1 /* ---------------------------------------------------------------------------
3 * (c) The GHC Team, 1998-2006
5 * The scheduler and thread-related functionality
7 * --------------------------------------------------------------------------*/
9 #include "PosixSource.h"
10 #define KEEP_LOCKCLOSURE
13 #include "sm/Storage.h"
17 #include "Interpreter.h"
19 #include "RtsSignals.h"
24 #include "ThreadLabels.h"
26 #include "Proftimer.h"
29 #include "sm/GC.h" // waitForGcThreads, releaseGCThreads, N
31 #include "Capability.h"
33 #include "AwaitEvent.h"
34 #if defined(mingw32_HOST_OS)
35 #include "win32/IOManager.h"
38 #include "RaiseAsync.h"
41 #include "ThreadPaused.h"
43 #ifdef HAVE_SYS_TYPES_H
44 #include <sys/types.h>
58 /* -----------------------------------------------------------------------------
60 * -------------------------------------------------------------------------- */
62 #if !defined(THREADED_RTS)
63 // Blocked/sleeping thrads
64 StgTSO *blocked_queue_hd = NULL;
65 StgTSO *blocked_queue_tl = NULL;
66 StgTSO *sleeping_queue = NULL; // perhaps replace with a hash table?
69 /* Threads blocked on blackholes.
70 * LOCK: sched_mutex+capability, or all capabilities
72 StgTSO *blackhole_queue = NULL;
74 /* The blackhole_queue should be checked for threads to wake up. See
75 * Schedule.h for more thorough comment.
76 * LOCK: none (doesn't matter if we miss an update)
78 rtsBool blackholes_need_checking = rtsFalse;
80 /* Set to true when the latest garbage collection failed to reclaim
81 * enough space, and the runtime should proceed to shut itself down in
82 * an orderly fashion (emitting profiling info etc.)
84 rtsBool heap_overflow = rtsFalse;
86 /* flag that tracks whether we have done any execution in this time slice.
87 * LOCK: currently none, perhaps we should lock (but needs to be
88 * updated in the fast path of the scheduler).
90 * NB. must be StgWord, we do xchg() on it.
92 volatile StgWord recent_activity = ACTIVITY_YES;
94 /* if this flag is set as well, give up execution
95 * LOCK: none (changes monotonically)
97 volatile StgWord sched_state = SCHED_RUNNING;
99 /* This is used in `TSO.h' and gcc 2.96 insists that this variable actually
100 * exists - earlier gccs apparently didn't.
106 * Set to TRUE when entering a shutdown state (via shutdownHaskellAndExit()) --
107 * in an MT setting, needed to signal that a worker thread shouldn't hang around
108 * in the scheduler when it is out of work.
110 rtsBool shutting_down_scheduler = rtsFalse;
113 * This mutex protects most of the global scheduler data in
114 * the THREADED_RTS runtime.
116 #if defined(THREADED_RTS)
120 #if !defined(mingw32_HOST_OS)
121 #define FORKPROCESS_PRIMOP_SUPPORTED
124 /* -----------------------------------------------------------------------------
125 * static function prototypes
126 * -------------------------------------------------------------------------- */
128 static Capability *schedule (Capability *initialCapability, Task *task);
131 // These function all encapsulate parts of the scheduler loop, and are
132 // abstracted only to make the structure and control flow of the
133 // scheduler clearer.
135 static void schedulePreLoop (void);
136 static void scheduleFindWork (Capability *cap);
137 #if defined(THREADED_RTS)
138 static void scheduleYield (Capability **pcap, Task *task, rtsBool);
140 static void scheduleStartSignalHandlers (Capability *cap);
141 static void scheduleCheckBlockedThreads (Capability *cap);
142 static void scheduleCheckWakeupThreads(Capability *cap USED_IF_NOT_THREADS);
143 static void scheduleCheckBlackHoles (Capability *cap);
144 static void scheduleDetectDeadlock (Capability *cap, Task *task);
145 static void schedulePushWork(Capability *cap, Task *task);
146 #if defined(THREADED_RTS)
147 static void scheduleActivateSpark(Capability *cap);
149 static void schedulePostRunThread(Capability *cap, StgTSO *t);
150 static rtsBool scheduleHandleHeapOverflow( Capability *cap, StgTSO *t );
151 static void scheduleHandleStackOverflow( Capability *cap, Task *task,
153 static rtsBool scheduleHandleYield( Capability *cap, StgTSO *t,
154 nat prev_what_next );
155 static void scheduleHandleThreadBlocked( StgTSO *t );
156 static rtsBool scheduleHandleThreadFinished( Capability *cap, Task *task,
158 static rtsBool scheduleNeedHeapProfile(rtsBool ready_to_gc);
159 static Capability *scheduleDoGC(Capability *cap, Task *task,
160 rtsBool force_major);
162 static rtsBool checkBlackHoles(Capability *cap);
164 static StgTSO *threadStackOverflow(Capability *cap, StgTSO *tso);
165 static StgTSO *threadStackUnderflow(Task *task, StgTSO *tso);
167 static void deleteThread (Capability *cap, StgTSO *tso);
168 static void deleteAllThreads (Capability *cap);
170 #ifdef FORKPROCESS_PRIMOP_SUPPORTED
171 static void deleteThread_(Capability *cap, StgTSO *tso);
174 /* -----------------------------------------------------------------------------
175 * Putting a thread on the run queue: different scheduling policies
176 * -------------------------------------------------------------------------- */
179 addToRunQueue( Capability *cap, StgTSO *t )
181 // this does round-robin scheduling; good for concurrency
182 appendToRunQueue(cap,t);
185 /* ---------------------------------------------------------------------------
186 Main scheduling loop.
188 We use round-robin scheduling, each thread returning to the
189 scheduler loop when one of these conditions is detected:
192 * timer expires (thread yields)
198 In a GranSim setup this loop iterates over the global event queue.
199 This revolves around the global event queue, which determines what
200 to do next. Therefore, it's more complicated than either the
201 concurrent or the parallel (GUM) setup.
202 This version has been entirely removed (JB 2008/08).
205 GUM iterates over incoming messages.
206 It starts with nothing to do (thus CurrentTSO == END_TSO_QUEUE),
207 and sends out a fish whenever it has nothing to do; in-between
208 doing the actual reductions (shared code below) it processes the
209 incoming messages and deals with delayed operations
210 (see PendingFetches).
211 This is not the ugliest code you could imagine, but it's bloody close.
213 (JB 2008/08) This version was formerly indicated by a PP-Flag PAR,
214 now by PP-flag PARALLEL_HASKELL. The Eden RTS (in GHC-6.x) uses it,
215 as well as future GUM versions. This file has been refurbished to
216 only contain valid code, which is however incomplete, refers to
217 invalid includes etc.
219 ------------------------------------------------------------------------ */
222 schedule (Capability *initialCapability, Task *task)
226 StgThreadReturnCode ret;
229 #if defined(THREADED_RTS)
230 rtsBool first = rtsTrue;
231 rtsBool force_yield = rtsFalse;
234 cap = initialCapability;
236 // Pre-condition: this task owns initialCapability.
237 // The sched_mutex is *NOT* held
238 // NB. on return, we still hold a capability.
240 debugTrace (DEBUG_sched, "cap %d: schedule()", initialCapability->no);
244 // -----------------------------------------------------------
245 // Scheduler loop starts here:
249 // Check whether we have re-entered the RTS from Haskell without
250 // going via suspendThread()/resumeThread (i.e. a 'safe' foreign
252 if (cap->in_haskell) {
253 errorBelch("schedule: re-entered unsafely.\n"
254 " Perhaps a 'foreign import unsafe' should be 'safe'?");
255 stg_exit(EXIT_FAILURE);
258 // The interruption / shutdown sequence.
260 // In order to cleanly shut down the runtime, we want to:
261 // * make sure that all main threads return to their callers
262 // with the state 'Interrupted'.
263 // * clean up all OS threads assocated with the runtime
264 // * free all memory etc.
266 // So the sequence for ^C goes like this:
268 // * ^C handler sets sched_state := SCHED_INTERRUPTING and
269 // arranges for some Capability to wake up
271 // * all threads in the system are halted, and the zombies are
272 // placed on the run queue for cleaning up. We acquire all
273 // the capabilities in order to delete the threads, this is
274 // done by scheduleDoGC() for convenience (because GC already
275 // needs to acquire all the capabilities). We can't kill
276 // threads involved in foreign calls.
278 // * somebody calls shutdownHaskell(), which calls exitScheduler()
280 // * sched_state := SCHED_SHUTTING_DOWN
282 // * all workers exit when the run queue on their capability
283 // drains. All main threads will also exit when their TSO
284 // reaches the head of the run queue and they can return.
286 // * eventually all Capabilities will shut down, and the RTS can
289 // * We might be left with threads blocked in foreign calls,
290 // we should really attempt to kill these somehow (TODO);
292 switch (sched_state) {
295 case SCHED_INTERRUPTING:
296 debugTrace(DEBUG_sched, "SCHED_INTERRUPTING");
297 #if defined(THREADED_RTS)
298 discardSparksCap(cap);
300 /* scheduleDoGC() deletes all the threads */
301 cap = scheduleDoGC(cap,task,rtsFalse);
303 // after scheduleDoGC(), we must be shutting down. Either some
304 // other Capability did the final GC, or we did it above,
305 // either way we can fall through to the SCHED_SHUTTING_DOWN
307 ASSERT(sched_state == SCHED_SHUTTING_DOWN);
310 case SCHED_SHUTTING_DOWN:
311 debugTrace(DEBUG_sched, "SCHED_SHUTTING_DOWN");
312 // If we are a worker, just exit. If we're a bound thread
313 // then we will exit below when we've removed our TSO from
315 if (task->tso == NULL && emptyRunQueue(cap)) {
320 barf("sched_state: %d", sched_state);
323 scheduleFindWork(cap);
325 /* work pushing, currently relevant only for THREADED_RTS:
326 (pushes threads, wakes up idle capabilities for stealing) */
327 schedulePushWork(cap,task);
329 scheduleDetectDeadlock(cap,task);
331 #if defined(THREADED_RTS)
332 cap = task->cap; // reload cap, it might have changed
335 // Normally, the only way we can get here with no threads to
336 // run is if a keyboard interrupt received during
337 // scheduleCheckBlockedThreads() or scheduleDetectDeadlock().
338 // Additionally, it is not fatal for the
339 // threaded RTS to reach here with no threads to run.
341 // win32: might be here due to awaitEvent() being abandoned
342 // as a result of a console event having been delivered.
344 #if defined(THREADED_RTS)
348 // // don't yield the first time, we want a chance to run this
349 // // thread for a bit, even if there are others banging at the
352 // ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
356 scheduleYield(&cap,task,force_yield);
357 force_yield = rtsFalse;
359 if (emptyRunQueue(cap)) continue; // look for work again
362 #if !defined(THREADED_RTS) && !defined(mingw32_HOST_OS)
363 if ( emptyRunQueue(cap) ) {
364 ASSERT(sched_state >= SCHED_INTERRUPTING);
369 // Get a thread to run
371 t = popRunQueue(cap);
373 // Sanity check the thread we're about to run. This can be
374 // expensive if there is lots of thread switching going on...
375 IF_DEBUG(sanity,checkTSO(t));
377 #if defined(THREADED_RTS)
378 // Check whether we can run this thread in the current task.
379 // If not, we have to pass our capability to the right task.
381 Task *bound = t->bound;
385 // yes, the Haskell thread is bound to the current native thread
387 debugTrace(DEBUG_sched,
388 "thread %lu bound to another OS thread",
389 (unsigned long)t->id);
390 // no, bound to a different Haskell thread: pass to that thread
391 pushOnRunQueue(cap,t);
395 // The thread we want to run is unbound.
397 debugTrace(DEBUG_sched,
398 "this OS thread cannot run thread %lu",
399 (unsigned long)t->id);
400 // no, the current native thread is bound to a different
401 // Haskell thread, so pass it to any worker thread
402 pushOnRunQueue(cap,t);
409 // If we're shutting down, and this thread has not yet been
410 // killed, kill it now. This sometimes happens when a finalizer
411 // thread is created by the final GC, or a thread previously
412 // in a foreign call returns.
413 if (sched_state >= SCHED_INTERRUPTING &&
414 !(t->what_next == ThreadComplete || t->what_next == ThreadKilled)) {
418 /* context switches are initiated by the timer signal, unless
419 * the user specified "context switch as often as possible", with
422 if (RtsFlags.ConcFlags.ctxtSwitchTicks == 0
423 && !emptyThreadQueues(cap)) {
424 cap->context_switch = 1;
429 // CurrentTSO is the thread to run. t might be different if we
430 // loop back to run_thread, so make sure to set CurrentTSO after
432 cap->r.rCurrentTSO = t;
434 startHeapProfTimer();
436 // Check for exceptions blocked on this thread
437 maybePerformBlockedException (cap, t);
439 // ----------------------------------------------------------------------
440 // Run the current thread
442 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
443 ASSERT(t->cap == cap);
444 ASSERT(t->bound ? t->bound->cap == cap : 1);
446 prev_what_next = t->what_next;
448 errno = t->saved_errno;
450 SetLastError(t->saved_winerror);
453 cap->in_haskell = rtsTrue;
457 #if defined(THREADED_RTS)
458 if (recent_activity == ACTIVITY_DONE_GC) {
459 // ACTIVITY_DONE_GC means we turned off the timer signal to
460 // conserve power (see #1623). Re-enable it here.
462 prev = xchg((P_)&recent_activity, ACTIVITY_YES);
463 if (prev == ACTIVITY_DONE_GC) {
467 recent_activity = ACTIVITY_YES;
471 traceSchedEvent(cap, EVENT_RUN_THREAD, t, 0);
473 switch (prev_what_next) {
477 /* Thread already finished, return to scheduler. */
478 ret = ThreadFinished;
484 r = StgRun((StgFunPtr) stg_returnToStackTop, &cap->r);
485 cap = regTableToCapability(r);
490 case ThreadInterpret:
491 cap = interpretBCO(cap);
496 barf("schedule: invalid what_next field");
499 cap->in_haskell = rtsFalse;
501 // The TSO might have moved, eg. if it re-entered the RTS and a GC
502 // happened. So find the new location:
503 t = cap->r.rCurrentTSO;
505 // We have run some Haskell code: there might be blackhole-blocked
506 // threads to wake up now.
507 // Lock-free test here should be ok, we're just setting a flag.
508 if ( blackhole_queue != END_TSO_QUEUE ) {
509 blackholes_need_checking = rtsTrue;
512 // And save the current errno in this thread.
513 // XXX: possibly bogus for SMP because this thread might already
514 // be running again, see code below.
515 t->saved_errno = errno;
517 // Similarly for Windows error code
518 t->saved_winerror = GetLastError();
521 traceSchedEvent (cap, EVENT_STOP_THREAD, t, ret);
523 #if defined(THREADED_RTS)
524 // If ret is ThreadBlocked, and this Task is bound to the TSO that
525 // blocked, we are in limbo - the TSO is now owned by whatever it
526 // is blocked on, and may in fact already have been woken up,
527 // perhaps even on a different Capability. It may be the case
528 // that task->cap != cap. We better yield this Capability
529 // immediately and return to normaility.
530 if (ret == ThreadBlocked) {
531 force_yield = rtsTrue;
536 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
537 ASSERT(t->cap == cap);
539 // ----------------------------------------------------------------------
541 // Costs for the scheduler are assigned to CCS_SYSTEM
543 #if defined(PROFILING)
547 schedulePostRunThread(cap,t);
549 if (ret != StackOverflow) {
550 t = threadStackUnderflow(task,t);
553 ready_to_gc = rtsFalse;
557 ready_to_gc = scheduleHandleHeapOverflow(cap,t);
561 scheduleHandleStackOverflow(cap,task,t);
565 if (scheduleHandleYield(cap, t, prev_what_next)) {
566 // shortcut for switching between compiler/interpreter:
572 scheduleHandleThreadBlocked(t);
576 if (scheduleHandleThreadFinished(cap, task, t)) return cap;
577 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
581 barf("schedule: invalid thread return code %d", (int)ret);
584 if (ready_to_gc || scheduleNeedHeapProfile(ready_to_gc)) {
585 cap = scheduleDoGC(cap,task,rtsFalse);
587 } /* end of while() */
590 /* ----------------------------------------------------------------------------
591 * Setting up the scheduler loop
592 * ------------------------------------------------------------------------- */
595 schedulePreLoop(void)
597 // initialisation for scheduler - what cannot go into initScheduler()
600 /* -----------------------------------------------------------------------------
603 * Search for work to do, and handle messages from elsewhere.
604 * -------------------------------------------------------------------------- */
607 scheduleFindWork (Capability *cap)
609 scheduleStartSignalHandlers(cap);
611 // Only check the black holes here if we've nothing else to do.
612 // During normal execution, the black hole list only gets checked
613 // at GC time, to avoid repeatedly traversing this possibly long
614 // list each time around the scheduler.
615 if (emptyRunQueue(cap)) { scheduleCheckBlackHoles(cap); }
617 scheduleCheckWakeupThreads(cap);
619 scheduleCheckBlockedThreads(cap);
621 #if defined(THREADED_RTS)
622 if (emptyRunQueue(cap)) { scheduleActivateSpark(cap); }
626 #if defined(THREADED_RTS)
627 STATIC_INLINE rtsBool
628 shouldYieldCapability (Capability *cap, Task *task)
630 // we need to yield this capability to someone else if..
631 // - another thread is initiating a GC
632 // - another Task is returning from a foreign call
633 // - the thread at the head of the run queue cannot be run
634 // by this Task (it is bound to another Task, or it is unbound
635 // and this task it bound).
636 return (waiting_for_gc ||
637 cap->returning_tasks_hd != NULL ||
638 (!emptyRunQueue(cap) && (task->tso == NULL
639 ? cap->run_queue_hd->bound != NULL
640 : cap->run_queue_hd->bound != task)));
643 // This is the single place where a Task goes to sleep. There are
644 // two reasons it might need to sleep:
645 // - there are no threads to run
646 // - we need to yield this Capability to someone else
647 // (see shouldYieldCapability())
649 // Careful: the scheduler loop is quite delicate. Make sure you run
650 // the tests in testsuite/concurrent (all ways) after modifying this,
651 // and also check the benchmarks in nofib/parallel for regressions.
654 scheduleYield (Capability **pcap, Task *task, rtsBool force_yield)
656 Capability *cap = *pcap;
658 // if we have work, and we don't need to give up the Capability, continue.
660 // The force_yield flag is used when a bound thread blocks. This
661 // is a particularly tricky situation: the current Task does not
662 // own the TSO any more, since it is on some queue somewhere, and
663 // might be woken up or manipulated by another thread at any time.
664 // The TSO and Task might be migrated to another Capability.
665 // Certain invariants might be in doubt, such as task->bound->cap
666 // == cap. We have to yield the current Capability immediately,
667 // no messing around.
670 !shouldYieldCapability(cap,task) &&
671 (!emptyRunQueue(cap) ||
672 !emptyWakeupQueue(cap) ||
673 blackholes_need_checking ||
674 sched_state >= SCHED_INTERRUPTING))
677 // otherwise yield (sleep), and keep yielding if necessary.
679 yieldCapability(&cap,task);
681 while (shouldYieldCapability(cap,task));
683 // note there may still be no threads on the run queue at this
684 // point, the caller has to check.
691 /* -----------------------------------------------------------------------------
694 * Push work to other Capabilities if we have some.
695 * -------------------------------------------------------------------------- */
698 schedulePushWork(Capability *cap USED_IF_THREADS,
699 Task *task USED_IF_THREADS)
701 /* following code not for PARALLEL_HASKELL. I kept the call general,
702 future GUM versions might use pushing in a distributed setup */
703 #if defined(THREADED_RTS)
705 Capability *free_caps[n_capabilities], *cap0;
708 // migration can be turned off with +RTS -qg
709 if (!RtsFlags.ParFlags.migrate) return;
711 // Check whether we have more threads on our run queue, or sparks
712 // in our pool, that we could hand to another Capability.
713 if (cap->run_queue_hd == END_TSO_QUEUE) {
714 if (sparkPoolSizeCap(cap) < 2) return;
716 if (cap->run_queue_hd->_link == END_TSO_QUEUE &&
717 sparkPoolSizeCap(cap) < 1) return;
720 // First grab as many free Capabilities as we can.
721 for (i=0, n_free_caps=0; i < n_capabilities; i++) {
722 cap0 = &capabilities[i];
723 if (cap != cap0 && tryGrabCapability(cap0,task)) {
724 if (!emptyRunQueue(cap0) || cap->returning_tasks_hd != NULL) {
725 // it already has some work, we just grabbed it at
726 // the wrong moment. Or maybe it's deadlocked!
727 releaseCapability(cap0);
729 free_caps[n_free_caps++] = cap0;
734 // we now have n_free_caps free capabilities stashed in
735 // free_caps[]. Share our run queue equally with them. This is
736 // probably the simplest thing we could do; improvements we might
737 // want to do include:
739 // - giving high priority to moving relatively new threads, on
740 // the gournds that they haven't had time to build up a
741 // working set in the cache on this CPU/Capability.
743 // - giving low priority to moving long-lived threads
745 if (n_free_caps > 0) {
746 StgTSO *prev, *t, *next;
747 rtsBool pushed_to_all;
749 debugTrace(DEBUG_sched,
750 "cap %d: %s and %d free capabilities, sharing...",
752 (!emptyRunQueue(cap) && cap->run_queue_hd->_link != END_TSO_QUEUE)?
753 "excess threads on run queue":"sparks to share (>=2)",
757 pushed_to_all = rtsFalse;
759 if (cap->run_queue_hd != END_TSO_QUEUE) {
760 prev = cap->run_queue_hd;
762 prev->_link = END_TSO_QUEUE;
763 for (; t != END_TSO_QUEUE; t = next) {
765 t->_link = END_TSO_QUEUE;
766 if (t->what_next == ThreadRelocated
767 || t->bound == task // don't move my bound thread
768 || tsoLocked(t)) { // don't move a locked thread
769 setTSOLink(cap, prev, t);
771 } else if (i == n_free_caps) {
772 pushed_to_all = rtsTrue;
775 setTSOLink(cap, prev, t);
778 debugTrace(DEBUG_sched, "pushing thread %lu to capability %d", (unsigned long)t->id, free_caps[i]->no);
779 appendToRunQueue(free_caps[i],t);
781 traceSchedEvent (cap, EVENT_MIGRATE_THREAD, t, free_caps[i]->no);
783 if (t->bound) { t->bound->cap = free_caps[i]; }
784 t->cap = free_caps[i];
788 cap->run_queue_tl = prev;
792 /* JB I left this code in place, it would work but is not necessary */
794 // If there are some free capabilities that we didn't push any
795 // threads to, then try to push a spark to each one.
796 if (!pushed_to_all) {
798 // i is the next free capability to push to
799 for (; i < n_free_caps; i++) {
800 if (emptySparkPoolCap(free_caps[i])) {
801 spark = tryStealSpark(cap->sparks);
803 debugTrace(DEBUG_sched, "pushing spark %p to capability %d", spark, free_caps[i]->no);
805 traceSchedEvent(free_caps[i], EVENT_STEAL_SPARK, t, cap->no);
807 newSpark(&(free_caps[i]->r), spark);
812 #endif /* SPARK_PUSHING */
814 // release the capabilities
815 for (i = 0; i < n_free_caps; i++) {
816 task->cap = free_caps[i];
817 releaseAndWakeupCapability(free_caps[i]);
820 task->cap = cap; // reset to point to our Capability.
822 #endif /* THREADED_RTS */
826 /* ----------------------------------------------------------------------------
827 * Start any pending signal handlers
828 * ------------------------------------------------------------------------- */
830 #if defined(RTS_USER_SIGNALS) && !defined(THREADED_RTS)
832 scheduleStartSignalHandlers(Capability *cap)
834 if (RtsFlags.MiscFlags.install_signal_handlers && signals_pending()) {
835 // safe outside the lock
836 startSignalHandlers(cap);
841 scheduleStartSignalHandlers(Capability *cap STG_UNUSED)
846 /* ----------------------------------------------------------------------------
847 * Check for blocked threads that can be woken up.
848 * ------------------------------------------------------------------------- */
851 scheduleCheckBlockedThreads(Capability *cap USED_IF_NOT_THREADS)
853 #if !defined(THREADED_RTS)
855 // Check whether any waiting threads need to be woken up. If the
856 // run queue is empty, and there are no other tasks running, we
857 // can wait indefinitely for something to happen.
859 if ( !emptyQueue(blocked_queue_hd) || !emptyQueue(sleeping_queue) )
861 awaitEvent( emptyRunQueue(cap) && !blackholes_need_checking );
867 /* ----------------------------------------------------------------------------
868 * Check for threads woken up by other Capabilities
869 * ------------------------------------------------------------------------- */
872 scheduleCheckWakeupThreads(Capability *cap USED_IF_THREADS)
874 #if defined(THREADED_RTS)
875 // Any threads that were woken up by other Capabilities get
876 // appended to our run queue.
877 if (!emptyWakeupQueue(cap)) {
878 ACQUIRE_LOCK(&cap->lock);
879 if (emptyRunQueue(cap)) {
880 cap->run_queue_hd = cap->wakeup_queue_hd;
881 cap->run_queue_tl = cap->wakeup_queue_tl;
883 setTSOLink(cap, cap->run_queue_tl, cap->wakeup_queue_hd);
884 cap->run_queue_tl = cap->wakeup_queue_tl;
886 cap->wakeup_queue_hd = cap->wakeup_queue_tl = END_TSO_QUEUE;
887 RELEASE_LOCK(&cap->lock);
892 /* ----------------------------------------------------------------------------
893 * Check for threads blocked on BLACKHOLEs that can be woken up
894 * ------------------------------------------------------------------------- */
896 scheduleCheckBlackHoles (Capability *cap)
898 if ( blackholes_need_checking ) // check without the lock first
900 ACQUIRE_LOCK(&sched_mutex);
901 if ( blackholes_need_checking ) {
902 blackholes_need_checking = rtsFalse;
903 // important that we reset the flag *before* checking the
904 // blackhole queue, otherwise we could get deadlock. This
905 // happens as follows: we wake up a thread that
906 // immediately runs on another Capability, blocks on a
907 // blackhole, and then we reset the blackholes_need_checking flag.
908 checkBlackHoles(cap);
910 RELEASE_LOCK(&sched_mutex);
914 /* ----------------------------------------------------------------------------
915 * Detect deadlock conditions and attempt to resolve them.
916 * ------------------------------------------------------------------------- */
919 scheduleDetectDeadlock (Capability *cap, Task *task)
922 * Detect deadlock: when we have no threads to run, there are no
923 * threads blocked, waiting for I/O, or sleeping, and all the
924 * other tasks are waiting for work, we must have a deadlock of
927 if ( emptyThreadQueues(cap) )
929 #if defined(THREADED_RTS)
931 * In the threaded RTS, we only check for deadlock if there
932 * has been no activity in a complete timeslice. This means
933 * we won't eagerly start a full GC just because we don't have
934 * any threads to run currently.
936 if (recent_activity != ACTIVITY_INACTIVE) return;
939 debugTrace(DEBUG_sched, "deadlocked, forcing major GC...");
941 // Garbage collection can release some new threads due to
942 // either (a) finalizers or (b) threads resurrected because
943 // they are unreachable and will therefore be sent an
944 // exception. Any threads thus released will be immediately
946 cap = scheduleDoGC (cap, task, rtsTrue/*force major GC*/);
947 // when force_major == rtsTrue. scheduleDoGC sets
948 // recent_activity to ACTIVITY_DONE_GC and turns off the timer
951 if ( !emptyRunQueue(cap) ) return;
953 #if defined(RTS_USER_SIGNALS) && !defined(THREADED_RTS)
954 /* If we have user-installed signal handlers, then wait
955 * for signals to arrive rather then bombing out with a
958 if ( RtsFlags.MiscFlags.install_signal_handlers && anyUserHandlers() ) {
959 debugTrace(DEBUG_sched,
960 "still deadlocked, waiting for signals...");
964 if (signals_pending()) {
965 startSignalHandlers(cap);
968 // either we have threads to run, or we were interrupted:
969 ASSERT(!emptyRunQueue(cap) || sched_state >= SCHED_INTERRUPTING);
975 #if !defined(THREADED_RTS)
976 /* Probably a real deadlock. Send the current main thread the
977 * Deadlock exception.
980 switch (task->tso->why_blocked) {
982 case BlockedOnBlackHole:
983 case BlockedOnException:
985 throwToSingleThreaded(cap, task->tso,
986 (StgClosure *)nonTermination_closure);
989 barf("deadlock: main thread blocked in a strange way");
998 /* ----------------------------------------------------------------------------
999 * Send pending messages (PARALLEL_HASKELL only)
1000 * ------------------------------------------------------------------------- */
1002 #if defined(PARALLEL_HASKELL)
1004 scheduleSendPendingMessages(void)
1007 # if defined(PAR) // global Mem.Mgmt., omit for now
1008 if (PendingFetches != END_BF_QUEUE) {
1013 if (RtsFlags.ParFlags.BufferTime) {
1014 // if we use message buffering, we must send away all message
1015 // packets which have become too old...
1021 /* ----------------------------------------------------------------------------
1022 * Activate spark threads (PARALLEL_HASKELL and THREADED_RTS)
1023 * ------------------------------------------------------------------------- */
1025 #if defined(THREADED_RTS)
1027 scheduleActivateSpark(Capability *cap)
1031 createSparkThread(cap);
1032 debugTrace(DEBUG_sched, "creating a spark thread");
1035 #endif // PARALLEL_HASKELL || THREADED_RTS
1037 /* ----------------------------------------------------------------------------
1038 * After running a thread...
1039 * ------------------------------------------------------------------------- */
1042 schedulePostRunThread (Capability *cap, StgTSO *t)
1044 // We have to be able to catch transactions that are in an
1045 // infinite loop as a result of seeing an inconsistent view of
1049 // [a,b] <- mapM readTVar [ta,tb]
1050 // when (a == b) loop
1052 // and a is never equal to b given a consistent view of memory.
1054 if (t -> trec != NO_TREC && t -> why_blocked == NotBlocked) {
1055 if (!stmValidateNestOfTransactions (t -> trec)) {
1056 debugTrace(DEBUG_sched | DEBUG_stm,
1057 "trec %p found wasting its time", t);
1059 // strip the stack back to the
1060 // ATOMICALLY_FRAME, aborting the (nested)
1061 // transaction, and saving the stack of any
1062 // partially-evaluated thunks on the heap.
1063 throwToSingleThreaded_(cap, t, NULL, rtsTrue);
1065 // ASSERT(get_itbl((StgClosure *)t->sp)->type == ATOMICALLY_FRAME);
1069 /* some statistics gathering in the parallel case */
1072 /* -----------------------------------------------------------------------------
1073 * Handle a thread that returned to the scheduler with ThreadHeepOverflow
1074 * -------------------------------------------------------------------------- */
1077 scheduleHandleHeapOverflow( Capability *cap, StgTSO *t )
1079 // did the task ask for a large block?
1080 if (cap->r.rHpAlloc > BLOCK_SIZE) {
1081 // if so, get one and push it on the front of the nursery.
1085 blocks = (lnat)BLOCK_ROUND_UP(cap->r.rHpAlloc) / BLOCK_SIZE;
1087 debugTrace(DEBUG_sched,
1088 "--<< thread %ld (%s) stopped: requesting a large block (size %ld)\n",
1089 (long)t->id, what_next_strs[t->what_next], blocks);
1091 // don't do this if the nursery is (nearly) full, we'll GC first.
1092 if (cap->r.rCurrentNursery->link != NULL ||
1093 cap->r.rNursery->n_blocks == 1) { // paranoia to prevent infinite loop
1094 // if the nursery has only one block.
1097 bd = allocGroup( blocks );
1099 cap->r.rNursery->n_blocks += blocks;
1101 // link the new group into the list
1102 bd->link = cap->r.rCurrentNursery;
1103 bd->u.back = cap->r.rCurrentNursery->u.back;
1104 if (cap->r.rCurrentNursery->u.back != NULL) {
1105 cap->r.rCurrentNursery->u.back->link = bd;
1107 cap->r.rNursery->blocks = bd;
1109 cap->r.rCurrentNursery->u.back = bd;
1111 // initialise it as a nursery block. We initialise the
1112 // step, gen_no, and flags field of *every* sub-block in
1113 // this large block, because this is easier than making
1114 // sure that we always find the block head of a large
1115 // block whenever we call Bdescr() (eg. evacuate() and
1116 // isAlive() in the GC would both have to do this, at
1120 for (x = bd; x < bd + blocks; x++) {
1121 x->step = cap->r.rNursery;
1127 // This assert can be a killer if the app is doing lots
1128 // of large block allocations.
1129 IF_DEBUG(sanity, checkNurserySanity(cap->r.rNursery));
1131 // now update the nursery to point to the new block
1132 cap->r.rCurrentNursery = bd;
1134 // we might be unlucky and have another thread get on the
1135 // run queue before us and steal the large block, but in that
1136 // case the thread will just end up requesting another large
1138 pushOnRunQueue(cap,t);
1139 return rtsFalse; /* not actually GC'ing */
1143 if (cap->r.rHpLim == NULL || cap->context_switch) {
1144 // Sometimes we miss a context switch, e.g. when calling
1145 // primitives in a tight loop, MAYBE_GC() doesn't check the
1146 // context switch flag, and we end up waiting for a GC.
1147 // See #1984, and concurrent/should_run/1984
1148 cap->context_switch = 0;
1149 addToRunQueue(cap,t);
1151 pushOnRunQueue(cap,t);
1154 /* actual GC is done at the end of the while loop in schedule() */
1157 /* -----------------------------------------------------------------------------
1158 * Handle a thread that returned to the scheduler with ThreadStackOverflow
1159 * -------------------------------------------------------------------------- */
1162 scheduleHandleStackOverflow (Capability *cap, Task *task, StgTSO *t)
1164 /* just adjust the stack for this thread, then pop it back
1168 /* enlarge the stack */
1169 StgTSO *new_t = threadStackOverflow(cap, t);
1171 /* The TSO attached to this Task may have moved, so update the
1174 if (task->tso == t) {
1177 pushOnRunQueue(cap,new_t);
1181 /* -----------------------------------------------------------------------------
1182 * Handle a thread that returned to the scheduler with ThreadYielding
1183 * -------------------------------------------------------------------------- */
1186 scheduleHandleYield( Capability *cap, StgTSO *t, nat prev_what_next )
1188 // Reset the context switch flag. We don't do this just before
1189 // running the thread, because that would mean we would lose ticks
1190 // during GC, which can lead to unfair scheduling (a thread hogs
1191 // the CPU because the tick always arrives during GC). This way
1192 // penalises threads that do a lot of allocation, but that seems
1193 // better than the alternative.
1194 cap->context_switch = 0;
1196 /* put the thread back on the run queue. Then, if we're ready to
1197 * GC, check whether this is the last task to stop. If so, wake
1198 * up the GC thread. getThread will block during a GC until the
1202 if (t->what_next != prev_what_next) {
1203 debugTrace(DEBUG_sched,
1204 "--<< thread %ld (%s) stopped to switch evaluators",
1205 (long)t->id, what_next_strs[t->what_next]);
1210 //debugBelch("&& Doing sanity check on yielding TSO %ld.", t->id);
1212 ASSERT(t->_link == END_TSO_QUEUE);
1214 // Shortcut if we're just switching evaluators: don't bother
1215 // doing stack squeezing (which can be expensive), just run the
1217 if (t->what_next != prev_what_next) {
1221 addToRunQueue(cap,t);
1226 /* -----------------------------------------------------------------------------
1227 * Handle a thread that returned to the scheduler with ThreadBlocked
1228 * -------------------------------------------------------------------------- */
1231 scheduleHandleThreadBlocked( StgTSO *t
1238 // We don't need to do anything. The thread is blocked, and it
1239 // has tidied up its stack and placed itself on whatever queue
1240 // it needs to be on.
1242 // ASSERT(t->why_blocked != NotBlocked);
1243 // Not true: for example,
1244 // - in THREADED_RTS, the thread may already have been woken
1245 // up by another Capability. This actually happens: try
1246 // conc023 +RTS -N2.
1247 // - the thread may have woken itself up already, because
1248 // threadPaused() might have raised a blocked throwTo
1249 // exception, see maybePerformBlockedException().
1252 traceThreadStatus(DEBUG_sched, t);
1256 /* -----------------------------------------------------------------------------
1257 * Handle a thread that returned to the scheduler with ThreadFinished
1258 * -------------------------------------------------------------------------- */
1261 scheduleHandleThreadFinished (Capability *cap STG_UNUSED, Task *task, StgTSO *t)
1263 /* Need to check whether this was a main thread, and if so,
1264 * return with the return value.
1266 * We also end up here if the thread kills itself with an
1267 * uncaught exception, see Exception.cmm.
1270 // blocked exceptions can now complete, even if the thread was in
1271 // blocked mode (see #2910). This unconditionally calls
1272 // lockTSO(), which ensures that we don't miss any threads that
1273 // are engaged in throwTo() with this thread as a target.
1274 awakenBlockedExceptionQueue (cap, t);
1277 // Check whether the thread that just completed was a bound
1278 // thread, and if so return with the result.
1280 // There is an assumption here that all thread completion goes
1281 // through this point; we need to make sure that if a thread
1282 // ends up in the ThreadKilled state, that it stays on the run
1283 // queue so it can be dealt with here.
1288 if (t->bound != task) {
1289 #if !defined(THREADED_RTS)
1290 // Must be a bound thread that is not the topmost one. Leave
1291 // it on the run queue until the stack has unwound to the
1292 // point where we can deal with this. Leaving it on the run
1293 // queue also ensures that the garbage collector knows about
1294 // this thread and its return value (it gets dropped from the
1295 // step->threads list so there's no other way to find it).
1296 appendToRunQueue(cap,t);
1299 // this cannot happen in the threaded RTS, because a
1300 // bound thread can only be run by the appropriate Task.
1301 barf("finished bound thread that isn't mine");
1305 ASSERT(task->tso == t);
1307 if (t->what_next == ThreadComplete) {
1309 // NOTE: return val is tso->sp[1] (see StgStartup.hc)
1310 *(task->ret) = (StgClosure *)task->tso->sp[1];
1312 task->stat = Success;
1315 *(task->ret) = NULL;
1317 if (sched_state >= SCHED_INTERRUPTING) {
1318 if (heap_overflow) {
1319 task->stat = HeapExhausted;
1321 task->stat = Interrupted;
1324 task->stat = Killed;
1328 removeThreadLabel((StgWord)task->tso->id);
1330 return rtsTrue; // tells schedule() to return
1336 /* -----------------------------------------------------------------------------
1337 * Perform a heap census
1338 * -------------------------------------------------------------------------- */
1341 scheduleNeedHeapProfile( rtsBool ready_to_gc STG_UNUSED )
1343 // When we have +RTS -i0 and we're heap profiling, do a census at
1344 // every GC. This lets us get repeatable runs for debugging.
1345 if (performHeapProfile ||
1346 (RtsFlags.ProfFlags.profileInterval==0 &&
1347 RtsFlags.ProfFlags.doHeapProfile && ready_to_gc)) {
1354 /* -----------------------------------------------------------------------------
1355 * Perform a garbage collection if necessary
1356 * -------------------------------------------------------------------------- */
1359 scheduleDoGC (Capability *cap, Task *task USED_IF_THREADS, rtsBool force_major)
1361 rtsBool heap_census;
1363 /* extern static volatile StgWord waiting_for_gc;
1364 lives inside capability.c */
1365 rtsBool gc_type, prev_pending_gc;
1369 if (sched_state == SCHED_SHUTTING_DOWN) {
1370 // The final GC has already been done, and the system is
1371 // shutting down. We'll probably deadlock if we try to GC
1377 if (sched_state < SCHED_INTERRUPTING
1378 && RtsFlags.ParFlags.parGcEnabled
1379 && N >= RtsFlags.ParFlags.parGcGen
1380 && ! oldest_gen->steps[0].mark)
1382 gc_type = PENDING_GC_PAR;
1384 gc_type = PENDING_GC_SEQ;
1387 // In order to GC, there must be no threads running Haskell code.
1388 // Therefore, the GC thread needs to hold *all* the capabilities,
1389 // and release them after the GC has completed.
1391 // This seems to be the simplest way: previous attempts involved
1392 // making all the threads with capabilities give up their
1393 // capabilities and sleep except for the *last* one, which
1394 // actually did the GC. But it's quite hard to arrange for all
1395 // the other tasks to sleep and stay asleep.
1398 /* Other capabilities are prevented from running yet more Haskell
1399 threads if waiting_for_gc is set. Tested inside
1400 yieldCapability() and releaseCapability() in Capability.c */
1402 prev_pending_gc = cas(&waiting_for_gc, 0, gc_type);
1403 if (prev_pending_gc) {
1405 debugTrace(DEBUG_sched, "someone else is trying to GC (%d)...",
1408 yieldCapability(&cap,task);
1409 } while (waiting_for_gc);
1410 return cap; // NOTE: task->cap might have changed here
1413 setContextSwitches();
1415 // The final shutdown GC is always single-threaded, because it's
1416 // possible that some of the Capabilities have no worker threads.
1418 if (gc_type == PENDING_GC_SEQ)
1420 traceSchedEvent(cap, EVENT_REQUEST_SEQ_GC, 0, 0);
1424 traceSchedEvent(cap, EVENT_REQUEST_PAR_GC, 0, 0);
1425 debugTrace(DEBUG_sched, "ready_to_gc, grabbing GC threads");
1428 // do this while the other Capabilities stop:
1429 if (cap) scheduleCheckBlackHoles(cap);
1431 if (gc_type == PENDING_GC_SEQ)
1433 // single-threaded GC: grab all the capabilities
1434 for (i=0; i < n_capabilities; i++) {
1435 debugTrace(DEBUG_sched, "ready_to_gc, grabbing all the capabilies (%d/%d)", i, n_capabilities);
1436 if (cap != &capabilities[i]) {
1437 Capability *pcap = &capabilities[i];
1438 // we better hope this task doesn't get migrated to
1439 // another Capability while we're waiting for this one.
1440 // It won't, because load balancing happens while we have
1441 // all the Capabilities, but even so it's a slightly
1442 // unsavoury invariant.
1444 waitForReturnCapability(&pcap, task);
1445 if (pcap != &capabilities[i]) {
1446 barf("scheduleDoGC: got the wrong capability");
1453 // multi-threaded GC: make sure all the Capabilities donate one
1455 waitForGcThreads(cap);
1458 #else /* !THREADED_RTS */
1460 // do this while the other Capabilities stop:
1461 if (cap) scheduleCheckBlackHoles(cap);
1465 IF_DEBUG(scheduler, printAllThreads());
1467 delete_threads_and_gc:
1469 * We now have all the capabilities; if we're in an interrupting
1470 * state, then we should take the opportunity to delete all the
1471 * threads in the system.
1473 if (sched_state == SCHED_INTERRUPTING) {
1474 deleteAllThreads(cap);
1475 sched_state = SCHED_SHUTTING_DOWN;
1478 heap_census = scheduleNeedHeapProfile(rtsTrue);
1480 #if defined(THREADED_RTS)
1481 traceSchedEvent(cap, EVENT_GC_START, 0, 0);
1482 // reset waiting_for_gc *before* GC, so that when the GC threads
1483 // emerge they don't immediately re-enter the GC.
1485 GarbageCollect(force_major || heap_census, gc_type, cap);
1487 GarbageCollect(force_major || heap_census, 0, cap);
1489 traceSchedEvent(cap, EVENT_GC_END, 0, 0);
1491 if (recent_activity == ACTIVITY_INACTIVE && force_major)
1493 // We are doing a GC because the system has been idle for a
1494 // timeslice and we need to check for deadlock. Record the
1495 // fact that we've done a GC and turn off the timer signal;
1496 // it will get re-enabled if we run any threads after the GC.
1497 recent_activity = ACTIVITY_DONE_GC;
1502 // the GC might have taken long enough for the timer to set
1503 // recent_activity = ACTIVITY_INACTIVE, but we aren't
1504 // necessarily deadlocked:
1505 recent_activity = ACTIVITY_YES;
1508 #if defined(THREADED_RTS)
1509 if (gc_type == PENDING_GC_PAR)
1511 releaseGCThreads(cap);
1516 debugTrace(DEBUG_sched, "performing heap census");
1518 performHeapProfile = rtsFalse;
1521 if (heap_overflow && sched_state < SCHED_INTERRUPTING) {
1522 // GC set the heap_overflow flag, so we should proceed with
1523 // an orderly shutdown now. Ultimately we want the main
1524 // thread to return to its caller with HeapExhausted, at which
1525 // point the caller should call hs_exit(). The first step is
1526 // to delete all the threads.
1528 // Another way to do this would be to raise an exception in
1529 // the main thread, which we really should do because it gives
1530 // the program a chance to clean up. But how do we find the
1531 // main thread? It should presumably be the same one that
1532 // gets ^C exceptions, but that's all done on the Haskell side
1533 // (GHC.TopHandler).
1534 sched_state = SCHED_INTERRUPTING;
1535 goto delete_threads_and_gc;
1540 Once we are all together... this would be the place to balance all
1541 spark pools. No concurrent stealing or adding of new sparks can
1542 occur. Should be defined in Sparks.c. */
1543 balanceSparkPoolsCaps(n_capabilities, capabilities);
1546 #if defined(THREADED_RTS)
1547 if (gc_type == PENDING_GC_SEQ) {
1548 // release our stash of capabilities.
1549 for (i = 0; i < n_capabilities; i++) {
1550 if (cap != &capabilities[i]) {
1551 task->cap = &capabilities[i];
1552 releaseCapability(&capabilities[i]);
1566 /* ---------------------------------------------------------------------------
1567 * Singleton fork(). Do not copy any running threads.
1568 * ------------------------------------------------------------------------- */
1571 forkProcess(HsStablePtr *entry
1572 #ifndef FORKPROCESS_PRIMOP_SUPPORTED
1577 #ifdef FORKPROCESS_PRIMOP_SUPPORTED
1584 #if defined(THREADED_RTS)
1585 if (RtsFlags.ParFlags.nNodes > 1) {
1586 errorBelch("forking not supported with +RTS -N<n> greater than 1");
1587 stg_exit(EXIT_FAILURE);
1591 debugTrace(DEBUG_sched, "forking!");
1593 // ToDo: for SMP, we should probably acquire *all* the capabilities
1596 // no funny business: hold locks while we fork, otherwise if some
1597 // other thread is holding a lock when the fork happens, the data
1598 // structure protected by the lock will forever be in an
1599 // inconsistent state in the child. See also #1391.
1600 ACQUIRE_LOCK(&sched_mutex);
1601 ACQUIRE_LOCK(&cap->lock);
1602 ACQUIRE_LOCK(&cap->running_task->lock);
1606 if (pid) { // parent
1608 RELEASE_LOCK(&sched_mutex);
1609 RELEASE_LOCK(&cap->lock);
1610 RELEASE_LOCK(&cap->running_task->lock);
1612 // just return the pid
1618 #if defined(THREADED_RTS)
1619 initMutex(&sched_mutex);
1620 initMutex(&cap->lock);
1621 initMutex(&cap->running_task->lock);
1624 // Now, all OS threads except the thread that forked are
1625 // stopped. We need to stop all Haskell threads, including
1626 // those involved in foreign calls. Also we need to delete
1627 // all Tasks, because they correspond to OS threads that are
1630 for (s = 0; s < total_steps; s++) {
1631 for (t = all_steps[s].threads; t != END_TSO_QUEUE; t = next) {
1632 if (t->what_next == ThreadRelocated) {
1635 next = t->global_link;
1636 // don't allow threads to catch the ThreadKilled
1637 // exception, but we do want to raiseAsync() because these
1638 // threads may be evaluating thunks that we need later.
1639 deleteThread_(cap,t);
1644 // Empty the run queue. It seems tempting to let all the
1645 // killed threads stay on the run queue as zombies to be
1646 // cleaned up later, but some of them correspond to bound
1647 // threads for which the corresponding Task does not exist.
1648 cap->run_queue_hd = END_TSO_QUEUE;
1649 cap->run_queue_tl = END_TSO_QUEUE;
1651 // Any suspended C-calling Tasks are no more, their OS threads
1653 cap->suspended_ccalling_tasks = NULL;
1655 // Empty the threads lists. Otherwise, the garbage
1656 // collector may attempt to resurrect some of these threads.
1657 for (s = 0; s < total_steps; s++) {
1658 all_steps[s].threads = END_TSO_QUEUE;
1661 // Wipe the task list, except the current Task.
1662 ACQUIRE_LOCK(&sched_mutex);
1663 for (task = all_tasks; task != NULL; task=task->all_link) {
1664 if (task != cap->running_task) {
1665 #if defined(THREADED_RTS)
1666 initMutex(&task->lock); // see #1391
1671 RELEASE_LOCK(&sched_mutex);
1673 #if defined(THREADED_RTS)
1674 // Wipe our spare workers list, they no longer exist. New
1675 // workers will be created if necessary.
1676 cap->spare_workers = NULL;
1677 cap->returning_tasks_hd = NULL;
1678 cap->returning_tasks_tl = NULL;
1681 // On Unix, all timers are reset in the child, so we need to start
1686 cap = rts_evalStableIO(cap, entry, NULL); // run the action
1687 rts_checkSchedStatus("forkProcess",cap);
1690 hs_exit(); // clean up and exit
1691 stg_exit(EXIT_SUCCESS);
1693 #else /* !FORKPROCESS_PRIMOP_SUPPORTED */
1694 barf("forkProcess#: primop not supported on this platform, sorry!\n");
1698 /* ---------------------------------------------------------------------------
1699 * Delete all the threads in the system
1700 * ------------------------------------------------------------------------- */
1703 deleteAllThreads ( Capability *cap )
1705 // NOTE: only safe to call if we own all capabilities.
1710 debugTrace(DEBUG_sched,"deleting all threads");
1711 for (s = 0; s < total_steps; s++) {
1712 for (t = all_steps[s].threads; t != END_TSO_QUEUE; t = next) {
1713 if (t->what_next == ThreadRelocated) {
1716 next = t->global_link;
1717 deleteThread(cap,t);
1722 // The run queue now contains a bunch of ThreadKilled threads. We
1723 // must not throw these away: the main thread(s) will be in there
1724 // somewhere, and the main scheduler loop has to deal with it.
1725 // Also, the run queue is the only thing keeping these threads from
1726 // being GC'd, and we don't want the "main thread has been GC'd" panic.
1728 #if !defined(THREADED_RTS)
1729 ASSERT(blocked_queue_hd == END_TSO_QUEUE);
1730 ASSERT(sleeping_queue == END_TSO_QUEUE);
1734 /* -----------------------------------------------------------------------------
1735 Managing the suspended_ccalling_tasks list.
1736 Locks required: sched_mutex
1737 -------------------------------------------------------------------------- */
1740 suspendTask (Capability *cap, Task *task)
1742 ASSERT(task->next == NULL && task->prev == NULL);
1743 task->next = cap->suspended_ccalling_tasks;
1745 if (cap->suspended_ccalling_tasks) {
1746 cap->suspended_ccalling_tasks->prev = task;
1748 cap->suspended_ccalling_tasks = task;
1752 recoverSuspendedTask (Capability *cap, Task *task)
1755 task->prev->next = task->next;
1757 ASSERT(cap->suspended_ccalling_tasks == task);
1758 cap->suspended_ccalling_tasks = task->next;
1761 task->next->prev = task->prev;
1763 task->next = task->prev = NULL;
1766 /* ---------------------------------------------------------------------------
1767 * Suspending & resuming Haskell threads.
1769 * When making a "safe" call to C (aka _ccall_GC), the task gives back
1770 * its capability before calling the C function. This allows another
1771 * task to pick up the capability and carry on running Haskell
1772 * threads. It also means that if the C call blocks, it won't lock
1775 * The Haskell thread making the C call is put to sleep for the
1776 * duration of the call, on the susepended_ccalling_threads queue. We
1777 * give out a token to the task, which it can use to resume the thread
1778 * on return from the C function.
1779 * ------------------------------------------------------------------------- */
1782 suspendThread (StgRegTable *reg)
1789 StgWord32 saved_winerror;
1792 saved_errno = errno;
1794 saved_winerror = GetLastError();
1797 /* assume that *reg is a pointer to the StgRegTable part of a Capability.
1799 cap = regTableToCapability(reg);
1801 task = cap->running_task;
1802 tso = cap->r.rCurrentTSO;
1804 traceSchedEvent(cap, EVENT_STOP_THREAD, tso, THREAD_SUSPENDED_FOREIGN_CALL);
1806 // XXX this might not be necessary --SDM
1807 tso->what_next = ThreadRunGHC;
1809 threadPaused(cap,tso);
1811 if ((tso->flags & TSO_BLOCKEX) == 0) {
1812 tso->why_blocked = BlockedOnCCall;
1813 tso->flags |= TSO_BLOCKEX;
1814 tso->flags &= ~TSO_INTERRUPTIBLE;
1816 tso->why_blocked = BlockedOnCCall_NoUnblockExc;
1819 // Hand back capability
1820 task->suspended_tso = tso;
1822 ACQUIRE_LOCK(&cap->lock);
1824 suspendTask(cap,task);
1825 cap->in_haskell = rtsFalse;
1826 releaseCapability_(cap,rtsFalse);
1828 RELEASE_LOCK(&cap->lock);
1830 errno = saved_errno;
1832 SetLastError(saved_winerror);
1838 resumeThread (void *task_)
1845 StgWord32 saved_winerror;
1848 saved_errno = errno;
1850 saved_winerror = GetLastError();
1854 // Wait for permission to re-enter the RTS with the result.
1855 waitForReturnCapability(&cap,task);
1856 // we might be on a different capability now... but if so, our
1857 // entry on the suspended_ccalling_tasks list will also have been
1860 // Remove the thread from the suspended list
1861 recoverSuspendedTask(cap,task);
1863 tso = task->suspended_tso;
1864 task->suspended_tso = NULL;
1865 tso->_link = END_TSO_QUEUE; // no write barrier reqd
1867 traceSchedEvent(cap, EVENT_RUN_THREAD, tso, tso->what_next);
1869 if (tso->why_blocked == BlockedOnCCall) {
1870 // avoid locking the TSO if we don't have to
1871 if (tso->blocked_exceptions != END_TSO_QUEUE) {
1872 awakenBlockedExceptionQueue(cap,tso);
1874 tso->flags &= ~(TSO_BLOCKEX | TSO_INTERRUPTIBLE);
1877 /* Reset blocking status */
1878 tso->why_blocked = NotBlocked;
1880 cap->r.rCurrentTSO = tso;
1881 cap->in_haskell = rtsTrue;
1882 errno = saved_errno;
1884 SetLastError(saved_winerror);
1887 /* We might have GC'd, mark the TSO dirty again */
1890 IF_DEBUG(sanity, checkTSO(tso));
1895 /* ---------------------------------------------------------------------------
1898 * scheduleThread puts a thread on the end of the runnable queue.
1899 * This will usually be done immediately after a thread is created.
1900 * The caller of scheduleThread must create the thread using e.g.
1901 * createThread and push an appropriate closure
1902 * on this thread's stack before the scheduler is invoked.
1903 * ------------------------------------------------------------------------ */
1906 scheduleThread(Capability *cap, StgTSO *tso)
1908 // The thread goes at the *end* of the run-queue, to avoid possible
1909 // starvation of any threads already on the queue.
1910 appendToRunQueue(cap,tso);
1914 scheduleThreadOn(Capability *cap, StgWord cpu USED_IF_THREADS, StgTSO *tso)
1916 #if defined(THREADED_RTS)
1917 tso->flags |= TSO_LOCKED; // we requested explicit affinity; don't
1918 // move this thread from now on.
1919 cpu %= RtsFlags.ParFlags.nNodes;
1920 if (cpu == cap->no) {
1921 appendToRunQueue(cap,tso);
1923 traceSchedEvent (cap, EVENT_MIGRATE_THREAD, tso, capabilities[cpu].no);
1924 wakeupThreadOnCapability(cap, &capabilities[cpu], tso);
1927 appendToRunQueue(cap,tso);
1932 scheduleWaitThread (StgTSO* tso, /*[out]*/HaskellObj* ret, Capability *cap)
1936 // We already created/initialised the Task
1937 task = cap->running_task;
1939 // This TSO is now a bound thread; make the Task and TSO
1940 // point to each other.
1946 task->stat = NoStatus;
1948 appendToRunQueue(cap,tso);
1950 debugTrace(DEBUG_sched, "new bound thread (%lu)", (unsigned long)tso->id);
1952 cap = schedule(cap,task);
1954 ASSERT(task->stat != NoStatus);
1955 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
1957 debugTrace(DEBUG_sched, "bound thread (%lu) finished", (unsigned long)task->tso->id);
1961 /* ----------------------------------------------------------------------------
1963 * ------------------------------------------------------------------------- */
1965 #if defined(THREADED_RTS)
1966 void OSThreadProcAttr
1967 workerStart(Task *task)
1971 // See startWorkerTask().
1972 ACQUIRE_LOCK(&task->lock);
1974 RELEASE_LOCK(&task->lock);
1976 if (RtsFlags.ParFlags.setAffinity) {
1977 setThreadAffinity(cap->no, n_capabilities);
1980 // set the thread-local pointer to the Task:
1983 // schedule() runs without a lock.
1984 cap = schedule(cap,task);
1986 // On exit from schedule(), we have a Capability, but possibly not
1987 // the same one we started with.
1989 // During shutdown, the requirement is that after all the
1990 // Capabilities are shut down, all workers that are shutting down
1991 // have finished workerTaskStop(). This is why we hold on to
1992 // cap->lock until we've finished workerTaskStop() below.
1994 // There may be workers still involved in foreign calls; those
1995 // will just block in waitForReturnCapability() because the
1996 // Capability has been shut down.
1998 ACQUIRE_LOCK(&cap->lock);
1999 releaseCapability_(cap,rtsFalse);
2000 workerTaskStop(task);
2001 RELEASE_LOCK(&cap->lock);
2005 /* ---------------------------------------------------------------------------
2008 * Initialise the scheduler. This resets all the queues - if the
2009 * queues contained any threads, they'll be garbage collected at the
2012 * ------------------------------------------------------------------------ */
2017 #if !defined(THREADED_RTS)
2018 blocked_queue_hd = END_TSO_QUEUE;
2019 blocked_queue_tl = END_TSO_QUEUE;
2020 sleeping_queue = END_TSO_QUEUE;
2023 blackhole_queue = END_TSO_QUEUE;
2025 sched_state = SCHED_RUNNING;
2026 recent_activity = ACTIVITY_YES;
2028 #if defined(THREADED_RTS)
2029 /* Initialise the mutex and condition variables used by
2031 initMutex(&sched_mutex);
2034 ACQUIRE_LOCK(&sched_mutex);
2036 /* A capability holds the state a native thread needs in
2037 * order to execute STG code. At least one capability is
2038 * floating around (only THREADED_RTS builds have more than one).
2044 #if defined(THREADED_RTS)
2048 #if defined(THREADED_RTS)
2050 * Eagerly start one worker to run each Capability, except for
2051 * Capability 0. The idea is that we're probably going to start a
2052 * bound thread on Capability 0 pretty soon, so we don't want a
2053 * worker task hogging it.
2058 for (i = 1; i < n_capabilities; i++) {
2059 cap = &capabilities[i];
2060 ACQUIRE_LOCK(&cap->lock);
2061 startWorkerTask(cap, workerStart);
2062 RELEASE_LOCK(&cap->lock);
2067 RELEASE_LOCK(&sched_mutex);
2072 rtsBool wait_foreign
2073 #if !defined(THREADED_RTS)
2074 __attribute__((unused))
2077 /* see Capability.c, shutdownCapability() */
2081 task = newBoundTask();
2083 // If we haven't killed all the threads yet, do it now.
2084 if (sched_state < SCHED_SHUTTING_DOWN) {
2085 sched_state = SCHED_INTERRUPTING;
2086 waitForReturnCapability(&task->cap,task);
2087 scheduleDoGC(task->cap,task,rtsFalse);
2088 releaseCapability(task->cap);
2090 sched_state = SCHED_SHUTTING_DOWN;
2092 #if defined(THREADED_RTS)
2096 for (i = 0; i < n_capabilities; i++) {
2097 shutdownCapability(&capabilities[i], task, wait_foreign);
2099 boundTaskExiting(task);
2105 freeScheduler( void )
2109 ACQUIRE_LOCK(&sched_mutex);
2110 still_running = freeTaskManager();
2111 // We can only free the Capabilities if there are no Tasks still
2112 // running. We might have a Task about to return from a foreign
2113 // call into waitForReturnCapability(), for example (actually,
2114 // this should be the *only* thing that a still-running Task can
2115 // do at this point, and it will block waiting for the
2117 if (still_running == 0) {
2119 if (n_capabilities != 1) {
2120 stgFree(capabilities);
2123 RELEASE_LOCK(&sched_mutex);
2124 #if defined(THREADED_RTS)
2125 closeMutex(&sched_mutex);
2129 /* -----------------------------------------------------------------------------
2132 This is the interface to the garbage collector from Haskell land.
2133 We provide this so that external C code can allocate and garbage
2134 collect when called from Haskell via _ccall_GC.
2135 -------------------------------------------------------------------------- */
2138 performGC_(rtsBool force_major)
2142 // We must grab a new Task here, because the existing Task may be
2143 // associated with a particular Capability, and chained onto the
2144 // suspended_ccalling_tasks queue.
2145 task = newBoundTask();
2147 waitForReturnCapability(&task->cap,task);
2148 scheduleDoGC(task->cap,task,force_major);
2149 releaseCapability(task->cap);
2150 boundTaskExiting(task);
2156 performGC_(rtsFalse);
2160 performMajorGC(void)
2162 performGC_(rtsTrue);
2165 /* -----------------------------------------------------------------------------
2168 If the thread has reached its maximum stack size, then raise the
2169 StackOverflow exception in the offending thread. Otherwise
2170 relocate the TSO into a larger chunk of memory and adjust its stack
2172 -------------------------------------------------------------------------- */
2175 threadStackOverflow(Capability *cap, StgTSO *tso)
2177 nat new_stack_size, stack_words;
2182 IF_DEBUG(sanity,checkTSO(tso));
2184 // don't allow throwTo() to modify the blocked_exceptions queue
2185 // while we are moving the TSO:
2186 lockClosure((StgClosure *)tso);
2188 if (tso->stack_size >= tso->max_stack_size && !(tso->flags & TSO_BLOCKEX)) {
2189 // NB. never raise a StackOverflow exception if the thread is
2190 // inside Control.Exceptino.block. It is impractical to protect
2191 // against stack overflow exceptions, since virtually anything
2192 // can raise one (even 'catch'), so this is the only sensible
2193 // thing to do here. See bug #767.
2195 debugTrace(DEBUG_gc,
2196 "threadStackOverflow of TSO %ld (%p): stack too large (now %ld; max is %ld)",
2197 (long)tso->id, tso, (long)tso->stack_size, (long)tso->max_stack_size);
2199 /* If we're debugging, just print out the top of the stack */
2200 printStackChunk(tso->sp, stg_min(tso->stack+tso->stack_size,
2203 // Send this thread the StackOverflow exception
2205 throwToSingleThreaded(cap, tso, (StgClosure *)stackOverflow_closure);
2209 /* Try to double the current stack size. If that takes us over the
2210 * maximum stack size for this thread, then use the maximum instead
2211 * (that is, unless we're already at or over the max size and we
2212 * can't raise the StackOverflow exception (see above), in which
2213 * case just double the size). Finally round up so the TSO ends up as
2214 * a whole number of blocks.
2216 if (tso->stack_size >= tso->max_stack_size) {
2217 new_stack_size = tso->stack_size * 2;
2219 new_stack_size = stg_min(tso->stack_size * 2, tso->max_stack_size);
2221 new_tso_size = (lnat)BLOCK_ROUND_UP(new_stack_size * sizeof(W_) +
2222 TSO_STRUCT_SIZE)/sizeof(W_);
2223 new_tso_size = round_to_mblocks(new_tso_size); /* Be MBLOCK-friendly */
2224 new_stack_size = new_tso_size - TSO_STRUCT_SIZEW;
2226 debugTrace(DEBUG_sched,
2227 "increasing stack size from %ld words to %d.",
2228 (long)tso->stack_size, new_stack_size);
2230 dest = (StgTSO *)allocateLocal(cap,new_tso_size);
2231 TICK_ALLOC_TSO(new_stack_size,0);
2233 /* copy the TSO block and the old stack into the new area */
2234 memcpy(dest,tso,TSO_STRUCT_SIZE);
2235 stack_words = tso->stack + tso->stack_size - tso->sp;
2236 new_sp = (P_)dest + new_tso_size - stack_words;
2237 memcpy(new_sp, tso->sp, stack_words * sizeof(W_));
2239 /* relocate the stack pointers... */
2241 dest->stack_size = new_stack_size;
2243 /* Mark the old TSO as relocated. We have to check for relocated
2244 * TSOs in the garbage collector and any primops that deal with TSOs.
2246 * It's important to set the sp value to just beyond the end
2247 * of the stack, so we don't attempt to scavenge any part of the
2250 tso->what_next = ThreadRelocated;
2251 setTSOLink(cap,tso,dest);
2252 tso->sp = (P_)&(tso->stack[tso->stack_size]);
2253 tso->why_blocked = NotBlocked;
2258 IF_DEBUG(sanity,checkTSO(dest));
2260 IF_DEBUG(scheduler,printTSO(dest));
2267 threadStackUnderflow (Task *task STG_UNUSED, StgTSO *tso)
2269 bdescr *bd, *new_bd;
2270 lnat free_w, tso_size_w;
2273 tso_size_w = tso_sizeW(tso);
2275 if (tso_size_w < MBLOCK_SIZE_W ||
2276 // TSO is less than 2 mblocks (since the first mblock is
2277 // shorter than MBLOCK_SIZE_W)
2278 (tso_size_w - BLOCKS_PER_MBLOCK*BLOCK_SIZE_W) % MBLOCK_SIZE_W != 0 ||
2279 // or TSO is not a whole number of megablocks (ensuring
2280 // precondition of splitLargeBlock() below)
2281 (tso_size_w <= round_up_to_mblocks(RtsFlags.GcFlags.initialStkSize)) ||
2282 // or TSO is smaller than the minimum stack size (rounded up)
2283 (nat)(tso->stack + tso->stack_size - tso->sp) > tso->stack_size / 4)
2284 // or stack is using more than 1/4 of the available space
2290 // don't allow throwTo() to modify the blocked_exceptions queue
2291 // while we are moving the TSO:
2292 lockClosure((StgClosure *)tso);
2294 // this is the number of words we'll free
2295 free_w = round_to_mblocks(tso_size_w/2);
2297 bd = Bdescr((StgPtr)tso);
2298 new_bd = splitLargeBlock(bd, free_w / BLOCK_SIZE_W);
2299 bd->free = bd->start + TSO_STRUCT_SIZEW;
2301 new_tso = (StgTSO *)new_bd->start;
2302 memcpy(new_tso,tso,TSO_STRUCT_SIZE);
2303 new_tso->stack_size = new_bd->free - new_tso->stack;
2305 debugTrace(DEBUG_sched, "thread %ld: reducing TSO size from %lu words to %lu",
2306 (long)tso->id, tso_size_w, tso_sizeW(new_tso));
2308 tso->what_next = ThreadRelocated;
2309 tso->_link = new_tso; // no write barrier reqd: same generation
2311 // The TSO attached to this Task may have moved, so update the
2313 if (task->tso == tso) {
2314 task->tso = new_tso;
2320 IF_DEBUG(sanity,checkTSO(new_tso));
2325 /* ---------------------------------------------------------------------------
2327 - usually called inside a signal handler so it mustn't do anything fancy.
2328 ------------------------------------------------------------------------ */
2331 interruptStgRts(void)
2333 sched_state = SCHED_INTERRUPTING;
2334 setContextSwitches();
2335 #if defined(THREADED_RTS)
2340 /* -----------------------------------------------------------------------------
2343 This function causes at least one OS thread to wake up and run the
2344 scheduler loop. It is invoked when the RTS might be deadlocked, or
2345 an external event has arrived that may need servicing (eg. a
2346 keyboard interrupt).
2348 In the single-threaded RTS we don't do anything here; we only have
2349 one thread anyway, and the event that caused us to want to wake up
2350 will have interrupted any blocking system call in progress anyway.
2351 -------------------------------------------------------------------------- */
2353 #if defined(THREADED_RTS)
2354 void wakeUpRts(void)
2356 // This forces the IO Manager thread to wakeup, which will
2357 // in turn ensure that some OS thread wakes up and runs the
2358 // scheduler loop, which will cause a GC and deadlock check.
2363 /* -----------------------------------------------------------------------------
2366 * Check the blackhole_queue for threads that can be woken up. We do
2367 * this periodically: before every GC, and whenever the run queue is
2370 * An elegant solution might be to just wake up all the blocked
2371 * threads with awakenBlockedQueue occasionally: they'll go back to
2372 * sleep again if the object is still a BLACKHOLE. Unfortunately this
2373 * doesn't give us a way to tell whether we've actually managed to
2374 * wake up any threads, so we would be busy-waiting.
2376 * -------------------------------------------------------------------------- */
2379 checkBlackHoles (Capability *cap)
2382 rtsBool any_woke_up = rtsFalse;
2385 // blackhole_queue is global:
2386 ASSERT_LOCK_HELD(&sched_mutex);
2388 debugTrace(DEBUG_sched, "checking threads blocked on black holes");
2390 // ASSUMES: sched_mutex
2391 prev = &blackhole_queue;
2392 t = blackhole_queue;
2393 while (t != END_TSO_QUEUE) {
2394 if (t->what_next == ThreadRelocated) {
2398 ASSERT(t->why_blocked == BlockedOnBlackHole);
2399 type = get_itbl(UNTAG_CLOSURE(t->block_info.closure))->type;
2400 if (type != BLACKHOLE && type != CAF_BLACKHOLE) {
2401 IF_DEBUG(sanity,checkTSO(t));
2402 t = unblockOne(cap, t);
2404 any_woke_up = rtsTrue;
2414 /* -----------------------------------------------------------------------------
2417 This is used for interruption (^C) and forking, and corresponds to
2418 raising an exception but without letting the thread catch the
2420 -------------------------------------------------------------------------- */
2423 deleteThread (Capability *cap, StgTSO *tso)
2425 // NOTE: must only be called on a TSO that we have exclusive
2426 // access to, because we will call throwToSingleThreaded() below.
2427 // The TSO must be on the run queue of the Capability we own, or
2428 // we must own all Capabilities.
2430 if (tso->why_blocked != BlockedOnCCall &&
2431 tso->why_blocked != BlockedOnCCall_NoUnblockExc) {
2432 throwToSingleThreaded(cap,tso,NULL);
2436 #ifdef FORKPROCESS_PRIMOP_SUPPORTED
2438 deleteThread_(Capability *cap, StgTSO *tso)
2439 { // for forkProcess only:
2440 // like deleteThread(), but we delete threads in foreign calls, too.
2442 if (tso->why_blocked == BlockedOnCCall ||
2443 tso->why_blocked == BlockedOnCCall_NoUnblockExc) {
2444 unblockOne(cap,tso);
2445 tso->what_next = ThreadKilled;
2447 deleteThread(cap,tso);
2452 /* -----------------------------------------------------------------------------
2453 raiseExceptionHelper
2455 This function is called by the raise# primitve, just so that we can
2456 move some of the tricky bits of raising an exception from C-- into
2457 C. Who knows, it might be a useful re-useable thing here too.
2458 -------------------------------------------------------------------------- */
2461 raiseExceptionHelper (StgRegTable *reg, StgTSO *tso, StgClosure *exception)
2463 Capability *cap = regTableToCapability(reg);
2464 StgThunk *raise_closure = NULL;
2466 StgRetInfoTable *info;
2468 // This closure represents the expression 'raise# E' where E
2469 // is the exception raise. It is used to overwrite all the
2470 // thunks which are currently under evaluataion.
2473 // OLD COMMENT (we don't have MIN_UPD_SIZE now):
2474 // LDV profiling: stg_raise_info has THUNK as its closure
2475 // type. Since a THUNK takes at least MIN_UPD_SIZE words in its
2476 // payload, MIN_UPD_SIZE is more approprate than 1. It seems that
2477 // 1 does not cause any problem unless profiling is performed.
2478 // However, when LDV profiling goes on, we need to linearly scan
2479 // small object pool, where raise_closure is stored, so we should
2480 // use MIN_UPD_SIZE.
2482 // raise_closure = (StgClosure *)RET_STGCALL1(P_,allocate,
2483 // sizeofW(StgClosure)+1);
2487 // Walk up the stack, looking for the catch frame. On the way,
2488 // we update any closures pointed to from update frames with the
2489 // raise closure that we just built.
2493 info = get_ret_itbl((StgClosure *)p);
2494 next = p + stack_frame_sizeW((StgClosure *)p);
2495 switch (info->i.type) {
2498 // Only create raise_closure if we need to.
2499 if (raise_closure == NULL) {
2501 (StgThunk *)allocateLocal(cap,sizeofW(StgThunk)+1);
2502 SET_HDR(raise_closure, &stg_raise_info, CCCS);
2503 raise_closure->payload[0] = exception;
2505 UPD_IND(((StgUpdateFrame *)p)->updatee,(StgClosure *)raise_closure);
2509 case ATOMICALLY_FRAME:
2510 debugTrace(DEBUG_stm, "found ATOMICALLY_FRAME at %p", p);
2512 return ATOMICALLY_FRAME;
2518 case CATCH_STM_FRAME:
2519 debugTrace(DEBUG_stm, "found CATCH_STM_FRAME at %p", p);
2521 return CATCH_STM_FRAME;
2527 case CATCH_RETRY_FRAME:
2536 /* -----------------------------------------------------------------------------
2537 findRetryFrameHelper
2539 This function is called by the retry# primitive. It traverses the stack
2540 leaving tso->sp referring to the frame which should handle the retry.
2542 This should either be a CATCH_RETRY_FRAME (if the retry# is within an orElse#)
2543 or should be a ATOMICALLY_FRAME (if the retry# reaches the top level).
2545 We skip CATCH_STM_FRAMEs (aborting and rolling back the nested tx that they
2546 create) because retries are not considered to be exceptions, despite the
2547 similar implementation.
2549 We should not expect to see CATCH_FRAME or STOP_FRAME because those should
2550 not be created within memory transactions.
2551 -------------------------------------------------------------------------- */
2554 findRetryFrameHelper (StgTSO *tso)
2557 StgRetInfoTable *info;
2561 info = get_ret_itbl((StgClosure *)p);
2562 next = p + stack_frame_sizeW((StgClosure *)p);
2563 switch (info->i.type) {
2565 case ATOMICALLY_FRAME:
2566 debugTrace(DEBUG_stm,
2567 "found ATOMICALLY_FRAME at %p during retry", p);
2569 return ATOMICALLY_FRAME;
2571 case CATCH_RETRY_FRAME:
2572 debugTrace(DEBUG_stm,
2573 "found CATCH_RETRY_FRAME at %p during retrry", p);
2575 return CATCH_RETRY_FRAME;
2577 case CATCH_STM_FRAME: {
2578 StgTRecHeader *trec = tso -> trec;
2579 StgTRecHeader *outer = trec -> enclosing_trec;
2580 debugTrace(DEBUG_stm,
2581 "found CATCH_STM_FRAME at %p during retry", p);
2582 debugTrace(DEBUG_stm, "trec=%p outer=%p", trec, outer);
2583 stmAbortTransaction(tso -> cap, trec);
2584 stmFreeAbortedTRec(tso -> cap, trec);
2585 tso -> trec = outer;
2592 ASSERT(info->i.type != CATCH_FRAME);
2593 ASSERT(info->i.type != STOP_FRAME);
2600 /* -----------------------------------------------------------------------------
2601 resurrectThreads is called after garbage collection on the list of
2602 threads found to be garbage. Each of these threads will be woken
2603 up and sent a signal: BlockedOnDeadMVar if the thread was blocked
2604 on an MVar, or NonTermination if the thread was blocked on a Black
2607 Locks: assumes we hold *all* the capabilities.
2608 -------------------------------------------------------------------------- */
2611 resurrectThreads (StgTSO *threads)
2617 for (tso = threads; tso != END_TSO_QUEUE; tso = next) {
2618 next = tso->global_link;
2620 step = Bdescr((P_)tso)->step;
2621 tso->global_link = step->threads;
2622 step->threads = tso;
2624 debugTrace(DEBUG_sched, "resurrecting thread %lu", (unsigned long)tso->id);
2626 // Wake up the thread on the Capability it was last on
2629 switch (tso->why_blocked) {
2631 /* Called by GC - sched_mutex lock is currently held. */
2632 throwToSingleThreaded(cap, tso,
2633 (StgClosure *)blockedIndefinitelyOnMVar_closure);
2635 case BlockedOnBlackHole:
2636 throwToSingleThreaded(cap, tso,
2637 (StgClosure *)nonTermination_closure);
2640 throwToSingleThreaded(cap, tso,
2641 (StgClosure *)blockedIndefinitelyOnSTM_closure);
2644 /* This might happen if the thread was blocked on a black hole
2645 * belonging to a thread that we've just woken up (raiseAsync
2646 * can wake up threads, remember...).
2649 case BlockedOnException:
2650 // throwTo should never block indefinitely: if the target
2651 // thread dies or completes, throwTo returns.
2652 barf("resurrectThreads: thread BlockedOnException");
2655 barf("resurrectThreads: thread blocked in a strange way");
2660 /* -----------------------------------------------------------------------------
2661 performPendingThrowTos is called after garbage collection, and
2662 passed a list of threads that were found to have pending throwTos
2663 (tso->blocked_exceptions was not empty), and were blocked.
2664 Normally this doesn't happen, because we would deliver the
2665 exception directly if the target thread is blocked, but there are
2666 small windows where it might occur on a multiprocessor (see
2669 NB. we must be holding all the capabilities at this point, just
2670 like resurrectThreads().
2671 -------------------------------------------------------------------------- */
2674 performPendingThrowTos (StgTSO *threads)
2678 Task *task, *saved_task;;
2684 for (tso = threads; tso != END_TSO_QUEUE; tso = next) {
2685 next = tso->global_link;
2687 step = Bdescr((P_)tso)->step;
2688 tso->global_link = step->threads;
2689 step->threads = tso;
2691 debugTrace(DEBUG_sched, "performing blocked throwTo to thread %lu", (unsigned long)tso->id);
2693 // We must pretend this Capability belongs to the current Task
2694 // for the time being, as invariants will be broken otherwise.
2695 // In fact the current Task has exclusive access to the systme
2696 // at this point, so this is just bookkeeping:
2697 task->cap = tso->cap;
2698 saved_task = tso->cap->running_task;
2699 tso->cap->running_task = task;
2700 maybePerformBlockedException(tso->cap, tso);
2701 tso->cap->running_task = saved_task;
2704 // Restore our original Capability: