1 /* ---------------------------------------------------------------------------
3 * (c) The GHC Team, 2003-2006
7 * A Capability represent the token required to execute STG code,
8 * and all the state an OS thread/task needs to run Haskell code:
9 * its STG registers, a pointer to its TSO, a nursery etc. During
10 * STG execution, a pointer to the capabilitity is kept in a
11 * register (BaseReg; actually it is a pointer to cap->r).
13 * Only in an THREADED_RTS build will there be multiple capabilities,
14 * for non-threaded builds there is only one global capability, namely
17 * --------------------------------------------------------------------------*/
19 #include "PosixSource.h"
22 #include "Capability.h"
26 #include "sm/GC.h" // for gcWorkerThread()
30 // one global capability, this is the Capability for non-threaded
31 // builds, and for +RTS -N1
32 Capability MainCapability;
34 nat n_capabilities = 0;
35 Capability *capabilities = NULL;
37 // Holds the Capability which last became free. This is used so that
38 // an in-call has a chance of quickly finding a free Capability.
39 // Maintaining a global free list of Capabilities would require global
40 // locking, so we don't do that.
41 Capability *last_free_capability = NULL;
43 /* GC indicator, in scope for the scheduler, init'ed to false */
44 volatile StgWord waiting_for_gc = 0;
46 /* Let foreign code get the current Capability -- assuming there is one!
47 * This is useful for unsafe foreign calls because they are called with
48 * the current Capability held, but they are not passed it. For example,
49 * see see the integer-gmp package which calls allocateLocal() in its
50 * stgAllocForGMP() function (which gets called by gmp functions).
52 Capability * rts_unsafeGetMyCapability (void)
54 #if defined(THREADED_RTS)
57 return &MainCapability;
61 #if defined(THREADED_RTS)
65 return blackholes_need_checking
66 || sched_state >= SCHED_INTERRUPTING
71 #if defined(THREADED_RTS)
73 findSpark (Capability *cap)
80 if (!emptyRunQueue(cap) || cap->returning_tasks_hd != NULL) {
81 // If there are other threads, don't try to run any new
82 // sparks: sparks might be speculative, we don't want to take
83 // resources away from the main computation.
90 // first try to get a spark from our own pool.
91 // We should be using reclaimSpark(), because it works without
92 // needing any atomic instructions:
93 // spark = reclaimSpark(cap->sparks);
94 // However, measurements show that this makes at least one benchmark
95 // slower (prsa) and doesn't affect the others.
96 spark = tryStealSpark(cap);
98 cap->sparks_converted++;
100 // Post event for running a spark from capability's own pool.
101 traceEventRunSpark(cap, cap->r.rCurrentTSO);
105 if (!emptySparkPoolCap(cap)) {
109 if (n_capabilities == 1) { return NULL; } // makes no sense...
111 debugTrace(DEBUG_sched,
112 "cap %d: Trying to steal work from other capabilities",
115 /* visit cap.s 0..n-1 in sequence until a theft succeeds. We could
116 start at a random place instead of 0 as well. */
117 for ( i=0 ; i < n_capabilities ; i++ ) {
118 robbed = &capabilities[i];
119 if (cap == robbed) // ourselves...
122 if (emptySparkPoolCap(robbed)) // nothing to steal here
125 spark = tryStealSpark(robbed);
126 if (spark == NULL && !emptySparkPoolCap(robbed)) {
127 // we conflicted with another thread while trying to steal;
133 cap->sparks_converted++;
135 traceEventStealSpark(cap, cap->r.rCurrentTSO, robbed->no);
139 // otherwise: no success, try next one
143 debugTrace(DEBUG_sched, "No sparks stolen");
147 // Returns True if any spark pool is non-empty at this moment in time
148 // The result is only valid for an instant, of course, so in a sense
149 // is immediately invalid, and should not be relied upon for
156 for (i=0; i < n_capabilities; i++) {
157 if (!emptySparkPoolCap(&capabilities[i])) {
165 /* -----------------------------------------------------------------------------
166 * Manage the returning_tasks lists.
168 * These functions require cap->lock
169 * -------------------------------------------------------------------------- */
171 #if defined(THREADED_RTS)
173 newReturningTask (Capability *cap, Task *task)
175 ASSERT_LOCK_HELD(&cap->lock);
176 ASSERT(task->next == NULL);
177 if (cap->returning_tasks_hd) {
178 ASSERT(cap->returning_tasks_tl->next == NULL);
179 cap->returning_tasks_tl->next = task;
181 cap->returning_tasks_hd = task;
183 cap->returning_tasks_tl = task;
187 popReturningTask (Capability *cap)
189 ASSERT_LOCK_HELD(&cap->lock);
191 task = cap->returning_tasks_hd;
193 cap->returning_tasks_hd = task->next;
194 if (!cap->returning_tasks_hd) {
195 cap->returning_tasks_tl = NULL;
202 /* ----------------------------------------------------------------------------
205 * The Capability is initially marked not free.
206 * ------------------------------------------------------------------------- */
209 initCapability( Capability *cap, nat i )
214 cap->in_haskell = rtsFalse;
216 cap->run_queue_hd = END_TSO_QUEUE;
217 cap->run_queue_tl = END_TSO_QUEUE;
219 #if defined(THREADED_RTS)
220 initMutex(&cap->lock);
221 cap->running_task = NULL; // indicates cap is free
222 cap->spare_workers = NULL;
223 cap->suspended_ccalls = NULL;
224 cap->returning_tasks_hd = NULL;
225 cap->returning_tasks_tl = NULL;
226 cap->inbox = (Message*)END_TSO_QUEUE;
227 cap->sparks_created = 0;
228 cap->sparks_converted = 0;
229 cap->sparks_pruned = 0;
232 cap->f.stgEagerBlackholeInfo = (W_)&__stg_EAGER_BLACKHOLE_info;
233 cap->f.stgGCEnter1 = (StgFunPtr)__stg_gc_enter_1;
234 cap->f.stgGCFun = (StgFunPtr)__stg_gc_fun;
236 cap->mut_lists = stgMallocBytes(sizeof(bdescr *) *
237 RtsFlags.GcFlags.generations,
239 cap->saved_mut_lists = stgMallocBytes(sizeof(bdescr *) *
240 RtsFlags.GcFlags.generations,
243 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
244 cap->mut_lists[g] = NULL;
247 cap->free_tvar_watch_queues = END_STM_WATCH_QUEUE;
248 cap->free_invariant_check_queues = END_INVARIANT_CHECK_QUEUE;
249 cap->free_trec_chunks = END_STM_CHUNK_LIST;
250 cap->free_trec_headers = NO_TREC;
251 cap->transaction_tokens = 0;
252 cap->context_switch = 0;
253 cap->pinned_object_block = NULL;
256 /* ---------------------------------------------------------------------------
257 * Function: initCapabilities()
259 * Purpose: set up the Capability handling. For the THREADED_RTS build,
260 * we keep a table of them, the size of which is
261 * controlled by the user via the RTS flag -N.
263 * ------------------------------------------------------------------------- */
265 initCapabilities( void )
267 #if defined(THREADED_RTS)
271 // We can't support multiple CPUs if BaseReg is not a register
272 if (RtsFlags.ParFlags.nNodes > 1) {
273 errorBelch("warning: multiple CPUs not supported in this build, reverting to 1");
274 RtsFlags.ParFlags.nNodes = 1;
278 n_capabilities = RtsFlags.ParFlags.nNodes;
280 if (n_capabilities == 1) {
281 capabilities = &MainCapability;
282 // THREADED_RTS must work on builds that don't have a mutable
283 // BaseReg (eg. unregisterised), so in this case
284 // capabilities[0] must coincide with &MainCapability.
286 capabilities = stgMallocBytes(n_capabilities * sizeof(Capability),
290 for (i = 0; i < n_capabilities; i++) {
291 initCapability(&capabilities[i], i);
294 debugTrace(DEBUG_sched, "allocated %d capabilities", n_capabilities);
296 #else /* !THREADED_RTS */
299 capabilities = &MainCapability;
300 initCapability(&MainCapability, 0);
304 // There are no free capabilities to begin with. We will start
305 // a worker Task to each Capability, which will quickly put the
306 // Capability on the free list when it finds nothing to do.
307 last_free_capability = &capabilities[0];
310 /* ----------------------------------------------------------------------------
311 * setContextSwitches: cause all capabilities to context switch as
313 * ------------------------------------------------------------------------- */
315 void setContextSwitches(void)
318 for (i=0; i < n_capabilities; i++) {
319 contextSwitchCapability(&capabilities[i]);
323 /* ----------------------------------------------------------------------------
324 * Give a Capability to a Task. The task must currently be sleeping
325 * on its condition variable.
327 * Requires cap->lock (modifies cap->running_task).
329 * When migrating a Task, the migrater must take task->lock before
330 * modifying task->cap, to synchronise with the waking up Task.
331 * Additionally, the migrater should own the Capability (when
332 * migrating the run queue), or cap->lock (when migrating
333 * returning_workers).
335 * ------------------------------------------------------------------------- */
337 #if defined(THREADED_RTS)
339 giveCapabilityToTask (Capability *cap USED_IF_DEBUG, Task *task)
341 ASSERT_LOCK_HELD(&cap->lock);
342 ASSERT(task->cap == cap);
343 debugTrace(DEBUG_sched, "passing capability %d to %s %p",
344 cap->no, task->incall->tso ? "bound task" : "worker",
346 ACQUIRE_LOCK(&task->lock);
347 task->wakeup = rtsTrue;
348 // the wakeup flag is needed because signalCondition() doesn't
349 // flag the condition if the thread is already runniing, but we want
351 signalCondition(&task->cond);
352 RELEASE_LOCK(&task->lock);
356 /* ----------------------------------------------------------------------------
357 * Function: releaseCapability(Capability*)
359 * Purpose: Letting go of a capability. Causes a
360 * 'returning worker' thread or a 'waiting worker'
361 * to wake up, in that order.
362 * ------------------------------------------------------------------------- */
364 #if defined(THREADED_RTS)
366 releaseCapability_ (Capability* cap,
367 rtsBool always_wakeup)
371 task = cap->running_task;
373 ASSERT_PARTIAL_CAPABILITY_INVARIANTS(cap,task);
375 cap->running_task = NULL;
377 // Check to see whether a worker thread can be given
378 // the go-ahead to return the result of an external call..
379 if (cap->returning_tasks_hd != NULL) {
380 giveCapabilityToTask(cap,cap->returning_tasks_hd);
381 // The Task pops itself from the queue (see waitForReturnCapability())
385 if (waiting_for_gc == PENDING_GC_SEQ) {
386 last_free_capability = cap; // needed?
387 debugTrace(DEBUG_sched, "GC pending, set capability %d free", cap->no);
392 // If the next thread on the run queue is a bound thread,
393 // give this Capability to the appropriate Task.
394 if (!emptyRunQueue(cap) && cap->run_queue_hd->bound) {
395 // Make sure we're not about to try to wake ourselves up
396 // ASSERT(task != cap->run_queue_hd->bound);
397 // assertion is false: in schedule() we force a yield after
398 // ThreadBlocked, but the thread may be back on the run queue
400 task = cap->run_queue_hd->bound->task;
401 giveCapabilityToTask(cap,task);
405 if (!cap->spare_workers) {
406 // Create a worker thread if we don't have one. If the system
407 // is interrupted, we only create a worker task if there
408 // are threads that need to be completed. If the system is
409 // shutting down, we never create a new worker.
410 if (sched_state < SCHED_SHUTTING_DOWN || !emptyRunQueue(cap)) {
411 debugTrace(DEBUG_sched,
412 "starting new worker on capability %d", cap->no);
413 startWorkerTask(cap);
418 // If we have an unbound thread on the run queue, or if there's
419 // anything else to do, give the Capability to a worker thread.
421 !emptyRunQueue(cap) || !emptyInbox(cap) ||
422 !emptySparkPoolCap(cap) || globalWorkToDo()) {
423 if (cap->spare_workers) {
424 giveCapabilityToTask(cap,cap->spare_workers);
425 // The worker Task pops itself from the queue;
430 last_free_capability = cap;
431 debugTrace(DEBUG_sched, "freeing capability %d", cap->no);
435 releaseCapability (Capability* cap USED_IF_THREADS)
437 ACQUIRE_LOCK(&cap->lock);
438 releaseCapability_(cap, rtsFalse);
439 RELEASE_LOCK(&cap->lock);
443 releaseAndWakeupCapability (Capability* cap USED_IF_THREADS)
445 ACQUIRE_LOCK(&cap->lock);
446 releaseCapability_(cap, rtsTrue);
447 RELEASE_LOCK(&cap->lock);
451 releaseCapabilityAndQueueWorker (Capability* cap USED_IF_THREADS)
455 ACQUIRE_LOCK(&cap->lock);
457 task = cap->running_task;
459 // If the current task is a worker, save it on the spare_workers
460 // list of this Capability. A worker can mark itself as stopped,
461 // in which case it is not replaced on the spare_worker queue.
462 // This happens when the system is shutting down (see
463 // Schedule.c:workerStart()).
464 if (!isBoundTask(task) && !task->stopped) {
465 task->next = cap->spare_workers;
466 cap->spare_workers = task;
468 // Bound tasks just float around attached to their TSOs.
470 releaseCapability_(cap,rtsFalse);
472 RELEASE_LOCK(&cap->lock);
476 /* ----------------------------------------------------------------------------
477 * waitForReturnCapability( Task *task )
479 * Purpose: when an OS thread returns from an external call,
480 * it calls waitForReturnCapability() (via Schedule.resumeThread())
481 * to wait for permission to enter the RTS & communicate the
482 * result of the external call back to the Haskell thread that
485 * ------------------------------------------------------------------------- */
487 waitForReturnCapability (Capability **pCap, Task *task)
489 #if !defined(THREADED_RTS)
491 MainCapability.running_task = task;
492 task->cap = &MainCapability;
493 *pCap = &MainCapability;
496 Capability *cap = *pCap;
499 // Try last_free_capability first
500 cap = last_free_capability;
501 if (cap->running_task) {
503 // otherwise, search for a free capability
505 for (i = 0; i < n_capabilities; i++) {
506 if (!capabilities[i].running_task) {
507 cap = &capabilities[i];
512 // Can't find a free one, use last_free_capability.
513 cap = last_free_capability;
517 // record the Capability as the one this Task is now assocated with.
521 ASSERT(task->cap == cap);
524 ACQUIRE_LOCK(&cap->lock);
526 debugTrace(DEBUG_sched, "returning; I want capability %d", cap->no);
528 if (!cap->running_task) {
529 // It's free; just grab it
530 cap->running_task = task;
531 RELEASE_LOCK(&cap->lock);
533 newReturningTask(cap,task);
534 RELEASE_LOCK(&cap->lock);
537 ACQUIRE_LOCK(&task->lock);
538 // task->lock held, cap->lock not held
539 if (!task->wakeup) waitCondition(&task->cond, &task->lock);
541 task->wakeup = rtsFalse;
542 RELEASE_LOCK(&task->lock);
544 // now check whether we should wake up...
545 ACQUIRE_LOCK(&cap->lock);
546 if (cap->running_task == NULL) {
547 if (cap->returning_tasks_hd != task) {
548 giveCapabilityToTask(cap,cap->returning_tasks_hd);
549 RELEASE_LOCK(&cap->lock);
552 cap->running_task = task;
553 popReturningTask(cap);
554 RELEASE_LOCK(&cap->lock);
557 RELEASE_LOCK(&cap->lock);
562 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
564 debugTrace(DEBUG_sched, "resuming capability %d", cap->no);
570 #if defined(THREADED_RTS)
571 /* ----------------------------------------------------------------------------
573 * ------------------------------------------------------------------------- */
576 yieldCapability (Capability** pCap, Task *task)
578 Capability *cap = *pCap;
580 if (waiting_for_gc == PENDING_GC_PAR) {
581 traceEventGcStart(cap);
583 traceEventGcEnd(cap);
587 debugTrace(DEBUG_sched, "giving up capability %d", cap->no);
589 // We must now release the capability and wait to be woken up
591 task->wakeup = rtsFalse;
592 releaseCapabilityAndQueueWorker(cap);
595 ACQUIRE_LOCK(&task->lock);
596 // task->lock held, cap->lock not held
597 if (!task->wakeup) waitCondition(&task->cond, &task->lock);
599 task->wakeup = rtsFalse;
600 RELEASE_LOCK(&task->lock);
602 debugTrace(DEBUG_sched, "woken up on capability %d", cap->no);
604 ACQUIRE_LOCK(&cap->lock);
605 if (cap->running_task != NULL) {
606 debugTrace(DEBUG_sched,
607 "capability %d is owned by another task", cap->no);
608 RELEASE_LOCK(&cap->lock);
612 if (task->incall->tso == NULL) {
613 ASSERT(cap->spare_workers != NULL);
614 // if we're not at the front of the queue, release it
615 // again. This is unlikely to happen.
616 if (cap->spare_workers != task) {
617 giveCapabilityToTask(cap,cap->spare_workers);
618 RELEASE_LOCK(&cap->lock);
621 cap->spare_workers = task->next;
624 cap->running_task = task;
625 RELEASE_LOCK(&cap->lock);
629 debugTrace(DEBUG_sched, "resuming capability %d", cap->no);
630 ASSERT(cap->running_task == task);
634 ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
639 /* ----------------------------------------------------------------------------
640 * Wake up a thread on a Capability.
642 * This is used when the current Task is running on a Capability and
643 * wishes to wake up a thread on a different Capability.
644 * ------------------------------------------------------------------------- */
647 wakeupThreadOnCapability (Capability *cap,
648 Capability *other_cap,
653 // ASSUMES: cap->lock is held (asserted in wakeupThreadOnCapability)
655 ASSERT(tso->bound->task->cap == tso->cap);
656 tso->bound->task->cap = other_cap;
658 tso->cap = other_cap;
660 ASSERT(tso->why_blocked != BlockedOnMsgWakeup ||
661 tso->block_info.closure->header.info == &stg_IND_info);
663 ASSERT(tso->block_info.closure->header.info != &stg_MSG_WAKEUP_info);
665 msg = (MessageWakeup*) allocate(cap, sizeofW(MessageWakeup));
666 msg->header.info = &stg_MSG_WAKEUP_info;
668 tso->block_info.closure = (StgClosure *)msg;
671 tso->why_blocked = BlockedOnMsgWakeup;
673 sendMessage(other_cap, (Message*)msg);
676 /* ----------------------------------------------------------------------------
679 * If a Capability is currently idle, wake up a Task on it. Used to
680 * get every Capability into the GC.
681 * ------------------------------------------------------------------------- */
684 prodCapability (Capability *cap, Task *task)
686 ACQUIRE_LOCK(&cap->lock);
687 if (!cap->running_task) {
688 cap->running_task = task;
689 releaseCapability_(cap,rtsTrue);
691 RELEASE_LOCK(&cap->lock);
694 /* ----------------------------------------------------------------------------
697 * At shutdown time, we want to let everything exit as cleanly as
698 * possible. For each capability, we let its run queue drain, and
699 * allow the workers to stop.
701 * This function should be called when interrupted and
702 * shutting_down_scheduler = rtsTrue, thus any worker that wakes up
703 * will exit the scheduler and call taskStop(), and any bound thread
704 * that wakes up will return to its caller. Runnable threads are
707 * ------------------------------------------------------------------------- */
710 shutdownCapability (Capability *cap, Task *task, rtsBool safe)
716 // Loop indefinitely until all the workers have exited and there
717 // are no Haskell threads left. We used to bail out after 50
718 // iterations of this loop, but that occasionally left a worker
719 // running which caused problems later (the closeMutex() below
720 // isn't safe, for one thing).
722 for (i = 0; /* i < 50 */; i++) {
723 ASSERT(sched_state == SCHED_SHUTTING_DOWN);
725 debugTrace(DEBUG_sched,
726 "shutting down capability %d, attempt %d", cap->no, i);
727 ACQUIRE_LOCK(&cap->lock);
728 if (cap->running_task) {
729 RELEASE_LOCK(&cap->lock);
730 debugTrace(DEBUG_sched, "not owner, yielding");
734 cap->running_task = task;
736 if (cap->spare_workers) {
737 // Look for workers that have died without removing
738 // themselves from the list; this could happen if the OS
739 // summarily killed the thread, for example. This
740 // actually happens on Windows when the system is
741 // terminating the program, and the RTS is running in a
745 for (t = cap->spare_workers; t != NULL; t = t->next) {
746 if (!osThreadIsAlive(t->id)) {
747 debugTrace(DEBUG_sched,
748 "worker thread %p has died unexpectedly", (void *)t->id);
750 cap->spare_workers = t->next;
752 prev->next = t->next;
759 if (!emptyRunQueue(cap) || cap->spare_workers) {
760 debugTrace(DEBUG_sched,
761 "runnable threads or workers still alive, yielding");
762 releaseCapability_(cap,rtsFalse); // this will wake up a worker
763 RELEASE_LOCK(&cap->lock);
768 // If "safe", then busy-wait for any threads currently doing
769 // foreign calls. If we're about to unload this DLL, for
770 // example, we need to be sure that there are no OS threads
771 // that will try to return to code that has been unloaded.
772 // We can be a bit more relaxed when this is a standalone
773 // program that is about to terminate, and let safe=false.
774 if (cap->suspended_ccalls && safe) {
775 debugTrace(DEBUG_sched,
776 "thread(s) are involved in foreign calls, yielding");
777 cap->running_task = NULL;
778 RELEASE_LOCK(&cap->lock);
779 // The IO manager thread might have been slow to start up,
780 // so the first attempt to kill it might not have
781 // succeeded. Just in case, try again - the kill message
782 // will only be sent once.
784 // To reproduce this deadlock: run ffi002(threaded1)
785 // repeatedly on a loaded machine.
791 traceEventShutdown(cap);
792 RELEASE_LOCK(&cap->lock);
795 // we now have the Capability, its run queue and spare workers
796 // list are both empty.
798 // ToDo: we can't drop this mutex, because there might still be
799 // threads performing foreign calls that will eventually try to
800 // return via resumeThread() and attempt to grab cap->lock.
801 // closeMutex(&cap->lock);
804 /* ----------------------------------------------------------------------------
807 * Attempt to gain control of a Capability if it is free.
809 * ------------------------------------------------------------------------- */
812 tryGrabCapability (Capability *cap, Task *task)
814 if (cap->running_task != NULL) return rtsFalse;
815 ACQUIRE_LOCK(&cap->lock);
816 if (cap->running_task != NULL) {
817 RELEASE_LOCK(&cap->lock);
821 cap->running_task = task;
822 RELEASE_LOCK(&cap->lock);
827 #endif /* THREADED_RTS */
830 freeCapability (Capability *cap)
832 stgFree(cap->mut_lists);
833 stgFree(cap->saved_mut_lists);
834 #if defined(THREADED_RTS)
835 freeSparkPool(cap->sparks);
840 freeCapabilities (void)
842 #if defined(THREADED_RTS)
844 for (i=0; i < n_capabilities; i++) {
845 freeCapability(&capabilities[i]);
848 freeCapability(&MainCapability);
852 /* ---------------------------------------------------------------------------
853 Mark everything directly reachable from the Capabilities. When
854 using multiple GC threads, each GC thread marks all Capabilities
855 for which (c `mod` n == 0), for Capability c and thread n.
856 ------------------------------------------------------------------------ */
859 markSomeCapabilities (evac_fn evac, void *user, nat i0, nat delta,
860 rtsBool prune_sparks USED_IF_THREADS)
866 // Each GC thread is responsible for following roots from the
867 // Capability of the same number. There will usually be the same
868 // or fewer Capabilities as GC threads, but just in case there
869 // are more, we mark every Capability whose number is the GC
870 // thread's index plus a multiple of the number of GC threads.
871 for (i = i0; i < n_capabilities; i += delta) {
872 cap = &capabilities[i];
873 evac(user, (StgClosure **)(void *)&cap->run_queue_hd);
874 evac(user, (StgClosure **)(void *)&cap->run_queue_tl);
875 #if defined(THREADED_RTS)
876 evac(user, (StgClosure **)(void *)&cap->inbox);
878 for (incall = cap->suspended_ccalls; incall != NULL;
879 incall=incall->next) {
880 evac(user, (StgClosure **)(void *)&incall->suspended_tso);
883 #if defined(THREADED_RTS)
885 pruneSparkQueue (evac, user, cap);
887 traverseSparkQueue (evac, user, cap);
892 #if !defined(THREADED_RTS)
893 evac(user, (StgClosure **)(void *)&blocked_queue_hd);
894 evac(user, (StgClosure **)(void *)&blocked_queue_tl);
895 evac(user, (StgClosure **)(void *)&sleeping_queue);
900 markCapabilities (evac_fn evac, void *user)
902 markSomeCapabilities(evac, user, 0, 1, rtsFalse);
905 /* -----------------------------------------------------------------------------
907 -------------------------------------------------------------------------- */
911 void sendMessage(Capability *cap, Message *msg)
913 ACQUIRE_LOCK(&cap->lock);
915 msg->link = cap->inbox;
918 if (cap->running_task == NULL) {
919 cap->running_task = myTask();
920 // precond for releaseCapability_()
921 releaseCapability_(cap,rtsFalse);
923 contextSwitchCapability(cap);
926 RELEASE_LOCK(&cap->lock);
929 #endif // THREADED_RTS