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"
20 #include "sm/Sanity.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 scheduleProcessInbox(Capability *cap);
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(Capability *cap, 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 (!isBoundTask(task) && 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 InCall *bound = t->bound;
384 if (bound->task == task) {
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.
396 if (task->incall->tso) {
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->task->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) {
466 } else if (recent_activity != ACTIVITY_INACTIVE) {
467 // If we reached ACTIVITY_INACTIVE, then don't reset it until
468 // we've done the GC. The thread running here might just be
469 // the IO manager thread that handle_tick() woke up via
471 recent_activity = ACTIVITY_YES;
475 traceEventRunThread(cap, t);
477 switch (prev_what_next) {
481 /* Thread already finished, return to scheduler. */
482 ret = ThreadFinished;
488 r = StgRun((StgFunPtr) stg_returnToStackTop, &cap->r);
489 cap = regTableToCapability(r);
494 case ThreadInterpret:
495 cap = interpretBCO(cap);
500 barf("schedule: invalid what_next field");
503 cap->in_haskell = rtsFalse;
505 // The TSO might have moved, eg. if it re-entered the RTS and a GC
506 // happened. So find the new location:
507 t = cap->r.rCurrentTSO;
509 // We have run some Haskell code: there might be blackhole-blocked
510 // threads to wake up now.
511 // Lock-free test here should be ok, we're just setting a flag.
512 if ( blackhole_queue != END_TSO_QUEUE ) {
513 blackholes_need_checking = rtsTrue;
516 // And save the current errno in this thread.
517 // XXX: possibly bogus for SMP because this thread might already
518 // be running again, see code below.
519 t->saved_errno = errno;
521 // Similarly for Windows error code
522 t->saved_winerror = GetLastError();
525 traceEventStopThread(cap, t, ret);
527 #if defined(THREADED_RTS)
528 // If ret is ThreadBlocked, and this Task is bound to the TSO that
529 // blocked, we are in limbo - the TSO is now owned by whatever it
530 // is blocked on, and may in fact already have been woken up,
531 // perhaps even on a different Capability. It may be the case
532 // that task->cap != cap. We better yield this Capability
533 // immediately and return to normaility.
534 if (ret == ThreadBlocked) {
535 force_yield = rtsTrue;
540 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
541 ASSERT(t->cap == cap);
543 // ----------------------------------------------------------------------
545 // Costs for the scheduler are assigned to CCS_SYSTEM
547 #if defined(PROFILING)
551 schedulePostRunThread(cap,t);
553 if (ret != StackOverflow) {
554 t = threadStackUnderflow(cap,task,t);
557 ready_to_gc = rtsFalse;
561 ready_to_gc = scheduleHandleHeapOverflow(cap,t);
565 scheduleHandleStackOverflow(cap,task,t);
569 if (scheduleHandleYield(cap, t, prev_what_next)) {
570 // shortcut for switching between compiler/interpreter:
576 scheduleHandleThreadBlocked(t);
580 if (scheduleHandleThreadFinished(cap, task, t)) return cap;
581 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
585 barf("schedule: invalid thread return code %d", (int)ret);
588 if (ready_to_gc || scheduleNeedHeapProfile(ready_to_gc)) {
589 cap = scheduleDoGC(cap,task,rtsFalse);
591 } /* end of while() */
594 /* ----------------------------------------------------------------------------
595 * Setting up the scheduler loop
596 * ------------------------------------------------------------------------- */
599 schedulePreLoop(void)
601 // initialisation for scheduler - what cannot go into initScheduler()
604 /* -----------------------------------------------------------------------------
607 * Search for work to do, and handle messages from elsewhere.
608 * -------------------------------------------------------------------------- */
611 scheduleFindWork (Capability *cap)
613 scheduleStartSignalHandlers(cap);
615 // Only check the black holes here if we've nothing else to do.
616 // During normal execution, the black hole list only gets checked
617 // at GC time, to avoid repeatedly traversing this possibly long
618 // list each time around the scheduler.
619 if (emptyRunQueue(cap)) { scheduleCheckBlackHoles(cap); }
621 scheduleProcessInbox(cap);
623 scheduleCheckBlockedThreads(cap);
625 #if defined(THREADED_RTS)
626 if (emptyRunQueue(cap)) { scheduleActivateSpark(cap); }
630 #if defined(THREADED_RTS)
631 STATIC_INLINE rtsBool
632 shouldYieldCapability (Capability *cap, Task *task)
634 // we need to yield this capability to someone else if..
635 // - another thread is initiating a GC
636 // - another Task is returning from a foreign call
637 // - the thread at the head of the run queue cannot be run
638 // by this Task (it is bound to another Task, or it is unbound
639 // and this task it bound).
640 return (waiting_for_gc ||
641 cap->returning_tasks_hd != NULL ||
642 (!emptyRunQueue(cap) && (task->incall->tso == NULL
643 ? cap->run_queue_hd->bound != NULL
644 : cap->run_queue_hd->bound != task->incall)));
647 // This is the single place where a Task goes to sleep. There are
648 // two reasons it might need to sleep:
649 // - there are no threads to run
650 // - we need to yield this Capability to someone else
651 // (see shouldYieldCapability())
653 // Careful: the scheduler loop is quite delicate. Make sure you run
654 // the tests in testsuite/concurrent (all ways) after modifying this,
655 // and also check the benchmarks in nofib/parallel for regressions.
658 scheduleYield (Capability **pcap, Task *task, rtsBool force_yield)
660 Capability *cap = *pcap;
662 // if we have work, and we don't need to give up the Capability, continue.
664 // The force_yield flag is used when a bound thread blocks. This
665 // is a particularly tricky situation: the current Task does not
666 // own the TSO any more, since it is on some queue somewhere, and
667 // might be woken up or manipulated by another thread at any time.
668 // The TSO and Task might be migrated to another Capability.
669 // Certain invariants might be in doubt, such as task->bound->cap
670 // == cap. We have to yield the current Capability immediately,
671 // no messing around.
674 !shouldYieldCapability(cap,task) &&
675 (!emptyRunQueue(cap) ||
677 blackholes_need_checking ||
678 sched_state >= SCHED_INTERRUPTING))
681 // otherwise yield (sleep), and keep yielding if necessary.
683 yieldCapability(&cap,task);
685 while (shouldYieldCapability(cap,task));
687 // note there may still be no threads on the run queue at this
688 // point, the caller has to check.
695 /* -----------------------------------------------------------------------------
698 * Push work to other Capabilities if we have some.
699 * -------------------------------------------------------------------------- */
702 schedulePushWork(Capability *cap USED_IF_THREADS,
703 Task *task USED_IF_THREADS)
705 /* following code not for PARALLEL_HASKELL. I kept the call general,
706 future GUM versions might use pushing in a distributed setup */
707 #if defined(THREADED_RTS)
709 Capability *free_caps[n_capabilities], *cap0;
712 // migration can be turned off with +RTS -qm
713 if (!RtsFlags.ParFlags.migrate) return;
715 // Check whether we have more threads on our run queue, or sparks
716 // in our pool, that we could hand to another Capability.
717 if (cap->run_queue_hd == END_TSO_QUEUE) {
718 if (sparkPoolSizeCap(cap) < 2) return;
720 if (cap->run_queue_hd->_link == END_TSO_QUEUE &&
721 sparkPoolSizeCap(cap) < 1) return;
724 // First grab as many free Capabilities as we can.
725 for (i=0, n_free_caps=0; i < n_capabilities; i++) {
726 cap0 = &capabilities[i];
727 if (cap != cap0 && tryGrabCapability(cap0,task)) {
728 if (!emptyRunQueue(cap0)
729 || cap->returning_tasks_hd != NULL
730 || cap->inbox != (Message*)END_TSO_QUEUE) {
731 // it already has some work, we just grabbed it at
732 // the wrong moment. Or maybe it's deadlocked!
733 releaseCapability(cap0);
735 free_caps[n_free_caps++] = cap0;
740 // we now have n_free_caps free capabilities stashed in
741 // free_caps[]. Share our run queue equally with them. This is
742 // probably the simplest thing we could do; improvements we might
743 // want to do include:
745 // - giving high priority to moving relatively new threads, on
746 // the gournds that they haven't had time to build up a
747 // working set in the cache on this CPU/Capability.
749 // - giving low priority to moving long-lived threads
751 if (n_free_caps > 0) {
752 StgTSO *prev, *t, *next;
753 rtsBool pushed_to_all;
755 debugTrace(DEBUG_sched,
756 "cap %d: %s and %d free capabilities, sharing...",
758 (!emptyRunQueue(cap) && cap->run_queue_hd->_link != END_TSO_QUEUE)?
759 "excess threads on run queue":"sparks to share (>=2)",
763 pushed_to_all = rtsFalse;
765 if (cap->run_queue_hd != END_TSO_QUEUE) {
766 prev = cap->run_queue_hd;
768 prev->_link = END_TSO_QUEUE;
769 for (; t != END_TSO_QUEUE; t = next) {
771 t->_link = END_TSO_QUEUE;
772 if (t->what_next == ThreadRelocated
773 || t->bound == task->incall // don't move my bound thread
774 || tsoLocked(t)) { // don't move a locked thread
775 setTSOLink(cap, prev, t);
777 } else if (i == n_free_caps) {
778 pushed_to_all = rtsTrue;
781 setTSOLink(cap, prev, t);
784 appendToRunQueue(free_caps[i],t);
786 traceEventMigrateThread (cap, t, free_caps[i]->no);
788 if (t->bound) { t->bound->task->cap = free_caps[i]; }
789 t->cap = free_caps[i];
793 cap->run_queue_tl = prev;
797 /* JB I left this code in place, it would work but is not necessary */
799 // If there are some free capabilities that we didn't push any
800 // threads to, then try to push a spark to each one.
801 if (!pushed_to_all) {
803 // i is the next free capability to push to
804 for (; i < n_free_caps; i++) {
805 if (emptySparkPoolCap(free_caps[i])) {
806 spark = tryStealSpark(cap->sparks);
808 debugTrace(DEBUG_sched, "pushing spark %p to capability %d", spark, free_caps[i]->no);
810 traceEventStealSpark(free_caps[i], t, cap->no);
812 newSpark(&(free_caps[i]->r), spark);
817 #endif /* SPARK_PUSHING */
819 // release the capabilities
820 for (i = 0; i < n_free_caps; i++) {
821 task->cap = free_caps[i];
822 releaseAndWakeupCapability(free_caps[i]);
825 task->cap = cap; // reset to point to our Capability.
827 #endif /* THREADED_RTS */
831 /* ----------------------------------------------------------------------------
832 * Start any pending signal handlers
833 * ------------------------------------------------------------------------- */
835 #if defined(RTS_USER_SIGNALS) && !defined(THREADED_RTS)
837 scheduleStartSignalHandlers(Capability *cap)
839 if (RtsFlags.MiscFlags.install_signal_handlers && signals_pending()) {
840 // safe outside the lock
841 startSignalHandlers(cap);
846 scheduleStartSignalHandlers(Capability *cap STG_UNUSED)
851 /* ----------------------------------------------------------------------------
852 * Check for blocked threads that can be woken up.
853 * ------------------------------------------------------------------------- */
856 scheduleCheckBlockedThreads(Capability *cap USED_IF_NOT_THREADS)
858 #if !defined(THREADED_RTS)
860 // Check whether any waiting threads need to be woken up. If the
861 // run queue is empty, and there are no other tasks running, we
862 // can wait indefinitely for something to happen.
864 if ( !emptyQueue(blocked_queue_hd) || !emptyQueue(sleeping_queue) )
866 awaitEvent( emptyRunQueue(cap) && !blackholes_need_checking );
872 /* ----------------------------------------------------------------------------
873 * Check for threads woken up by other Capabilities
874 * ------------------------------------------------------------------------- */
876 #if defined(THREADED_RTS)
878 executeMessage (Capability *cap, Message *m)
880 const StgInfoTable *i;
883 write_barrier(); // allow m->header to be modified by another thread
885 if (i == &stg_MSG_WAKEUP_info)
887 MessageWakeup *w = (MessageWakeup *)m;
888 StgTSO *tso = w->tso;
889 debugTraceCap(DEBUG_sched, cap, "message: wakeup thread %ld",
891 ASSERT(tso->cap == cap);
892 ASSERT(tso->why_blocked == BlockedOnMsgWakeup);
893 ASSERT(tso->block_info.closure == (StgClosure *)m);
894 tso->why_blocked = NotBlocked;
895 appendToRunQueue(cap, tso);
897 else if (i == &stg_MSG_THROWTO_info)
899 MessageThrowTo *t = (MessageThrowTo *)m;
901 const StgInfoTable *i;
903 i = lockClosure((StgClosure*)m);
904 if (i != &stg_MSG_THROWTO_info) {
905 unlockClosure((StgClosure*)m, i);
909 debugTraceCap(DEBUG_sched, cap, "message: throwTo %ld -> %ld",
910 (lnat)t->source->id, (lnat)t->target->id);
912 ASSERT(t->source->why_blocked == BlockedOnMsgThrowTo);
913 ASSERT(t->source->block_info.closure == (StgClosure *)m);
915 r = throwToMsg(cap, t);
918 case THROWTO_SUCCESS:
919 ASSERT(t->source->sp[0] == (StgWord)&stg_block_throwto_info);
921 unblockOne(cap, t->source);
922 // this message is done
923 unlockClosure((StgClosure*)m, &stg_IND_info);
925 case THROWTO_BLOCKED:
926 // unlock the message
927 unlockClosure((StgClosure*)m, &stg_MSG_THROWTO_info);
931 else if (i == &stg_IND_info)
933 // message was revoked
936 else if (i == &stg_WHITEHOLE_info)
942 barf("executeMessage: %p", i);
948 scheduleProcessInbox (Capability *cap USED_IF_THREADS)
950 #if defined(THREADED_RTS)
953 while (!emptyInbox(cap)) {
954 ACQUIRE_LOCK(&cap->lock);
956 cap->inbox = m->link;
957 RELEASE_LOCK(&cap->lock);
958 executeMessage(cap, (Message *)m);
963 /* ----------------------------------------------------------------------------
964 * Check for threads blocked on BLACKHOLEs that can be woken up
965 * ------------------------------------------------------------------------- */
967 scheduleCheckBlackHoles (Capability *cap)
969 if ( blackholes_need_checking ) // check without the lock first
971 ACQUIRE_LOCK(&sched_mutex);
972 if ( blackholes_need_checking ) {
973 blackholes_need_checking = rtsFalse;
974 // important that we reset the flag *before* checking the
975 // blackhole queue, otherwise we could get deadlock. This
976 // happens as follows: we wake up a thread that
977 // immediately runs on another Capability, blocks on a
978 // blackhole, and then we reset the blackholes_need_checking flag.
979 checkBlackHoles(cap);
981 RELEASE_LOCK(&sched_mutex);
985 /* ----------------------------------------------------------------------------
986 * Detect deadlock conditions and attempt to resolve them.
987 * ------------------------------------------------------------------------- */
990 scheduleDetectDeadlock (Capability *cap, Task *task)
993 * Detect deadlock: when we have no threads to run, there are no
994 * threads blocked, waiting for I/O, or sleeping, and all the
995 * other tasks are waiting for work, we must have a deadlock of
998 if ( emptyThreadQueues(cap) )
1000 #if defined(THREADED_RTS)
1002 * In the threaded RTS, we only check for deadlock if there
1003 * has been no activity in a complete timeslice. This means
1004 * we won't eagerly start a full GC just because we don't have
1005 * any threads to run currently.
1007 if (recent_activity != ACTIVITY_INACTIVE) return;
1010 debugTrace(DEBUG_sched, "deadlocked, forcing major GC...");
1012 // Garbage collection can release some new threads due to
1013 // either (a) finalizers or (b) threads resurrected because
1014 // they are unreachable and will therefore be sent an
1015 // exception. Any threads thus released will be immediately
1017 cap = scheduleDoGC (cap, task, rtsTrue/*force major GC*/);
1018 // when force_major == rtsTrue. scheduleDoGC sets
1019 // recent_activity to ACTIVITY_DONE_GC and turns off the timer
1022 if ( !emptyRunQueue(cap) ) return;
1024 #if defined(RTS_USER_SIGNALS) && !defined(THREADED_RTS)
1025 /* If we have user-installed signal handlers, then wait
1026 * for signals to arrive rather then bombing out with a
1029 if ( RtsFlags.MiscFlags.install_signal_handlers && anyUserHandlers() ) {
1030 debugTrace(DEBUG_sched,
1031 "still deadlocked, waiting for signals...");
1035 if (signals_pending()) {
1036 startSignalHandlers(cap);
1039 // either we have threads to run, or we were interrupted:
1040 ASSERT(!emptyRunQueue(cap) || sched_state >= SCHED_INTERRUPTING);
1046 #if !defined(THREADED_RTS)
1047 /* Probably a real deadlock. Send the current main thread the
1048 * Deadlock exception.
1050 if (task->incall->tso) {
1051 switch (task->incall->tso->why_blocked) {
1053 case BlockedOnBlackHole:
1054 case BlockedOnMsgThrowTo:
1056 throwToSingleThreaded(cap, task->incall->tso,
1057 (StgClosure *)nonTermination_closure);
1060 barf("deadlock: main thread blocked in a strange way");
1069 /* ----------------------------------------------------------------------------
1070 * Send pending messages (PARALLEL_HASKELL only)
1071 * ------------------------------------------------------------------------- */
1073 #if defined(PARALLEL_HASKELL)
1075 scheduleSendPendingMessages(void)
1078 # if defined(PAR) // global Mem.Mgmt., omit for now
1079 if (PendingFetches != END_BF_QUEUE) {
1084 if (RtsFlags.ParFlags.BufferTime) {
1085 // if we use message buffering, we must send away all message
1086 // packets which have become too old...
1092 /* ----------------------------------------------------------------------------
1093 * Activate spark threads (PARALLEL_HASKELL and THREADED_RTS)
1094 * ------------------------------------------------------------------------- */
1096 #if defined(THREADED_RTS)
1098 scheduleActivateSpark(Capability *cap)
1102 createSparkThread(cap);
1103 debugTrace(DEBUG_sched, "creating a spark thread");
1106 #endif // PARALLEL_HASKELL || THREADED_RTS
1108 /* ----------------------------------------------------------------------------
1109 * After running a thread...
1110 * ------------------------------------------------------------------------- */
1113 schedulePostRunThread (Capability *cap, StgTSO *t)
1115 // We have to be able to catch transactions that are in an
1116 // infinite loop as a result of seeing an inconsistent view of
1120 // [a,b] <- mapM readTVar [ta,tb]
1121 // when (a == b) loop
1123 // and a is never equal to b given a consistent view of memory.
1125 if (t -> trec != NO_TREC && t -> why_blocked == NotBlocked) {
1126 if (!stmValidateNestOfTransactions (t -> trec)) {
1127 debugTrace(DEBUG_sched | DEBUG_stm,
1128 "trec %p found wasting its time", t);
1130 // strip the stack back to the
1131 // ATOMICALLY_FRAME, aborting the (nested)
1132 // transaction, and saving the stack of any
1133 // partially-evaluated thunks on the heap.
1134 throwToSingleThreaded_(cap, t, NULL, rtsTrue);
1136 // ASSERT(get_itbl((StgClosure *)t->sp)->type == ATOMICALLY_FRAME);
1140 /* some statistics gathering in the parallel case */
1143 /* -----------------------------------------------------------------------------
1144 * Handle a thread that returned to the scheduler with ThreadHeepOverflow
1145 * -------------------------------------------------------------------------- */
1148 scheduleHandleHeapOverflow( Capability *cap, StgTSO *t )
1150 // did the task ask for a large block?
1151 if (cap->r.rHpAlloc > BLOCK_SIZE) {
1152 // if so, get one and push it on the front of the nursery.
1156 blocks = (lnat)BLOCK_ROUND_UP(cap->r.rHpAlloc) / BLOCK_SIZE;
1158 debugTrace(DEBUG_sched,
1159 "--<< thread %ld (%s) stopped: requesting a large block (size %ld)\n",
1160 (long)t->id, what_next_strs[t->what_next], blocks);
1162 // don't do this if the nursery is (nearly) full, we'll GC first.
1163 if (cap->r.rCurrentNursery->link != NULL ||
1164 cap->r.rNursery->n_blocks == 1) { // paranoia to prevent infinite loop
1165 // if the nursery has only one block.
1168 bd = allocGroup( blocks );
1170 cap->r.rNursery->n_blocks += blocks;
1172 // link the new group into the list
1173 bd->link = cap->r.rCurrentNursery;
1174 bd->u.back = cap->r.rCurrentNursery->u.back;
1175 if (cap->r.rCurrentNursery->u.back != NULL) {
1176 cap->r.rCurrentNursery->u.back->link = bd;
1178 cap->r.rNursery->blocks = bd;
1180 cap->r.rCurrentNursery->u.back = bd;
1182 // initialise it as a nursery block. We initialise the
1183 // step, gen_no, and flags field of *every* sub-block in
1184 // this large block, because this is easier than making
1185 // sure that we always find the block head of a large
1186 // block whenever we call Bdescr() (eg. evacuate() and
1187 // isAlive() in the GC would both have to do this, at
1191 for (x = bd; x < bd + blocks; x++) {
1192 initBdescr(x,g0,g0);
1198 // This assert can be a killer if the app is doing lots
1199 // of large block allocations.
1200 IF_DEBUG(sanity, checkNurserySanity(cap->r.rNursery));
1202 // now update the nursery to point to the new block
1203 cap->r.rCurrentNursery = bd;
1205 // we might be unlucky and have another thread get on the
1206 // run queue before us and steal the large block, but in that
1207 // case the thread will just end up requesting another large
1209 pushOnRunQueue(cap,t);
1210 return rtsFalse; /* not actually GC'ing */
1214 if (cap->r.rHpLim == NULL || cap->context_switch) {
1215 // Sometimes we miss a context switch, e.g. when calling
1216 // primitives in a tight loop, MAYBE_GC() doesn't check the
1217 // context switch flag, and we end up waiting for a GC.
1218 // See #1984, and concurrent/should_run/1984
1219 cap->context_switch = 0;
1220 addToRunQueue(cap,t);
1222 pushOnRunQueue(cap,t);
1225 /* actual GC is done at the end of the while loop in schedule() */
1228 /* -----------------------------------------------------------------------------
1229 * Handle a thread that returned to the scheduler with ThreadStackOverflow
1230 * -------------------------------------------------------------------------- */
1233 scheduleHandleStackOverflow (Capability *cap, Task *task, StgTSO *t)
1235 /* just adjust the stack for this thread, then pop it back
1239 /* enlarge the stack */
1240 StgTSO *new_t = threadStackOverflow(cap, t);
1242 /* The TSO attached to this Task may have moved, so update the
1245 if (task->incall->tso == t) {
1246 task->incall->tso = new_t;
1248 pushOnRunQueue(cap,new_t);
1252 /* -----------------------------------------------------------------------------
1253 * Handle a thread that returned to the scheduler with ThreadYielding
1254 * -------------------------------------------------------------------------- */
1257 scheduleHandleYield( Capability *cap, StgTSO *t, nat prev_what_next )
1259 /* put the thread back on the run queue. Then, if we're ready to
1260 * GC, check whether this is the last task to stop. If so, wake
1261 * up the GC thread. getThread will block during a GC until the
1265 ASSERT(t->_link == END_TSO_QUEUE);
1267 // Shortcut if we're just switching evaluators: don't bother
1268 // doing stack squeezing (which can be expensive), just run the
1270 if (cap->context_switch == 0 && t->what_next != prev_what_next) {
1271 debugTrace(DEBUG_sched,
1272 "--<< thread %ld (%s) stopped to switch evaluators",
1273 (long)t->id, what_next_strs[t->what_next]);
1277 // Reset the context switch flag. We don't do this just before
1278 // running the thread, because that would mean we would lose ticks
1279 // during GC, which can lead to unfair scheduling (a thread hogs
1280 // the CPU because the tick always arrives during GC). This way
1281 // penalises threads that do a lot of allocation, but that seems
1282 // better than the alternative.
1283 cap->context_switch = 0;
1286 //debugBelch("&& Doing sanity check on yielding TSO %ld.", t->id);
1289 addToRunQueue(cap,t);
1294 /* -----------------------------------------------------------------------------
1295 * Handle a thread that returned to the scheduler with ThreadBlocked
1296 * -------------------------------------------------------------------------- */
1299 scheduleHandleThreadBlocked( StgTSO *t
1306 // We don't need to do anything. The thread is blocked, and it
1307 // has tidied up its stack and placed itself on whatever queue
1308 // it needs to be on.
1310 // ASSERT(t->why_blocked != NotBlocked);
1311 // Not true: for example,
1312 // - in THREADED_RTS, the thread may already have been woken
1313 // up by another Capability. This actually happens: try
1314 // conc023 +RTS -N2.
1315 // - the thread may have woken itself up already, because
1316 // threadPaused() might have raised a blocked throwTo
1317 // exception, see maybePerformBlockedException().
1320 traceThreadStatus(DEBUG_sched, t);
1324 /* -----------------------------------------------------------------------------
1325 * Handle a thread that returned to the scheduler with ThreadFinished
1326 * -------------------------------------------------------------------------- */
1329 scheduleHandleThreadFinished (Capability *cap STG_UNUSED, Task *task, StgTSO *t)
1331 /* Need to check whether this was a main thread, and if so,
1332 * return with the return value.
1334 * We also end up here if the thread kills itself with an
1335 * uncaught exception, see Exception.cmm.
1338 // blocked exceptions can now complete, even if the thread was in
1339 // blocked mode (see #2910).
1340 awakenBlockedExceptionQueue (cap, t);
1343 // Check whether the thread that just completed was a bound
1344 // thread, and if so return with the result.
1346 // There is an assumption here that all thread completion goes
1347 // through this point; we need to make sure that if a thread
1348 // ends up in the ThreadKilled state, that it stays on the run
1349 // queue so it can be dealt with here.
1354 if (t->bound != task->incall) {
1355 #if !defined(THREADED_RTS)
1356 // Must be a bound thread that is not the topmost one. Leave
1357 // it on the run queue until the stack has unwound to the
1358 // point where we can deal with this. Leaving it on the run
1359 // queue also ensures that the garbage collector knows about
1360 // this thread and its return value (it gets dropped from the
1361 // step->threads list so there's no other way to find it).
1362 appendToRunQueue(cap,t);
1365 // this cannot happen in the threaded RTS, because a
1366 // bound thread can only be run by the appropriate Task.
1367 barf("finished bound thread that isn't mine");
1371 ASSERT(task->incall->tso == t);
1373 if (t->what_next == ThreadComplete) {
1375 // NOTE: return val is tso->sp[1] (see StgStartup.hc)
1376 *(task->ret) = (StgClosure *)task->incall->tso->sp[1];
1378 task->stat = Success;
1381 *(task->ret) = NULL;
1383 if (sched_state >= SCHED_INTERRUPTING) {
1384 if (heap_overflow) {
1385 task->stat = HeapExhausted;
1387 task->stat = Interrupted;
1390 task->stat = Killed;
1394 removeThreadLabel((StgWord)task->incall->tso->id);
1397 // We no longer consider this thread and task to be bound to
1398 // each other. The TSO lives on until it is GC'd, but the
1399 // task is about to be released by the caller, and we don't
1400 // want anyone following the pointer from the TSO to the
1401 // defunct task (which might have already been
1402 // re-used). This was a real bug: the GC updated
1403 // tso->bound->tso which lead to a deadlock.
1405 task->incall->tso = NULL;
1407 return rtsTrue; // tells schedule() to return
1413 /* -----------------------------------------------------------------------------
1414 * Perform a heap census
1415 * -------------------------------------------------------------------------- */
1418 scheduleNeedHeapProfile( rtsBool ready_to_gc STG_UNUSED )
1420 // When we have +RTS -i0 and we're heap profiling, do a census at
1421 // every GC. This lets us get repeatable runs for debugging.
1422 if (performHeapProfile ||
1423 (RtsFlags.ProfFlags.profileInterval==0 &&
1424 RtsFlags.ProfFlags.doHeapProfile && ready_to_gc)) {
1431 /* -----------------------------------------------------------------------------
1432 * Perform a garbage collection if necessary
1433 * -------------------------------------------------------------------------- */
1436 scheduleDoGC (Capability *cap, Task *task USED_IF_THREADS, rtsBool force_major)
1438 rtsBool heap_census;
1440 /* extern static volatile StgWord waiting_for_gc;
1441 lives inside capability.c */
1442 rtsBool gc_type, prev_pending_gc;
1446 if (sched_state == SCHED_SHUTTING_DOWN) {
1447 // The final GC has already been done, and the system is
1448 // shutting down. We'll probably deadlock if we try to GC
1454 if (sched_state < SCHED_INTERRUPTING
1455 && RtsFlags.ParFlags.parGcEnabled
1456 && N >= RtsFlags.ParFlags.parGcGen
1457 && ! oldest_gen->mark)
1459 gc_type = PENDING_GC_PAR;
1461 gc_type = PENDING_GC_SEQ;
1464 // In order to GC, there must be no threads running Haskell code.
1465 // Therefore, the GC thread needs to hold *all* the capabilities,
1466 // and release them after the GC has completed.
1468 // This seems to be the simplest way: previous attempts involved
1469 // making all the threads with capabilities give up their
1470 // capabilities and sleep except for the *last* one, which
1471 // actually did the GC. But it's quite hard to arrange for all
1472 // the other tasks to sleep and stay asleep.
1475 /* Other capabilities are prevented from running yet more Haskell
1476 threads if waiting_for_gc is set. Tested inside
1477 yieldCapability() and releaseCapability() in Capability.c */
1479 prev_pending_gc = cas(&waiting_for_gc, 0, gc_type);
1480 if (prev_pending_gc) {
1482 debugTrace(DEBUG_sched, "someone else is trying to GC (%d)...",
1485 yieldCapability(&cap,task);
1486 } while (waiting_for_gc);
1487 return cap; // NOTE: task->cap might have changed here
1490 setContextSwitches();
1492 // The final shutdown GC is always single-threaded, because it's
1493 // possible that some of the Capabilities have no worker threads.
1495 if (gc_type == PENDING_GC_SEQ)
1497 traceEventRequestSeqGc(cap);
1501 traceEventRequestParGc(cap);
1502 debugTrace(DEBUG_sched, "ready_to_gc, grabbing GC threads");
1505 // do this while the other Capabilities stop:
1506 if (cap) scheduleCheckBlackHoles(cap);
1508 if (gc_type == PENDING_GC_SEQ)
1510 // single-threaded GC: grab all the capabilities
1511 for (i=0; i < n_capabilities; i++) {
1512 debugTrace(DEBUG_sched, "ready_to_gc, grabbing all the capabilies (%d/%d)", i, n_capabilities);
1513 if (cap != &capabilities[i]) {
1514 Capability *pcap = &capabilities[i];
1515 // we better hope this task doesn't get migrated to
1516 // another Capability while we're waiting for this one.
1517 // It won't, because load balancing happens while we have
1518 // all the Capabilities, but even so it's a slightly
1519 // unsavoury invariant.
1521 waitForReturnCapability(&pcap, task);
1522 if (pcap != &capabilities[i]) {
1523 barf("scheduleDoGC: got the wrong capability");
1530 // multi-threaded GC: make sure all the Capabilities donate one
1532 waitForGcThreads(cap);
1535 #else /* !THREADED_RTS */
1537 // do this while the other Capabilities stop:
1538 if (cap) scheduleCheckBlackHoles(cap);
1542 IF_DEBUG(scheduler, printAllThreads());
1544 delete_threads_and_gc:
1546 * We now have all the capabilities; if we're in an interrupting
1547 * state, then we should take the opportunity to delete all the
1548 * threads in the system.
1550 if (sched_state == SCHED_INTERRUPTING) {
1551 deleteAllThreads(cap);
1552 sched_state = SCHED_SHUTTING_DOWN;
1555 heap_census = scheduleNeedHeapProfile(rtsTrue);
1557 traceEventGcStart(cap);
1558 #if defined(THREADED_RTS)
1559 // reset waiting_for_gc *before* GC, so that when the GC threads
1560 // emerge they don't immediately re-enter the GC.
1562 GarbageCollect(force_major || heap_census, gc_type, cap);
1564 GarbageCollect(force_major || heap_census, 0, cap);
1566 traceEventGcEnd(cap);
1568 if (recent_activity == ACTIVITY_INACTIVE && force_major)
1570 // We are doing a GC because the system has been idle for a
1571 // timeslice and we need to check for deadlock. Record the
1572 // fact that we've done a GC and turn off the timer signal;
1573 // it will get re-enabled if we run any threads after the GC.
1574 recent_activity = ACTIVITY_DONE_GC;
1579 // the GC might have taken long enough for the timer to set
1580 // recent_activity = ACTIVITY_INACTIVE, but we aren't
1581 // necessarily deadlocked:
1582 recent_activity = ACTIVITY_YES;
1585 #if defined(THREADED_RTS)
1586 if (gc_type == PENDING_GC_PAR)
1588 releaseGCThreads(cap);
1593 debugTrace(DEBUG_sched, "performing heap census");
1595 performHeapProfile = rtsFalse;
1598 if (heap_overflow && sched_state < SCHED_INTERRUPTING) {
1599 // GC set the heap_overflow flag, so we should proceed with
1600 // an orderly shutdown now. Ultimately we want the main
1601 // thread to return to its caller with HeapExhausted, at which
1602 // point the caller should call hs_exit(). The first step is
1603 // to delete all the threads.
1605 // Another way to do this would be to raise an exception in
1606 // the main thread, which we really should do because it gives
1607 // the program a chance to clean up. But how do we find the
1608 // main thread? It should presumably be the same one that
1609 // gets ^C exceptions, but that's all done on the Haskell side
1610 // (GHC.TopHandler).
1611 sched_state = SCHED_INTERRUPTING;
1612 goto delete_threads_and_gc;
1617 Once we are all together... this would be the place to balance all
1618 spark pools. No concurrent stealing or adding of new sparks can
1619 occur. Should be defined in Sparks.c. */
1620 balanceSparkPoolsCaps(n_capabilities, capabilities);
1623 #if defined(THREADED_RTS)
1624 if (gc_type == PENDING_GC_SEQ) {
1625 // release our stash of capabilities.
1626 for (i = 0; i < n_capabilities; i++) {
1627 if (cap != &capabilities[i]) {
1628 task->cap = &capabilities[i];
1629 releaseCapability(&capabilities[i]);
1643 /* ---------------------------------------------------------------------------
1644 * Singleton fork(). Do not copy any running threads.
1645 * ------------------------------------------------------------------------- */
1648 forkProcess(HsStablePtr *entry
1649 #ifndef FORKPROCESS_PRIMOP_SUPPORTED
1654 #ifdef FORKPROCESS_PRIMOP_SUPPORTED
1660 #if defined(THREADED_RTS)
1661 if (RtsFlags.ParFlags.nNodes > 1) {
1662 errorBelch("forking not supported with +RTS -N<n> greater than 1");
1663 stg_exit(EXIT_FAILURE);
1667 debugTrace(DEBUG_sched, "forking!");
1669 // ToDo: for SMP, we should probably acquire *all* the capabilities
1672 // no funny business: hold locks while we fork, otherwise if some
1673 // other thread is holding a lock when the fork happens, the data
1674 // structure protected by the lock will forever be in an
1675 // inconsistent state in the child. See also #1391.
1676 ACQUIRE_LOCK(&sched_mutex);
1677 ACQUIRE_LOCK(&cap->lock);
1678 ACQUIRE_LOCK(&cap->running_task->lock);
1682 if (pid) { // parent
1684 RELEASE_LOCK(&sched_mutex);
1685 RELEASE_LOCK(&cap->lock);
1686 RELEASE_LOCK(&cap->running_task->lock);
1688 // just return the pid
1694 #if defined(THREADED_RTS)
1695 initMutex(&sched_mutex);
1696 initMutex(&cap->lock);
1697 initMutex(&cap->running_task->lock);
1700 // Now, all OS threads except the thread that forked are
1701 // stopped. We need to stop all Haskell threads, including
1702 // those involved in foreign calls. Also we need to delete
1703 // all Tasks, because they correspond to OS threads that are
1706 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
1707 for (t = generations[g].threads; t != END_TSO_QUEUE; t = next) {
1708 if (t->what_next == ThreadRelocated) {
1711 next = t->global_link;
1712 // don't allow threads to catch the ThreadKilled
1713 // exception, but we do want to raiseAsync() because these
1714 // threads may be evaluating thunks that we need later.
1715 deleteThread_(cap,t);
1717 // stop the GC from updating the InCall to point to
1718 // the TSO. This is only necessary because the
1719 // OSThread bound to the TSO has been killed, and
1720 // won't get a chance to exit in the usual way (see
1721 // also scheduleHandleThreadFinished).
1727 // Empty the run queue. It seems tempting to let all the
1728 // killed threads stay on the run queue as zombies to be
1729 // cleaned up later, but some of them correspond to bound
1730 // threads for which the corresponding Task does not exist.
1731 cap->run_queue_hd = END_TSO_QUEUE;
1732 cap->run_queue_tl = END_TSO_QUEUE;
1734 // Any suspended C-calling Tasks are no more, their OS threads
1736 cap->suspended_ccalls = NULL;
1738 // Empty the threads lists. Otherwise, the garbage
1739 // collector may attempt to resurrect some of these threads.
1740 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
1741 generations[g].threads = END_TSO_QUEUE;
1744 discardTasksExcept(cap->running_task);
1746 #if defined(THREADED_RTS)
1747 // Wipe our spare workers list, they no longer exist. New
1748 // workers will be created if necessary.
1749 cap->spare_workers = NULL;
1750 cap->returning_tasks_hd = NULL;
1751 cap->returning_tasks_tl = NULL;
1754 // On Unix, all timers are reset in the child, so we need to start
1759 #if defined(THREADED_RTS)
1760 cap = ioManagerStartCap(cap);
1763 cap = rts_evalStableIO(cap, entry, NULL); // run the action
1764 rts_checkSchedStatus("forkProcess",cap);
1767 hs_exit(); // clean up and exit
1768 stg_exit(EXIT_SUCCESS);
1770 #else /* !FORKPROCESS_PRIMOP_SUPPORTED */
1771 barf("forkProcess#: primop not supported on this platform, sorry!\n");
1775 /* ---------------------------------------------------------------------------
1776 * Delete all the threads in the system
1777 * ------------------------------------------------------------------------- */
1780 deleteAllThreads ( Capability *cap )
1782 // NOTE: only safe to call if we own all capabilities.
1787 debugTrace(DEBUG_sched,"deleting all threads");
1788 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
1789 for (t = generations[g].threads; t != END_TSO_QUEUE; t = next) {
1790 if (t->what_next == ThreadRelocated) {
1793 next = t->global_link;
1794 deleteThread(cap,t);
1799 // The run queue now contains a bunch of ThreadKilled threads. We
1800 // must not throw these away: the main thread(s) will be in there
1801 // somewhere, and the main scheduler loop has to deal with it.
1802 // Also, the run queue is the only thing keeping these threads from
1803 // being GC'd, and we don't want the "main thread has been GC'd" panic.
1805 #if !defined(THREADED_RTS)
1806 ASSERT(blocked_queue_hd == END_TSO_QUEUE);
1807 ASSERT(sleeping_queue == END_TSO_QUEUE);
1811 /* -----------------------------------------------------------------------------
1812 Managing the suspended_ccalls list.
1813 Locks required: sched_mutex
1814 -------------------------------------------------------------------------- */
1817 suspendTask (Capability *cap, Task *task)
1821 incall = task->incall;
1822 ASSERT(incall->next == NULL && incall->prev == NULL);
1823 incall->next = cap->suspended_ccalls;
1824 incall->prev = NULL;
1825 if (cap->suspended_ccalls) {
1826 cap->suspended_ccalls->prev = incall;
1828 cap->suspended_ccalls = incall;
1832 recoverSuspendedTask (Capability *cap, Task *task)
1836 incall = task->incall;
1838 incall->prev->next = incall->next;
1840 ASSERT(cap->suspended_ccalls == incall);
1841 cap->suspended_ccalls = incall->next;
1844 incall->next->prev = incall->prev;
1846 incall->next = incall->prev = NULL;
1849 /* ---------------------------------------------------------------------------
1850 * Suspending & resuming Haskell threads.
1852 * When making a "safe" call to C (aka _ccall_GC), the task gives back
1853 * its capability before calling the C function. This allows another
1854 * task to pick up the capability and carry on running Haskell
1855 * threads. It also means that if the C call blocks, it won't lock
1858 * The Haskell thread making the C call is put to sleep for the
1859 * duration of the call, on the susepended_ccalling_threads queue. We
1860 * give out a token to the task, which it can use to resume the thread
1861 * on return from the C function.
1862 * ------------------------------------------------------------------------- */
1865 suspendThread (StgRegTable *reg)
1872 StgWord32 saved_winerror;
1875 saved_errno = errno;
1877 saved_winerror = GetLastError();
1880 /* assume that *reg is a pointer to the StgRegTable part of a Capability.
1882 cap = regTableToCapability(reg);
1884 task = cap->running_task;
1885 tso = cap->r.rCurrentTSO;
1887 traceEventStopThread(cap, tso, THREAD_SUSPENDED_FOREIGN_CALL);
1889 // XXX this might not be necessary --SDM
1890 tso->what_next = ThreadRunGHC;
1892 threadPaused(cap,tso);
1894 if ((tso->flags & TSO_BLOCKEX) == 0) {
1895 tso->why_blocked = BlockedOnCCall;
1896 tso->flags |= TSO_BLOCKEX;
1897 tso->flags &= ~TSO_INTERRUPTIBLE;
1899 tso->why_blocked = BlockedOnCCall_NoUnblockExc;
1902 // Hand back capability
1903 task->incall->suspended_tso = tso;
1904 task->incall->suspended_cap = cap;
1906 ACQUIRE_LOCK(&cap->lock);
1908 suspendTask(cap,task);
1909 cap->in_haskell = rtsFalse;
1910 releaseCapability_(cap,rtsFalse);
1912 RELEASE_LOCK(&cap->lock);
1914 errno = saved_errno;
1916 SetLastError(saved_winerror);
1922 resumeThread (void *task_)
1930 StgWord32 saved_winerror;
1933 saved_errno = errno;
1935 saved_winerror = GetLastError();
1938 incall = task->incall;
1939 cap = incall->suspended_cap;
1942 // Wait for permission to re-enter the RTS with the result.
1943 waitForReturnCapability(&cap,task);
1944 // we might be on a different capability now... but if so, our
1945 // entry on the suspended_ccalls list will also have been
1948 // Remove the thread from the suspended list
1949 recoverSuspendedTask(cap,task);
1951 tso = incall->suspended_tso;
1952 incall->suspended_tso = NULL;
1953 incall->suspended_cap = NULL;
1954 tso->_link = END_TSO_QUEUE; // no write barrier reqd
1956 traceEventRunThread(cap, tso);
1958 if (tso->why_blocked == BlockedOnCCall) {
1959 // avoid locking the TSO if we don't have to
1960 if (tso->blocked_exceptions != END_BLOCKED_EXCEPTIONS_QUEUE) {
1961 awakenBlockedExceptionQueue(cap,tso);
1963 tso->flags &= ~(TSO_BLOCKEX | TSO_INTERRUPTIBLE);
1966 /* Reset blocking status */
1967 tso->why_blocked = NotBlocked;
1969 cap->r.rCurrentTSO = tso;
1970 cap->in_haskell = rtsTrue;
1971 errno = saved_errno;
1973 SetLastError(saved_winerror);
1976 /* We might have GC'd, mark the TSO dirty again */
1979 IF_DEBUG(sanity, checkTSO(tso));
1984 /* ---------------------------------------------------------------------------
1987 * scheduleThread puts a thread on the end of the runnable queue.
1988 * This will usually be done immediately after a thread is created.
1989 * The caller of scheduleThread must create the thread using e.g.
1990 * createThread and push an appropriate closure
1991 * on this thread's stack before the scheduler is invoked.
1992 * ------------------------------------------------------------------------ */
1995 scheduleThread(Capability *cap, StgTSO *tso)
1997 // The thread goes at the *end* of the run-queue, to avoid possible
1998 // starvation of any threads already on the queue.
1999 appendToRunQueue(cap,tso);
2003 scheduleThreadOn(Capability *cap, StgWord cpu USED_IF_THREADS, StgTSO *tso)
2005 #if defined(THREADED_RTS)
2006 tso->flags |= TSO_LOCKED; // we requested explicit affinity; don't
2007 // move this thread from now on.
2008 cpu %= RtsFlags.ParFlags.nNodes;
2009 if (cpu == cap->no) {
2010 appendToRunQueue(cap,tso);
2012 traceEventMigrateThread (cap, tso, capabilities[cpu].no);
2013 wakeupThreadOnCapability(cap, &capabilities[cpu], tso);
2016 appendToRunQueue(cap,tso);
2021 scheduleWaitThread (StgTSO* tso, /*[out]*/HaskellObj* ret, Capability *cap)
2026 // We already created/initialised the Task
2027 task = cap->running_task;
2029 // This TSO is now a bound thread; make the Task and TSO
2030 // point to each other.
2031 tso->bound = task->incall;
2034 task->incall->tso = tso;
2036 task->stat = NoStatus;
2038 appendToRunQueue(cap,tso);
2041 debugTrace(DEBUG_sched, "new bound thread (%lu)", (unsigned long)id);
2043 cap = schedule(cap,task);
2045 ASSERT(task->stat != NoStatus);
2046 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
2048 debugTrace(DEBUG_sched, "bound thread (%lu) finished", (unsigned long)id);
2052 /* ----------------------------------------------------------------------------
2054 * ------------------------------------------------------------------------- */
2056 #if defined(THREADED_RTS)
2057 void scheduleWorker (Capability *cap, Task *task)
2059 // schedule() runs without a lock.
2060 cap = schedule(cap,task);
2062 // On exit from schedule(), we have a Capability, but possibly not
2063 // the same one we started with.
2065 // During shutdown, the requirement is that after all the
2066 // Capabilities are shut down, all workers that are shutting down
2067 // have finished workerTaskStop(). This is why we hold on to
2068 // cap->lock until we've finished workerTaskStop() below.
2070 // There may be workers still involved in foreign calls; those
2071 // will just block in waitForReturnCapability() because the
2072 // Capability has been shut down.
2074 ACQUIRE_LOCK(&cap->lock);
2075 releaseCapability_(cap,rtsFalse);
2076 workerTaskStop(task);
2077 RELEASE_LOCK(&cap->lock);
2081 /* ---------------------------------------------------------------------------
2084 * Initialise the scheduler. This resets all the queues - if the
2085 * queues contained any threads, they'll be garbage collected at the
2088 * ------------------------------------------------------------------------ */
2093 #if !defined(THREADED_RTS)
2094 blocked_queue_hd = END_TSO_QUEUE;
2095 blocked_queue_tl = END_TSO_QUEUE;
2096 sleeping_queue = END_TSO_QUEUE;
2099 blackhole_queue = END_TSO_QUEUE;
2101 sched_state = SCHED_RUNNING;
2102 recent_activity = ACTIVITY_YES;
2104 #if defined(THREADED_RTS)
2105 /* Initialise the mutex and condition variables used by
2107 initMutex(&sched_mutex);
2110 ACQUIRE_LOCK(&sched_mutex);
2112 /* A capability holds the state a native thread needs in
2113 * order to execute STG code. At least one capability is
2114 * floating around (only THREADED_RTS builds have more than one).
2120 #if defined(THREADED_RTS)
2124 RELEASE_LOCK(&sched_mutex);
2126 #if defined(THREADED_RTS)
2128 * Eagerly start one worker to run each Capability, except for
2129 * Capability 0. The idea is that we're probably going to start a
2130 * bound thread on Capability 0 pretty soon, so we don't want a
2131 * worker task hogging it.
2136 for (i = 1; i < n_capabilities; i++) {
2137 cap = &capabilities[i];
2138 ACQUIRE_LOCK(&cap->lock);
2139 startWorkerTask(cap);
2140 RELEASE_LOCK(&cap->lock);
2148 rtsBool wait_foreign
2149 #if !defined(THREADED_RTS)
2150 __attribute__((unused))
2153 /* see Capability.c, shutdownCapability() */
2157 task = newBoundTask();
2159 // If we haven't killed all the threads yet, do it now.
2160 if (sched_state < SCHED_SHUTTING_DOWN) {
2161 sched_state = SCHED_INTERRUPTING;
2162 waitForReturnCapability(&task->cap,task);
2163 scheduleDoGC(task->cap,task,rtsFalse);
2164 ASSERT(task->incall->tso == NULL);
2165 releaseCapability(task->cap);
2167 sched_state = SCHED_SHUTTING_DOWN;
2169 #if defined(THREADED_RTS)
2173 for (i = 0; i < n_capabilities; i++) {
2174 ASSERT(task->incall->tso == NULL);
2175 shutdownCapability(&capabilities[i], task, wait_foreign);
2180 boundTaskExiting(task);
2184 freeScheduler( void )
2188 ACQUIRE_LOCK(&sched_mutex);
2189 still_running = freeTaskManager();
2190 // We can only free the Capabilities if there are no Tasks still
2191 // running. We might have a Task about to return from a foreign
2192 // call into waitForReturnCapability(), for example (actually,
2193 // this should be the *only* thing that a still-running Task can
2194 // do at this point, and it will block waiting for the
2196 if (still_running == 0) {
2198 if (n_capabilities != 1) {
2199 stgFree(capabilities);
2202 RELEASE_LOCK(&sched_mutex);
2203 #if defined(THREADED_RTS)
2204 closeMutex(&sched_mutex);
2208 /* -----------------------------------------------------------------------------
2211 This is the interface to the garbage collector from Haskell land.
2212 We provide this so that external C code can allocate and garbage
2213 collect when called from Haskell via _ccall_GC.
2214 -------------------------------------------------------------------------- */
2217 performGC_(rtsBool force_major)
2221 // We must grab a new Task here, because the existing Task may be
2222 // associated with a particular Capability, and chained onto the
2223 // suspended_ccalls queue.
2224 task = newBoundTask();
2226 waitForReturnCapability(&task->cap,task);
2227 scheduleDoGC(task->cap,task,force_major);
2228 releaseCapability(task->cap);
2229 boundTaskExiting(task);
2235 performGC_(rtsFalse);
2239 performMajorGC(void)
2241 performGC_(rtsTrue);
2244 /* -----------------------------------------------------------------------------
2247 If the thread has reached its maximum stack size, then raise the
2248 StackOverflow exception in the offending thread. Otherwise
2249 relocate the TSO into a larger chunk of memory and adjust its stack
2251 -------------------------------------------------------------------------- */
2254 threadStackOverflow(Capability *cap, StgTSO *tso)
2256 nat new_stack_size, stack_words;
2261 IF_DEBUG(sanity,checkTSO(tso));
2263 if (tso->stack_size >= tso->max_stack_size
2264 && !(tso->flags & TSO_BLOCKEX)) {
2265 // NB. never raise a StackOverflow exception if the thread is
2266 // inside Control.Exceptino.block. It is impractical to protect
2267 // against stack overflow exceptions, since virtually anything
2268 // can raise one (even 'catch'), so this is the only sensible
2269 // thing to do here. See bug #767.
2272 if (tso->flags & TSO_SQUEEZED) {
2275 // #3677: In a stack overflow situation, stack squeezing may
2276 // reduce the stack size, but we don't know whether it has been
2277 // reduced enough for the stack check to succeed if we try
2278 // again. Fortunately stack squeezing is idempotent, so all we
2279 // need to do is record whether *any* squeezing happened. If we
2280 // are at the stack's absolute -K limit, and stack squeezing
2281 // happened, then we try running the thread again. The
2282 // TSO_SQUEEZED flag is set by threadPaused() to tell us whether
2283 // squeezing happened or not.
2285 debugTrace(DEBUG_gc,
2286 "threadStackOverflow of TSO %ld (%p): stack too large (now %ld; max is %ld)",
2287 (long)tso->id, tso, (long)tso->stack_size, (long)tso->max_stack_size);
2289 /* If we're debugging, just print out the top of the stack */
2290 printStackChunk(tso->sp, stg_min(tso->stack+tso->stack_size,
2293 // Send this thread the StackOverflow exception
2294 throwToSingleThreaded(cap, tso, (StgClosure *)stackOverflow_closure);
2299 // We also want to avoid enlarging the stack if squeezing has
2300 // already released some of it. However, we don't want to get into
2301 // a pathalogical situation where a thread has a nearly full stack
2302 // (near its current limit, but not near the absolute -K limit),
2303 // keeps allocating a little bit, squeezing removes a little bit,
2304 // and then it runs again. So to avoid this, if we squeezed *and*
2305 // there is still less than BLOCK_SIZE_W words free, then we enlarge
2306 // the stack anyway.
2307 if ((tso->flags & TSO_SQUEEZED) &&
2308 ((W_)(tso->sp - tso->stack) >= BLOCK_SIZE_W)) {
2312 /* Try to double the current stack size. If that takes us over the
2313 * maximum stack size for this thread, then use the maximum instead
2314 * (that is, unless we're already at or over the max size and we
2315 * can't raise the StackOverflow exception (see above), in which
2316 * case just double the size). Finally round up so the TSO ends up as
2317 * a whole number of blocks.
2319 if (tso->stack_size >= tso->max_stack_size) {
2320 new_stack_size = tso->stack_size * 2;
2322 new_stack_size = stg_min(tso->stack_size * 2, tso->max_stack_size);
2324 new_tso_size = (lnat)BLOCK_ROUND_UP(new_stack_size * sizeof(W_) +
2325 TSO_STRUCT_SIZE)/sizeof(W_);
2326 new_tso_size = round_to_mblocks(new_tso_size); /* Be MBLOCK-friendly */
2327 new_stack_size = new_tso_size - TSO_STRUCT_SIZEW;
2329 debugTrace(DEBUG_sched,
2330 "increasing stack size from %ld words to %d.",
2331 (long)tso->stack_size, new_stack_size);
2333 dest = (StgTSO *)allocate(cap,new_tso_size);
2334 TICK_ALLOC_TSO(new_stack_size,0);
2336 /* copy the TSO block and the old stack into the new area */
2337 memcpy(dest,tso,TSO_STRUCT_SIZE);
2338 stack_words = tso->stack + tso->stack_size - tso->sp;
2339 new_sp = (P_)dest + new_tso_size - stack_words;
2340 memcpy(new_sp, tso->sp, stack_words * sizeof(W_));
2342 /* relocate the stack pointers... */
2344 dest->stack_size = new_stack_size;
2346 /* Mark the old TSO as relocated. We have to check for relocated
2347 * TSOs in the garbage collector and any primops that deal with TSOs.
2349 * It's important to set the sp value to just beyond the end
2350 * of the stack, so we don't attempt to scavenge any part of the
2353 tso->what_next = ThreadRelocated;
2354 setTSOLink(cap,tso,dest);
2355 tso->sp = (P_)&(tso->stack[tso->stack_size]);
2356 tso->why_blocked = NotBlocked;
2358 IF_DEBUG(sanity,checkTSO(dest));
2360 IF_DEBUG(scheduler,printTSO(dest));
2367 threadStackUnderflow (Capability *cap, Task *task, StgTSO *tso)
2369 bdescr *bd, *new_bd;
2370 lnat free_w, tso_size_w;
2373 tso_size_w = tso_sizeW(tso);
2375 if (tso_size_w < MBLOCK_SIZE_W ||
2376 // TSO is less than 2 mblocks (since the first mblock is
2377 // shorter than MBLOCK_SIZE_W)
2378 (tso_size_w - BLOCKS_PER_MBLOCK*BLOCK_SIZE_W) % MBLOCK_SIZE_W != 0 ||
2379 // or TSO is not a whole number of megablocks (ensuring
2380 // precondition of splitLargeBlock() below)
2381 (tso_size_w <= round_up_to_mblocks(RtsFlags.GcFlags.initialStkSize)) ||
2382 // or TSO is smaller than the minimum stack size (rounded up)
2383 (nat)(tso->stack + tso->stack_size - tso->sp) > tso->stack_size / 4)
2384 // or stack is using more than 1/4 of the available space
2390 // this is the number of words we'll free
2391 free_w = round_to_mblocks(tso_size_w/2);
2393 bd = Bdescr((StgPtr)tso);
2394 new_bd = splitLargeBlock(bd, free_w / BLOCK_SIZE_W);
2395 bd->free = bd->start + TSO_STRUCT_SIZEW;
2397 new_tso = (StgTSO *)new_bd->start;
2398 memcpy(new_tso,tso,TSO_STRUCT_SIZE);
2399 new_tso->stack_size = new_bd->free - new_tso->stack;
2401 // The original TSO was dirty and probably on the mutable
2402 // list. The new TSO is not yet on the mutable list, so we better
2405 new_tso->flags &= ~TSO_LINK_DIRTY;
2406 dirty_TSO(cap, new_tso);
2408 debugTrace(DEBUG_sched, "thread %ld: reducing TSO size from %lu words to %lu",
2409 (long)tso->id, tso_size_w, tso_sizeW(new_tso));
2411 tso->what_next = ThreadRelocated;
2412 tso->_link = new_tso; // no write barrier reqd: same generation
2414 // The TSO attached to this Task may have moved, so update the
2416 if (task->incall->tso == tso) {
2417 task->incall->tso = new_tso;
2420 IF_DEBUG(sanity,checkTSO(new_tso));
2425 /* ---------------------------------------------------------------------------
2427 - usually called inside a signal handler so it mustn't do anything fancy.
2428 ------------------------------------------------------------------------ */
2431 interruptStgRts(void)
2433 sched_state = SCHED_INTERRUPTING;
2434 setContextSwitches();
2435 #if defined(THREADED_RTS)
2440 /* -----------------------------------------------------------------------------
2443 This function causes at least one OS thread to wake up and run the
2444 scheduler loop. It is invoked when the RTS might be deadlocked, or
2445 an external event has arrived that may need servicing (eg. a
2446 keyboard interrupt).
2448 In the single-threaded RTS we don't do anything here; we only have
2449 one thread anyway, and the event that caused us to want to wake up
2450 will have interrupted any blocking system call in progress anyway.
2451 -------------------------------------------------------------------------- */
2453 #if defined(THREADED_RTS)
2454 void wakeUpRts(void)
2456 // This forces the IO Manager thread to wakeup, which will
2457 // in turn ensure that some OS thread wakes up and runs the
2458 // scheduler loop, which will cause a GC and deadlock check.
2463 /* -----------------------------------------------------------------------------
2466 * Check the blackhole_queue for threads that can be woken up. We do
2467 * this periodically: before every GC, and whenever the run queue is
2470 * An elegant solution might be to just wake up all the blocked
2471 * threads with awakenBlockedQueue occasionally: they'll go back to
2472 * sleep again if the object is still a BLACKHOLE. Unfortunately this
2473 * doesn't give us a way to tell whether we've actually managed to
2474 * wake up any threads, so we would be busy-waiting.
2476 * -------------------------------------------------------------------------- */
2479 checkBlackHoles (Capability *cap)
2482 rtsBool any_woke_up = rtsFalse;
2485 // blackhole_queue is global:
2486 ASSERT_LOCK_HELD(&sched_mutex);
2488 debugTrace(DEBUG_sched, "checking threads blocked on black holes");
2490 // ASSUMES: sched_mutex
2491 prev = &blackhole_queue;
2492 t = blackhole_queue;
2493 while (t != END_TSO_QUEUE) {
2494 if (t->what_next == ThreadRelocated) {
2498 ASSERT(t->why_blocked == BlockedOnBlackHole);
2499 type = get_itbl(UNTAG_CLOSURE(t->block_info.closure))->type;
2500 if (type != BLACKHOLE && type != CAF_BLACKHOLE) {
2501 IF_DEBUG(sanity,checkTSO(t));
2502 t = unblockOne(cap, t);
2504 any_woke_up = rtsTrue;
2514 /* -----------------------------------------------------------------------------
2517 This is used for interruption (^C) and forking, and corresponds to
2518 raising an exception but without letting the thread catch the
2520 -------------------------------------------------------------------------- */
2523 deleteThread (Capability *cap, StgTSO *tso)
2525 // NOTE: must only be called on a TSO that we have exclusive
2526 // access to, because we will call throwToSingleThreaded() below.
2527 // The TSO must be on the run queue of the Capability we own, or
2528 // we must own all Capabilities.
2530 if (tso->why_blocked != BlockedOnCCall &&
2531 tso->why_blocked != BlockedOnCCall_NoUnblockExc) {
2532 throwToSingleThreaded(cap,tso,NULL);
2536 #ifdef FORKPROCESS_PRIMOP_SUPPORTED
2538 deleteThread_(Capability *cap, StgTSO *tso)
2539 { // for forkProcess only:
2540 // like deleteThread(), but we delete threads in foreign calls, too.
2542 if (tso->why_blocked == BlockedOnCCall ||
2543 tso->why_blocked == BlockedOnCCall_NoUnblockExc) {
2544 unblockOne(cap,tso);
2545 tso->what_next = ThreadKilled;
2547 deleteThread(cap,tso);
2552 /* -----------------------------------------------------------------------------
2553 raiseExceptionHelper
2555 This function is called by the raise# primitve, just so that we can
2556 move some of the tricky bits of raising an exception from C-- into
2557 C. Who knows, it might be a useful re-useable thing here too.
2558 -------------------------------------------------------------------------- */
2561 raiseExceptionHelper (StgRegTable *reg, StgTSO *tso, StgClosure *exception)
2563 Capability *cap = regTableToCapability(reg);
2564 StgThunk *raise_closure = NULL;
2566 StgRetInfoTable *info;
2568 // This closure represents the expression 'raise# E' where E
2569 // is the exception raise. It is used to overwrite all the
2570 // thunks which are currently under evaluataion.
2573 // OLD COMMENT (we don't have MIN_UPD_SIZE now):
2574 // LDV profiling: stg_raise_info has THUNK as its closure
2575 // type. Since a THUNK takes at least MIN_UPD_SIZE words in its
2576 // payload, MIN_UPD_SIZE is more approprate than 1. It seems that
2577 // 1 does not cause any problem unless profiling is performed.
2578 // However, when LDV profiling goes on, we need to linearly scan
2579 // small object pool, where raise_closure is stored, so we should
2580 // use MIN_UPD_SIZE.
2582 // raise_closure = (StgClosure *)RET_STGCALL1(P_,allocate,
2583 // sizeofW(StgClosure)+1);
2587 // Walk up the stack, looking for the catch frame. On the way,
2588 // we update any closures pointed to from update frames with the
2589 // raise closure that we just built.
2593 info = get_ret_itbl((StgClosure *)p);
2594 next = p + stack_frame_sizeW((StgClosure *)p);
2595 switch (info->i.type) {
2598 // Only create raise_closure if we need to.
2599 if (raise_closure == NULL) {
2601 (StgThunk *)allocate(cap,sizeofW(StgThunk)+1);
2602 SET_HDR(raise_closure, &stg_raise_info, CCCS);
2603 raise_closure->payload[0] = exception;
2605 UPD_IND(cap, ((StgUpdateFrame *)p)->updatee,
2606 (StgClosure *)raise_closure);
2610 case ATOMICALLY_FRAME:
2611 debugTrace(DEBUG_stm, "found ATOMICALLY_FRAME at %p", p);
2613 return ATOMICALLY_FRAME;
2619 case CATCH_STM_FRAME:
2620 debugTrace(DEBUG_stm, "found CATCH_STM_FRAME at %p", p);
2622 return CATCH_STM_FRAME;
2628 case CATCH_RETRY_FRAME:
2637 /* -----------------------------------------------------------------------------
2638 findRetryFrameHelper
2640 This function is called by the retry# primitive. It traverses the stack
2641 leaving tso->sp referring to the frame which should handle the retry.
2643 This should either be a CATCH_RETRY_FRAME (if the retry# is within an orElse#)
2644 or should be a ATOMICALLY_FRAME (if the retry# reaches the top level).
2646 We skip CATCH_STM_FRAMEs (aborting and rolling back the nested tx that they
2647 create) because retries are not considered to be exceptions, despite the
2648 similar implementation.
2650 We should not expect to see CATCH_FRAME or STOP_FRAME because those should
2651 not be created within memory transactions.
2652 -------------------------------------------------------------------------- */
2655 findRetryFrameHelper (StgTSO *tso)
2658 StgRetInfoTable *info;
2662 info = get_ret_itbl((StgClosure *)p);
2663 next = p + stack_frame_sizeW((StgClosure *)p);
2664 switch (info->i.type) {
2666 case ATOMICALLY_FRAME:
2667 debugTrace(DEBUG_stm,
2668 "found ATOMICALLY_FRAME at %p during retry", p);
2670 return ATOMICALLY_FRAME;
2672 case CATCH_RETRY_FRAME:
2673 debugTrace(DEBUG_stm,
2674 "found CATCH_RETRY_FRAME at %p during retrry", p);
2676 return CATCH_RETRY_FRAME;
2678 case CATCH_STM_FRAME: {
2679 StgTRecHeader *trec = tso -> trec;
2680 StgTRecHeader *outer = trec -> enclosing_trec;
2681 debugTrace(DEBUG_stm,
2682 "found CATCH_STM_FRAME at %p during retry", p);
2683 debugTrace(DEBUG_stm, "trec=%p outer=%p", trec, outer);
2684 stmAbortTransaction(tso -> cap, trec);
2685 stmFreeAbortedTRec(tso -> cap, trec);
2686 tso -> trec = outer;
2693 ASSERT(info->i.type != CATCH_FRAME);
2694 ASSERT(info->i.type != STOP_FRAME);
2701 /* -----------------------------------------------------------------------------
2702 resurrectThreads is called after garbage collection on the list of
2703 threads found to be garbage. Each of these threads will be woken
2704 up and sent a signal: BlockedOnDeadMVar if the thread was blocked
2705 on an MVar, or NonTermination if the thread was blocked on a Black
2708 Locks: assumes we hold *all* the capabilities.
2709 -------------------------------------------------------------------------- */
2712 resurrectThreads (StgTSO *threads)
2718 for (tso = threads; tso != END_TSO_QUEUE; tso = next) {
2719 next = tso->global_link;
2721 gen = Bdescr((P_)tso)->gen;
2722 tso->global_link = gen->threads;
2725 debugTrace(DEBUG_sched, "resurrecting thread %lu", (unsigned long)tso->id);
2727 // Wake up the thread on the Capability it was last on
2730 switch (tso->why_blocked) {
2732 /* Called by GC - sched_mutex lock is currently held. */
2733 throwToSingleThreaded(cap, tso,
2734 (StgClosure *)blockedIndefinitelyOnMVar_closure);
2736 case BlockedOnBlackHole:
2737 throwToSingleThreaded(cap, tso,
2738 (StgClosure *)nonTermination_closure);
2741 throwToSingleThreaded(cap, tso,
2742 (StgClosure *)blockedIndefinitelyOnSTM_closure);
2745 /* This might happen if the thread was blocked on a black hole
2746 * belonging to a thread that we've just woken up (raiseAsync
2747 * can wake up threads, remember...).
2751 barf("resurrectThreads: thread blocked in a strange way: %d",