "### thread %lu bound to another OS thread", (unsigned long)t->id);
438 // no, bound to a different Haskell thread: pass to that thread
439 pushOnRunQueue(cap,t);
443 // The thread we want to run is unbound.
445 debugTrace(DEBUG_sched,
446 "### this OS thread cannot run thread %lu", (unsigned long)t->id);
447 // no, the current native thread is bound to a different
448 // Haskell thread, so pass it to any worker thread
449 pushOnRunQueue(cap,t);
456 /* context switches are initiated by the timer signal, unless
457 * the user specified "context switch as often as possible", with
460 if (RtsFlags.ConcFlags.ctxtSwitchTicks == 0
461 && !emptyThreadQueues(cap)) {
462 cap->context_switch = 1;
467 // CurrentTSO is the thread to run. t might be different if we
468 // loop back to run_thread, so make sure to set CurrentTSO after
470 cap->r.rCurrentTSO = t;
472 debugTrace(DEBUG_sched, "-->> running thread %ld %s ...",
473 (long)t->id, whatNext_strs[t->what_next]);
475 startHeapProfTimer();
477 // Check for exceptions blocked on this thread
478 maybePerformBlockedException (cap, t);
480 // ----------------------------------------------------------------------
481 // Run the current thread
483 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
484 ASSERT(t->cap == cap);
485 ASSERT(t->bound ? t->bound->cap == cap : 1);
487 prev_what_next = t->what_next;
489 errno = t->saved_errno;
491 SetLastError(t->saved_winerror);
494 cap->in_haskell = rtsTrue;
498 #if defined(THREADED_RTS)
499 if (recent_activity == ACTIVITY_DONE_GC) {
500 // ACTIVITY_DONE_GC means we turned off the timer signal to
501 // conserve power (see #1623). Re-enable it here.
503 prev = xchg((P_)&recent_activity, ACTIVITY_YES);
504 if (prev == ACTIVITY_DONE_GC) {
508 recent_activity = ACTIVITY_YES;
512 switch (prev_what_next) {
516 /* Thread already finished, return to scheduler. */
517 ret = ThreadFinished;
523 r = StgRun((StgFunPtr) stg_returnToStackTop, &cap->r);
524 cap = regTableToCapability(r);
529 case ThreadInterpret:
530 cap = interpretBCO(cap);
535 barf("schedule: invalid what_next field");
538 cap->in_haskell = rtsFalse;
540 // The TSO might have moved, eg. if it re-entered the RTS and a GC
541 // happened. So find the new location:
542 t = cap->r.rCurrentTSO;
544 // We have run some Haskell code: there might be blackhole-blocked
545 // threads to wake up now.
546 // Lock-free test here should be ok, we're just setting a flag.
547 if ( blackhole_queue != END_TSO_QUEUE ) {
548 blackholes_need_checking = rtsTrue;
551 // And save the current errno in this thread.
552 // XXX: possibly bogus for SMP because this thread might already
553 // be running again, see code below.
554 t->saved_errno = errno;
556 // Similarly for Windows error code
557 t->saved_winerror = GetLastError();
560 #if defined(THREADED_RTS)
561 // If ret is ThreadBlocked, and this Task is bound to the TSO that
562 // blocked, we are in limbo - the TSO is now owned by whatever it
563 // is blocked on, and may in fact already have been woken up,
564 // perhaps even on a different Capability. It may be the case
565 // that task->cap != cap. We better yield this Capability
566 // immediately and return to normaility.
567 if (ret == ThreadBlocked) {
568 debugTrace(DEBUG_sched,
569 "--<< thread %lu (%s) stopped: blocked",
570 (unsigned long)t->id, whatNext_strs[t->what_next]);
575 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
576 ASSERT(t->cap == cap);
578 // ----------------------------------------------------------------------
580 // Costs for the scheduler are assigned to CCS_SYSTEM
582 #if defined(PROFILING)
586 schedulePostRunThread(cap,t);
588 t = threadStackUnderflow(task,t);
590 ready_to_gc = rtsFalse;
594 ready_to_gc = scheduleHandleHeapOverflow(cap,t);
598 scheduleHandleStackOverflow(cap,task,t);
602 if (scheduleHandleYield(cap, t, prev_what_next)) {
603 // shortcut for switching between compiler/interpreter:
609 scheduleHandleThreadBlocked(t);
613 if (scheduleHandleThreadFinished(cap, task, t)) return cap;
614 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
618 barf("schedule: invalid thread return code %d", (int)ret);
621 if (ready_to_gc || scheduleNeedHeapProfile(ready_to_gc)) {
622 cap = scheduleDoGC(cap,task,rtsFalse);
624 } /* end of while() */
627 /* ----------------------------------------------------------------------------
628 * Setting up the scheduler loop
629 * ------------------------------------------------------------------------- */
632 schedulePreLoop(void)
634 // initialisation for scheduler - what cannot go into initScheduler()
637 /* -----------------------------------------------------------------------------
640 * Search for work to do, and handle messages from elsewhere.
641 * -------------------------------------------------------------------------- */
644 scheduleFindWork (Capability *cap)
646 scheduleStartSignalHandlers(cap);
648 // Only check the black holes here if we've nothing else to do.
649 // During normal execution, the black hole list only gets checked
650 // at GC time, to avoid repeatedly traversing this possibly long
651 // list each time around the scheduler.
652 if (emptyRunQueue(cap)) { scheduleCheckBlackHoles(cap); }
654 scheduleCheckWakeupThreads(cap);
656 scheduleCheckBlockedThreads(cap);
658 #if defined(THREADED_RTS) || defined(PARALLEL_HASKELL)
659 if (emptyRunQueue(cap)) { scheduleActivateSpark(cap); }
662 #if defined(PARALLEL_HASKELL)
663 // if messages have been buffered...
664 scheduleSendPendingMessages();
667 #if defined(PARALLEL_HASKELL)
668 if (emptyRunQueue(cap)) {
669 receivedFinish = scheduleGetRemoteWork(cap);
670 continue; // a new round, (hopefully) with new work
672 in GUM, this a) sends out a FISH and returns IF no fish is
674 b) (blocking) awaits and receives messages
676 in Eden, this is only the blocking receive, as b) in GUM.
682 #if defined(THREADED_RTS)
683 STATIC_INLINE rtsBool
684 shouldYieldCapability (Capability *cap, Task *task)
686 // we need to yield this capability to someone else if..
687 // - another thread is initiating a GC
688 // - another Task is returning from a foreign call
689 // - the thread at the head of the run queue cannot be run
690 // by this Task (it is bound to another Task, or it is unbound
691 // and this task it bound).
692 return (waiting_for_gc ||
693 cap->returning_tasks_hd != NULL ||
694 (!emptyRunQueue(cap) && (task->tso == NULL
695 ? cap->run_queue_hd->bound != NULL
696 : cap->run_queue_hd->bound != task)));
699 // This is the single place where a Task goes to sleep. There are
700 // two reasons it might need to sleep:
701 // - there are no threads to run
702 // - we need to yield this Capability to someone else
703 // (see shouldYieldCapability())
705 // Careful: the scheduler loop is quite delicate. Make sure you run
706 // the tests in testsuite/concurrent (all ways) after modifying this,
707 // and also check the benchmarks in nofib/parallel for regressions.
710 scheduleYield (Capability **pcap, Task *task)
712 Capability *cap = *pcap;
714 // if we have work, and we don't need to give up the Capability, continue.
715 if (!shouldYieldCapability(cap,task) &&
716 (!emptyRunQueue(cap) ||
717 blackholes_need_checking ||
718 sched_state >= SCHED_INTERRUPTING))
721 // otherwise yield (sleep), and keep yielding if necessary.
723 yieldCapability(&cap,task);
725 while (shouldYieldCapability(cap,task));
727 // note there may still be no threads on the run queue at this
728 // point, the caller has to check.
735 /* -----------------------------------------------------------------------------
738 * Push work to other Capabilities if we have some.
739 * -------------------------------------------------------------------------- */
742 schedulePushWork(Capability *cap USED_IF_THREADS,
743 Task *task USED_IF_THREADS)
745 /* following code not for PARALLEL_HASKELL. I kept the call general,
746 future GUM versions might use pushing in a distributed setup */
747 #if defined(THREADED_RTS)
749 Capability *free_caps[n_capabilities], *cap0;
752 // migration can be turned off with +RTS -qg
753 if (!RtsFlags.ParFlags.migrate) return;
755 // Check whether we have more threads on our run queue, or sparks
756 // in our pool, that we could hand to another Capability.
757 if ((emptyRunQueue(cap) || cap->run_queue_hd->_link == END_TSO_QUEUE)
758 && sparkPoolSizeCap(cap) < 2) {
762 // First grab as many free Capabilities as we can.
763 for (i=0, n_free_caps=0; i < n_capabilities; i++) {
764 cap0 = &capabilities[i];
765 if (cap != cap0 && tryGrabCapability(cap0,task)) {
766 if (!emptyRunQueue(cap0) || cap->returning_tasks_hd != NULL) {
767 // it already has some work, we just grabbed it at
768 // the wrong moment. Or maybe it's deadlocked!
769 releaseCapability(cap0);
771 free_caps[n_free_caps++] = cap0;
776 // we now have n_free_caps free capabilities stashed in
777 // free_caps[]. Share our run queue equally with them. This is
778 // probably the simplest thing we could do; improvements we might
779 // want to do include:
781 // - giving high priority to moving relatively new threads, on
782 // the gournds that they haven't had time to build up a
783 // working set in the cache on this CPU/Capability.
785 // - giving low priority to moving long-lived threads
787 if (n_free_caps > 0) {
788 StgTSO *prev, *t, *next;
789 rtsBool pushed_to_all;
791 debugTrace(DEBUG_sched,
792 "cap %d: %s and %d free capabilities, sharing...",
794 (!emptyRunQueue(cap) && cap->run_queue_hd->_link != END_TSO_QUEUE)?
795 "excess threads on run queue":"sparks to share (>=2)",
799 pushed_to_all = rtsFalse;
801 if (cap->run_queue_hd != END_TSO_QUEUE) {
802 prev = cap->run_queue_hd;
804 prev->_link = END_TSO_QUEUE;
805 for (; t != END_TSO_QUEUE; t = next) {
807 t->_link = END_TSO_QUEUE;
808 if (t->what_next == ThreadRelocated
809 || t->bound == task // don't move my bound thread
810 || tsoLocked(t)) { // don't move a locked thread
811 setTSOLink(cap, prev, t);
813 } else if (i == n_free_caps) {
814 pushed_to_all = rtsTrue;
817 setTSOLink(cap, prev, t);
820 debugTrace(DEBUG_sched, "pushing thread %lu to capability %d", (unsigned long)t->id, free_caps[i]->no);
821 appendToRunQueue(free_caps[i],t);
822 if (t->bound) { t->bound->cap = free_caps[i]; }
823 t->cap = free_caps[i];
827 cap->run_queue_tl = prev;
831 /* JB I left this code in place, it would work but is not necessary */
833 // If there are some free capabilities that we didn't push any
834 // threads to, then try to push a spark to each one.
835 if (!pushed_to_all) {
837 // i is the next free capability to push to
838 for (; i < n_free_caps; i++) {
839 if (emptySparkPoolCap(free_caps[i])) {
840 spark = tryStealSpark(cap->sparks);
842 debugTrace(DEBUG_sched, "pushing spark %p to capability %d", spark, free_caps[i]->no);
843 newSpark(&(free_caps[i]->r), spark);
848 #endif /* SPARK_PUSHING */
850 // release the capabilities
851 for (i = 0; i < n_free_caps; i++) {
852 task->cap = free_caps[i];
853 releaseAndWakeupCapability(free_caps[i]);
856 task->cap = cap; // reset to point to our Capability.
858 #endif /* THREADED_RTS */
862 /* ----------------------------------------------------------------------------
863 * Start any pending signal handlers
864 * ------------------------------------------------------------------------- */
866 #if defined(RTS_USER_SIGNALS) && !defined(THREADED_RTS)
868 scheduleStartSignalHandlers(Capability *cap)
870 if (RtsFlags.MiscFlags.install_signal_handlers && signals_pending()) {
871 // safe outside the lock
872 startSignalHandlers(cap);
877 scheduleStartSignalHandlers(Capability *cap STG_UNUSED)
882 /* ----------------------------------------------------------------------------
883 * Check for blocked threads that can be woken up.
884 * ------------------------------------------------------------------------- */
887 scheduleCheckBlockedThreads(Capability *cap USED_IF_NOT_THREADS)
889 #if !defined(THREADED_RTS)
891 // Check whether any waiting threads need to be woken up. If the
892 // run queue is empty, and there are no other tasks running, we
893 // can wait indefinitely for something to happen.
895 if ( !emptyQueue(blocked_queue_hd) || !emptyQueue(sleeping_queue) )
897 awaitEvent( emptyRunQueue(cap) && !blackholes_need_checking );
903 /* ----------------------------------------------------------------------------
904 * Check for threads woken up by other Capabilities
905 * ------------------------------------------------------------------------- */
908 scheduleCheckWakeupThreads(Capability *cap USED_IF_THREADS)
910 #if defined(THREADED_RTS)
911 // Any threads that were woken up by other Capabilities get
912 // appended to our run queue.
913 if (!emptyWakeupQueue(cap)) {
914 ACQUIRE_LOCK(&cap->lock);
915 if (emptyRunQueue(cap)) {
916 cap->run_queue_hd = cap->wakeup_queue_hd;
917 cap->run_queue_tl = cap->wakeup_queue_tl;
919 setTSOLink(cap, cap->run_queue_tl, cap->wakeup_queue_hd);
920 cap->run_queue_tl = cap->wakeup_queue_tl;
922 cap->wakeup_queue_hd = cap->wakeup_queue_tl = END_TSO_QUEUE;
923 RELEASE_LOCK(&cap->lock);
928 /* ----------------------------------------------------------------------------
929 * Check for threads blocked on BLACKHOLEs that can be woken up
930 * ------------------------------------------------------------------------- */
932 scheduleCheckBlackHoles (Capability *cap)
934 if ( blackholes_need_checking ) // check without the lock first
936 ACQUIRE_LOCK(&sched_mutex);
937 if ( blackholes_need_checking ) {
938 blackholes_need_checking = rtsFalse;
939 // important that we reset the flag *before* checking the
940 // blackhole queue, otherwise we could get deadlock. This
941 // happens as follows: we wake up a thread that
942 // immediately runs on another Capability, blocks on a
943 // blackhole, and then we reset the blackholes_need_checking flag.
944 checkBlackHoles(cap);
946 RELEASE_LOCK(&sched_mutex);
950 /* ----------------------------------------------------------------------------
951 * Detect deadlock conditions and attempt to resolve them.
952 * ------------------------------------------------------------------------- */
955 scheduleDetectDeadlock (Capability *cap, Task *task)
958 #if defined(PARALLEL_HASKELL)
959 // ToDo: add deadlock detection in GUM (similar to THREADED_RTS) -- HWL
964 * Detect deadlock: when we have no threads to run, there are no
965 * threads blocked, waiting for I/O, or sleeping, and all the
966 * other tasks are waiting for work, we must have a deadlock of
969 if ( emptyThreadQueues(cap) )
971 #if defined(THREADED_RTS)
973 * In the threaded RTS, we only check for deadlock if there
974 * has been no activity in a complete timeslice. This means
975 * we won't eagerly start a full GC just because we don't have
976 * any threads to run currently.
978 if (recent_activity != ACTIVITY_INACTIVE) return;
981 debugTrace(DEBUG_sched, "deadlocked, forcing major GC...");
983 // Garbage collection can release some new threads due to
984 // either (a) finalizers or (b) threads resurrected because
985 // they are unreachable and will therefore be sent an
986 // exception. Any threads thus released will be immediately
988 cap = scheduleDoGC (cap, task, rtsTrue/*force major GC*/);
990 recent_activity = ACTIVITY_DONE_GC;
991 // disable timer signals (see #1623)
994 if ( !emptyRunQueue(cap) ) return;
996 #if defined(RTS_USER_SIGNALS) && !defined(THREADED_RTS)
997 /* If we have user-installed signal handlers, then wait
998 * for signals to arrive rather then bombing out with a
1001 if ( RtsFlags.MiscFlags.install_signal_handlers && anyUserHandlers() ) {
1002 debugTrace(DEBUG_sched,
1003 "still deadlocked, waiting for signals...");
1007 if (signals_pending()) {
1008 startSignalHandlers(cap);
1011 // either we have threads to run, or we were interrupted:
1012 ASSERT(!emptyRunQueue(cap) || sched_state >= SCHED_INTERRUPTING);
1018 #if !defined(THREADED_RTS)
1019 /* Probably a real deadlock. Send the current main thread the
1020 * Deadlock exception.
1023 switch (task->tso->why_blocked) {
1025 case BlockedOnBlackHole:
1026 case BlockedOnException:
1028 throwToSingleThreaded(cap, task->tso,
1029 (StgClosure *)nonTermination_closure);
1032 barf("deadlock: main thread blocked in a strange way");
1041 /* ----------------------------------------------------------------------------
1042 * Send pending messages (PARALLEL_HASKELL only)
1043 * ------------------------------------------------------------------------- */
1045 #if defined(PARALLEL_HASKELL)
1047 scheduleSendPendingMessages(void)
1050 # if defined(PAR) // global Mem.Mgmt., omit for now
1051 if (PendingFetches != END_BF_QUEUE) {
1056 if (RtsFlags.ParFlags.BufferTime) {
1057 // if we use message buffering, we must send away all message
1058 // packets which have become too old...
1064 /* ----------------------------------------------------------------------------
1065 * Activate spark threads (PARALLEL_HASKELL and THREADED_RTS)
1066 * ------------------------------------------------------------------------- */
1068 #if defined(PARALLEL_HASKELL) || defined(THREADED_RTS)
1070 scheduleActivateSpark(Capability *cap)
1074 createSparkThread(cap);
1075 debugTrace(DEBUG_sched, "creating a spark thread");
1078 #endif // PARALLEL_HASKELL || THREADED_RTS
1080 /* ----------------------------------------------------------------------------
1081 * Get work from a remote node (PARALLEL_HASKELL only)
1082 * ------------------------------------------------------------------------- */
1084 #if defined(PARALLEL_HASKELL)
1085 static rtsBool /* return value used in PARALLEL_HASKELL only */
1086 scheduleGetRemoteWork (Capability *cap STG_UNUSED)
1088 #if defined(PARALLEL_HASKELL)
1089 rtsBool receivedFinish = rtsFalse;
1091 // idle() , i.e. send all buffers, wait for work
1092 if (RtsFlags.ParFlags.BufferTime) {
1093 IF_PAR_DEBUG(verbose,
1094 debugBelch("...send all pending data,"));
1097 for (i=1; i<=nPEs; i++)
1098 sendImmediately(i); // send all messages away immediately
1102 /* this would be the place for fishing in GUM...
1104 if (no-earlier-fish-around)
1105 sendFish(choosePe());
1108 // Eden:just look for incoming messages (blocking receive)
1109 IF_PAR_DEBUG(verbose,
1110 debugBelch("...wait for incoming messages...\n"));
1111 processMessages(cap, &receivedFinish); // blocking receive...
1114 return receivedFinish;
1115 // reenter scheduling look after having received something
1117 #else /* !PARALLEL_HASKELL, i.e. THREADED_RTS */
1119 return rtsFalse; /* return value unused in THREADED_RTS */
1121 #endif /* PARALLEL_HASKELL */
1123 #endif // PARALLEL_HASKELL || THREADED_RTS
1125 /* ----------------------------------------------------------------------------
1126 * After running a thread...
1127 * ------------------------------------------------------------------------- */
1130 schedulePostRunThread (Capability *cap, StgTSO *t)
1132 // We have to be able to catch transactions that are in an
1133 // infinite loop as a result of seeing an inconsistent view of
1137 // [a,b] <- mapM readTVar [ta,tb]
1138 // when (a == b) loop
1140 // and a is never equal to b given a consistent view of memory.
1142 if (t -> trec != NO_TREC && t -> why_blocked == NotBlocked) {
1143 if (!stmValidateNestOfTransactions (t -> trec)) {
1144 debugTrace(DEBUG_sched | DEBUG_stm,
1145 "trec %p found wasting its time", t);
1147 // strip the stack back to the
1148 // ATOMICALLY_FRAME, aborting the (nested)
1149 // transaction, and saving the stack of any
1150 // partially-evaluated thunks on the heap.
1151 throwToSingleThreaded_(cap, t, NULL, rtsTrue, NULL);
1153 ASSERT(get_itbl((StgClosure *)t->sp)->type == ATOMICALLY_FRAME);
1157 /* some statistics gathering in the parallel case */
1160 /* -----------------------------------------------------------------------------
1161 * Handle a thread that returned to the scheduler with ThreadHeepOverflow
1162 * -------------------------------------------------------------------------- */
1165 scheduleHandleHeapOverflow( Capability *cap, StgTSO *t )
1167 // did the task ask for a large block?
1168 if (cap->r.rHpAlloc > BLOCK_SIZE) {
1169 // if so, get one and push it on the front of the nursery.
1173 blocks = (lnat)BLOCK_ROUND_UP(cap->r.rHpAlloc) / BLOCK_SIZE;
1175 debugTrace(DEBUG_sched,
1176 "--<< thread %ld (%s) stopped: requesting a large block (size %ld)\n",
1177 (long)t->id, whatNext_strs[t->what_next], blocks);
1179 // don't do this if the nursery is (nearly) full, we'll GC first.
1180 if (cap->r.rCurrentNursery->link != NULL ||
1181 cap->r.rNursery->n_blocks == 1) { // paranoia to prevent infinite loop
1182 // if the nursery has only one block.
1185 bd = allocGroup( blocks );
1187 cap->r.rNursery->n_blocks += blocks;
1189 // link the new group into the list
1190 bd->link = cap->r.rCurrentNursery;
1191 bd->u.back = cap->r.rCurrentNursery->u.back;
1192 if (cap->r.rCurrentNursery->u.back != NULL) {
1193 cap->r.rCurrentNursery->u.back->link = bd;
1195 #if !defined(THREADED_RTS)
1196 ASSERT(g0s0->blocks == cap->r.rCurrentNursery &&
1197 g0s0 == cap->r.rNursery);
1199 cap->r.rNursery->blocks = bd;
1201 cap->r.rCurrentNursery->u.back = bd;
1203 // initialise it as a nursery block. We initialise the
1204 // step, gen_no, and flags field of *every* sub-block in
1205 // this large block, because this is easier than making
1206 // sure that we always find the block head of a large
1207 // block whenever we call Bdescr() (eg. evacuate() and
1208 // isAlive() in the GC would both have to do this, at
1212 for (x = bd; x < bd + blocks; x++) {
1213 x->step = cap->r.rNursery;
1219 // This assert can be a killer if the app is doing lots
1220 // of large block allocations.
1221 IF_DEBUG(sanity, checkNurserySanity(cap->r.rNursery));
1223 // now update the nursery to point to the new block
1224 cap->r.rCurrentNursery = bd;
1226 // we might be unlucky and have another thread get on the
1227 // run queue before us and steal the large block, but in that
1228 // case the thread will just end up requesting another large
1230 pushOnRunQueue(cap,t);
1231 return rtsFalse; /* not actually GC'ing */
1235 debugTrace(DEBUG_sched,
1236 "--<< thread %ld (%s) stopped: HeapOverflow",
1237 (long)t->id, whatNext_strs[t->what_next]);
1239 if (cap->context_switch) {
1240 // Sometimes we miss a context switch, e.g. when calling
1241 // primitives in a tight loop, MAYBE_GC() doesn't check the
1242 // context switch flag, and we end up waiting for a GC.
1243 // See #1984, and concurrent/should_run/1984
1244 cap->context_switch = 0;
1245 addToRunQueue(cap,t);
1247 pushOnRunQueue(cap,t);
1250 /* actual GC is done at the end of the while loop in schedule() */
1253 /* -----------------------------------------------------------------------------
1254 * Handle a thread that returned to the scheduler with ThreadStackOverflow
1255 * -------------------------------------------------------------------------- */
1258 scheduleHandleStackOverflow (Capability *cap, Task *task, StgTSO *t)
1260 debugTrace (DEBUG_sched,
1261 "--<< thread %ld (%s) stopped, StackOverflow",
1262 (long)t->id, whatNext_strs[t->what_next]);
1264 /* just adjust the stack for this thread, then pop it back
1268 /* enlarge the stack */
1269 StgTSO *new_t = threadStackOverflow(cap, t);
1271 /* The TSO attached to this Task may have moved, so update the
1274 if (task->tso == t) {
1277 pushOnRunQueue(cap,new_t);
1281 /* -----------------------------------------------------------------------------
1282 * Handle a thread that returned to the scheduler with ThreadYielding
1283 * -------------------------------------------------------------------------- */
1286 scheduleHandleYield( Capability *cap, StgTSO *t, nat prev_what_next )
1288 // Reset the context switch flag. We don't do this just before
1289 // running the thread, because that would mean we would lose ticks
1290 // during GC, which can lead to unfair scheduling (a thread hogs
1291 // the CPU because the tick always arrives during GC). This way
1292 // penalises threads that do a lot of allocation, but that seems
1293 // better than the alternative.
1294 cap->context_switch = 0;
1296 /* put the thread back on the run queue. Then, if we're ready to
1297 * GC, check whether this is the last task to stop. If so, wake
1298 * up the GC thread. getThread will block during a GC until the
1302 if (t->what_next != prev_what_next) {
1303 debugTrace(DEBUG_sched,
1304 "--<< thread %ld (%s) stopped to switch evaluators",
1305 (long)t->id, whatNext_strs[t->what_next]);
1307 debugTrace(DEBUG_sched,
1308 "--<< thread %ld (%s) stopped, yielding",
1309 (long)t->id, whatNext_strs[t->what_next]);
1314 //debugBelch("&& Doing sanity check on yielding TSO %ld.", t->id);
1316 ASSERT(t->_link == END_TSO_QUEUE);
1318 // Shortcut if we're just switching evaluators: don't bother
1319 // doing stack squeezing (which can be expensive), just run the
1321 if (t->what_next != prev_what_next) {
1325 addToRunQueue(cap,t);
1330 /* -----------------------------------------------------------------------------
1331 * Handle a thread that returned to the scheduler with ThreadBlocked
1332 * -------------------------------------------------------------------------- */
1335 scheduleHandleThreadBlocked( StgTSO *t
1336 #if !defined(GRAN) && !defined(DEBUG)
1342 // We don't need to do anything. The thread is blocked, and it
1343 // has tidied up its stack and placed itself on whatever queue
1344 // it needs to be on.
1346 // ASSERT(t->why_blocked != NotBlocked);
1347 // Not true: for example,
1348 // - in THREADED_RTS, the thread may already have been woken
1349 // up by another Capability. This actually happens: try
1350 // conc023 +RTS -N2.
1351 // - the thread may have woken itself up already, because
1352 // threadPaused() might have raised a blocked throwTo
1353 // exception, see maybePerformBlockedException().
1356 if (traceClass(DEBUG_sched)) {
1357 debugTraceBegin("--<< thread %lu (%s) stopped: ",
1358 (unsigned long)t->id, whatNext_strs[t->what_next]);
1359 printThreadBlockage(t);
1365 /* -----------------------------------------------------------------------------
1366 * Handle a thread that returned to the scheduler with ThreadFinished
1367 * -------------------------------------------------------------------------- */
1370 scheduleHandleThreadFinished (Capability *cap STG_UNUSED, Task *task, StgTSO *t)
1372 /* Need to check whether this was a main thread, and if so,
1373 * return with the return value.
1375 * We also end up here if the thread kills itself with an
1376 * uncaught exception, see Exception.cmm.
1378 debugTrace(DEBUG_sched, "--++ thread %lu (%s) finished",
1379 (unsigned long)t->id, whatNext_strs[t->what_next]);
1382 // Check whether the thread that just completed was a bound
1383 // thread, and if so return with the result.
1385 // There is an assumption here that all thread completion goes
1386 // through this point; we need to make sure that if a thread
1387 // ends up in the ThreadKilled state, that it stays on the run
1388 // queue so it can be dealt with here.
1393 if (t->bound != task) {
1394 #if !defined(THREADED_RTS)
1395 // Must be a bound thread that is not the topmost one. Leave
1396 // it on the run queue until the stack has unwound to the
1397 // point where we can deal with this. Leaving it on the run
1398 // queue also ensures that the garbage collector knows about
1399 // this thread and its return value (it gets dropped from the
1400 // step->threads list so there's no other way to find it).
1401 appendToRunQueue(cap,t);
1404 // this cannot happen in the threaded RTS, because a
1405 // bound thread can only be run by the appropriate Task.
1406 barf("finished bound thread that isn't mine");
1410 ASSERT(task->tso == t);
1412 if (t->what_next == ThreadComplete) {
1414 // NOTE: return val is tso->sp[1] (see StgStartup.hc)
1415 *(task->ret) = (StgClosure *)task->tso->sp[1];
1417 task->stat = Success;
1420 *(task->ret) = NULL;
1422 if (sched_state >= SCHED_INTERRUPTING) {
1423 task->stat = Interrupted;
1425 task->stat = Killed;
1429 removeThreadLabel((StgWord)task->tso->id);
1431 return rtsTrue; // tells schedule() to return
1437 /* -----------------------------------------------------------------------------
1438 * Perform a heap census
1439 * -------------------------------------------------------------------------- */
1442 scheduleNeedHeapProfile( rtsBool ready_to_gc STG_UNUSED )
1444 // When we have +RTS -i0 and we're heap profiling, do a census at
1445 // every GC. This lets us get repeatable runs for debugging.
1446 if (performHeapProfile ||
1447 (RtsFlags.ProfFlags.profileInterval==0 &&
1448 RtsFlags.ProfFlags.doHeapProfile && ready_to_gc)) {
1455 /* -----------------------------------------------------------------------------
1456 * Perform a garbage collection if necessary
1457 * -------------------------------------------------------------------------- */
1460 scheduleDoGC (Capability *cap, Task *task USED_IF_THREADS, rtsBool force_major)
1462 rtsBool heap_census;
1464 /* extern static volatile StgWord waiting_for_gc;
1465 lives inside capability.c */
1466 rtsBool was_waiting;
1471 // In order to GC, there must be no threads running Haskell code.
1472 // Therefore, the GC thread needs to hold *all* the capabilities,
1473 // and release them after the GC has completed.
1475 // This seems to be the simplest way: previous attempts involved
1476 // making all the threads with capabilities give up their
1477 // capabilities and sleep except for the *last* one, which
1478 // actually did the GC. But it's quite hard to arrange for all
1479 // the other tasks to sleep and stay asleep.
1482 /* Other capabilities are prevented from running yet more Haskell
1483 threads if waiting_for_gc is set. Tested inside
1484 yieldCapability() and releaseCapability() in Capability.c */
1486 was_waiting = cas(&waiting_for_gc, 0, 1);
1489 debugTrace(DEBUG_sched, "someone else is trying to GC...");
1490 if (cap) yieldCapability(&cap,task);
1491 } while (waiting_for_gc);
1492 return cap; // NOTE: task->cap might have changed here
1495 setContextSwitches();
1496 for (i=0; i < n_capabilities; i++) {
1497 debugTrace(DEBUG_sched, "ready_to_gc, grabbing all the capabilies (%d/%d)", i, n_capabilities);
1498 if (cap != &capabilities[i]) {
1499 Capability *pcap = &capabilities[i];
1500 // we better hope this task doesn't get migrated to
1501 // another Capability while we're waiting for this one.
1502 // It won't, because load balancing happens while we have
1503 // all the Capabilities, but even so it's a slightly
1504 // unsavoury invariant.
1506 waitForReturnCapability(&pcap, task);
1507 if (pcap != &capabilities[i]) {
1508 barf("scheduleDoGC: got the wrong capability");
1513 waiting_for_gc = rtsFalse;
1516 // so this happens periodically:
1517 if (cap) scheduleCheckBlackHoles(cap);
1519 IF_DEBUG(scheduler, printAllThreads());
1522 * We now have all the capabilities; if we're in an interrupting
1523 * state, then we should take the opportunity to delete all the
1524 * threads in the system.
1526 if (sched_state >= SCHED_INTERRUPTING) {
1527 deleteAllThreads(&capabilities[0]);
1528 sched_state = SCHED_SHUTTING_DOWN;
1531 heap_census = scheduleNeedHeapProfile(rtsTrue);
1533 /* everybody back, start the GC.
1534 * Could do it in this thread, or signal a condition var
1535 * to do it in another thread. Either way, we need to
1536 * broadcast on gc_pending_cond afterward.
1538 #if defined(THREADED_RTS)
1539 debugTrace(DEBUG_sched, "doing GC");
1541 GarbageCollect(force_major || heap_census);
1544 debugTrace(DEBUG_sched, "performing heap census");
1546 performHeapProfile = rtsFalse;
1551 Once we are all together... this would be the place to balance all
1552 spark pools. No concurrent stealing or adding of new sparks can
1553 occur. Should be defined in Sparks.c. */
1554 balanceSparkPoolsCaps(n_capabilities, capabilities);
1557 #if defined(THREADED_RTS)
1558 // release our stash of capabilities.
1559 for (i = 0; i < n_capabilities; i++) {
1560 if (cap != &capabilities[i]) {
1561 task->cap = &capabilities[i];
1562 releaseCapability(&capabilities[i]);
1575 /* ---------------------------------------------------------------------------
1576 * Singleton fork(). Do not copy any running threads.
1577 * ------------------------------------------------------------------------- */
1580 forkProcess(HsStablePtr *entry
1581 #ifndef FORKPROCESS_PRIMOP_SUPPORTED
1586 #ifdef FORKPROCESS_PRIMOP_SUPPORTED
1593 #if defined(THREADED_RTS)
1594 if (RtsFlags.ParFlags.nNodes > 1) {
1595 errorBelch("forking not supported with +RTS -N<n> greater than 1");
1596 stg_exit(EXIT_FAILURE);
1600 debugTrace(DEBUG_sched, "forking!");
1602 // ToDo: for SMP, we should probably acquire *all* the capabilities
1605 // no funny business: hold locks while we fork, otherwise if some
1606 // other thread is holding a lock when the fork happens, the data
1607 // structure protected by the lock will forever be in an
1608 // inconsistent state in the child. See also #1391.
1609 ACQUIRE_LOCK(&sched_mutex);
1610 ACQUIRE_LOCK(&cap->lock);
1611 ACQUIRE_LOCK(&cap->running_task->lock);
1615 if (pid) { // parent
1617 RELEASE_LOCK(&sched_mutex);
1618 RELEASE_LOCK(&cap->lock);
1619 RELEASE_LOCK(&cap->running_task->lock);
1621 // just return the pid
1627 #if defined(THREADED_RTS)
1628 initMutex(&sched_mutex);
1629 initMutex(&cap->lock);
1630 initMutex(&cap->running_task->lock);
1633 // Now, all OS threads except the thread that forked are
1634 // stopped. We need to stop all Haskell threads, including
1635 // those involved in foreign calls. Also we need to delete
1636 // all Tasks, because they correspond to OS threads that are
1639 for (s = 0; s < total_steps; s++) {
1640 for (t = all_steps[s].threads; t != END_TSO_QUEUE; t = next) {
1641 if (t->what_next == ThreadRelocated) {
1644 next = t->global_link;
1645 // don't allow threads to catch the ThreadKilled
1646 // exception, but we do want to raiseAsync() because these
1647 // threads may be evaluating thunks that we need later.
1648 deleteThread_(cap,t);
1653 // Empty the run queue. It seems tempting to let all the
1654 // killed threads stay on the run queue as zombies to be
1655 // cleaned up later, but some of them correspond to bound
1656 // threads for which the corresponding Task does not exist.
1657 cap->run_queue_hd = END_TSO_QUEUE;
1658 cap->run_queue_tl = END_TSO_QUEUE;
1660 // Any suspended C-calling Tasks are no more, their OS threads
1662 cap->suspended_ccalling_tasks = NULL;
1664 // Empty the threads lists. Otherwise, the garbage
1665 // collector may attempt to resurrect some of these threads.
1666 for (s = 0; s < total_steps; s++) {
1667 all_steps[s].threads = END_TSO_QUEUE;
1670 // Wipe the task list, except the current Task.
1671 ACQUIRE_LOCK(&sched_mutex);
1672 for (task = all_tasks; task != NULL; task=task->all_link) {
1673 if (task != cap->running_task) {
1674 #if defined(THREADED_RTS)
1675 initMutex(&task->lock); // see #1391
1680 RELEASE_LOCK(&sched_mutex);
1682 #if defined(THREADED_RTS)
1683 // Wipe our spare workers list, they no longer exist. New
1684 // workers will be created if necessary.
1685 cap->spare_workers = NULL;
1686 cap->returning_tasks_hd = NULL;
1687 cap->returning_tasks_tl = NULL;
1690 // On Unix, all timers are reset in the child, so we need to start
1695 cap = rts_evalStableIO(cap, entry, NULL); // run the action
1696 rts_checkSchedStatus("forkProcess",cap);
1699 hs_exit(); // clean up and exit
1700 stg_exit(EXIT_SUCCESS);
1702 #else /* !FORKPROCESS_PRIMOP_SUPPORTED */
1703 barf("forkProcess#: primop not supported on this platform, sorry!\n");
1708 /* ---------------------------------------------------------------------------
1709 * Delete all the threads in the system
1710 * ------------------------------------------------------------------------- */
1713 deleteAllThreads ( Capability *cap )
1715 // NOTE: only safe to call if we own all capabilities.
1720 debugTrace(DEBUG_sched,"deleting all threads");
1721 for (s = 0; s < total_steps; s++) {
1722 for (t = all_steps[s].threads; t != END_TSO_QUEUE; t = next) {
1723 if (t->what_next == ThreadRelocated) {
1726 next = t->global_link;
1727 deleteThread(cap,t);
1732 // The run queue now contains a bunch of ThreadKilled threads. We
1733 // must not throw these away: the main thread(s) will be in there
1734 // somewhere, and the main scheduler loop has to deal with it.
1735 // Also, the run queue is the only thing keeping these threads from
1736 // being GC'd, and we don't want the "main thread has been GC'd" panic.
1738 #if !defined(THREADED_RTS)
1739 ASSERT(blocked_queue_hd == END_TSO_QUEUE);
1740 ASSERT(sleeping_queue == END_TSO_QUEUE);
1744 /* -----------------------------------------------------------------------------
1745 Managing the suspended_ccalling_tasks list.
1746 Locks required: sched_mutex
1747 -------------------------------------------------------------------------- */
1750 suspendTask (Capability *cap, Task *task)
1752 ASSERT(task->next == NULL && task->prev == NULL);
1753 task->next = cap->suspended_ccalling_tasks;
1755 if (cap->suspended_ccalling_tasks) {
1756 cap->suspended_ccalling_tasks->prev = task;
1758 cap->suspended_ccalling_tasks = task;
1762 recoverSuspendedTask (Capability *cap, Task *task)
1765 task->prev->next = task->next;
1767 ASSERT(cap->suspended_ccalling_tasks == task);
1768 cap->suspended_ccalling_tasks = task->next;
1771 task->next->prev = task->prev;
1773 task->next = task->prev = NULL;
1776 /* ---------------------------------------------------------------------------
1777 * Suspending & resuming Haskell threads.
1779 * When making a "safe" call to C (aka _ccall_GC), the task gives back
1780 * its capability before calling the C function. This allows another
1781 * task to pick up the capability and carry on running Haskell
1782 * threads. It also means that if the C call blocks, it won't lock
1785 * The Haskell thread making the C call is put to sleep for the
1786 * duration of the call, on the susepended_ccalling_threads queue. We
1787 * give out a token to the task, which it can use to resume the thread
1788 * on return from the C function.
1789 * ------------------------------------------------------------------------- */
1792 suspendThread (StgRegTable *reg)
1799 StgWord32 saved_winerror;
1802 saved_errno = errno;
1804 saved_winerror = GetLastError();
1807 /* assume that *reg is a pointer to the StgRegTable part of a Capability.
1809 cap = regTableToCapability(reg);
1811 task = cap->running_task;
1812 tso = cap->r.rCurrentTSO;
1814 debugTrace(DEBUG_sched,
1815 "thread %lu did a safe foreign call",
1816 (unsigned long)cap->r.rCurrentTSO->id);
1818 // XXX this might not be necessary --SDM
1819 tso->what_next = ThreadRunGHC;
1821 threadPaused(cap,tso);
1823 if ((tso->flags & TSO_BLOCKEX) == 0) {
1824 tso->why_blocked = BlockedOnCCall;
1825 tso->flags |= TSO_BLOCKEX;
1826 tso->flags &= ~TSO_INTERRUPTIBLE;
1828 tso->why_blocked = BlockedOnCCall_NoUnblockExc;
1831 // Hand back capability
1832 task->suspended_tso = tso;
1834 ACQUIRE_LOCK(&cap->lock);
1836 suspendTask(cap,task);
1837 cap->in_haskell = rtsFalse;
1838 releaseCapability_(cap,rtsFalse);
1840 RELEASE_LOCK(&cap->lock);
1842 #if defined(THREADED_RTS)
1843 /* Preparing to leave the RTS, so ensure there's a native thread/task
1844 waiting to take over.
1846 debugTrace(DEBUG_sched, "thread %lu: leaving RTS", (unsigned long)tso->id);
1849 errno = saved_errno;
1851 SetLastError(saved_winerror);
1857 resumeThread (void *task_)
1864 StgWord32 saved_winerror;
1867 saved_errno = errno;
1869 saved_winerror = GetLastError();
1873 // Wait for permission to re-enter the RTS with the result.
1874 waitForReturnCapability(&cap,task);
1875 // we might be on a different capability now... but if so, our
1876 // entry on the suspended_ccalling_tasks list will also have been
1879 // Remove the thread from the suspended list
1880 recoverSuspendedTask(cap,task);
1882 tso = task->suspended_tso;
1883 task->suspended_tso = NULL;
1884 tso->_link = END_TSO_QUEUE; // no write barrier reqd
1885 debugTrace(DEBUG_sched, "thread %lu: re-entering RTS", (unsigned long)tso->id);
1887 if (tso->why_blocked == BlockedOnCCall) {
1888 awakenBlockedExceptionQueue(cap,tso);
1889 tso->flags &= ~(TSO_BLOCKEX | TSO_INTERRUPTIBLE);
1892 /* Reset blocking status */
1893 tso->why_blocked = NotBlocked;
1895 cap->r.rCurrentTSO = tso;
1896 cap->in_haskell = rtsTrue;
1897 errno = saved_errno;
1899 SetLastError(saved_winerror);
1902 /* We might have GC'd, mark the TSO dirty again */
1905 IF_DEBUG(sanity, checkTSO(tso));
1910 /* ---------------------------------------------------------------------------
1913 * scheduleThread puts a thread on the end of the runnable queue.
1914 * This will usually be done immediately after a thread is created.
1915 * The caller of scheduleThread must create the thread using e.g.
1916 * createThread and push an appropriate closure
1917 * on this thread's stack before the scheduler is invoked.
1918 * ------------------------------------------------------------------------ */
1921 scheduleThread(Capability *cap, StgTSO *tso)
1923 // The thread goes at the *end* of the run-queue, to avoid possible
1924 // starvation of any threads already on the queue.
1925 appendToRunQueue(cap,tso);
1929 scheduleThreadOn(Capability *cap, StgWord cpu USED_IF_THREADS, StgTSO *tso)
1931 #if defined(THREADED_RTS)
1932 tso->flags |= TSO_LOCKED; // we requested explicit affinity; don't
1933 // move this thread from now on.
1934 cpu %= RtsFlags.ParFlags.nNodes;
1935 if (cpu == cap->no) {
1936 appendToRunQueue(cap,tso);
1938 wakeupThreadOnCapability(cap, &capabilities[cpu], tso);
1941 appendToRunQueue(cap,tso);
1946 scheduleWaitThread (StgTSO* tso, /*[out]*/HaskellObj* ret, Capability *cap)
1950 // We already created/initialised the Task
1951 task = cap->running_task;
1953 // This TSO is now a bound thread; make the Task and TSO
1954 // point to each other.
1960 task->stat = NoStatus;
1962 appendToRunQueue(cap,tso);
1964 debugTrace(DEBUG_sched, "new bound thread (%lu)", (unsigned long)tso->id);
1966 cap = schedule(cap,task);
1968 ASSERT(task->stat != NoStatus);
1969 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
1971 debugTrace(DEBUG_sched, "bound thread (%lu) finished", (unsigned long)task->tso->id);
1975 /* ----------------------------------------------------------------------------
1977 * ------------------------------------------------------------------------- */
1979 #if defined(THREADED_RTS)
1980 void OSThreadProcAttr
1981 workerStart(Task *task)
1985 // See startWorkerTask().
1986 ACQUIRE_LOCK(&task->lock);
1988 RELEASE_LOCK(&task->lock);
1990 // set the thread-local pointer to the Task:
1993 // schedule() runs without a lock.
1994 cap = schedule(cap,task);
1996 // On exit from schedule(), we have a Capability.
1997 releaseCapability(cap);
1998 workerTaskStop(task);
2002 /* ---------------------------------------------------------------------------
2005 * Initialise the scheduler. This resets all the queues - if the
2006 * queues contained any threads, they'll be garbage collected at the
2009 * ------------------------------------------------------------------------ */
2014 #if !defined(THREADED_RTS)
2015 blocked_queue_hd = END_TSO_QUEUE;
2016 blocked_queue_tl = END_TSO_QUEUE;
2017 sleeping_queue = END_TSO_QUEUE;
2020 blackhole_queue = END_TSO_QUEUE;
2022 sched_state = SCHED_RUNNING;
2023 recent_activity = ACTIVITY_YES;
2025 #if defined(THREADED_RTS)
2026 /* Initialise the mutex and condition variables used by
2028 initMutex(&sched_mutex);
2031 ACQUIRE_LOCK(&sched_mutex);
2033 /* A capability holds the state a native thread needs in
2034 * order to execute STG code. At least one capability is
2035 * floating around (only THREADED_RTS builds have more than one).
2041 #if defined(THREADED_RTS) || defined(PARALLEL_HASKELL)
2045 #if defined(THREADED_RTS)
2047 * Eagerly start one worker to run each Capability, except for
2048 * Capability 0. The idea is that we're probably going to start a
2049 * bound thread on Capability 0 pretty soon, so we don't want a
2050 * worker task hogging it.
2055 for (i = 1; i < n_capabilities; i++) {
2056 cap = &capabilities[i];
2057 ACQUIRE_LOCK(&cap->lock);
2058 startWorkerTask(cap, workerStart);
2059 RELEASE_LOCK(&cap->lock);
2064 trace(TRACE_sched, "start: %d capabilities", n_capabilities);
2066 RELEASE_LOCK(&sched_mutex);
2071 rtsBool wait_foreign
2072 #if !defined(THREADED_RTS)
2073 __attribute__((unused))
2076 /* see Capability.c, shutdownCapability() */
2080 #if defined(THREADED_RTS)
2081 ACQUIRE_LOCK(&sched_mutex);
2082 task = newBoundTask();
2083 RELEASE_LOCK(&sched_mutex);
2086 // If we haven't killed all the threads yet, do it now.
2087 if (sched_state < SCHED_SHUTTING_DOWN) {
2088 sched_state = SCHED_INTERRUPTING;
2089 scheduleDoGC(NULL,task,rtsFalse);
2091 sched_state = SCHED_SHUTTING_DOWN;
2093 #if defined(THREADED_RTS)
2097 for (i = 0; i < n_capabilities; i++) {
2098 shutdownCapability(&capabilities[i], task, wait_foreign);
2100 boundTaskExiting(task);
2107 freeScheduler( void )
2111 if (n_capabilities != 1) {
2112 stgFree(capabilities);
2114 #if defined(THREADED_RTS)
2115 closeMutex(&sched_mutex);
2119 /* -----------------------------------------------------------------------------
2122 This is the interface to the garbage collector from Haskell land.
2123 We provide this so that external C code can allocate and garbage
2124 collect when called from Haskell via _ccall_GC.
2125 -------------------------------------------------------------------------- */
2128 performGC_(rtsBool force_major)
2131 // We must grab a new Task here, because the existing Task may be
2132 // associated with a particular Capability, and chained onto the
2133 // suspended_ccalling_tasks queue.
2134 ACQUIRE_LOCK(&sched_mutex);
2135 task = newBoundTask();
2136 RELEASE_LOCK(&sched_mutex);
2137 scheduleDoGC(NULL,task,force_major);
2138 boundTaskExiting(task);
2144 performGC_(rtsFalse);
2148 performMajorGC(void)
2150 performGC_(rtsTrue);
2153 /* -----------------------------------------------------------------------------
2156 If the thread has reached its maximum stack size, then raise the
2157 StackOverflow exception in the offending thread. Otherwise
2158 relocate the TSO into a larger chunk of memory and adjust its stack
2160 -------------------------------------------------------------------------- */
2163 threadStackOverflow(Capability *cap, StgTSO *tso)
2165 nat new_stack_size, stack_words;
2170 IF_DEBUG(sanity,checkTSO(tso));
2172 // don't allow throwTo() to modify the blocked_exceptions queue
2173 // while we are moving the TSO:
2174 lockClosure((StgClosure *)tso);
2176 if (tso->stack_size >= tso->max_stack_size && !(tso->flags & TSO_BLOCKEX)) {
2177 // NB. never raise a StackOverflow exception if the thread is
2178 // inside Control.Exceptino.block. It is impractical to protect
2179 // against stack overflow exceptions, since virtually anything
2180 // can raise one (even 'catch'), so this is the only sensible
2181 // thing to do here. See bug #767.
2183 debugTrace(DEBUG_gc,
2184 "threadStackOverflow of TSO %ld (%p): stack too large (now %ld; max is %ld)",
2185 (long)tso->id, tso, (long)tso->stack_size, (long)tso->max_stack_size);
2187 /* If we're debugging, just print out the top of the stack */
2188 printStackChunk(tso->sp, stg_min(tso->stack+tso->stack_size,
2191 // Send this thread the StackOverflow exception
2193 throwToSingleThreaded(cap, tso, (StgClosure *)stackOverflow_closure);
2197 /* Try to double the current stack size. If that takes us over the
2198 * maximum stack size for this thread, then use the maximum instead
2199 * (that is, unless we're already at or over the max size and we
2200 * can't raise the StackOverflow exception (see above), in which
2201 * case just double the size). Finally round up so the TSO ends up as
2202 * a whole number of blocks.
2204 if (tso->stack_size >= tso->max_stack_size) {
2205 new_stack_size = tso->stack_size * 2;
2207 new_stack_size = stg_min(tso->stack_size * 2, tso->max_stack_size);
2209 new_tso_size = (lnat)BLOCK_ROUND_UP(new_stack_size * sizeof(W_) +
2210 TSO_STRUCT_SIZE)/sizeof(W_);
2211 new_tso_size = round_to_mblocks(new_tso_size); /* Be MBLOCK-friendly */
2212 new_stack_size = new_tso_size - TSO_STRUCT_SIZEW;
2214 debugTrace(DEBUG_sched,
2215 "increasing stack size from %ld words to %d.",
2216 (long)tso->stack_size, new_stack_size);
2218 dest = (StgTSO *)allocateLocal(cap,new_tso_size);
2219 TICK_ALLOC_TSO(new_stack_size,0);
2221 /* copy the TSO block and the old stack into the new area */
2222 memcpy(dest,tso,TSO_STRUCT_SIZE);
2223 stack_words = tso->stack + tso->stack_size - tso->sp;
2224 new_sp = (P_)dest + new_tso_size - stack_words;
2225 memcpy(new_sp, tso->sp, stack_words * sizeof(W_));
2227 /* relocate the stack pointers... */
2229 dest->stack_size = new_stack_size;
2231 /* Mark the old TSO as relocated. We have to check for relocated
2232 * TSOs in the garbage collector and any primops that deal with TSOs.
2234 * It's important to set the sp value to just beyond the end
2235 * of the stack, so we don't attempt to scavenge any part of the
2238 tso->what_next = ThreadRelocated;
2239 setTSOLink(cap,tso,dest);
2240 tso->sp = (P_)&(tso->stack[tso->stack_size]);
2241 tso->why_blocked = NotBlocked;
2243 IF_PAR_DEBUG(verbose,
2244 debugBelch("@@ threadStackOverflow of TSO %d (now at %p): stack size increased to %ld\n",
2245 tso->id, tso, tso->stack_size);
2246 /* If we're debugging, just print out the top of the stack */
2247 printStackChunk(tso->sp, stg_min(tso->stack+tso->stack_size,
2253 IF_DEBUG(sanity,checkTSO(dest));
2255 IF_DEBUG(scheduler,printTSO(dest));
2262 threadStackUnderflow (Task *task STG_UNUSED, StgTSO *tso)
2264 bdescr *bd, *new_bd;
2265 lnat free_w, tso_size_w;
2268 tso_size_w = tso_sizeW(tso);
2270 if (tso_size_w < MBLOCK_SIZE_W ||
2271 (nat)(tso->stack + tso->stack_size - tso->sp) > tso->stack_size / 4)
2276 // don't allow throwTo() to modify the blocked_exceptions queue
2277 // while we are moving the TSO:
2278 lockClosure((StgClosure *)tso);
2280 // this is the number of words we'll free
2281 free_w = round_to_mblocks(tso_size_w/2);
2283 bd = Bdescr((StgPtr)tso);
2284 new_bd = splitLargeBlock(bd, free_w / BLOCK_SIZE_W);
2285 bd->free = bd->start + TSO_STRUCT_SIZEW;
2287 new_tso = (StgTSO *)new_bd->start;
2288 memcpy(new_tso,tso,TSO_STRUCT_SIZE);
2289 new_tso->stack_size = new_bd->free - new_tso->stack;
2291 debugTrace(DEBUG_sched, "thread %ld: reducing TSO size from %lu words to %lu",
2292 (long)tso->id, tso_size_w, tso_sizeW(new_tso));
2294 tso->what_next = ThreadRelocated;
2295 tso->_link = new_tso; // no write barrier reqd: same generation
2297 // The TSO attached to this Task may have moved, so update the
2299 if (task->tso == tso) {
2300 task->tso = new_tso;
2306 IF_DEBUG(sanity,checkTSO(new_tso));
2311 /* ---------------------------------------------------------------------------
2313 - usually called inside a signal handler so it mustn't do anything fancy.
2314 ------------------------------------------------------------------------ */
2317 interruptStgRts(void)
2319 sched_state = SCHED_INTERRUPTING;
2320 setContextSwitches();
2324 /* -----------------------------------------------------------------------------
2327 This function causes at least one OS thread to wake up and run the
2328 scheduler loop. It is invoked when the RTS might be deadlocked, or
2329 an external event has arrived that may need servicing (eg. a
2330 keyboard interrupt).
2332 In the single-threaded RTS we don't do anything here; we only have
2333 one thread anyway, and the event that caused us to want to wake up
2334 will have interrupted any blocking system call in progress anyway.
2335 -------------------------------------------------------------------------- */
2340 #if defined(THREADED_RTS)
2341 // This forces the IO Manager thread to wakeup, which will
2342 // in turn ensure that some OS thread wakes up and runs the
2343 // scheduler loop, which will cause a GC and deadlock check.
2348 /* -----------------------------------------------------------------------------
2351 * Check the blackhole_queue for threads that can be woken up. We do
2352 * this periodically: before every GC, and whenever the run queue is
2355 * An elegant solution might be to just wake up all the blocked
2356 * threads with awakenBlockedQueue occasionally: they'll go back to
2357 * sleep again if the object is still a BLACKHOLE. Unfortunately this
2358 * doesn't give us a way to tell whether we've actually managed to
2359 * wake up any threads, so we would be busy-waiting.
2361 * -------------------------------------------------------------------------- */
2364 checkBlackHoles (Capability *cap)
2367 rtsBool any_woke_up = rtsFalse;
2370 // blackhole_queue is global:
2371 ASSERT_LOCK_HELD(&sched_mutex);
2373 debugTrace(DEBUG_sched, "checking threads blocked on black holes");
2375 // ASSUMES: sched_mutex
2376 prev = &blackhole_queue;
2377 t = blackhole_queue;
2378 while (t != END_TSO_QUEUE) {
2379 ASSERT(t->why_blocked == BlockedOnBlackHole);
2380 type = get_itbl(UNTAG_CLOSURE(t->block_info.closure))->type;
2381 if (type != BLACKHOLE && type != CAF_BLACKHOLE) {
2382 IF_DEBUG(sanity,checkTSO(t));
2383 t = unblockOne(cap, t);
2385 any_woke_up = rtsTrue;
2395 /* -----------------------------------------------------------------------------
2398 This is used for interruption (^C) and forking, and corresponds to
2399 raising an exception but without letting the thread catch the
2401 -------------------------------------------------------------------------- */
2404 deleteThread (Capability *cap, StgTSO *tso)
2406 // NOTE: must only be called on a TSO that we have exclusive
2407 // access to, because we will call throwToSingleThreaded() below.
2408 // The TSO must be on the run queue of the Capability we own, or
2409 // we must own all Capabilities.
2411 if (tso->why_blocked != BlockedOnCCall &&
2412 tso->why_blocked != BlockedOnCCall_NoUnblockExc) {
2413 throwToSingleThreaded(cap,tso,NULL);
2417 #ifdef FORKPROCESS_PRIMOP_SUPPORTED
2419 deleteThread_(Capability *cap, StgTSO *tso)
2420 { // for forkProcess only:
2421 // like deleteThread(), but we delete threads in foreign calls, too.
2423 if (tso->why_blocked == BlockedOnCCall ||
2424 tso->why_blocked == BlockedOnCCall_NoUnblockExc) {
2425 unblockOne(cap,tso);
2426 tso->what_next = ThreadKilled;
2428 deleteThread(cap,tso);
2433 /* -----------------------------------------------------------------------------
2434 raiseExceptionHelper
2436 This function is called by the raise# primitve, just so that we can
2437 move some of the tricky bits of raising an exception from C-- into
2438 C. Who knows, it might be a useful re-useable thing here too.
2439 -------------------------------------------------------------------------- */
2442 raiseExceptionHelper (StgRegTable *reg, StgTSO *tso, StgClosure *exception)
2444 Capability *cap = regTableToCapability(reg);
2445 StgThunk *raise_closure = NULL;
2447 StgRetInfoTable *info;
2449 // This closure represents the expression 'raise# E' where E
2450 // is the exception raise. It is used to overwrite all the
2451 // thunks which are currently under evaluataion.
2454 // OLD COMMENT (we don't have MIN_UPD_SIZE now):
2455 // LDV profiling: stg_raise_info has THUNK as its closure
2456 // type. Since a THUNK takes at least MIN_UPD_SIZE words in its
2457 // payload, MIN_UPD_SIZE is more approprate than 1. It seems that
2458 // 1 does not cause any problem unless profiling is performed.
2459 // However, when LDV profiling goes on, we need to linearly scan
2460 // small object pool, where raise_closure is stored, so we should
2461 // use MIN_UPD_SIZE.
2463 // raise_closure = (StgClosure *)RET_STGCALL1(P_,allocate,
2464 // sizeofW(StgClosure)+1);
2468 // Walk up the stack, looking for the catch frame. On the way,
2469 // we update any closures pointed to from update frames with the
2470 // raise closure that we just built.
2474 info = get_ret_itbl((StgClosure *)p);
2475 next = p + stack_frame_sizeW((StgClosure *)p);
2476 switch (info->i.type) {
2479 // Only create raise_closure if we need to.
2480 if (raise_closure == NULL) {
2482 (StgThunk *)allocateLocal(cap,sizeofW(StgThunk)+1);
2483 SET_HDR(raise_closure, &stg_raise_info, CCCS);
2484 raise_closure->payload[0] = exception;
2486 UPD_IND(((StgUpdateFrame *)p)->updatee,(StgClosure *)raise_closure);
2490 case ATOMICALLY_FRAME:
2491 debugTrace(DEBUG_stm, "found ATOMICALLY_FRAME at %p", p);
2493 return ATOMICALLY_FRAME;
2499 case CATCH_STM_FRAME:
2500 debugTrace(DEBUG_stm, "found CATCH_STM_FRAME at %p", p);
2502 return CATCH_STM_FRAME;
2508 case CATCH_RETRY_FRAME:
2517 /* -----------------------------------------------------------------------------
2518 findRetryFrameHelper
2520 This function is called by the retry# primitive. It traverses the stack
2521 leaving tso->sp referring to the frame which should handle the retry.
2523 This should either be a CATCH_RETRY_FRAME (if the retry# is within an orElse#)
2524 or should be a ATOMICALLY_FRAME (if the retry# reaches the top level).
2526 We skip CATCH_STM_FRAMEs (aborting and rolling back the nested tx that they
2527 create) because retries are not considered to be exceptions, despite the
2528 similar implementation.
2530 We should not expect to see CATCH_FRAME or STOP_FRAME because those should
2531 not be created within memory transactions.
2532 -------------------------------------------------------------------------- */
2535 findRetryFrameHelper (StgTSO *tso)
2538 StgRetInfoTable *info;
2542 info = get_ret_itbl((StgClosure *)p);
2543 next = p + stack_frame_sizeW((StgClosure *)p);
2544 switch (info->i.type) {
2546 case ATOMICALLY_FRAME:
2547 debugTrace(DEBUG_stm,
2548 "found ATOMICALLY_FRAME at %p during retry", p);
2550 return ATOMICALLY_FRAME;
2552 case CATCH_RETRY_FRAME:
2553 debugTrace(DEBUG_stm,
2554 "found CATCH_RETRY_FRAME at %p during retrry", p);
2556 return CATCH_RETRY_FRAME;
2558 case CATCH_STM_FRAME: {
2559 StgTRecHeader *trec = tso -> trec;
2560 StgTRecHeader *outer = stmGetEnclosingTRec(trec);
2561 debugTrace(DEBUG_stm,
2562 "found CATCH_STM_FRAME at %p during retry", p);
2563 debugTrace(DEBUG_stm, "trec=%p outer=%p", trec, outer);
2564 stmAbortTransaction(tso -> cap, trec);
2565 stmFreeAbortedTRec(tso -> cap, trec);
2566 tso -> trec = outer;
2573 ASSERT(info->i.type != CATCH_FRAME);
2574 ASSERT(info->i.type != STOP_FRAME);
2581 /* -----------------------------------------------------------------------------
2582 resurrectThreads is called after garbage collection on the list of
2583 threads found to be garbage. Each of these threads will be woken
2584 up and sent a signal: BlockedOnDeadMVar if the thread was blocked
2585 on an MVar, or NonTermination if the thread was blocked on a Black
2588 Locks: assumes we hold *all* the capabilities.
2589 -------------------------------------------------------------------------- */
2592 resurrectThreads (StgTSO *threads)
2598 for (tso = threads; tso != END_TSO_QUEUE; tso = next) {
2599 next = tso->global_link;
2601 step = Bdescr((P_)tso)->step;
2602 tso->global_link = step->threads;
2603 step->threads = tso;
2605 debugTrace(DEBUG_sched, "resurrecting thread %lu", (unsigned long)tso->id);
2607 // Wake up the thread on the Capability it was last on
2610 switch (tso->why_blocked) {
2612 case BlockedOnException:
2613 /* Called by GC - sched_mutex lock is currently held. */
2614 throwToSingleThreaded(cap, tso,
2615 (StgClosure *)blockedOnDeadMVar_closure);
2617 case BlockedOnBlackHole:
2618 throwToSingleThreaded(cap, tso,
2619 (StgClosure *)nonTermination_closure);
2622 throwToSingleThreaded(cap, tso,
2623 (StgClosure *)blockedIndefinitely_closure);
2626 /* This might happen if the thread was blocked on a black hole
2627 * belonging to a thread that we've just woken up (raiseAsync
2628 * can wake up threads, remember...).
2632 barf("resurrectThreads: thread blocked in a strange way");
2637 /* -----------------------------------------------------------------------------
2638 performPendingThrowTos is called after garbage collection, and
2639 passed a list of threads that were found to have pending throwTos
2640 (tso->blocked_exceptions was not empty), and were blocked.
2641 Normally this doesn't happen, because we would deliver the
2642 exception directly if the target thread is blocked, but there are
2643 small windows where it might occur on a multiprocessor (see
2646 NB. we must be holding all the capabilities at this point, just
2647 like resurrectThreads().
2648 -------------------------------------------------------------------------- */
2651 performPendingThrowTos (StgTSO *threads)
2657 for (tso = threads; tso != END_TSO_QUEUE; tso = next) {
2658 next = tso->global_link;
2660 step = Bdescr((P_)tso)->step;
2661 tso->global_link = step->threads;
2662 step->threads = tso;
2664 debugTrace(DEBUG_sched, "performing blocked throwTo to thread %lu", (unsigned long)tso->id);
2667 maybePerformBlockedException(cap, tso);