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 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(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 (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) {
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 scheduleCheckWakeupThreads(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->tso == NULL
643 ? cap->run_queue_hd->bound != NULL
644 : cap->run_queue_hd->bound != task)));
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) ||
676 !emptyWakeupQueue(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 -qg
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) || cap->returning_tasks_hd != NULL) {
729 // it already has some work, we just grabbed it at
730 // the wrong moment. Or maybe it's deadlocked!
731 releaseCapability(cap0);
733 free_caps[n_free_caps++] = cap0;
738 // we now have n_free_caps free capabilities stashed in
739 // free_caps[]. Share our run queue equally with them. This is
740 // probably the simplest thing we could do; improvements we might
741 // want to do include:
743 // - giving high priority to moving relatively new threads, on
744 // the gournds that they haven't had time to build up a
745 // working set in the cache on this CPU/Capability.
747 // - giving low priority to moving long-lived threads
749 if (n_free_caps > 0) {
750 StgTSO *prev, *t, *next;
751 rtsBool pushed_to_all;
753 debugTrace(DEBUG_sched,
754 "cap %d: %s and %d free capabilities, sharing...",
756 (!emptyRunQueue(cap) && cap->run_queue_hd->_link != END_TSO_QUEUE)?
757 "excess threads on run queue":"sparks to share (>=2)",
761 pushed_to_all = rtsFalse;
763 if (cap->run_queue_hd != END_TSO_QUEUE) {
764 prev = cap->run_queue_hd;
766 prev->_link = END_TSO_QUEUE;
767 for (; t != END_TSO_QUEUE; t = next) {
769 t->_link = END_TSO_QUEUE;
770 if (t->what_next == ThreadRelocated
771 || t->bound == task // don't move my bound thread
772 || tsoLocked(t)) { // don't move a locked thread
773 setTSOLink(cap, prev, t);
775 } else if (i == n_free_caps) {
776 pushed_to_all = rtsTrue;
779 setTSOLink(cap, prev, t);
782 debugTrace(DEBUG_sched, "pushing thread %lu to capability %d", (unsigned long)t->id, free_caps[i]->no);
783 appendToRunQueue(free_caps[i],t);
785 traceEventMigrateThread (cap, t, free_caps[i]->no);
787 if (t->bound) { t->bound->cap = free_caps[i]; }
788 t->cap = free_caps[i];
792 cap->run_queue_tl = prev;
796 /* JB I left this code in place, it would work but is not necessary */
798 // If there are some free capabilities that we didn't push any
799 // threads to, then try to push a spark to each one.
800 if (!pushed_to_all) {
802 // i is the next free capability to push to
803 for (; i < n_free_caps; i++) {
804 if (emptySparkPoolCap(free_caps[i])) {
805 spark = tryStealSpark(cap->sparks);
807 debugTrace(DEBUG_sched, "pushing spark %p to capability %d", spark, free_caps[i]->no);
809 traceEventStealSpark(free_caps[i], t, cap->no);
811 newSpark(&(free_caps[i]->r), spark);
816 #endif /* SPARK_PUSHING */
818 // release the capabilities
819 for (i = 0; i < n_free_caps; i++) {
820 task->cap = free_caps[i];
821 releaseAndWakeupCapability(free_caps[i]);
824 task->cap = cap; // reset to point to our Capability.
826 #endif /* THREADED_RTS */
830 /* ----------------------------------------------------------------------------
831 * Start any pending signal handlers
832 * ------------------------------------------------------------------------- */
834 #if defined(RTS_USER_SIGNALS) && !defined(THREADED_RTS)
836 scheduleStartSignalHandlers(Capability *cap)
838 if (RtsFlags.MiscFlags.install_signal_handlers && signals_pending()) {
839 // safe outside the lock
840 startSignalHandlers(cap);
845 scheduleStartSignalHandlers(Capability *cap STG_UNUSED)
850 /* ----------------------------------------------------------------------------
851 * Check for blocked threads that can be woken up.
852 * ------------------------------------------------------------------------- */
855 scheduleCheckBlockedThreads(Capability *cap USED_IF_NOT_THREADS)
857 #if !defined(THREADED_RTS)
859 // Check whether any waiting threads need to be woken up. If the
860 // run queue is empty, and there are no other tasks running, we
861 // can wait indefinitely for something to happen.
863 if ( !emptyQueue(blocked_queue_hd) || !emptyQueue(sleeping_queue) )
865 awaitEvent( emptyRunQueue(cap) && !blackholes_need_checking );
871 /* ----------------------------------------------------------------------------
872 * Check for threads woken up by other Capabilities
873 * ------------------------------------------------------------------------- */
876 scheduleCheckWakeupThreads(Capability *cap USED_IF_THREADS)
878 #if defined(THREADED_RTS)
879 // Any threads that were woken up by other Capabilities get
880 // appended to our run queue.
881 if (!emptyWakeupQueue(cap)) {
882 ACQUIRE_LOCK(&cap->lock);
883 if (emptyRunQueue(cap)) {
884 cap->run_queue_hd = cap->wakeup_queue_hd;
885 cap->run_queue_tl = cap->wakeup_queue_tl;
887 setTSOLink(cap, cap->run_queue_tl, cap->wakeup_queue_hd);
888 cap->run_queue_tl = cap->wakeup_queue_tl;
890 cap->wakeup_queue_hd = cap->wakeup_queue_tl = END_TSO_QUEUE;
891 RELEASE_LOCK(&cap->lock);
896 /* ----------------------------------------------------------------------------
897 * Check for threads blocked on BLACKHOLEs that can be woken up
898 * ------------------------------------------------------------------------- */
900 scheduleCheckBlackHoles (Capability *cap)
902 if ( blackholes_need_checking ) // check without the lock first
904 ACQUIRE_LOCK(&sched_mutex);
905 if ( blackholes_need_checking ) {
906 blackholes_need_checking = rtsFalse;
907 // important that we reset the flag *before* checking the
908 // blackhole queue, otherwise we could get deadlock. This
909 // happens as follows: we wake up a thread that
910 // immediately runs on another Capability, blocks on a
911 // blackhole, and then we reset the blackholes_need_checking flag.
912 checkBlackHoles(cap);
914 RELEASE_LOCK(&sched_mutex);
918 /* ----------------------------------------------------------------------------
919 * Detect deadlock conditions and attempt to resolve them.
920 * ------------------------------------------------------------------------- */
923 scheduleDetectDeadlock (Capability *cap, Task *task)
926 * Detect deadlock: when we have no threads to run, there are no
927 * threads blocked, waiting for I/O, or sleeping, and all the
928 * other tasks are waiting for work, we must have a deadlock of
931 if ( emptyThreadQueues(cap) )
933 #if defined(THREADED_RTS)
935 * In the threaded RTS, we only check for deadlock if there
936 * has been no activity in a complete timeslice. This means
937 * we won't eagerly start a full GC just because we don't have
938 * any threads to run currently.
940 if (recent_activity != ACTIVITY_INACTIVE) return;
943 debugTrace(DEBUG_sched, "deadlocked, forcing major GC...");
945 // Garbage collection can release some new threads due to
946 // either (a) finalizers or (b) threads resurrected because
947 // they are unreachable and will therefore be sent an
948 // exception. Any threads thus released will be immediately
950 cap = scheduleDoGC (cap, task, rtsTrue/*force major GC*/);
951 // when force_major == rtsTrue. scheduleDoGC sets
952 // recent_activity to ACTIVITY_DONE_GC and turns off the timer
955 if ( !emptyRunQueue(cap) ) return;
957 #if defined(RTS_USER_SIGNALS) && !defined(THREADED_RTS)
958 /* If we have user-installed signal handlers, then wait
959 * for signals to arrive rather then bombing out with a
962 if ( RtsFlags.MiscFlags.install_signal_handlers && anyUserHandlers() ) {
963 debugTrace(DEBUG_sched,
964 "still deadlocked, waiting for signals...");
968 if (signals_pending()) {
969 startSignalHandlers(cap);
972 // either we have threads to run, or we were interrupted:
973 ASSERT(!emptyRunQueue(cap) || sched_state >= SCHED_INTERRUPTING);
979 #if !defined(THREADED_RTS)
980 /* Probably a real deadlock. Send the current main thread the
981 * Deadlock exception.
984 switch (task->tso->why_blocked) {
986 case BlockedOnBlackHole:
987 case BlockedOnException:
989 throwToSingleThreaded(cap, task->tso,
990 (StgClosure *)nonTermination_closure);
993 barf("deadlock: main thread blocked in a strange way");
1002 /* ----------------------------------------------------------------------------
1003 * Send pending messages (PARALLEL_HASKELL only)
1004 * ------------------------------------------------------------------------- */
1006 #if defined(PARALLEL_HASKELL)
1008 scheduleSendPendingMessages(void)
1011 # if defined(PAR) // global Mem.Mgmt., omit for now
1012 if (PendingFetches != END_BF_QUEUE) {
1017 if (RtsFlags.ParFlags.BufferTime) {
1018 // if we use message buffering, we must send away all message
1019 // packets which have become too old...
1025 /* ----------------------------------------------------------------------------
1026 * Activate spark threads (PARALLEL_HASKELL and THREADED_RTS)
1027 * ------------------------------------------------------------------------- */
1029 #if defined(THREADED_RTS)
1031 scheduleActivateSpark(Capability *cap)
1035 createSparkThread(cap);
1036 debugTrace(DEBUG_sched, "creating a spark thread");
1039 #endif // PARALLEL_HASKELL || THREADED_RTS
1041 /* ----------------------------------------------------------------------------
1042 * After running a thread...
1043 * ------------------------------------------------------------------------- */
1046 schedulePostRunThread (Capability *cap, StgTSO *t)
1048 // We have to be able to catch transactions that are in an
1049 // infinite loop as a result of seeing an inconsistent view of
1053 // [a,b] <- mapM readTVar [ta,tb]
1054 // when (a == b) loop
1056 // and a is never equal to b given a consistent view of memory.
1058 if (t -> trec != NO_TREC && t -> why_blocked == NotBlocked) {
1059 if (!stmValidateNestOfTransactions (t -> trec)) {
1060 debugTrace(DEBUG_sched | DEBUG_stm,
1061 "trec %p found wasting its time", t);
1063 // strip the stack back to the
1064 // ATOMICALLY_FRAME, aborting the (nested)
1065 // transaction, and saving the stack of any
1066 // partially-evaluated thunks on the heap.
1067 throwToSingleThreaded_(cap, t, NULL, rtsTrue);
1069 // ASSERT(get_itbl((StgClosure *)t->sp)->type == ATOMICALLY_FRAME);
1073 /* some statistics gathering in the parallel case */
1076 /* -----------------------------------------------------------------------------
1077 * Handle a thread that returned to the scheduler with ThreadHeepOverflow
1078 * -------------------------------------------------------------------------- */
1081 scheduleHandleHeapOverflow( Capability *cap, StgTSO *t )
1083 // did the task ask for a large block?
1084 if (cap->r.rHpAlloc > BLOCK_SIZE) {
1085 // if so, get one and push it on the front of the nursery.
1089 blocks = (lnat)BLOCK_ROUND_UP(cap->r.rHpAlloc) / BLOCK_SIZE;
1091 debugTrace(DEBUG_sched,
1092 "--<< thread %ld (%s) stopped: requesting a large block (size %ld)\n",
1093 (long)t->id, what_next_strs[t->what_next], blocks);
1095 // don't do this if the nursery is (nearly) full, we'll GC first.
1096 if (cap->r.rCurrentNursery->link != NULL ||
1097 cap->r.rNursery->n_blocks == 1) { // paranoia to prevent infinite loop
1098 // if the nursery has only one block.
1101 bd = allocGroup( blocks );
1103 cap->r.rNursery->n_blocks += blocks;
1105 // link the new group into the list
1106 bd->link = cap->r.rCurrentNursery;
1107 bd->u.back = cap->r.rCurrentNursery->u.back;
1108 if (cap->r.rCurrentNursery->u.back != NULL) {
1109 cap->r.rCurrentNursery->u.back->link = bd;
1111 cap->r.rNursery->blocks = bd;
1113 cap->r.rCurrentNursery->u.back = bd;
1115 // initialise it as a nursery block. We initialise the
1116 // step, gen_no, and flags field of *every* sub-block in
1117 // this large block, because this is easier than making
1118 // sure that we always find the block head of a large
1119 // block whenever we call Bdescr() (eg. evacuate() and
1120 // isAlive() in the GC would both have to do this, at
1124 for (x = bd; x < bd + blocks; x++) {
1125 initBdescr(x,g0,g0);
1131 // This assert can be a killer if the app is doing lots
1132 // of large block allocations.
1133 IF_DEBUG(sanity, checkNurserySanity(cap->r.rNursery));
1135 // now update the nursery to point to the new block
1136 cap->r.rCurrentNursery = bd;
1138 // we might be unlucky and have another thread get on the
1139 // run queue before us and steal the large block, but in that
1140 // case the thread will just end up requesting another large
1142 pushOnRunQueue(cap,t);
1143 return rtsFalse; /* not actually GC'ing */
1147 if (cap->r.rHpLim == NULL || cap->context_switch) {
1148 // Sometimes we miss a context switch, e.g. when calling
1149 // primitives in a tight loop, MAYBE_GC() doesn't check the
1150 // context switch flag, and we end up waiting for a GC.
1151 // See #1984, and concurrent/should_run/1984
1152 cap->context_switch = 0;
1153 addToRunQueue(cap,t);
1155 pushOnRunQueue(cap,t);
1158 /* actual GC is done at the end of the while loop in schedule() */
1161 /* -----------------------------------------------------------------------------
1162 * Handle a thread that returned to the scheduler with ThreadStackOverflow
1163 * -------------------------------------------------------------------------- */
1166 scheduleHandleStackOverflow (Capability *cap, Task *task, StgTSO *t)
1168 /* just adjust the stack for this thread, then pop it back
1172 /* enlarge the stack */
1173 StgTSO *new_t = threadStackOverflow(cap, t);
1175 /* The TSO attached to this Task may have moved, so update the
1178 if (task->tso == t) {
1181 pushOnRunQueue(cap,new_t);
1185 /* -----------------------------------------------------------------------------
1186 * Handle a thread that returned to the scheduler with ThreadYielding
1187 * -------------------------------------------------------------------------- */
1190 scheduleHandleYield( Capability *cap, StgTSO *t, nat prev_what_next )
1192 // Reset the context switch flag. We don't do this just before
1193 // running the thread, because that would mean we would lose ticks
1194 // during GC, which can lead to unfair scheduling (a thread hogs
1195 // the CPU because the tick always arrives during GC). This way
1196 // penalises threads that do a lot of allocation, but that seems
1197 // better than the alternative.
1198 cap->context_switch = 0;
1200 /* put the thread back on the run queue. Then, if we're ready to
1201 * GC, check whether this is the last task to stop. If so, wake
1202 * up the GC thread. getThread will block during a GC until the
1206 if (t->what_next != prev_what_next) {
1207 debugTrace(DEBUG_sched,
1208 "--<< thread %ld (%s) stopped to switch evaluators",
1209 (long)t->id, what_next_strs[t->what_next]);
1213 ASSERT(t->_link == END_TSO_QUEUE);
1215 // Shortcut if we're just switching evaluators: don't bother
1216 // doing stack squeezing (which can be expensive), just run the
1218 if (t->what_next != prev_what_next) {
1223 //debugBelch("&& Doing sanity check on yielding TSO %ld.", t->id);
1226 addToRunQueue(cap,t);
1231 /* -----------------------------------------------------------------------------
1232 * Handle a thread that returned to the scheduler with ThreadBlocked
1233 * -------------------------------------------------------------------------- */
1236 scheduleHandleThreadBlocked( StgTSO *t
1243 // We don't need to do anything. The thread is blocked, and it
1244 // has tidied up its stack and placed itself on whatever queue
1245 // it needs to be on.
1247 // ASSERT(t->why_blocked != NotBlocked);
1248 // Not true: for example,
1249 // - in THREADED_RTS, the thread may already have been woken
1250 // up by another Capability. This actually happens: try
1251 // conc023 +RTS -N2.
1252 // - the thread may have woken itself up already, because
1253 // threadPaused() might have raised a blocked throwTo
1254 // exception, see maybePerformBlockedException().
1257 traceThreadStatus(DEBUG_sched, t);
1261 /* -----------------------------------------------------------------------------
1262 * Handle a thread that returned to the scheduler with ThreadFinished
1263 * -------------------------------------------------------------------------- */
1266 scheduleHandleThreadFinished (Capability *cap STG_UNUSED, Task *task, StgTSO *t)
1268 /* Need to check whether this was a main thread, and if so,
1269 * return with the return value.
1271 * We also end up here if the thread kills itself with an
1272 * uncaught exception, see Exception.cmm.
1275 // blocked exceptions can now complete, even if the thread was in
1276 // blocked mode (see #2910). This unconditionally calls
1277 // lockTSO(), which ensures that we don't miss any threads that
1278 // are engaged in throwTo() with this thread as a target.
1279 awakenBlockedExceptionQueue (cap, t);
1282 // Check whether the thread that just completed was a bound
1283 // thread, and if so return with the result.
1285 // There is an assumption here that all thread completion goes
1286 // through this point; we need to make sure that if a thread
1287 // ends up in the ThreadKilled state, that it stays on the run
1288 // queue so it can be dealt with here.
1293 if (t->bound != task) {
1294 #if !defined(THREADED_RTS)
1295 // Must be a bound thread that is not the topmost one. Leave
1296 // it on the run queue until the stack has unwound to the
1297 // point where we can deal with this. Leaving it on the run
1298 // queue also ensures that the garbage collector knows about
1299 // this thread and its return value (it gets dropped from the
1300 // step->threads list so there's no other way to find it).
1301 appendToRunQueue(cap,t);
1304 // this cannot happen in the threaded RTS, because a
1305 // bound thread can only be run by the appropriate Task.
1306 barf("finished bound thread that isn't mine");
1310 ASSERT(task->tso == t);
1312 if (t->what_next == ThreadComplete) {
1314 // NOTE: return val is tso->sp[1] (see StgStartup.hc)
1315 *(task->ret) = (StgClosure *)task->tso->sp[1];
1317 task->stat = Success;
1320 *(task->ret) = NULL;
1322 if (sched_state >= SCHED_INTERRUPTING) {
1323 if (heap_overflow) {
1324 task->stat = HeapExhausted;
1326 task->stat = Interrupted;
1329 task->stat = Killed;
1333 removeThreadLabel((StgWord)task->tso->id);
1335 return rtsTrue; // tells schedule() to return
1341 /* -----------------------------------------------------------------------------
1342 * Perform a heap census
1343 * -------------------------------------------------------------------------- */
1346 scheduleNeedHeapProfile( rtsBool ready_to_gc STG_UNUSED )
1348 // When we have +RTS -i0 and we're heap profiling, do a census at
1349 // every GC. This lets us get repeatable runs for debugging.
1350 if (performHeapProfile ||
1351 (RtsFlags.ProfFlags.profileInterval==0 &&
1352 RtsFlags.ProfFlags.doHeapProfile && ready_to_gc)) {
1359 /* -----------------------------------------------------------------------------
1360 * Perform a garbage collection if necessary
1361 * -------------------------------------------------------------------------- */
1364 scheduleDoGC (Capability *cap, Task *task USED_IF_THREADS, rtsBool force_major)
1366 rtsBool heap_census;
1368 /* extern static volatile StgWord waiting_for_gc;
1369 lives inside capability.c */
1370 rtsBool gc_type, prev_pending_gc;
1374 if (sched_state == SCHED_SHUTTING_DOWN) {
1375 // The final GC has already been done, and the system is
1376 // shutting down. We'll probably deadlock if we try to GC
1382 if (sched_state < SCHED_INTERRUPTING
1383 && RtsFlags.ParFlags.parGcEnabled
1384 && N >= RtsFlags.ParFlags.parGcGen
1385 && ! oldest_gen->mark)
1387 gc_type = PENDING_GC_PAR;
1389 gc_type = PENDING_GC_SEQ;
1392 // In order to GC, there must be no threads running Haskell code.
1393 // Therefore, the GC thread needs to hold *all* the capabilities,
1394 // and release them after the GC has completed.
1396 // This seems to be the simplest way: previous attempts involved
1397 // making all the threads with capabilities give up their
1398 // capabilities and sleep except for the *last* one, which
1399 // actually did the GC. But it's quite hard to arrange for all
1400 // the other tasks to sleep and stay asleep.
1403 /* Other capabilities are prevented from running yet more Haskell
1404 threads if waiting_for_gc is set. Tested inside
1405 yieldCapability() and releaseCapability() in Capability.c */
1407 prev_pending_gc = cas(&waiting_for_gc, 0, gc_type);
1408 if (prev_pending_gc) {
1410 debugTrace(DEBUG_sched, "someone else is trying to GC (%d)...",
1413 yieldCapability(&cap,task);
1414 } while (waiting_for_gc);
1415 return cap; // NOTE: task->cap might have changed here
1418 setContextSwitches();
1420 // The final shutdown GC is always single-threaded, because it's
1421 // possible that some of the Capabilities have no worker threads.
1423 if (gc_type == PENDING_GC_SEQ)
1425 traceEventRequestSeqGc(cap);
1429 traceEventRequestParGc(cap);
1430 debugTrace(DEBUG_sched, "ready_to_gc, grabbing GC threads");
1433 // do this while the other Capabilities stop:
1434 if (cap) scheduleCheckBlackHoles(cap);
1436 if (gc_type == PENDING_GC_SEQ)
1438 // single-threaded GC: grab all the capabilities
1439 for (i=0; i < n_capabilities; i++) {
1440 debugTrace(DEBUG_sched, "ready_to_gc, grabbing all the capabilies (%d/%d)", i, n_capabilities);
1441 if (cap != &capabilities[i]) {
1442 Capability *pcap = &capabilities[i];
1443 // we better hope this task doesn't get migrated to
1444 // another Capability while we're waiting for this one.
1445 // It won't, because load balancing happens while we have
1446 // all the Capabilities, but even so it's a slightly
1447 // unsavoury invariant.
1449 waitForReturnCapability(&pcap, task);
1450 if (pcap != &capabilities[i]) {
1451 barf("scheduleDoGC: got the wrong capability");
1458 // multi-threaded GC: make sure all the Capabilities donate one
1460 waitForGcThreads(cap);
1463 #else /* !THREADED_RTS */
1465 // do this while the other Capabilities stop:
1466 if (cap) scheduleCheckBlackHoles(cap);
1470 IF_DEBUG(scheduler, printAllThreads());
1472 delete_threads_and_gc:
1474 * We now have all the capabilities; if we're in an interrupting
1475 * state, then we should take the opportunity to delete all the
1476 * threads in the system.
1478 if (sched_state == SCHED_INTERRUPTING) {
1479 deleteAllThreads(cap);
1480 sched_state = SCHED_SHUTTING_DOWN;
1483 heap_census = scheduleNeedHeapProfile(rtsTrue);
1485 traceEventGcStart(cap);
1486 #if defined(THREADED_RTS)
1487 // reset waiting_for_gc *before* GC, so that when the GC threads
1488 // emerge they don't immediately re-enter the GC.
1490 GarbageCollect(force_major || heap_census, gc_type, cap);
1492 GarbageCollect(force_major || heap_census, 0, cap);
1494 traceEventGcEnd(cap);
1496 if (recent_activity == ACTIVITY_INACTIVE && force_major)
1498 // We are doing a GC because the system has been idle for a
1499 // timeslice and we need to check for deadlock. Record the
1500 // fact that we've done a GC and turn off the timer signal;
1501 // it will get re-enabled if we run any threads after the GC.
1502 recent_activity = ACTIVITY_DONE_GC;
1507 // the GC might have taken long enough for the timer to set
1508 // recent_activity = ACTIVITY_INACTIVE, but we aren't
1509 // necessarily deadlocked:
1510 recent_activity = ACTIVITY_YES;
1513 #if defined(THREADED_RTS)
1514 if (gc_type == PENDING_GC_PAR)
1516 releaseGCThreads(cap);
1521 debugTrace(DEBUG_sched, "performing heap census");
1523 performHeapProfile = rtsFalse;
1526 if (heap_overflow && sched_state < SCHED_INTERRUPTING) {
1527 // GC set the heap_overflow flag, so we should proceed with
1528 // an orderly shutdown now. Ultimately we want the main
1529 // thread to return to its caller with HeapExhausted, at which
1530 // point the caller should call hs_exit(). The first step is
1531 // to delete all the threads.
1533 // Another way to do this would be to raise an exception in
1534 // the main thread, which we really should do because it gives
1535 // the program a chance to clean up. But how do we find the
1536 // main thread? It should presumably be the same one that
1537 // gets ^C exceptions, but that's all done on the Haskell side
1538 // (GHC.TopHandler).
1539 sched_state = SCHED_INTERRUPTING;
1540 goto delete_threads_and_gc;
1545 Once we are all together... this would be the place to balance all
1546 spark pools. No concurrent stealing or adding of new sparks can
1547 occur. Should be defined in Sparks.c. */
1548 balanceSparkPoolsCaps(n_capabilities, capabilities);
1551 #if defined(THREADED_RTS)
1552 if (gc_type == PENDING_GC_SEQ) {
1553 // release our stash of capabilities.
1554 for (i = 0; i < n_capabilities; i++) {
1555 if (cap != &capabilities[i]) {
1556 task->cap = &capabilities[i];
1557 releaseCapability(&capabilities[i]);
1571 /* ---------------------------------------------------------------------------
1572 * Singleton fork(). Do not copy any running threads.
1573 * ------------------------------------------------------------------------- */
1576 forkProcess(HsStablePtr *entry
1577 #ifndef FORKPROCESS_PRIMOP_SUPPORTED
1582 #ifdef FORKPROCESS_PRIMOP_SUPPORTED
1589 #if defined(THREADED_RTS)
1590 if (RtsFlags.ParFlags.nNodes > 1) {
1591 errorBelch("forking not supported with +RTS -N<n> greater than 1");
1592 stg_exit(EXIT_FAILURE);
1596 debugTrace(DEBUG_sched, "forking!");
1598 // ToDo: for SMP, we should probably acquire *all* the capabilities
1601 // no funny business: hold locks while we fork, otherwise if some
1602 // other thread is holding a lock when the fork happens, the data
1603 // structure protected by the lock will forever be in an
1604 // inconsistent state in the child. See also #1391.
1605 ACQUIRE_LOCK(&sched_mutex);
1606 ACQUIRE_LOCK(&cap->lock);
1607 ACQUIRE_LOCK(&cap->running_task->lock);
1611 if (pid) { // parent
1613 RELEASE_LOCK(&sched_mutex);
1614 RELEASE_LOCK(&cap->lock);
1615 RELEASE_LOCK(&cap->running_task->lock);
1617 // just return the pid
1623 #if defined(THREADED_RTS)
1624 initMutex(&sched_mutex);
1625 initMutex(&cap->lock);
1626 initMutex(&cap->running_task->lock);
1629 // Now, all OS threads except the thread that forked are
1630 // stopped. We need to stop all Haskell threads, including
1631 // those involved in foreign calls. Also we need to delete
1632 // all Tasks, because they correspond to OS threads that are
1635 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
1636 for (t = generations[g].threads; t != END_TSO_QUEUE; t = next) {
1637 if (t->what_next == ThreadRelocated) {
1640 next = t->global_link;
1641 // don't allow threads to catch the ThreadKilled
1642 // exception, but we do want to raiseAsync() because these
1643 // threads may be evaluating thunks that we need later.
1644 deleteThread_(cap,t);
1649 // Empty the run queue. It seems tempting to let all the
1650 // killed threads stay on the run queue as zombies to be
1651 // cleaned up later, but some of them correspond to bound
1652 // threads for which the corresponding Task does not exist.
1653 cap->run_queue_hd = END_TSO_QUEUE;
1654 cap->run_queue_tl = END_TSO_QUEUE;
1656 // Any suspended C-calling Tasks are no more, their OS threads
1658 cap->suspended_ccalling_tasks = NULL;
1660 // Empty the threads lists. Otherwise, the garbage
1661 // collector may attempt to resurrect some of these threads.
1662 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
1663 generations[g].threads = END_TSO_QUEUE;
1666 // Wipe the task list, except the current Task.
1667 ACQUIRE_LOCK(&sched_mutex);
1668 for (task = all_tasks; task != NULL; task=task->all_link) {
1669 if (task != cap->running_task) {
1670 #if defined(THREADED_RTS)
1671 initMutex(&task->lock); // see #1391
1676 RELEASE_LOCK(&sched_mutex);
1678 #if defined(THREADED_RTS)
1679 // Wipe our spare workers list, they no longer exist. New
1680 // workers will be created if necessary.
1681 cap->spare_workers = NULL;
1682 cap->returning_tasks_hd = NULL;
1683 cap->returning_tasks_tl = NULL;
1686 // On Unix, all timers are reset in the child, so we need to start
1691 #if defined(THREADED_RTS)
1692 cap = ioManagerStartCap(cap);
1695 cap = rts_evalStableIO(cap, entry, NULL); // run the action
1696 rts_checkSchedStatus("forkProcess",cap);
1699 hs_exit(); // clean up and exit
1700 stg_exit(EXIT_SUCCESS);
1702 #else /* !FORKPROCESS_PRIMOP_SUPPORTED */
1703 barf("forkProcess#: primop not supported on this platform, sorry!\n");
1707 /* ---------------------------------------------------------------------------
1708 * Delete all the threads in the system
1709 * ------------------------------------------------------------------------- */
1712 deleteAllThreads ( Capability *cap )
1714 // NOTE: only safe to call if we own all capabilities.
1719 debugTrace(DEBUG_sched,"deleting all threads");
1720 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
1721 for (t = generations[g].threads; t != END_TSO_QUEUE; t = next) {
1722 if (t->what_next == ThreadRelocated) {
1725 next = t->global_link;
1726 deleteThread(cap,t);
1731 // The run queue now contains a bunch of ThreadKilled threads. We
1732 // must not throw these away: the main thread(s) will be in there
1733 // somewhere, and the main scheduler loop has to deal with it.
1734 // Also, the run queue is the only thing keeping these threads from
1735 // being GC'd, and we don't want the "main thread has been GC'd" panic.
1737 #if !defined(THREADED_RTS)
1738 ASSERT(blocked_queue_hd == END_TSO_QUEUE);
1739 ASSERT(sleeping_queue == END_TSO_QUEUE);
1743 /* -----------------------------------------------------------------------------
1744 Managing the suspended_ccalling_tasks list.
1745 Locks required: sched_mutex
1746 -------------------------------------------------------------------------- */
1749 suspendTask (Capability *cap, Task *task)
1751 ASSERT(task->next == NULL && task->prev == NULL);
1752 task->next = cap->suspended_ccalling_tasks;
1754 if (cap->suspended_ccalling_tasks) {
1755 cap->suspended_ccalling_tasks->prev = task;
1757 cap->suspended_ccalling_tasks = task;
1761 recoverSuspendedTask (Capability *cap, Task *task)
1764 task->prev->next = task->next;
1766 ASSERT(cap->suspended_ccalling_tasks == task);
1767 cap->suspended_ccalling_tasks = task->next;
1770 task->next->prev = task->prev;
1772 task->next = task->prev = NULL;
1775 /* ---------------------------------------------------------------------------
1776 * Suspending & resuming Haskell threads.
1778 * When making a "safe" call to C (aka _ccall_GC), the task gives back
1779 * its capability before calling the C function. This allows another
1780 * task to pick up the capability and carry on running Haskell
1781 * threads. It also means that if the C call blocks, it won't lock
1784 * The Haskell thread making the C call is put to sleep for the
1785 * duration of the call, on the susepended_ccalling_threads queue. We
1786 * give out a token to the task, which it can use to resume the thread
1787 * on return from the C function.
1788 * ------------------------------------------------------------------------- */
1791 suspendThread (StgRegTable *reg)
1798 StgWord32 saved_winerror;
1801 saved_errno = errno;
1803 saved_winerror = GetLastError();
1806 /* assume that *reg is a pointer to the StgRegTable part of a Capability.
1808 cap = regTableToCapability(reg);
1810 task = cap->running_task;
1811 tso = cap->r.rCurrentTSO;
1813 traceEventStopThread(cap, tso, THREAD_SUSPENDED_FOREIGN_CALL);
1815 // XXX this might not be necessary --SDM
1816 tso->what_next = ThreadRunGHC;
1818 threadPaused(cap,tso);
1820 if ((tso->flags & TSO_BLOCKEX) == 0) {
1821 tso->why_blocked = BlockedOnCCall;
1822 tso->flags |= TSO_BLOCKEX;
1823 tso->flags &= ~TSO_INTERRUPTIBLE;
1825 tso->why_blocked = BlockedOnCCall_NoUnblockExc;
1828 // Hand back capability
1829 task->suspended_tso = tso;
1831 ACQUIRE_LOCK(&cap->lock);
1833 suspendTask(cap,task);
1834 cap->in_haskell = rtsFalse;
1835 releaseCapability_(cap,rtsFalse);
1837 RELEASE_LOCK(&cap->lock);
1839 errno = saved_errno;
1841 SetLastError(saved_winerror);
1847 resumeThread (void *task_)
1854 StgWord32 saved_winerror;
1857 saved_errno = errno;
1859 saved_winerror = GetLastError();
1863 // Wait for permission to re-enter the RTS with the result.
1864 waitForReturnCapability(&cap,task);
1865 // we might be on a different capability now... but if so, our
1866 // entry on the suspended_ccalling_tasks list will also have been
1869 // Remove the thread from the suspended list
1870 recoverSuspendedTask(cap,task);
1872 tso = task->suspended_tso;
1873 task->suspended_tso = NULL;
1874 tso->_link = END_TSO_QUEUE; // no write barrier reqd
1876 traceEventRunThread(cap, tso);
1878 if (tso->why_blocked == BlockedOnCCall) {
1879 // avoid locking the TSO if we don't have to
1880 if (tso->blocked_exceptions != END_TSO_QUEUE) {
1881 awakenBlockedExceptionQueue(cap,tso);
1883 tso->flags &= ~(TSO_BLOCKEX | TSO_INTERRUPTIBLE);
1886 /* Reset blocking status */
1887 tso->why_blocked = NotBlocked;
1889 cap->r.rCurrentTSO = tso;
1890 cap->in_haskell = rtsTrue;
1891 errno = saved_errno;
1893 SetLastError(saved_winerror);
1896 /* We might have GC'd, mark the TSO dirty again */
1899 IF_DEBUG(sanity, checkTSO(tso));
1904 /* ---------------------------------------------------------------------------
1907 * scheduleThread puts a thread on the end of the runnable queue.
1908 * This will usually be done immediately after a thread is created.
1909 * The caller of scheduleThread must create the thread using e.g.
1910 * createThread and push an appropriate closure
1911 * on this thread's stack before the scheduler is invoked.
1912 * ------------------------------------------------------------------------ */
1915 scheduleThread(Capability *cap, StgTSO *tso)
1917 // The thread goes at the *end* of the run-queue, to avoid possible
1918 // starvation of any threads already on the queue.
1919 appendToRunQueue(cap,tso);
1923 scheduleThreadOn(Capability *cap, StgWord cpu USED_IF_THREADS, StgTSO *tso)
1925 #if defined(THREADED_RTS)
1926 tso->flags |= TSO_LOCKED; // we requested explicit affinity; don't
1927 // move this thread from now on.
1928 cpu %= RtsFlags.ParFlags.nNodes;
1929 if (cpu == cap->no) {
1930 appendToRunQueue(cap,tso);
1932 traceEventMigrateThread (cap, tso, capabilities[cpu].no);
1933 wakeupThreadOnCapability(cap, &capabilities[cpu], tso);
1936 appendToRunQueue(cap,tso);
1941 scheduleWaitThread (StgTSO* tso, /*[out]*/HaskellObj* ret, Capability *cap)
1945 // We already created/initialised the Task
1946 task = cap->running_task;
1948 // This TSO is now a bound thread; make the Task and TSO
1949 // point to each other.
1955 task->stat = NoStatus;
1957 appendToRunQueue(cap,tso);
1959 debugTrace(DEBUG_sched, "new bound thread (%lu)", (unsigned long)tso->id);
1961 cap = schedule(cap,task);
1963 ASSERT(task->stat != NoStatus);
1964 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
1966 debugTrace(DEBUG_sched, "bound thread (%lu) finished", (unsigned long)task->tso->id);
1970 /* ----------------------------------------------------------------------------
1972 * ------------------------------------------------------------------------- */
1974 #if defined(THREADED_RTS)
1975 void OSThreadProcAttr
1976 workerStart(Task *task)
1980 // See startWorkerTask().
1981 ACQUIRE_LOCK(&task->lock);
1983 RELEASE_LOCK(&task->lock);
1985 if (RtsFlags.ParFlags.setAffinity) {
1986 setThreadAffinity(cap->no, n_capabilities);
1989 // set the thread-local pointer to the Task:
1992 // schedule() runs without a lock.
1993 cap = schedule(cap,task);
1995 // On exit from schedule(), we have a Capability, but possibly not
1996 // the same one we started with.
1998 // During shutdown, the requirement is that after all the
1999 // Capabilities are shut down, all workers that are shutting down
2000 // have finished workerTaskStop(). This is why we hold on to
2001 // cap->lock until we've finished workerTaskStop() below.
2003 // There may be workers still involved in foreign calls; those
2004 // will just block in waitForReturnCapability() because the
2005 // Capability has been shut down.
2007 ACQUIRE_LOCK(&cap->lock);
2008 releaseCapability_(cap,rtsFalse);
2009 workerTaskStop(task);
2010 RELEASE_LOCK(&cap->lock);
2014 /* ---------------------------------------------------------------------------
2017 * Initialise the scheduler. This resets all the queues - if the
2018 * queues contained any threads, they'll be garbage collected at the
2021 * ------------------------------------------------------------------------ */
2026 #if !defined(THREADED_RTS)
2027 blocked_queue_hd = END_TSO_QUEUE;
2028 blocked_queue_tl = END_TSO_QUEUE;
2029 sleeping_queue = END_TSO_QUEUE;
2032 blackhole_queue = END_TSO_QUEUE;
2034 sched_state = SCHED_RUNNING;
2035 recent_activity = ACTIVITY_YES;
2037 #if defined(THREADED_RTS)
2038 /* Initialise the mutex and condition variables used by
2040 initMutex(&sched_mutex);
2043 ACQUIRE_LOCK(&sched_mutex);
2045 /* A capability holds the state a native thread needs in
2046 * order to execute STG code. At least one capability is
2047 * floating around (only THREADED_RTS builds have more than one).
2053 #if defined(THREADED_RTS)
2057 #if defined(THREADED_RTS)
2059 * Eagerly start one worker to run each Capability, except for
2060 * Capability 0. The idea is that we're probably going to start a
2061 * bound thread on Capability 0 pretty soon, so we don't want a
2062 * worker task hogging it.
2067 for (i = 1; i < n_capabilities; i++) {
2068 cap = &capabilities[i];
2069 ACQUIRE_LOCK(&cap->lock);
2070 startWorkerTask(cap, workerStart);
2071 RELEASE_LOCK(&cap->lock);
2076 RELEASE_LOCK(&sched_mutex);
2081 rtsBool wait_foreign
2082 #if !defined(THREADED_RTS)
2083 __attribute__((unused))
2086 /* see Capability.c, shutdownCapability() */
2090 task = newBoundTask();
2092 // If we haven't killed all the threads yet, do it now.
2093 if (sched_state < SCHED_SHUTTING_DOWN) {
2094 sched_state = SCHED_INTERRUPTING;
2095 waitForReturnCapability(&task->cap,task);
2096 scheduleDoGC(task->cap,task,rtsFalse);
2097 releaseCapability(task->cap);
2099 sched_state = SCHED_SHUTTING_DOWN;
2101 #if defined(THREADED_RTS)
2105 for (i = 0; i < n_capabilities; i++) {
2106 shutdownCapability(&capabilities[i], task, wait_foreign);
2111 boundTaskExiting(task);
2115 freeScheduler( void )
2119 ACQUIRE_LOCK(&sched_mutex);
2120 still_running = freeTaskManager();
2121 // We can only free the Capabilities if there are no Tasks still
2122 // running. We might have a Task about to return from a foreign
2123 // call into waitForReturnCapability(), for example (actually,
2124 // this should be the *only* thing that a still-running Task can
2125 // do at this point, and it will block waiting for the
2127 if (still_running == 0) {
2129 if (n_capabilities != 1) {
2130 stgFree(capabilities);
2133 RELEASE_LOCK(&sched_mutex);
2134 #if defined(THREADED_RTS)
2135 closeMutex(&sched_mutex);
2139 /* -----------------------------------------------------------------------------
2142 This is the interface to the garbage collector from Haskell land.
2143 We provide this so that external C code can allocate and garbage
2144 collect when called from Haskell via _ccall_GC.
2145 -------------------------------------------------------------------------- */
2148 performGC_(rtsBool force_major)
2152 // We must grab a new Task here, because the existing Task may be
2153 // associated with a particular Capability, and chained onto the
2154 // suspended_ccalling_tasks queue.
2155 task = newBoundTask();
2157 waitForReturnCapability(&task->cap,task);
2158 scheduleDoGC(task->cap,task,force_major);
2159 releaseCapability(task->cap);
2160 boundTaskExiting(task);
2166 performGC_(rtsFalse);
2170 performMajorGC(void)
2172 performGC_(rtsTrue);
2175 /* -----------------------------------------------------------------------------
2178 If the thread has reached its maximum stack size, then raise the
2179 StackOverflow exception in the offending thread. Otherwise
2180 relocate the TSO into a larger chunk of memory and adjust its stack
2182 -------------------------------------------------------------------------- */
2185 threadStackOverflow(Capability *cap, StgTSO *tso)
2187 nat new_stack_size, stack_words;
2192 IF_DEBUG(sanity,checkTSO(tso));
2194 // don't allow throwTo() to modify the blocked_exceptions queue
2195 // while we are moving the TSO:
2196 lockClosure((StgClosure *)tso);
2198 if (tso->stack_size >= tso->max_stack_size
2199 && !(tso->flags & TSO_BLOCKEX)) {
2200 // NB. never raise a StackOverflow exception if the thread is
2201 // inside Control.Exceptino.block. It is impractical to protect
2202 // against stack overflow exceptions, since virtually anything
2203 // can raise one (even 'catch'), so this is the only sensible
2204 // thing to do here. See bug #767.
2207 if (tso->flags & TSO_SQUEEZED) {
2211 // #3677: In a stack overflow situation, stack squeezing may
2212 // reduce the stack size, but we don't know whether it has been
2213 // reduced enough for the stack check to succeed if we try
2214 // again. Fortunately stack squeezing is idempotent, so all we
2215 // need to do is record whether *any* squeezing happened. If we
2216 // are at the stack's absolute -K limit, and stack squeezing
2217 // happened, then we try running the thread again. The
2218 // TSO_SQUEEZED flag is set by threadPaused() to tell us whether
2219 // squeezing happened or not.
2221 debugTrace(DEBUG_gc,
2222 "threadStackOverflow of TSO %ld (%p): stack too large (now %ld; max is %ld)",
2223 (long)tso->id, tso, (long)tso->stack_size, (long)tso->max_stack_size);
2225 /* If we're debugging, just print out the top of the stack */
2226 printStackChunk(tso->sp, stg_min(tso->stack+tso->stack_size,
2229 // Send this thread the StackOverflow exception
2231 throwToSingleThreaded(cap, tso, (StgClosure *)stackOverflow_closure);
2236 // We also want to avoid enlarging the stack if squeezing has
2237 // already released some of it. However, we don't want to get into
2238 // a pathalogical situation where a thread has a nearly full stack
2239 // (near its current limit, but not near the absolute -K limit),
2240 // keeps allocating a little bit, squeezing removes a little bit,
2241 // and then it runs again. So to avoid this, if we squeezed *and*
2242 // there is still less than BLOCK_SIZE_W words free, then we enlarge
2243 // the stack anyway.
2244 if ((tso->flags & TSO_SQUEEZED) &&
2245 ((W_)(tso->sp - tso->stack) >= BLOCK_SIZE_W)) {
2250 /* Try to double the current stack size. If that takes us over the
2251 * maximum stack size for this thread, then use the maximum instead
2252 * (that is, unless we're already at or over the max size and we
2253 * can't raise the StackOverflow exception (see above), in which
2254 * case just double the size). Finally round up so the TSO ends up as
2255 * a whole number of blocks.
2257 if (tso->stack_size >= tso->max_stack_size) {
2258 new_stack_size = tso->stack_size * 2;
2260 new_stack_size = stg_min(tso->stack_size * 2, tso->max_stack_size);
2262 new_tso_size = (lnat)BLOCK_ROUND_UP(new_stack_size * sizeof(W_) +
2263 TSO_STRUCT_SIZE)/sizeof(W_);
2264 new_tso_size = round_to_mblocks(new_tso_size); /* Be MBLOCK-friendly */
2265 new_stack_size = new_tso_size - TSO_STRUCT_SIZEW;
2267 debugTrace(DEBUG_sched,
2268 "increasing stack size from %ld words to %d.",
2269 (long)tso->stack_size, new_stack_size);
2271 dest = (StgTSO *)allocate(cap,new_tso_size);
2272 TICK_ALLOC_TSO(new_stack_size,0);
2274 /* copy the TSO block and the old stack into the new area */
2275 memcpy(dest,tso,TSO_STRUCT_SIZE);
2276 stack_words = tso->stack + tso->stack_size - tso->sp;
2277 new_sp = (P_)dest + new_tso_size - stack_words;
2278 memcpy(new_sp, tso->sp, stack_words * sizeof(W_));
2280 /* relocate the stack pointers... */
2282 dest->stack_size = new_stack_size;
2284 /* Mark the old TSO as relocated. We have to check for relocated
2285 * TSOs in the garbage collector and any primops that deal with TSOs.
2287 * It's important to set the sp value to just beyond the end
2288 * of the stack, so we don't attempt to scavenge any part of the
2291 tso->what_next = ThreadRelocated;
2292 setTSOLink(cap,tso,dest);
2293 tso->sp = (P_)&(tso->stack[tso->stack_size]);
2294 tso->why_blocked = NotBlocked;
2299 IF_DEBUG(sanity,checkTSO(dest));
2301 IF_DEBUG(scheduler,printTSO(dest));
2308 threadStackUnderflow (Capability *cap, Task *task, StgTSO *tso)
2310 bdescr *bd, *new_bd;
2311 lnat free_w, tso_size_w;
2314 tso_size_w = tso_sizeW(tso);
2316 if (tso_size_w < MBLOCK_SIZE_W ||
2317 // TSO is less than 2 mblocks (since the first mblock is
2318 // shorter than MBLOCK_SIZE_W)
2319 (tso_size_w - BLOCKS_PER_MBLOCK*BLOCK_SIZE_W) % MBLOCK_SIZE_W != 0 ||
2320 // or TSO is not a whole number of megablocks (ensuring
2321 // precondition of splitLargeBlock() below)
2322 (tso_size_w <= round_up_to_mblocks(RtsFlags.GcFlags.initialStkSize)) ||
2323 // or TSO is smaller than the minimum stack size (rounded up)
2324 (nat)(tso->stack + tso->stack_size - tso->sp) > tso->stack_size / 4)
2325 // or stack is using more than 1/4 of the available space
2331 // don't allow throwTo() to modify the blocked_exceptions queue
2332 // while we are moving the TSO:
2333 lockClosure((StgClosure *)tso);
2335 // this is the number of words we'll free
2336 free_w = round_to_mblocks(tso_size_w/2);
2338 bd = Bdescr((StgPtr)tso);
2339 new_bd = splitLargeBlock(bd, free_w / BLOCK_SIZE_W);
2340 bd->free = bd->start + TSO_STRUCT_SIZEW;
2342 new_tso = (StgTSO *)new_bd->start;
2343 memcpy(new_tso,tso,TSO_STRUCT_SIZE);
2344 new_tso->stack_size = new_bd->free - new_tso->stack;
2346 // The original TSO was dirty and probably on the mutable
2347 // list. The new TSO is not yet on the mutable list, so we better
2350 new_tso->flags &= ~TSO_LINK_DIRTY;
2351 dirty_TSO(cap, new_tso);
2353 debugTrace(DEBUG_sched, "thread %ld: reducing TSO size from %lu words to %lu",
2354 (long)tso->id, tso_size_w, tso_sizeW(new_tso));
2356 tso->what_next = ThreadRelocated;
2357 tso->_link = new_tso; // no write barrier reqd: same generation
2359 // The TSO attached to this Task may have moved, so update the
2361 if (task->tso == tso) {
2362 task->tso = new_tso;
2368 IF_DEBUG(sanity,checkTSO(new_tso));
2373 /* ---------------------------------------------------------------------------
2375 - usually called inside a signal handler so it mustn't do anything fancy.
2376 ------------------------------------------------------------------------ */
2379 interruptStgRts(void)
2381 sched_state = SCHED_INTERRUPTING;
2382 setContextSwitches();
2383 #if defined(THREADED_RTS)
2388 /* -----------------------------------------------------------------------------
2391 This function causes at least one OS thread to wake up and run the
2392 scheduler loop. It is invoked when the RTS might be deadlocked, or
2393 an external event has arrived that may need servicing (eg. a
2394 keyboard interrupt).
2396 In the single-threaded RTS we don't do anything here; we only have
2397 one thread anyway, and the event that caused us to want to wake up
2398 will have interrupted any blocking system call in progress anyway.
2399 -------------------------------------------------------------------------- */
2401 #if defined(THREADED_RTS)
2402 void wakeUpRts(void)
2404 // This forces the IO Manager thread to wakeup, which will
2405 // in turn ensure that some OS thread wakes up and runs the
2406 // scheduler loop, which will cause a GC and deadlock check.
2411 /* -----------------------------------------------------------------------------
2414 * Check the blackhole_queue for threads that can be woken up. We do
2415 * this periodically: before every GC, and whenever the run queue is
2418 * An elegant solution might be to just wake up all the blocked
2419 * threads with awakenBlockedQueue occasionally: they'll go back to
2420 * sleep again if the object is still a BLACKHOLE. Unfortunately this
2421 * doesn't give us a way to tell whether we've actually managed to
2422 * wake up any threads, so we would be busy-waiting.
2424 * -------------------------------------------------------------------------- */
2427 checkBlackHoles (Capability *cap)
2430 rtsBool any_woke_up = rtsFalse;
2433 // blackhole_queue is global:
2434 ASSERT_LOCK_HELD(&sched_mutex);
2436 debugTrace(DEBUG_sched, "checking threads blocked on black holes");
2438 // ASSUMES: sched_mutex
2439 prev = &blackhole_queue;
2440 t = blackhole_queue;
2441 while (t != END_TSO_QUEUE) {
2442 if (t->what_next == ThreadRelocated) {
2446 ASSERT(t->why_blocked == BlockedOnBlackHole);
2447 type = get_itbl(UNTAG_CLOSURE(t->block_info.closure))->type;
2448 if (type != BLACKHOLE && type != CAF_BLACKHOLE) {
2449 IF_DEBUG(sanity,checkTSO(t));
2450 t = unblockOne(cap, t);
2452 any_woke_up = rtsTrue;
2462 /* -----------------------------------------------------------------------------
2465 This is used for interruption (^C) and forking, and corresponds to
2466 raising an exception but without letting the thread catch the
2468 -------------------------------------------------------------------------- */
2471 deleteThread (Capability *cap, StgTSO *tso)
2473 // NOTE: must only be called on a TSO that we have exclusive
2474 // access to, because we will call throwToSingleThreaded() below.
2475 // The TSO must be on the run queue of the Capability we own, or
2476 // we must own all Capabilities.
2478 if (tso->why_blocked != BlockedOnCCall &&
2479 tso->why_blocked != BlockedOnCCall_NoUnblockExc) {
2480 throwToSingleThreaded(cap,tso,NULL);
2484 #ifdef FORKPROCESS_PRIMOP_SUPPORTED
2486 deleteThread_(Capability *cap, StgTSO *tso)
2487 { // for forkProcess only:
2488 // like deleteThread(), but we delete threads in foreign calls, too.
2490 if (tso->why_blocked == BlockedOnCCall ||
2491 tso->why_blocked == BlockedOnCCall_NoUnblockExc) {
2492 unblockOne(cap,tso);
2493 tso->what_next = ThreadKilled;
2495 deleteThread(cap,tso);
2500 /* -----------------------------------------------------------------------------
2501 raiseExceptionHelper
2503 This function is called by the raise# primitve, just so that we can
2504 move some of the tricky bits of raising an exception from C-- into
2505 C. Who knows, it might be a useful re-useable thing here too.
2506 -------------------------------------------------------------------------- */
2509 raiseExceptionHelper (StgRegTable *reg, StgTSO *tso, StgClosure *exception)
2511 Capability *cap = regTableToCapability(reg);
2512 StgThunk *raise_closure = NULL;
2514 StgRetInfoTable *info;
2516 // This closure represents the expression 'raise# E' where E
2517 // is the exception raise. It is used to overwrite all the
2518 // thunks which are currently under evaluataion.
2521 // OLD COMMENT (we don't have MIN_UPD_SIZE now):
2522 // LDV profiling: stg_raise_info has THUNK as its closure
2523 // type. Since a THUNK takes at least MIN_UPD_SIZE words in its
2524 // payload, MIN_UPD_SIZE is more approprate than 1. It seems that
2525 // 1 does not cause any problem unless profiling is performed.
2526 // However, when LDV profiling goes on, we need to linearly scan
2527 // small object pool, where raise_closure is stored, so we should
2528 // use MIN_UPD_SIZE.
2530 // raise_closure = (StgClosure *)RET_STGCALL1(P_,allocate,
2531 // sizeofW(StgClosure)+1);
2535 // Walk up the stack, looking for the catch frame. On the way,
2536 // we update any closures pointed to from update frames with the
2537 // raise closure that we just built.
2541 info = get_ret_itbl((StgClosure *)p);
2542 next = p + stack_frame_sizeW((StgClosure *)p);
2543 switch (info->i.type) {
2546 // Only create raise_closure if we need to.
2547 if (raise_closure == NULL) {
2549 (StgThunk *)allocate(cap,sizeofW(StgThunk)+1);
2550 SET_HDR(raise_closure, &stg_raise_info, CCCS);
2551 raise_closure->payload[0] = exception;
2553 UPD_IND(cap, ((StgUpdateFrame *)p)->updatee,
2554 (StgClosure *)raise_closure);
2558 case ATOMICALLY_FRAME:
2559 debugTrace(DEBUG_stm, "found ATOMICALLY_FRAME at %p", p);
2561 return ATOMICALLY_FRAME;
2567 case CATCH_STM_FRAME:
2568 debugTrace(DEBUG_stm, "found CATCH_STM_FRAME at %p", p);
2570 return CATCH_STM_FRAME;
2576 case CATCH_RETRY_FRAME:
2585 /* -----------------------------------------------------------------------------
2586 findRetryFrameHelper
2588 This function is called by the retry# primitive. It traverses the stack
2589 leaving tso->sp referring to the frame which should handle the retry.
2591 This should either be a CATCH_RETRY_FRAME (if the retry# is within an orElse#)
2592 or should be a ATOMICALLY_FRAME (if the retry# reaches the top level).
2594 We skip CATCH_STM_FRAMEs (aborting and rolling back the nested tx that they
2595 create) because retries are not considered to be exceptions, despite the
2596 similar implementation.
2598 We should not expect to see CATCH_FRAME or STOP_FRAME because those should
2599 not be created within memory transactions.
2600 -------------------------------------------------------------------------- */
2603 findRetryFrameHelper (StgTSO *tso)
2606 StgRetInfoTable *info;
2610 info = get_ret_itbl((StgClosure *)p);
2611 next = p + stack_frame_sizeW((StgClosure *)p);
2612 switch (info->i.type) {
2614 case ATOMICALLY_FRAME:
2615 debugTrace(DEBUG_stm,
2616 "found ATOMICALLY_FRAME at %p during retry", p);
2618 return ATOMICALLY_FRAME;
2620 case CATCH_RETRY_FRAME:
2621 debugTrace(DEBUG_stm,
2622 "found CATCH_RETRY_FRAME at %p during retrry", p);
2624 return CATCH_RETRY_FRAME;
2626 case CATCH_STM_FRAME: {
2627 StgTRecHeader *trec = tso -> trec;
2628 StgTRecHeader *outer = trec -> enclosing_trec;
2629 debugTrace(DEBUG_stm,
2630 "found CATCH_STM_FRAME at %p during retry", p);
2631 debugTrace(DEBUG_stm, "trec=%p outer=%p", trec, outer);
2632 stmAbortTransaction(tso -> cap, trec);
2633 stmFreeAbortedTRec(tso -> cap, trec);
2634 tso -> trec = outer;
2641 ASSERT(info->i.type != CATCH_FRAME);
2642 ASSERT(info->i.type != STOP_FRAME);
2649 /* -----------------------------------------------------------------------------
2650 resurrectThreads is called after garbage collection on the list of
2651 threads found to be garbage. Each of these threads will be woken
2652 up and sent a signal: BlockedOnDeadMVar if the thread was blocked
2653 on an MVar, or NonTermination if the thread was blocked on a Black
2656 Locks: assumes we hold *all* the capabilities.
2657 -------------------------------------------------------------------------- */
2660 resurrectThreads (StgTSO *threads)
2666 for (tso = threads; tso != END_TSO_QUEUE; tso = next) {
2667 next = tso->global_link;
2669 gen = Bdescr((P_)tso)->gen;
2670 tso->global_link = gen->threads;
2673 debugTrace(DEBUG_sched, "resurrecting thread %lu", (unsigned long)tso->id);
2675 // Wake up the thread on the Capability it was last on
2678 switch (tso->why_blocked) {
2680 /* Called by GC - sched_mutex lock is currently held. */
2681 throwToSingleThreaded(cap, tso,
2682 (StgClosure *)blockedIndefinitelyOnMVar_closure);
2684 case BlockedOnBlackHole:
2685 throwToSingleThreaded(cap, tso,
2686 (StgClosure *)nonTermination_closure);
2689 throwToSingleThreaded(cap, tso,
2690 (StgClosure *)blockedIndefinitelyOnSTM_closure);
2693 /* This might happen if the thread was blocked on a black hole
2694 * belonging to a thread that we've just woken up (raiseAsync
2695 * can wake up threads, remember...).
2698 case BlockedOnException:
2699 // throwTo should never block indefinitely: if the target
2700 // thread dies or completes, throwTo returns.
2701 barf("resurrectThreads: thread BlockedOnException");
2704 barf("resurrectThreads: thread blocked in a strange way");
2709 /* -----------------------------------------------------------------------------
2710 performPendingThrowTos is called after garbage collection, and
2711 passed a list of threads that were found to have pending throwTos
2712 (tso->blocked_exceptions was not empty), and were blocked.
2713 Normally this doesn't happen, because we would deliver the
2714 exception directly if the target thread is blocked, but there are
2715 small windows where it might occur on a multiprocessor (see
2718 NB. we must be holding all the capabilities at this point, just
2719 like resurrectThreads().
2720 -------------------------------------------------------------------------- */
2723 performPendingThrowTos (StgTSO *threads)
2727 Task *task, *saved_task;;
2733 for (tso = threads; tso != END_TSO_QUEUE; tso = next) {
2734 next = tso->global_link;
2736 gen = Bdescr((P_)tso)->gen;
2737 tso->global_link = gen->threads;
2740 debugTrace(DEBUG_sched, "performing blocked throwTo to thread %lu", (unsigned long)tso->id);
2742 // We must pretend this Capability belongs to the current Task
2743 // for the time being, as invariants will be broken otherwise.
2744 // In fact the current Task has exclusive access to the systme
2745 // at this point, so this is just bookkeeping:
2746 task->cap = tso->cap;
2747 saved_task = tso->cap->running_task;
2748 tso->cap->running_task = task;
2749 maybePerformBlockedException(tso->cap, tso);
2750 tso->cap->running_task = saved_task;
2753 // Restore our original Capability: