/* --------------------------------------------------------------------------- * * (c) The GHC Team, 1998-2006 * * The scheduler and thread-related functionality * * --------------------------------------------------------------------------*/ #include "PosixSource.h" #define KEEP_LOCKCLOSURE #include "Rts.h" #include "SchedAPI.h" #include "RtsUtils.h" #include "RtsFlags.h" #include "OSThreads.h" #include "Storage.h" #include "StgRun.h" #include "Hooks.h" #include "Schedule.h" #include "StgMiscClosures.h" #include "Interpreter.h" #include "Printer.h" #include "RtsSignals.h" #include "Sanity.h" #include "Stats.h" #include "STM.h" #include "Timer.h" #include "Prelude.h" #include "ThreadLabels.h" #include "LdvProfile.h" #include "Updates.h" #include "Proftimer.h" #include "ProfHeap.h" #if defined(GRAN) || defined(PARALLEL_HASKELL) # include "GranSimRts.h" # include "GranSim.h" # include "ParallelRts.h" # include "Parallel.h" # include "ParallelDebug.h" # include "FetchMe.h" # include "HLC.h" #endif #include "Sparks.h" #include "Capability.h" #include "Task.h" #include "AwaitEvent.h" #if defined(mingw32_HOST_OS) #include "win32/IOManager.h" #endif #include "Trace.h" #include "RaiseAsync.h" #include "Threads.h" #include "ThrIOManager.h" #ifdef HAVE_SYS_TYPES_H #include #endif #ifdef HAVE_UNISTD_H #include #endif #include #include #include #ifdef HAVE_ERRNO_H #include #endif // Turn off inlining when debugging - it obfuscates things #ifdef DEBUG # undef STATIC_INLINE # define STATIC_INLINE static #endif /* ----------------------------------------------------------------------------- * Global variables * -------------------------------------------------------------------------- */ #if defined(GRAN) StgTSO* ActiveTSO = NULL; /* for assigning system costs; GranSim-Light only */ /* rtsTime TimeOfNextEvent, EndOfTimeSlice; now in GranSim.c */ /* In GranSim we have a runnable and a blocked queue for each processor. In order to minimise code changes new arrays run_queue_hds/tls are created. run_queue_hd is then a short cut (macro) for run_queue_hds[CurrentProc] (see GranSim.h). -- HWL */ StgTSO *run_queue_hds[MAX_PROC], *run_queue_tls[MAX_PROC]; StgTSO *blocked_queue_hds[MAX_PROC], *blocked_queue_tls[MAX_PROC]; StgTSO *ccalling_threadss[MAX_PROC]; /* We use the same global list of threads (all_threads) in GranSim as in the std RTS (i.e. we are cheating). However, we don't use this list in the GranSim specific code at the moment (so we are only potentially cheating). */ #else /* !GRAN */ #if !defined(THREADED_RTS) // Blocked/sleeping thrads StgTSO *blocked_queue_hd = NULL; StgTSO *blocked_queue_tl = NULL; StgTSO *sleeping_queue = NULL; // perhaps replace with a hash table? #endif /* Threads blocked on blackholes. * LOCK: sched_mutex+capability, or all capabilities */ StgTSO *blackhole_queue = NULL; #endif /* The blackhole_queue should be checked for threads to wake up. See * Schedule.h for more thorough comment. * LOCK: none (doesn't matter if we miss an update) */ rtsBool blackholes_need_checking = rtsFalse; /* flag set by signal handler to precipitate a context switch * LOCK: none (just an advisory flag) */ int context_switch = 0; /* flag that tracks whether we have done any execution in this time slice. * LOCK: currently none, perhaps we should lock (but needs to be * updated in the fast path of the scheduler). */ nat recent_activity = ACTIVITY_YES; /* if this flag is set as well, give up execution * LOCK: none (changes once, from false->true) */ rtsBool sched_state = SCHED_RUNNING; #if defined(GRAN) StgTSO *CurrentTSO; #endif /* This is used in `TSO.h' and gcc 2.96 insists that this variable actually * exists - earlier gccs apparently didn't. * -= chak */ StgTSO dummy_tso; /* * Set to TRUE when entering a shutdown state (via shutdownHaskellAndExit()) -- * in an MT setting, needed to signal that a worker thread shouldn't hang around * in the scheduler when it is out of work. */ rtsBool shutting_down_scheduler = rtsFalse; /* * This mutex protects most of the global scheduler data in * the THREADED_RTS runtime. */ #if defined(THREADED_RTS) Mutex sched_mutex; #endif #if defined(PARALLEL_HASKELL) StgTSO *LastTSO; rtsTime TimeOfLastYield; rtsBool emitSchedule = rtsTrue; #endif #if !defined(mingw32_HOST_OS) #define FORKPROCESS_PRIMOP_SUPPORTED #endif /* ----------------------------------------------------------------------------- * static function prototypes * -------------------------------------------------------------------------- */ static Capability *schedule (Capability *initialCapability, Task *task); // // These function all encapsulate parts of the scheduler loop, and are // abstracted only to make the structure and control flow of the // scheduler clearer. // static void schedulePreLoop (void); #if defined(THREADED_RTS) static void schedulePushWork(Capability *cap, Task *task); #endif static void scheduleStartSignalHandlers (Capability *cap); static void scheduleCheckBlockedThreads (Capability *cap); static void scheduleCheckWakeupThreads(Capability *cap USED_IF_NOT_THREADS); static void scheduleCheckBlackHoles (Capability *cap); static void scheduleDetectDeadlock (Capability *cap, Task *task); #if defined(GRAN) static StgTSO *scheduleProcessEvent(rtsEvent *event); #endif #if defined(PARALLEL_HASKELL) static StgTSO *scheduleSendPendingMessages(void); static void scheduleActivateSpark(void); static rtsBool scheduleGetRemoteWork(rtsBool *receivedFinish); #endif #if defined(PAR) || defined(GRAN) static void scheduleGranParReport(void); #endif static void schedulePostRunThread(StgTSO *t); static rtsBool scheduleHandleHeapOverflow( Capability *cap, StgTSO *t ); static void scheduleHandleStackOverflow( Capability *cap, Task *task, StgTSO *t); static rtsBool scheduleHandleYield( Capability *cap, StgTSO *t, nat prev_what_next ); static void scheduleHandleThreadBlocked( StgTSO *t ); static rtsBool scheduleHandleThreadFinished( Capability *cap, Task *task, StgTSO *t ); static rtsBool scheduleNeedHeapProfile(rtsBool ready_to_gc); static Capability *scheduleDoGC(Capability *cap, Task *task, rtsBool force_major); static rtsBool checkBlackHoles(Capability *cap); static StgTSO *threadStackOverflow(Capability *cap, StgTSO *tso); static StgTSO *threadStackUnderflow(Task *task, StgTSO *tso); static void deleteThread (Capability *cap, StgTSO *tso); static void deleteAllThreads (Capability *cap); #ifdef FORKPROCESS_PRIMOP_SUPPORTED static void deleteThread_(Capability *cap, StgTSO *tso); #endif #if defined(PARALLEL_HASKELL) StgTSO * createSparkThread(rtsSpark spark); StgTSO * activateSpark (rtsSpark spark); #endif #ifdef DEBUG static char *whatNext_strs[] = { "(unknown)", "ThreadRunGHC", "ThreadInterpret", "ThreadKilled", "ThreadRelocated", "ThreadComplete" }; #endif /* ----------------------------------------------------------------------------- * Putting a thread on the run queue: different scheduling policies * -------------------------------------------------------------------------- */ STATIC_INLINE void addToRunQueue( Capability *cap, StgTSO *t ) { #if defined(PARALLEL_HASKELL) if (RtsFlags.ParFlags.doFairScheduling) { // this does round-robin scheduling; good for concurrency appendToRunQueue(cap,t); } else { // this does unfair scheduling; good for parallelism pushOnRunQueue(cap,t); } #else // this does round-robin scheduling; good for concurrency appendToRunQueue(cap,t); #endif } /* --------------------------------------------------------------------------- Main scheduling loop. We use round-robin scheduling, each thread returning to the scheduler loop when one of these conditions is detected: * out of heap space * timer expires (thread yields) * thread blocks * thread ends * stack overflow GRAN version: In a GranSim setup this loop iterates over the global event queue. This revolves around the global event queue, which determines what to do next. Therefore, it's more complicated than either the concurrent or the parallel (GUM) setup. GUM version: GUM iterates over incoming messages. It starts with nothing to do (thus CurrentTSO == END_TSO_QUEUE), and sends out a fish whenever it has nothing to do; in-between doing the actual reductions (shared code below) it processes the incoming messages and deals with delayed operations (see PendingFetches). This is not the ugliest code you could imagine, but it's bloody close. ------------------------------------------------------------------------ */ static Capability * schedule (Capability *initialCapability, Task *task) { StgTSO *t; Capability *cap; StgThreadReturnCode ret; #if defined(GRAN) rtsEvent *event; #elif defined(PARALLEL_HASKELL) StgTSO *tso; GlobalTaskId pe; rtsBool receivedFinish = rtsFalse; # if defined(DEBUG) nat tp_size, sp_size; // stats only # endif #endif nat prev_what_next; rtsBool ready_to_gc; #if defined(THREADED_RTS) rtsBool first = rtsTrue; #endif cap = initialCapability; // Pre-condition: this task owns initialCapability. // The sched_mutex is *NOT* held // NB. on return, we still hold a capability. debugTrace (DEBUG_sched, "### NEW SCHEDULER LOOP (task: %p, cap: %p)", task, initialCapability); schedulePreLoop(); // ----------------------------------------------------------- // Scheduler loop starts here: #if defined(PARALLEL_HASKELL) #define TERMINATION_CONDITION (!receivedFinish) #elif defined(GRAN) #define TERMINATION_CONDITION ((event = get_next_event()) != (rtsEvent*)NULL) #else #define TERMINATION_CONDITION rtsTrue #endif while (TERMINATION_CONDITION) { #if defined(GRAN) /* Choose the processor with the next event */ CurrentProc = event->proc; CurrentTSO = event->tso; #endif #if defined(THREADED_RTS) if (first) { // don't yield the first time, we want a chance to run this // thread for a bit, even if there are others banging at the // door. first = rtsFalse; ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task); } else { // Yield the capability to higher-priority tasks if necessary. yieldCapability(&cap, task); } #endif #if defined(THREADED_RTS) schedulePushWork(cap,task); #endif // Check whether we have re-entered the RTS from Haskell without // going via suspendThread()/resumeThread (i.e. a 'safe' foreign // call). if (cap->in_haskell) { errorBelch("schedule: re-entered unsafely.\n" " Perhaps a 'foreign import unsafe' should be 'safe'?"); stg_exit(EXIT_FAILURE); } // The interruption / shutdown sequence. // // In order to cleanly shut down the runtime, we want to: // * make sure that all main threads return to their callers // with the state 'Interrupted'. // * clean up all OS threads assocated with the runtime // * free all memory etc. // // So the sequence for ^C goes like this: // // * ^C handler sets sched_state := SCHED_INTERRUPTING and // arranges for some Capability to wake up // // * all threads in the system are halted, and the zombies are // placed on the run queue for cleaning up. We acquire all // the capabilities in order to delete the threads, this is // done by scheduleDoGC() for convenience (because GC already // needs to acquire all the capabilities). We can't kill // threads involved in foreign calls. // // * somebody calls shutdownHaskell(), which calls exitScheduler() // // * sched_state := SCHED_SHUTTING_DOWN // // * all workers exit when the run queue on their capability // drains. All main threads will also exit when their TSO // reaches the head of the run queue and they can return. // // * eventually all Capabilities will shut down, and the RTS can // exit. // // * We might be left with threads blocked in foreign calls, // we should really attempt to kill these somehow (TODO); switch (sched_state) { case SCHED_RUNNING: break; case SCHED_INTERRUPTING: debugTrace(DEBUG_sched, "SCHED_INTERRUPTING"); #if defined(THREADED_RTS) discardSparksCap(cap); #endif /* scheduleDoGC() deletes all the threads */ cap = scheduleDoGC(cap,task,rtsFalse); break; case SCHED_SHUTTING_DOWN: debugTrace(DEBUG_sched, "SCHED_SHUTTING_DOWN"); // If we are a worker, just exit. If we're a bound thread // then we will exit below when we've removed our TSO from // the run queue. if (task->tso == NULL && emptyRunQueue(cap)) { return cap; } break; default: barf("sched_state: %d", sched_state); } #if defined(THREADED_RTS) // If the run queue is empty, take a spark and turn it into a thread. { if (emptyRunQueue(cap)) { StgClosure *spark; spark = findSpark(cap); if (spark != NULL) { debugTrace(DEBUG_sched, "turning spark of closure %p into a thread", (StgClosure *)spark); createSparkThread(cap,spark); } } } #endif // THREADED_RTS scheduleStartSignalHandlers(cap); // Only check the black holes here if we've nothing else to do. // During normal execution, the black hole list only gets checked // at GC time, to avoid repeatedly traversing this possibly long // list each time around the scheduler. if (emptyRunQueue(cap)) { scheduleCheckBlackHoles(cap); } scheduleCheckWakeupThreads(cap); scheduleCheckBlockedThreads(cap); scheduleDetectDeadlock(cap,task); #if defined(THREADED_RTS) cap = task->cap; // reload cap, it might have changed #endif // Normally, the only way we can get here with no threads to // run is if a keyboard interrupt received during // scheduleCheckBlockedThreads() or scheduleDetectDeadlock(). // Additionally, it is not fatal for the // threaded RTS to reach here with no threads to run. // // win32: might be here due to awaitEvent() being abandoned // as a result of a console event having been delivered. if ( emptyRunQueue(cap) ) { #if !defined(THREADED_RTS) && !defined(mingw32_HOST_OS) ASSERT(sched_state >= SCHED_INTERRUPTING); #endif continue; // nothing to do } #if defined(PARALLEL_HASKELL) scheduleSendPendingMessages(); if (emptyRunQueue(cap) && scheduleActivateSpark()) continue; #if defined(SPARKS) ASSERT(next_fish_to_send_at==0); // i.e. no delayed fishes left! #endif /* If we still have no work we need to send a FISH to get a spark from another PE */ if (emptyRunQueue(cap)) { if (!scheduleGetRemoteWork(&receivedFinish)) continue; ASSERT(rtsFalse); // should not happen at the moment } // from here: non-empty run queue. // TODO: merge above case with this, only one call processMessages() ! if (PacketsWaiting()) { /* process incoming messages, if any pending... only in else because getRemoteWork waits for messages as well */ receivedFinish = processMessages(); } #endif #if defined(GRAN) scheduleProcessEvent(event); #endif // // Get a thread to run // t = popRunQueue(cap); #if defined(GRAN) || defined(PAR) scheduleGranParReport(); // some kind of debuging output #else // Sanity check the thread we're about to run. This can be // expensive if there is lots of thread switching going on... IF_DEBUG(sanity,checkTSO(t)); #endif #if defined(THREADED_RTS) // Check whether we can run this thread in the current task. // If not, we have to pass our capability to the right task. { Task *bound = t->bound; if (bound) { if (bound == task) { debugTrace(DEBUG_sched, "### Running thread %lu in bound thread", (unsigned long)t->id); // yes, the Haskell thread is bound to the current native thread } else { debugTrace(DEBUG_sched, "### thread %lu bound to another OS thread", (unsigned long)t->id); // no, bound to a different Haskell thread: pass to that thread pushOnRunQueue(cap,t); continue; } } else { // The thread we want to run is unbound. if (task->tso) { debugTrace(DEBUG_sched, "### this OS thread cannot run thread %lu", (unsigned long)t->id); // no, the current native thread is bound to a different // Haskell thread, so pass it to any worker thread pushOnRunQueue(cap,t); continue; } } } #endif /* context switches are initiated by the timer signal, unless * the user specified "context switch as often as possible", with * +RTS -C0 */ if (RtsFlags.ConcFlags.ctxtSwitchTicks == 0 && !emptyThreadQueues(cap)) { context_switch = 1; } run_thread: // CurrentTSO is the thread to run. t might be different if we // loop back to run_thread, so make sure to set CurrentTSO after // that. cap->r.rCurrentTSO = t; debugTrace(DEBUG_sched, "-->> running thread %ld %s ...", (long)t->id, whatNext_strs[t->what_next]); startHeapProfTimer(); // Check for exceptions blocked on this thread maybePerformBlockedException (cap, t); // ---------------------------------------------------------------------- // Run the current thread ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task); ASSERT(t->cap == cap); prev_what_next = t->what_next; errno = t->saved_errno; #if mingw32_HOST_OS SetLastError(t->saved_winerror); #endif cap->in_haskell = rtsTrue; dirty_TSO(cap,t); #if defined(THREADED_RTS) if (recent_activity == ACTIVITY_DONE_GC) { // ACTIVITY_DONE_GC means we turned off the timer signal to // conserve power (see #1623). Re-enable it here. nat prev; prev = xchg((P_)&recent_activity, ACTIVITY_YES); if (prev == ACTIVITY_DONE_GC) { startTimer(); } } else { recent_activity = ACTIVITY_YES; } #endif switch (prev_what_next) { case ThreadKilled: case ThreadComplete: /* Thread already finished, return to scheduler. */ ret = ThreadFinished; break; case ThreadRunGHC: { StgRegTable *r; r = StgRun((StgFunPtr) stg_returnToStackTop, &cap->r); cap = regTableToCapability(r); ret = r->rRet; break; } case ThreadInterpret: cap = interpretBCO(cap); ret = cap->r.rRet; break; default: barf("schedule: invalid what_next field"); } cap->in_haskell = rtsFalse; // The TSO might have moved, eg. if it re-entered the RTS and a GC // happened. So find the new location: t = cap->r.rCurrentTSO; // We have run some Haskell code: there might be blackhole-blocked // threads to wake up now. // Lock-free test here should be ok, we're just setting a flag. if ( blackhole_queue != END_TSO_QUEUE ) { blackholes_need_checking = rtsTrue; } // And save the current errno in this thread. // XXX: possibly bogus for SMP because this thread might already // be running again, see code below. t->saved_errno = errno; #if mingw32_HOST_OS // Similarly for Windows error code t->saved_winerror = GetLastError(); #endif #if defined(THREADED_RTS) // If ret is ThreadBlocked, and this Task is bound to the TSO that // blocked, we are in limbo - the TSO is now owned by whatever it // is blocked on, and may in fact already have been woken up, // perhaps even on a different Capability. It may be the case // that task->cap != cap. We better yield this Capability // immediately and return to normaility. if (ret == ThreadBlocked) { debugTrace(DEBUG_sched, "--<< thread %lu (%s) stopped: blocked", (unsigned long)t->id, whatNext_strs[t->what_next]); continue; } #endif ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task); ASSERT(t->cap == cap); // ---------------------------------------------------------------------- // Costs for the scheduler are assigned to CCS_SYSTEM stopHeapProfTimer(); #if defined(PROFILING) CCCS = CCS_SYSTEM; #endif schedulePostRunThread(t); t = threadStackUnderflow(task,t); ready_to_gc = rtsFalse; switch (ret) { case HeapOverflow: ready_to_gc = scheduleHandleHeapOverflow(cap,t); break; case StackOverflow: scheduleHandleStackOverflow(cap,task,t); break; case ThreadYielding: if (scheduleHandleYield(cap, t, prev_what_next)) { // shortcut for switching between compiler/interpreter: goto run_thread; } break; case ThreadBlocked: scheduleHandleThreadBlocked(t); break; case ThreadFinished: if (scheduleHandleThreadFinished(cap, task, t)) return cap; ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task); break; default: barf("schedule: invalid thread return code %d", (int)ret); } if (ready_to_gc || scheduleNeedHeapProfile(ready_to_gc)) { cap = scheduleDoGC(cap,task,rtsFalse); } } /* end of while() */ } /* ---------------------------------------------------------------------------- * Setting up the scheduler loop * ------------------------------------------------------------------------- */ static void schedulePreLoop(void) { #if defined(GRAN) /* set up first event to get things going */ /* ToDo: assign costs for system setup and init MainTSO ! */ new_event(CurrentProc, CurrentProc, CurrentTime[CurrentProc], ContinueThread, CurrentTSO, (StgClosure*)NULL, (rtsSpark*)NULL); debugTrace (DEBUG_gran, "GRAN: Init CurrentTSO (in schedule) = %p", CurrentTSO); IF_DEBUG(gran, G_TSO(CurrentTSO, 5)); if (RtsFlags.GranFlags.Light) { /* Save current time; GranSim Light only */ CurrentTSO->gran.clock = CurrentTime[CurrentProc]; } #endif } /* ----------------------------------------------------------------------------- * schedulePushWork() * * Push work to other Capabilities if we have some. * -------------------------------------------------------------------------- */ #if defined(THREADED_RTS) static void schedulePushWork(Capability *cap USED_IF_THREADS, Task *task USED_IF_THREADS) { Capability *free_caps[n_capabilities], *cap0; nat i, n_free_caps; // migration can be turned off with +RTS -qg if (!RtsFlags.ParFlags.migrate) return; // Check whether we have more threads on our run queue, or sparks // in our pool, that we could hand to another Capability. if ((emptyRunQueue(cap) || cap->run_queue_hd->_link == END_TSO_QUEUE) && sparkPoolSizeCap(cap) < 2) { return; } // First grab as many free Capabilities as we can. for (i=0, n_free_caps=0; i < n_capabilities; i++) { cap0 = &capabilities[i]; if (cap != cap0 && tryGrabCapability(cap0,task)) { if (!emptyRunQueue(cap0) || cap->returning_tasks_hd != NULL) { // it already has some work, we just grabbed it at // the wrong moment. Or maybe it's deadlocked! releaseCapability(cap0); } else { free_caps[n_free_caps++] = cap0; } } } // we now have n_free_caps free capabilities stashed in // free_caps[]. Share our run queue equally with them. This is // probably the simplest thing we could do; improvements we might // want to do include: // // - giving high priority to moving relatively new threads, on // the gournds that they haven't had time to build up a // working set in the cache on this CPU/Capability. // // - giving low priority to moving long-lived threads if (n_free_caps > 0) { StgTSO *prev, *t, *next; rtsBool pushed_to_all; debugTrace(DEBUG_sched, "excess threads on run queue and %d free capabilities, sharing...", n_free_caps); i = 0; pushed_to_all = rtsFalse; if (cap->run_queue_hd != END_TSO_QUEUE) { prev = cap->run_queue_hd; t = prev->_link; prev->_link = END_TSO_QUEUE; for (; t != END_TSO_QUEUE; t = next) { next = t->_link; t->_link = END_TSO_QUEUE; if (t->what_next == ThreadRelocated || t->bound == task // don't move my bound thread || tsoLocked(t)) { // don't move a locked thread setTSOLink(cap, prev, t); prev = t; } else if (i == n_free_caps) { pushed_to_all = rtsTrue; i = 0; // keep one for us setTSOLink(cap, prev, t); prev = t; } else { debugTrace(DEBUG_sched, "pushing thread %lu to capability %d", (unsigned long)t->id, free_caps[i]->no); appendToRunQueue(free_caps[i],t); if (t->bound) { t->bound->cap = free_caps[i]; } t->cap = free_caps[i]; i++; } } cap->run_queue_tl = prev; } // If there are some free capabilities that we didn't push any // threads to, then try to push a spark to each one. if (!pushed_to_all) { StgClosure *spark; // i is the next free capability to push to for (; i < n_free_caps; i++) { if (emptySparkPoolCap(free_caps[i])) { spark = findSpark(cap); if (spark != NULL) { debugTrace(DEBUG_sched, "pushing spark %p to capability %d", spark, free_caps[i]->no); newSpark(&(free_caps[i]->r), spark); } } } } // release the capabilities for (i = 0; i < n_free_caps; i++) { task->cap = free_caps[i]; releaseCapability(free_caps[i]); } } task->cap = cap; // reset to point to our Capability. } #endif /* ---------------------------------------------------------------------------- * Start any pending signal handlers * ------------------------------------------------------------------------- */ #if defined(RTS_USER_SIGNALS) && !defined(THREADED_RTS) static void scheduleStartSignalHandlers(Capability *cap) { if (RtsFlags.MiscFlags.install_signal_handlers && signals_pending()) { // safe outside the lock startSignalHandlers(cap); } } #else static void scheduleStartSignalHandlers(Capability *cap STG_UNUSED) { } #endif /* ---------------------------------------------------------------------------- * Check for blocked threads that can be woken up. * ------------------------------------------------------------------------- */ static void scheduleCheckBlockedThreads(Capability *cap USED_IF_NOT_THREADS) { #if !defined(THREADED_RTS) // // Check whether any waiting threads need to be woken up. If the // run queue is empty, and there are no other tasks running, we // can wait indefinitely for something to happen. // if ( !emptyQueue(blocked_queue_hd) || !emptyQueue(sleeping_queue) ) { awaitEvent( emptyRunQueue(cap) && !blackholes_need_checking ); } #endif } /* ---------------------------------------------------------------------------- * Check for threads woken up by other Capabilities * ------------------------------------------------------------------------- */ static void scheduleCheckWakeupThreads(Capability *cap USED_IF_THREADS) { #if defined(THREADED_RTS) // Any threads that were woken up by other Capabilities get // appended to our run queue. if (!emptyWakeupQueue(cap)) { ACQUIRE_LOCK(&cap->lock); if (emptyRunQueue(cap)) { cap->run_queue_hd = cap->wakeup_queue_hd; cap->run_queue_tl = cap->wakeup_queue_tl; } else { setTSOLink(cap, cap->run_queue_tl, cap->wakeup_queue_hd); cap->run_queue_tl = cap->wakeup_queue_tl; } cap->wakeup_queue_hd = cap->wakeup_queue_tl = END_TSO_QUEUE; RELEASE_LOCK(&cap->lock); } #endif } /* ---------------------------------------------------------------------------- * Check for threads blocked on BLACKHOLEs that can be woken up * ------------------------------------------------------------------------- */ static void scheduleCheckBlackHoles (Capability *cap) { if ( blackholes_need_checking ) // check without the lock first { ACQUIRE_LOCK(&sched_mutex); if ( blackholes_need_checking ) { checkBlackHoles(cap); blackholes_need_checking = rtsFalse; } RELEASE_LOCK(&sched_mutex); } } /* ---------------------------------------------------------------------------- * Detect deadlock conditions and attempt to resolve them. * ------------------------------------------------------------------------- */ static void scheduleDetectDeadlock (Capability *cap, Task *task) { #if defined(PARALLEL_HASKELL) // ToDo: add deadlock detection in GUM (similar to THREADED_RTS) -- HWL return; #endif /* * Detect deadlock: when we have no threads to run, there are no * threads blocked, waiting for I/O, or sleeping, and all the * other tasks are waiting for work, we must have a deadlock of * some description. */ if ( emptyThreadQueues(cap) ) { #if defined(THREADED_RTS) /* * In the threaded RTS, we only check for deadlock if there * has been no activity in a complete timeslice. This means * we won't eagerly start a full GC just because we don't have * any threads to run currently. */ if (recent_activity != ACTIVITY_INACTIVE) return; #endif debugTrace(DEBUG_sched, "deadlocked, forcing major GC..."); // Garbage collection can release some new threads due to // either (a) finalizers or (b) threads resurrected because // they are unreachable and will therefore be sent an // exception. Any threads thus released will be immediately // runnable. cap = scheduleDoGC (cap, task, rtsTrue/*force major GC*/); recent_activity = ACTIVITY_DONE_GC; // disable timer signals (see #1623) stopTimer(); if ( !emptyRunQueue(cap) ) return; #if defined(RTS_USER_SIGNALS) && !defined(THREADED_RTS) /* If we have user-installed signal handlers, then wait * for signals to arrive rather then bombing out with a * deadlock. */ if ( RtsFlags.MiscFlags.install_signal_handlers && anyUserHandlers() ) { debugTrace(DEBUG_sched, "still deadlocked, waiting for signals..."); awaitUserSignals(); if (signals_pending()) { startSignalHandlers(cap); } // either we have threads to run, or we were interrupted: ASSERT(!emptyRunQueue(cap) || sched_state >= SCHED_INTERRUPTING); return; } #endif #if !defined(THREADED_RTS) /* Probably a real deadlock. Send the current main thread the * Deadlock exception. */ if (task->tso) { switch (task->tso->why_blocked) { case BlockedOnSTM: case BlockedOnBlackHole: case BlockedOnException: case BlockedOnMVar: throwToSingleThreaded(cap, task->tso, (StgClosure *)nonTermination_closure); return; default: barf("deadlock: main thread blocked in a strange way"); } } return; #endif } } /* ---------------------------------------------------------------------------- * Process an event (GRAN only) * ------------------------------------------------------------------------- */ #if defined(GRAN) static StgTSO * scheduleProcessEvent(rtsEvent *event) { StgTSO *t; if (RtsFlags.GranFlags.Light) GranSimLight_enter_system(event, &ActiveTSO); // adjust ActiveTSO etc /* adjust time based on time-stamp */ if (event->time > CurrentTime[CurrentProc] && event->evttype != ContinueThread) CurrentTime[CurrentProc] = event->time; /* Deal with the idle PEs (may issue FindWork or MoveSpark events) */ if (!RtsFlags.GranFlags.Light) handleIdlePEs(); IF_DEBUG(gran, debugBelch("GRAN: switch by event-type\n")); /* main event dispatcher in GranSim */ switch (event->evttype) { /* Should just be continuing execution */ case ContinueThread: IF_DEBUG(gran, debugBelch("GRAN: doing ContinueThread\n")); /* ToDo: check assertion ASSERT(run_queue_hd != (StgTSO*)NULL && run_queue_hd != END_TSO_QUEUE); */ /* Ignore ContinueThreads for fetching threads (if synchr comm) */ if (!RtsFlags.GranFlags.DoAsyncFetch && procStatus[CurrentProc]==Fetching) { debugBelch("ghuH: Spurious ContinueThread while Fetching ignored; TSO %d (%p) [PE %d]\n", CurrentTSO->id, CurrentTSO, CurrentProc); goto next_thread; } /* Ignore ContinueThreads for completed threads */ if (CurrentTSO->what_next == ThreadComplete) { debugBelch("ghuH: found a ContinueThread event for completed thread %d (%p) [PE %d] (ignoring ContinueThread)\n", CurrentTSO->id, CurrentTSO, CurrentProc); goto next_thread; } /* Ignore ContinueThreads for threads that are being migrated */ if (PROCS(CurrentTSO)==Nowhere) { debugBelch("ghuH: trying to run the migrating TSO %d (%p) [PE %d] (ignoring ContinueThread)\n", CurrentTSO->id, CurrentTSO, CurrentProc); goto next_thread; } /* The thread should be at the beginning of the run queue */ if (CurrentTSO!=run_queue_hds[CurrentProc]) { debugBelch("ghuH: TSO %d (%p) [PE %d] is not at the start of the run_queue when doing a ContinueThread\n", CurrentTSO->id, CurrentTSO, CurrentProc); break; // run the thread anyway } /* new_event(proc, proc, CurrentTime[proc], FindWork, (StgTSO*)NULL, (StgClosure*)NULL, (rtsSpark*)NULL); goto next_thread; */ /* Catches superfluous CONTINUEs -- should be unnecessary */ break; // now actually run the thread; DaH Qu'vam yImuHbej case FetchNode: do_the_fetchnode(event); goto next_thread; /* handle next event in event queue */ case GlobalBlock: do_the_globalblock(event); goto next_thread; /* handle next event in event queue */ case FetchReply: do_the_fetchreply(event); goto next_thread; /* handle next event in event queue */ case UnblockThread: /* Move from the blocked queue to the tail of */ do_the_unblock(event); goto next_thread; /* handle next event in event queue */ case ResumeThread: /* Move from the blocked queue to the tail of */ /* the runnable queue ( i.e. Qu' SImqa'lu') */ event->tso->gran.blocktime += CurrentTime[CurrentProc] - event->tso->gran.blockedat; do_the_startthread(event); goto next_thread; /* handle next event in event queue */ case StartThread: do_the_startthread(event); goto next_thread; /* handle next event in event queue */ case MoveThread: do_the_movethread(event); goto next_thread; /* handle next event in event queue */ case MoveSpark: do_the_movespark(event); goto next_thread; /* handle next event in event queue */ case FindWork: do_the_findwork(event); goto next_thread; /* handle next event in event queue */ default: barf("Illegal event type %u\n", event->evttype); } /* switch */ /* This point was scheduler_loop in the old RTS */ IF_DEBUG(gran, debugBelch("GRAN: after main switch\n")); TimeOfLastEvent = CurrentTime[CurrentProc]; TimeOfNextEvent = get_time_of_next_event(); IgnoreEvents=(TimeOfNextEvent==0); // HWL HACK // CurrentTSO = ThreadQueueHd; IF_DEBUG(gran, debugBelch("GRAN: time of next event is: %ld\n", TimeOfNextEvent)); if (RtsFlags.GranFlags.Light) GranSimLight_leave_system(event, &ActiveTSO); EndOfTimeSlice = CurrentTime[CurrentProc]+RtsFlags.GranFlags.time_slice; IF_DEBUG(gran, debugBelch("GRAN: end of time-slice is %#lx\n", EndOfTimeSlice)); /* in a GranSim setup the TSO stays on the run queue */ t = CurrentTSO; /* Take a thread from the run queue. */ POP_RUN_QUEUE(t); // take_off_run_queue(t); IF_DEBUG(gran, debugBelch("GRAN: About to run current thread, which is\n"); G_TSO(t,5)); context_switch = 0; // turned on via GranYield, checking events and time slice IF_DEBUG(gran, DumpGranEvent(GR_SCHEDULE, t)); procStatus[CurrentProc] = Busy; } #endif // GRAN /* ---------------------------------------------------------------------------- * Send pending messages (PARALLEL_HASKELL only) * ------------------------------------------------------------------------- */ #if defined(PARALLEL_HASKELL) static StgTSO * scheduleSendPendingMessages(void) { StgSparkPool *pool; rtsSpark spark; StgTSO *t; # if defined(PAR) // global Mem.Mgmt., omit for now if (PendingFetches != END_BF_QUEUE) { processFetches(); } # endif if (RtsFlags.ParFlags.BufferTime) { // if we use message buffering, we must send away all message // packets which have become too old... sendOldBuffers(); } } #endif /* ---------------------------------------------------------------------------- * Activate spark threads (PARALLEL_HASKELL only) * ------------------------------------------------------------------------- */ #if defined(PARALLEL_HASKELL) static void scheduleActivateSpark(void) { #if defined(SPARKS) ASSERT(emptyRunQueue()); /* We get here if the run queue is empty and want some work. We try to turn a spark into a thread, and add it to the run queue, from where it will be picked up in the next iteration of the scheduler loop. */ /* :-[ no local threads => look out for local sparks */ /* the spark pool for the current PE */ pool = &(cap.r.rSparks); // JB: cap = (old) MainCap if (advisory_thread_count < RtsFlags.ParFlags.maxThreads && pool->hd < pool->tl) { /* * ToDo: add GC code check that we really have enough heap afterwards!! * Old comment: * If we're here (no runnable threads) and we have pending * sparks, we must have a space problem. Get enough space * to turn one of those pending sparks into a * thread... */ spark = findSpark(rtsFalse); /* get a spark */ if (spark != (rtsSpark) NULL) { tso = createThreadFromSpark(spark); /* turn the spark into a thread */ IF_PAR_DEBUG(fish, // schedule, debugBelch("==== schedule: Created TSO %d (%p); %d threads active\n", tso->id, tso, advisory_thread_count)); if (tso==END_TSO_QUEUE) { /* failed to activate spark->back to loop */ IF_PAR_DEBUG(fish, // schedule, debugBelch("==^^ failed to create thread from spark @ %lx\n", spark)); return rtsFalse; /* failed to generate a thread */ } /* otherwise fall through & pick-up new tso */ } else { IF_PAR_DEBUG(fish, // schedule, debugBelch("==^^ no local sparks (spark pool contains only NFs: %d)\n", spark_queue_len(pool))); return rtsFalse; /* failed to generate a thread */ } return rtsTrue; /* success in generating a thread */ } else { /* no more threads permitted or pool empty */ return rtsFalse; /* failed to generateThread */ } #else tso = NULL; // avoid compiler warning only return rtsFalse; /* dummy in non-PAR setup */ #endif // SPARKS } #endif // PARALLEL_HASKELL /* ---------------------------------------------------------------------------- * Get work from a remote node (PARALLEL_HASKELL only) * ------------------------------------------------------------------------- */ #if defined(PARALLEL_HASKELL) static rtsBool scheduleGetRemoteWork(rtsBool *receivedFinish) { ASSERT(emptyRunQueue()); if (RtsFlags.ParFlags.BufferTime) { IF_PAR_DEBUG(verbose, debugBelch("...send all pending data,")); { nat i; for (i=1; i<=nPEs; i++) sendImmediately(i); // send all messages away immediately } } # ifndef SPARKS //++EDEN++ idle() , i.e. send all buffers, wait for work // suppress fishing in EDEN... just look for incoming messages // (blocking receive) IF_PAR_DEBUG(verbose, debugBelch("...wait for incoming messages...\n")); *receivedFinish = processMessages(); // blocking receive... // and reenter scheduling loop after having received something // (return rtsFalse below) # else /* activate SPARKS machinery */ /* We get here, if we have no work, tried to activate a local spark, but still have no work. We try to get a remote spark, by sending a FISH message. Thread migration should be added here, and triggered when a sequence of fishes returns without work. */ delay = (RtsFlags.ParFlags.fishDelay!=0ll ? RtsFlags.ParFlags.fishDelay : 0ll); /* =8-[ no local sparks => look for work on other PEs */ /* * We really have absolutely no work. Send out a fish * (there may be some out there already), and wait for * something to arrive. We clearly can't run any threads * until a SCHEDULE or RESUME arrives, and so that's what * we're hoping to see. (Of course, we still have to * respond to other types of messages.) */ rtsTime now = msTime() /*CURRENT_TIME*/; IF_PAR_DEBUG(verbose, debugBelch("-- now=%ld\n", now)); IF_PAR_DEBUG(fish, // verbose, if (outstandingFishes < RtsFlags.ParFlags.maxFishes && (last_fish_arrived_at!=0 && last_fish_arrived_at+delay > now)) { debugBelch("--$$ <%llu> delaying FISH until %llu (last fish %llu, delay %llu)\n", now, last_fish_arrived_at+delay, last_fish_arrived_at, delay); }); if (outstandingFishes < RtsFlags.ParFlags.maxFishes && advisory_thread_count < RtsFlags.ParFlags.maxThreads) { // send a FISH, but when? if (last_fish_arrived_at==0 || (last_fish_arrived_at+delay <= now)) { // send FISH now! /* outstandingFishes is set in sendFish, processFish; avoid flooding system with fishes via delay */ next_fish_to_send_at = 0; } else { /* ToDo: this should be done in the main scheduling loop to avoid the busy wait here; not so bad if fish delay is very small */ int iq = 0; // DEBUGGING -- HWL next_fish_to_send_at = last_fish_arrived_at+delay; // remember when to send /* send a fish when ready, but process messages that arrive in the meantime */ do { if (PacketsWaiting()) { iq++; // DEBUGGING *receivedFinish = processMessages(); } now = msTime(); } while (!*receivedFinish || now sent delayed fish (%d processMessages); active/total threads=%d/%d\n",now,iq,run_queue_len(),advisory_thread_count)); } // JB: IMHO, this should all be hidden inside sendFish(...) /* pe = choosePE(); sendFish(pe, thisPE, NEW_FISH_AGE, NEW_FISH_HISTORY, NEW_FISH_HUNGER); // Global statistics: count no. of fishes if (RtsFlags.ParFlags.ParStats.Global && RtsFlags.GcFlags.giveStats > NO_GC_STATS) { globalParStats.tot_fish_mess++; } */ /* delayed fishes must have been sent by now! */ next_fish_to_send_at = 0; } *receivedFinish = processMessages(); # endif /* SPARKS */ return rtsFalse; /* NB: this function always returns rtsFalse, meaning the scheduler loop continues with the next iteration; rationale: return code means success in finding work; we enter this function if there is no local work, thus have to send a fish which takes time until it arrives with work; in the meantime we should process messages in the main loop; */ } #endif // PARALLEL_HASKELL /* ---------------------------------------------------------------------------- * PAR/GRAN: Report stats & debugging info(?) * ------------------------------------------------------------------------- */ #if defined(PAR) || defined(GRAN) static void scheduleGranParReport(void) { ASSERT(run_queue_hd != END_TSO_QUEUE); /* Take a thread from the run queue, if we have work */ POP_RUN_QUEUE(t); // take_off_run_queue(END_TSO_QUEUE); /* If this TSO has got its outport closed in the meantime, * it mustn't be run. Instead, we have to clean it up as if it was finished. * It has to be marked as TH_DEAD for this purpose. * If it is TH_TERM instead, it is supposed to have finished in the normal way. JB: TODO: investigate wether state change field could be nuked entirely and replaced by the normal tso state (whatnext field). All we want to do is to kill tsos from outside. */ /* ToDo: write something to the log-file if (RTSflags.ParFlags.granSimStats && !sameThread) DumpGranEvent(GR_SCHEDULE, RunnableThreadsHd); CurrentTSO = t; */ /* the spark pool for the current PE */ pool = &(cap.r.rSparks); // cap = (old) MainCap IF_DEBUG(scheduler, debugBelch("--=^ %d threads, %d sparks on [%#x]\n", run_queue_len(), spark_queue_len(pool), CURRENT_PROC)); IF_PAR_DEBUG(fish, debugBelch("--=^ %d threads, %d sparks on [%#x]\n", run_queue_len(), spark_queue_len(pool), CURRENT_PROC)); if (RtsFlags.ParFlags.ParStats.Full && (t->par.sparkname != (StgInt)0) && // only log spark generated threads (emitSchedule || // forced emit (t && LastTSO && t->id != LastTSO->id))) { /* we are running a different TSO, so write a schedule event to log file NB: If we use fair scheduling we also have to write a deschedule event for LastTSO; with unfair scheduling we know that the previous tso has blocked whenever we switch to another tso, so we don't need it in GUM for now */ IF_PAR_DEBUG(fish, // schedule, debugBelch("____ scheduling spark generated thread %d (%lx) (%lx) via a forced emit\n",t->id,t,t->par.sparkname)); DumpRawGranEvent(CURRENT_PROC, CURRENT_PROC, GR_SCHEDULE, t, (StgClosure *)NULL, 0, 0); emitSchedule = rtsFalse; } } #endif /* ---------------------------------------------------------------------------- * After running a thread... * ------------------------------------------------------------------------- */ static void schedulePostRunThread (StgTSO *t) { // We have to be able to catch transactions that are in an // infinite loop as a result of seeing an inconsistent view of // memory, e.g. // // atomically $ do // [a,b] <- mapM readTVar [ta,tb] // when (a == b) loop // // and a is never equal to b given a consistent view of memory. // if (t -> trec != NO_TREC && t -> why_blocked == NotBlocked) { if (!stmValidateNestOfTransactions (t -> trec)) { debugTrace(DEBUG_sched | DEBUG_stm, "trec %p found wasting its time", t); // strip the stack back to the // ATOMICALLY_FRAME, aborting the (nested) // transaction, and saving the stack of any // partially-evaluated thunks on the heap. throwToSingleThreaded_(&capabilities[0], t, NULL, rtsTrue, NULL); ASSERT(get_itbl((StgClosure *)t->sp)->type == ATOMICALLY_FRAME); } } #if defined(PAR) /* HACK 675: if the last thread didn't yield, make sure to print a SCHEDULE event to the log file when StgRunning the next thread, even if it is the same one as before */ LastTSO = t; TimeOfLastYield = CURRENT_TIME; #endif /* some statistics gathering in the parallel case */ #if defined(GRAN) || defined(PAR) || defined(EDEN) switch (ret) { case HeapOverflow: # if defined(GRAN) IF_DEBUG(gran, DumpGranEvent(GR_DESCHEDULE, t)); globalGranStats.tot_heapover++; # elif defined(PAR) globalParStats.tot_heapover++; # endif break; case StackOverflow: # if defined(GRAN) IF_DEBUG(gran, DumpGranEvent(GR_DESCHEDULE, t)); globalGranStats.tot_stackover++; # elif defined(PAR) // IF_DEBUG(par, // DumpGranEvent(GR_DESCHEDULE, t); globalParStats.tot_stackover++; # endif break; case ThreadYielding: # if defined(GRAN) IF_DEBUG(gran, DumpGranEvent(GR_DESCHEDULE, t)); globalGranStats.tot_yields++; # elif defined(PAR) // IF_DEBUG(par, // DumpGranEvent(GR_DESCHEDULE, t); globalParStats.tot_yields++; # endif break; case ThreadBlocked: # if defined(GRAN) debugTrace(DEBUG_sched, "--<< thread %ld (%p; %s) stopped, blocking on node %p [PE %d] with BQ: ", t->id, t, whatNext_strs[t->what_next], t->block_info.closure, (t->block_info.closure==(StgClosure*)NULL ? 99 : where_is(t->block_info.closure))); if (t->block_info.closure!=(StgClosure*)NULL) print_bq(t->block_info.closure); debugBelch("\n")); // ??? needed; should emit block before IF_DEBUG(gran, DumpGranEvent(GR_DESCHEDULE, t)); prune_eventq(t, (StgClosure *)NULL); // prune ContinueThreads for t /* ngoq Dogh! ASSERT(procStatus[CurrentProc]==Busy || ((procStatus[CurrentProc]==Fetching) && (t->block_info.closure!=(StgClosure*)NULL))); if (run_queue_hds[CurrentProc] == END_TSO_QUEUE && !(!RtsFlags.GranFlags.DoAsyncFetch && procStatus[CurrentProc]==Fetching)) procStatus[CurrentProc] = Idle; */ # elif defined(PAR) //++PAR++ blockThread() writes the event (change?) # endif break; case ThreadFinished: break; default: barf("parGlobalStats: unknown return code"); break; } #endif } /* ----------------------------------------------------------------------------- * Handle a thread that returned to the scheduler with ThreadHeepOverflow * -------------------------------------------------------------------------- */ static rtsBool scheduleHandleHeapOverflow( Capability *cap, StgTSO *t ) { // did the task ask for a large block? if (cap->r.rHpAlloc > BLOCK_SIZE) { // if so, get one and push it on the front of the nursery. bdescr *bd; lnat blocks; blocks = (lnat)BLOCK_ROUND_UP(cap->r.rHpAlloc) / BLOCK_SIZE; debugTrace(DEBUG_sched, "--<< thread %ld (%s) stopped: requesting a large block (size %ld)\n", (long)t->id, whatNext_strs[t->what_next], blocks); // don't do this if the nursery is (nearly) full, we'll GC first. if (cap->r.rCurrentNursery->link != NULL || cap->r.rNursery->n_blocks == 1) { // paranoia to prevent infinite loop // if the nursery has only one block. ACQUIRE_SM_LOCK bd = allocGroup( blocks ); RELEASE_SM_LOCK cap->r.rNursery->n_blocks += blocks; // link the new group into the list bd->link = cap->r.rCurrentNursery; bd->u.back = cap->r.rCurrentNursery->u.back; if (cap->r.rCurrentNursery->u.back != NULL) { cap->r.rCurrentNursery->u.back->link = bd; } else { #if !defined(THREADED_RTS) ASSERT(g0s0->blocks == cap->r.rCurrentNursery && g0s0 == cap->r.rNursery); #endif cap->r.rNursery->blocks = bd; } cap->r.rCurrentNursery->u.back = bd; // initialise it as a nursery block. We initialise the // step, gen_no, and flags field of *every* sub-block in // this large block, because this is easier than making // sure that we always find the block head of a large // block whenever we call Bdescr() (eg. evacuate() and // isAlive() in the GC would both have to do this, at // least). { bdescr *x; for (x = bd; x < bd + blocks; x++) { x->step = cap->r.rNursery; x->gen_no = 0; x->flags = 0; } } // This assert can be a killer if the app is doing lots // of large block allocations. IF_DEBUG(sanity, checkNurserySanity(cap->r.rNursery)); // now update the nursery to point to the new block cap->r.rCurrentNursery = bd; // we might be unlucky and have another thread get on the // run queue before us and steal the large block, but in that // case the thread will just end up requesting another large // block. pushOnRunQueue(cap,t); return rtsFalse; /* not actually GC'ing */ } } debugTrace(DEBUG_sched, "--<< thread %ld (%s) stopped: HeapOverflow", (long)t->id, whatNext_strs[t->what_next]); #if defined(GRAN) ASSERT(!is_on_queue(t,CurrentProc)); #elif defined(PARALLEL_HASKELL) /* Currently we emit a DESCHEDULE event before GC in GUM. ToDo: either add separate event to distinguish SYSTEM time from rest or just nuke this DESCHEDULE (and the following SCHEDULE) */ if (0 && RtsFlags.ParFlags.ParStats.Full) { DumpRawGranEvent(CURRENT_PROC, CURRENT_PROC, GR_DESCHEDULE, t, (StgClosure *)NULL, 0, 0); emitSchedule = rtsTrue; } #endif if (context_switch) { // Sometimes we miss a context switch, e.g. when calling // primitives in a tight loop, MAYBE_GC() doesn't check the // context switch flag, and we end up waiting for a GC. // See #1984, and concurrent/should_run/1984 context_switch = 0; addToRunQueue(cap,t); } else { pushOnRunQueue(cap,t); } return rtsTrue; /* actual GC is done at the end of the while loop in schedule() */ } /* ----------------------------------------------------------------------------- * Handle a thread that returned to the scheduler with ThreadStackOverflow * -------------------------------------------------------------------------- */ static void scheduleHandleStackOverflow (Capability *cap, Task *task, StgTSO *t) { debugTrace (DEBUG_sched, "--<< thread %ld (%s) stopped, StackOverflow", (long)t->id, whatNext_strs[t->what_next]); /* just adjust the stack for this thread, then pop it back * on the run queue. */ { /* enlarge the stack */ StgTSO *new_t = threadStackOverflow(cap, t); /* The TSO attached to this Task may have moved, so update the * pointer to it. */ if (task->tso == t) { task->tso = new_t; } pushOnRunQueue(cap,new_t); } } /* ----------------------------------------------------------------------------- * Handle a thread that returned to the scheduler with ThreadYielding * -------------------------------------------------------------------------- */ static rtsBool scheduleHandleYield( Capability *cap, StgTSO *t, nat prev_what_next ) { // Reset the context switch flag. We don't do this just before // running the thread, because that would mean we would lose ticks // during GC, which can lead to unfair scheduling (a thread hogs // the CPU because the tick always arrives during GC). This way // penalises threads that do a lot of allocation, but that seems // better than the alternative. context_switch = 0; /* put the thread back on the run queue. Then, if we're ready to * GC, check whether this is the last task to stop. If so, wake * up the GC thread. getThread will block during a GC until the * GC is finished. */ #ifdef DEBUG if (t->what_next != prev_what_next) { debugTrace(DEBUG_sched, "--<< thread %ld (%s) stopped to switch evaluators", (long)t->id, whatNext_strs[t->what_next]); } else { debugTrace(DEBUG_sched, "--<< thread %ld (%s) stopped, yielding", (long)t->id, whatNext_strs[t->what_next]); } #endif IF_DEBUG(sanity, //debugBelch("&& Doing sanity check on yielding TSO %ld.", t->id); checkTSO(t)); ASSERT(t->_link == END_TSO_QUEUE); // Shortcut if we're just switching evaluators: don't bother // doing stack squeezing (which can be expensive), just run the // thread. if (t->what_next != prev_what_next) { return rtsTrue; } #if defined(GRAN) ASSERT(!is_on_queue(t,CurrentProc)); IF_DEBUG(sanity, //debugBelch("&& Doing sanity check on all ThreadQueues (and their TSOs)."); checkThreadQsSanity(rtsTrue)); #endif addToRunQueue(cap,t); #if defined(GRAN) /* add a ContinueThread event to actually process the thread */ new_event(CurrentProc, CurrentProc, CurrentTime[CurrentProc], ContinueThread, t, (StgClosure*)NULL, (rtsSpark*)NULL); IF_GRAN_DEBUG(bq, debugBelch("GRAN: eventq and runnableq after adding yielded thread to queue again:\n"); G_EVENTQ(0); G_CURR_THREADQ(0)); #endif return rtsFalse; } /* ----------------------------------------------------------------------------- * Handle a thread that returned to the scheduler with ThreadBlocked * -------------------------------------------------------------------------- */ static void scheduleHandleThreadBlocked( StgTSO *t #if !defined(GRAN) && !defined(DEBUG) STG_UNUSED #endif ) { #if defined(GRAN) IF_DEBUG(scheduler, debugBelch("--<< thread %ld (%p; %s) stopped, blocking on node %p [PE %d] with BQ: \n", t->id, t, whatNext_strs[t->what_next], t->block_info.closure, (t->block_info.closure==(StgClosure*)NULL ? 99 : where_is(t->block_info.closure))); if (t->block_info.closure!=(StgClosure*)NULL) print_bq(t->block_info.closure)); // ??? needed; should emit block before IF_DEBUG(gran, DumpGranEvent(GR_DESCHEDULE, t)); prune_eventq(t, (StgClosure *)NULL); // prune ContinueThreads for t /* ngoq Dogh! ASSERT(procStatus[CurrentProc]==Busy || ((procStatus[CurrentProc]==Fetching) && (t->block_info.closure!=(StgClosure*)NULL))); if (run_queue_hds[CurrentProc] == END_TSO_QUEUE && !(!RtsFlags.GranFlags.DoAsyncFetch && procStatus[CurrentProc]==Fetching)) procStatus[CurrentProc] = Idle; */ #elif defined(PAR) IF_DEBUG(scheduler, debugBelch("--<< thread %ld (%p; %s) stopped, blocking on node %p with BQ: \n", t->id, t, whatNext_strs[t->what_next], t->block_info.closure)); IF_PAR_DEBUG(bq, if (t->block_info.closure!=(StgClosure*)NULL) print_bq(t->block_info.closure)); /* Send a fetch (if BlockedOnGA) and dump event to log file */ blockThread(t); /* whatever we schedule next, we must log that schedule */ emitSchedule = rtsTrue; #else /* !GRAN */ // We don't need to do anything. The thread is blocked, and it // has tidied up its stack and placed itself on whatever queue // it needs to be on. // ASSERT(t->why_blocked != NotBlocked); // Not true: for example, // - in THREADED_RTS, the thread may already have been woken // up by another Capability. This actually happens: try // conc023 +RTS -N2. // - the thread may have woken itself up already, because // threadPaused() might have raised a blocked throwTo // exception, see maybePerformBlockedException(). #ifdef DEBUG if (traceClass(DEBUG_sched)) { debugTraceBegin("--<< thread %lu (%s) stopped: ", (unsigned long)t->id, whatNext_strs[t->what_next]); printThreadBlockage(t); debugTraceEnd(); } #endif /* Only for dumping event to log file ToDo: do I need this in GranSim, too? blockThread(t); */ #endif } /* ----------------------------------------------------------------------------- * Handle a thread that returned to the scheduler with ThreadFinished * -------------------------------------------------------------------------- */ static rtsBool scheduleHandleThreadFinished (Capability *cap STG_UNUSED, Task *task, StgTSO *t) { /* Need to check whether this was a main thread, and if so, * return with the return value. * * We also end up here if the thread kills itself with an * uncaught exception, see Exception.cmm. */ debugTrace(DEBUG_sched, "--++ thread %lu (%s) finished", (unsigned long)t->id, whatNext_strs[t->what_next]); #if defined(GRAN) endThread(t, CurrentProc); // clean-up the thread #elif defined(PARALLEL_HASKELL) /* For now all are advisory -- HWL */ //if(t->priority==AdvisoryPriority) ?? advisory_thread_count--; // JB: Caution with this counter, buggy! # if defined(DIST) if(t->dist.priority==RevalPriority) FinishReval(t); # endif # if defined(EDENOLD) // the thread could still have an outport... (BUG) if (t->eden.outport != -1) { // delete the outport for the tso which has finished... IF_PAR_DEBUG(eden_ports, debugBelch("WARNING: Scheduler removes outport %d for TSO %d.\n", t->eden.outport, t->id)); deleteOPT(t); } // thread still in the process (HEAVY BUG! since outport has just been closed...) if (t->eden.epid != -1) { IF_PAR_DEBUG(eden_ports, debugBelch("WARNING: Scheduler removes TSO %d from process %d .\n", t->id, t->eden.epid)); removeTSOfromProcess(t); } # endif # if defined(PAR) if (RtsFlags.ParFlags.ParStats.Full && !RtsFlags.ParFlags.ParStats.Suppressed) DumpEndEvent(CURRENT_PROC, t, rtsFalse /* not mandatory */); // t->par only contains statistics: left out for now... IF_PAR_DEBUG(fish, debugBelch("**** end thread: ended sparked thread %d (%lx); sparkname: %lx\n", t->id,t,t->par.sparkname)); # endif #endif // PARALLEL_HASKELL // // Check whether the thread that just completed was a bound // thread, and if so return with the result. // // There is an assumption here that all thread completion goes // through this point; we need to make sure that if a thread // ends up in the ThreadKilled state, that it stays on the run // queue so it can be dealt with here. // if (t->bound) { if (t->bound != task) { #if !defined(THREADED_RTS) // Must be a bound thread that is not the topmost one. Leave // it on the run queue until the stack has unwound to the // point where we can deal with this. Leaving it on the run // queue also ensures that the garbage collector knows about // this thread and its return value (it gets dropped from the // step->threads list so there's no other way to find it). appendToRunQueue(cap,t); return rtsFalse; #else // this cannot happen in the threaded RTS, because a // bound thread can only be run by the appropriate Task. barf("finished bound thread that isn't mine"); #endif } ASSERT(task->tso == t); if (t->what_next == ThreadComplete) { if (task->ret) { // NOTE: return val is tso->sp[1] (see StgStartup.hc) *(task->ret) = (StgClosure *)task->tso->sp[1]; } task->stat = Success; } else { if (task->ret) { *(task->ret) = NULL; } if (sched_state >= SCHED_INTERRUPTING) { task->stat = Interrupted; } else { task->stat = Killed; } } #ifdef DEBUG removeThreadLabel((StgWord)task->tso->id); #endif return rtsTrue; // tells schedule() to return } return rtsFalse; } /* ----------------------------------------------------------------------------- * Perform a heap census * -------------------------------------------------------------------------- */ static rtsBool scheduleNeedHeapProfile( rtsBool ready_to_gc STG_UNUSED ) { // When we have +RTS -i0 and we're heap profiling, do a census at // every GC. This lets us get repeatable runs for debugging. if (performHeapProfile || (RtsFlags.ProfFlags.profileInterval==0 && RtsFlags.ProfFlags.doHeapProfile && ready_to_gc)) { return rtsTrue; } else { return rtsFalse; } } /* ----------------------------------------------------------------------------- * Perform a garbage collection if necessary * -------------------------------------------------------------------------- */ static Capability * scheduleDoGC (Capability *cap, Task *task USED_IF_THREADS, rtsBool force_major) { StgTSO *t; rtsBool heap_census; #ifdef THREADED_RTS static volatile StgWord waiting_for_gc; rtsBool was_waiting; nat i; #endif #ifdef THREADED_RTS // In order to GC, there must be no threads running Haskell code. // Therefore, the GC thread needs to hold *all* the capabilities, // and release them after the GC has completed. // // This seems to be the simplest way: previous attempts involved // making all the threads with capabilities give up their // capabilities and sleep except for the *last* one, which // actually did the GC. But it's quite hard to arrange for all // the other tasks to sleep and stay asleep. // was_waiting = cas(&waiting_for_gc, 0, 1); if (was_waiting) { do { debugTrace(DEBUG_sched, "someone else is trying to GC..."); if (cap) yieldCapability(&cap,task); } while (waiting_for_gc); return cap; // NOTE: task->cap might have changed here } for (i=0; i < n_capabilities; i++) { debugTrace(DEBUG_sched, "ready_to_gc, grabbing all the capabilies (%d/%d)", i, n_capabilities); if (cap != &capabilities[i]) { Capability *pcap = &capabilities[i]; // we better hope this task doesn't get migrated to // another Capability while we're waiting for this one. // It won't, because load balancing happens while we have // all the Capabilities, but even so it's a slightly // unsavoury invariant. task->cap = pcap; context_switch = 1; waitForReturnCapability(&pcap, task); if (pcap != &capabilities[i]) { barf("scheduleDoGC: got the wrong capability"); } } } waiting_for_gc = rtsFalse; #endif // so this happens periodically: if (cap) scheduleCheckBlackHoles(cap); IF_DEBUG(scheduler, printAllThreads()); /* * We now have all the capabilities; if we're in an interrupting * state, then we should take the opportunity to delete all the * threads in the system. */ if (sched_state >= SCHED_INTERRUPTING) { deleteAllThreads(&capabilities[0]); sched_state = SCHED_SHUTTING_DOWN; } heap_census = scheduleNeedHeapProfile(rtsTrue); /* everybody back, start the GC. * Could do it in this thread, or signal a condition var * to do it in another thread. Either way, we need to * broadcast on gc_pending_cond afterward. */ #if defined(THREADED_RTS) debugTrace(DEBUG_sched, "doing GC"); #endif GarbageCollect(force_major || heap_census); if (heap_census) { debugTrace(DEBUG_sched, "performing heap census"); heapCensus(); performHeapProfile = rtsFalse; } #if defined(THREADED_RTS) // release our stash of capabilities. for (i = 0; i < n_capabilities; i++) { if (cap != &capabilities[i]) { task->cap = &capabilities[i]; releaseCapability(&capabilities[i]); } } if (cap) { task->cap = cap; } else { task->cap = NULL; } #endif #if defined(GRAN) /* add a ContinueThread event to continue execution of current thread */ new_event(CurrentProc, CurrentProc, CurrentTime[CurrentProc], ContinueThread, t, (StgClosure*)NULL, (rtsSpark*)NULL); IF_GRAN_DEBUG(bq, debugBelch("GRAN: eventq and runnableq after Garbage collection:\n\n"); G_EVENTQ(0); G_CURR_THREADQ(0)); #endif /* GRAN */ return cap; } /* --------------------------------------------------------------------------- * Singleton fork(). Do not copy any running threads. * ------------------------------------------------------------------------- */ pid_t forkProcess(HsStablePtr *entry #ifndef FORKPROCESS_PRIMOP_SUPPORTED STG_UNUSED #endif ) { #ifdef FORKPROCESS_PRIMOP_SUPPORTED Task *task; pid_t pid; StgTSO* t,*next; Capability *cap; nat s; #if defined(THREADED_RTS) if (RtsFlags.ParFlags.nNodes > 1) { errorBelch("forking not supported with +RTS -N greater than 1"); stg_exit(EXIT_FAILURE); } #endif debugTrace(DEBUG_sched, "forking!"); // ToDo: for SMP, we should probably acquire *all* the capabilities cap = rts_lock(); // no funny business: hold locks while we fork, otherwise if some // other thread is holding a lock when the fork happens, the data // structure protected by the lock will forever be in an // inconsistent state in the child. See also #1391. ACQUIRE_LOCK(&sched_mutex); ACQUIRE_LOCK(&cap->lock); ACQUIRE_LOCK(&cap->running_task->lock); pid = fork(); if (pid) { // parent RELEASE_LOCK(&sched_mutex); RELEASE_LOCK(&cap->lock); RELEASE_LOCK(&cap->running_task->lock); // just return the pid rts_unlock(cap); return pid; } else { // child #if defined(THREADED_RTS) initMutex(&sched_mutex); initMutex(&cap->lock); initMutex(&cap->running_task->lock); #endif // Now, all OS threads except the thread that forked are // stopped. We need to stop all Haskell threads, including // those involved in foreign calls. Also we need to delete // all Tasks, because they correspond to OS threads that are // now gone. for (s = 0; s < total_steps; s++) { for (t = all_steps[s].threads; t != END_TSO_QUEUE; t = next) { if (t->what_next == ThreadRelocated) { next = t->_link; } else { next = t->global_link; // don't allow threads to catch the ThreadKilled // exception, but we do want to raiseAsync() because these // threads may be evaluating thunks that we need later. deleteThread_(cap,t); } } } // Empty the run queue. It seems tempting to let all the // killed threads stay on the run queue as zombies to be // cleaned up later, but some of them correspond to bound // threads for which the corresponding Task does not exist. cap->run_queue_hd = END_TSO_QUEUE; cap->run_queue_tl = END_TSO_QUEUE; // Any suspended C-calling Tasks are no more, their OS threads // don't exist now: cap->suspended_ccalling_tasks = NULL; // Empty the threads lists. Otherwise, the garbage // collector may attempt to resurrect some of these threads. for (s = 0; s < total_steps; s++) { all_steps[s].threads = END_TSO_QUEUE; } // Wipe the task list, except the current Task. ACQUIRE_LOCK(&sched_mutex); for (task = all_tasks; task != NULL; task=task->all_link) { if (task != cap->running_task) { #if defined(THREADED_RTS) initMutex(&task->lock); // see #1391 #endif discardTask(task); } } RELEASE_LOCK(&sched_mutex); #if defined(THREADED_RTS) // Wipe our spare workers list, they no longer exist. New // workers will be created if necessary. cap->spare_workers = NULL; cap->returning_tasks_hd = NULL; cap->returning_tasks_tl = NULL; #endif // On Unix, all timers are reset in the child, so we need to start // the timer again. initTimer(); startTimer(); cap = rts_evalStableIO(cap, entry, NULL); // run the action rts_checkSchedStatus("forkProcess",cap); rts_unlock(cap); hs_exit(); // clean up and exit stg_exit(EXIT_SUCCESS); } #else /* !FORKPROCESS_PRIMOP_SUPPORTED */ barf("forkProcess#: primop not supported on this platform, sorry!\n"); return -1; #endif } /* --------------------------------------------------------------------------- * Delete all the threads in the system * ------------------------------------------------------------------------- */ static void deleteAllThreads ( Capability *cap ) { // NOTE: only safe to call if we own all capabilities. StgTSO* t, *next; nat s; debugTrace(DEBUG_sched,"deleting all threads"); for (s = 0; s < total_steps; s++) { for (t = all_steps[s].threads; t != END_TSO_QUEUE; t = next) { if (t->what_next == ThreadRelocated) { next = t->_link; } else { next = t->global_link; deleteThread(cap,t); } } } // The run queue now contains a bunch of ThreadKilled threads. We // must not throw these away: the main thread(s) will be in there // somewhere, and the main scheduler loop has to deal with it. // Also, the run queue is the only thing keeping these threads from // being GC'd, and we don't want the "main thread has been GC'd" panic. #if !defined(THREADED_RTS) ASSERT(blocked_queue_hd == END_TSO_QUEUE); ASSERT(sleeping_queue == END_TSO_QUEUE); #endif } /* ----------------------------------------------------------------------------- Managing the suspended_ccalling_tasks list. Locks required: sched_mutex -------------------------------------------------------------------------- */ STATIC_INLINE void suspendTask (Capability *cap, Task *task) { ASSERT(task->next == NULL && task->prev == NULL); task->next = cap->suspended_ccalling_tasks; task->prev = NULL; if (cap->suspended_ccalling_tasks) { cap->suspended_ccalling_tasks->prev = task; } cap->suspended_ccalling_tasks = task; } STATIC_INLINE void recoverSuspendedTask (Capability *cap, Task *task) { if (task->prev) { task->prev->next = task->next; } else { ASSERT(cap->suspended_ccalling_tasks == task); cap->suspended_ccalling_tasks = task->next; } if (task->next) { task->next->prev = task->prev; } task->next = task->prev = NULL; } /* --------------------------------------------------------------------------- * Suspending & resuming Haskell threads. * * When making a "safe" call to C (aka _ccall_GC), the task gives back * its capability before calling the C function. This allows another * task to pick up the capability and carry on running Haskell * threads. It also means that if the C call blocks, it won't lock * the whole system. * * The Haskell thread making the C call is put to sleep for the * duration of the call, on the susepended_ccalling_threads queue. We * give out a token to the task, which it can use to resume the thread * on return from the C function. * ------------------------------------------------------------------------- */ void * suspendThread (StgRegTable *reg) { Capability *cap; int saved_errno; StgTSO *tso; Task *task; #if mingw32_HOST_OS StgWord32 saved_winerror; #endif saved_errno = errno; #if mingw32_HOST_OS saved_winerror = GetLastError(); #endif /* assume that *reg is a pointer to the StgRegTable part of a Capability. */ cap = regTableToCapability(reg); task = cap->running_task; tso = cap->r.rCurrentTSO; debugTrace(DEBUG_sched, "thread %lu did a safe foreign call", (unsigned long)cap->r.rCurrentTSO->id); // XXX this might not be necessary --SDM tso->what_next = ThreadRunGHC; threadPaused(cap,tso); if ((tso->flags & TSO_BLOCKEX) == 0) { tso->why_blocked = BlockedOnCCall; tso->flags |= TSO_BLOCKEX; tso->flags &= ~TSO_INTERRUPTIBLE; } else { tso->why_blocked = BlockedOnCCall_NoUnblockExc; } // Hand back capability task->suspended_tso = tso; ACQUIRE_LOCK(&cap->lock); suspendTask(cap,task); cap->in_haskell = rtsFalse; releaseCapability_(cap); RELEASE_LOCK(&cap->lock); #if defined(THREADED_RTS) /* Preparing to leave the RTS, so ensure there's a native thread/task waiting to take over. */ debugTrace(DEBUG_sched, "thread %lu: leaving RTS", (unsigned long)tso->id); #endif errno = saved_errno; #if mingw32_HOST_OS SetLastError(saved_winerror); #endif return task; } StgRegTable * resumeThread (void *task_) { StgTSO *tso; Capability *cap; Task *task = task_; int saved_errno; #if mingw32_HOST_OS StgWord32 saved_winerror; #endif saved_errno = errno; #if mingw32_HOST_OS saved_winerror = GetLastError(); #endif cap = task->cap; // Wait for permission to re-enter the RTS with the result. waitForReturnCapability(&cap,task); // we might be on a different capability now... but if so, our // entry on the suspended_ccalling_tasks list will also have been // migrated. // Remove the thread from the suspended list recoverSuspendedTask(cap,task); tso = task->suspended_tso; task->suspended_tso = NULL; tso->_link = END_TSO_QUEUE; // no write barrier reqd debugTrace(DEBUG_sched, "thread %lu: re-entering RTS", (unsigned long)tso->id); if (tso->why_blocked == BlockedOnCCall) { awakenBlockedExceptionQueue(cap,tso); tso->flags &= ~(TSO_BLOCKEX | TSO_INTERRUPTIBLE); } /* Reset blocking status */ tso->why_blocked = NotBlocked; cap->r.rCurrentTSO = tso; cap->in_haskell = rtsTrue; errno = saved_errno; #if mingw32_HOST_OS SetLastError(saved_winerror); #endif /* We might have GC'd, mark the TSO dirty again */ dirty_TSO(cap,tso); IF_DEBUG(sanity, checkTSO(tso)); return &cap->r; } /* --------------------------------------------------------------------------- * scheduleThread() * * scheduleThread puts a thread on the end of the runnable queue. * This will usually be done immediately after a thread is created. * The caller of scheduleThread must create the thread using e.g. * createThread and push an appropriate closure * on this thread's stack before the scheduler is invoked. * ------------------------------------------------------------------------ */ void scheduleThread(Capability *cap, StgTSO *tso) { // The thread goes at the *end* of the run-queue, to avoid possible // starvation of any threads already on the queue. appendToRunQueue(cap,tso); } void scheduleThreadOn(Capability *cap, StgWord cpu USED_IF_THREADS, StgTSO *tso) { #if defined(THREADED_RTS) tso->flags |= TSO_LOCKED; // we requested explicit affinity; don't // move this thread from now on. cpu %= RtsFlags.ParFlags.nNodes; if (cpu == cap->no) { appendToRunQueue(cap,tso); } else { migrateThreadToCapability_lock(&capabilities[cpu],tso); } #else appendToRunQueue(cap,tso); #endif } Capability * scheduleWaitThread (StgTSO* tso, /*[out]*/HaskellObj* ret, Capability *cap) { Task *task; // We already created/initialised the Task task = cap->running_task; // This TSO is now a bound thread; make the Task and TSO // point to each other. tso->bound = task; tso->cap = cap; task->tso = tso; task->ret = ret; task->stat = NoStatus; appendToRunQueue(cap,tso); debugTrace(DEBUG_sched, "new bound thread (%lu)", (unsigned long)tso->id); #if defined(GRAN) /* GranSim specific init */ CurrentTSO = m->tso; // the TSO to run procStatus[MainProc] = Busy; // status of main PE CurrentProc = MainProc; // PE to run it on #endif cap = schedule(cap,task); ASSERT(task->stat != NoStatus); ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task); debugTrace(DEBUG_sched, "bound thread (%lu) finished", (unsigned long)task->tso->id); return cap; } /* ---------------------------------------------------------------------------- * Starting Tasks * ------------------------------------------------------------------------- */ #if defined(THREADED_RTS) void workerStart(Task *task) { Capability *cap; // See startWorkerTask(). ACQUIRE_LOCK(&task->lock); cap = task->cap; RELEASE_LOCK(&task->lock); // set the thread-local pointer to the Task: taskEnter(task); // schedule() runs without a lock. cap = schedule(cap,task); // On exit from schedule(), we have a Capability. releaseCapability(cap); workerTaskStop(task); } #endif /* --------------------------------------------------------------------------- * initScheduler() * * Initialise the scheduler. This resets all the queues - if the * queues contained any threads, they'll be garbage collected at the * next pass. * * ------------------------------------------------------------------------ */ void initScheduler(void) { #if defined(GRAN) nat i; for (i=0; i<=MAX_PROC; i++) { run_queue_hds[i] = END_TSO_QUEUE; run_queue_tls[i] = END_TSO_QUEUE; blocked_queue_hds[i] = END_TSO_QUEUE; blocked_queue_tls[i] = END_TSO_QUEUE; ccalling_threadss[i] = END_TSO_QUEUE; blackhole_queue[i] = END_TSO_QUEUE; sleeping_queue = END_TSO_QUEUE; } #elif !defined(THREADED_RTS) blocked_queue_hd = END_TSO_QUEUE; blocked_queue_tl = END_TSO_QUEUE; sleeping_queue = END_TSO_QUEUE; #endif blackhole_queue = END_TSO_QUEUE; context_switch = 0; sched_state = SCHED_RUNNING; recent_activity = ACTIVITY_YES; #if defined(THREADED_RTS) /* Initialise the mutex and condition variables used by * the scheduler. */ initMutex(&sched_mutex); #endif ACQUIRE_LOCK(&sched_mutex); /* A capability holds the state a native thread needs in * order to execute STG code. At least one capability is * floating around (only THREADED_RTS builds have more than one). */ initCapabilities(); initTaskManager(); #if defined(THREADED_RTS) || defined(PARALLEL_HASKELL) initSparkPools(); #endif #if defined(THREADED_RTS) /* * Eagerly start one worker to run each Capability, except for * Capability 0. The idea is that we're probably going to start a * bound thread on Capability 0 pretty soon, so we don't want a * worker task hogging it. */ { nat i; Capability *cap; for (i = 1; i < n_capabilities; i++) { cap = &capabilities[i]; ACQUIRE_LOCK(&cap->lock); startWorkerTask(cap, workerStart); RELEASE_LOCK(&cap->lock); } } #endif trace(TRACE_sched, "start: %d capabilities", n_capabilities); RELEASE_LOCK(&sched_mutex); } void exitScheduler( rtsBool wait_foreign #if !defined(THREADED_RTS) __attribute__((unused)) #endif ) /* see Capability.c, shutdownCapability() */ { Task *task = NULL; #if defined(THREADED_RTS) ACQUIRE_LOCK(&sched_mutex); task = newBoundTask(); RELEASE_LOCK(&sched_mutex); #endif // If we haven't killed all the threads yet, do it now. if (sched_state < SCHED_SHUTTING_DOWN) { sched_state = SCHED_INTERRUPTING; scheduleDoGC(NULL,task,rtsFalse); } sched_state = SCHED_SHUTTING_DOWN; #if defined(THREADED_RTS) { nat i; for (i = 0; i < n_capabilities; i++) { shutdownCapability(&capabilities[i], task, wait_foreign); } boundTaskExiting(task); stopTaskManager(); } #else freeCapability(&MainCapability); #endif } void freeScheduler( void ) { freeTaskManager(); if (n_capabilities != 1) { stgFree(capabilities); } #if defined(THREADED_RTS) closeMutex(&sched_mutex); #endif } /* ----------------------------------------------------------------------------- performGC This is the interface to the garbage collector from Haskell land. We provide this so that external C code can allocate and garbage collect when called from Haskell via _ccall_GC. -------------------------------------------------------------------------- */ static void performGC_(rtsBool force_major) { Task *task; // We must grab a new Task here, because the existing Task may be // associated with a particular Capability, and chained onto the // suspended_ccalling_tasks queue. ACQUIRE_LOCK(&sched_mutex); task = newBoundTask(); RELEASE_LOCK(&sched_mutex); scheduleDoGC(NULL,task,force_major); boundTaskExiting(task); } void performGC(void) { performGC_(rtsFalse); } void performMajorGC(void) { performGC_(rtsTrue); } /* ----------------------------------------------------------------------------- Stack overflow If the thread has reached its maximum stack size, then raise the StackOverflow exception in the offending thread. Otherwise relocate the TSO into a larger chunk of memory and adjust its stack size appropriately. -------------------------------------------------------------------------- */ static StgTSO * threadStackOverflow(Capability *cap, StgTSO *tso) { nat new_stack_size, stack_words; lnat new_tso_size; StgPtr new_sp; StgTSO *dest; IF_DEBUG(sanity,checkTSO(tso)); // don't allow throwTo() to modify the blocked_exceptions queue // while we are moving the TSO: lockClosure((StgClosure *)tso); if (tso->stack_size >= tso->max_stack_size && !(tso->flags & TSO_BLOCKEX)) { // NB. never raise a StackOverflow exception if the thread is // inside Control.Exceptino.block. It is impractical to protect // against stack overflow exceptions, since virtually anything // can raise one (even 'catch'), so this is the only sensible // thing to do here. See bug #767. debugTrace(DEBUG_gc, "threadStackOverflow of TSO %ld (%p): stack too large (now %ld; max is %ld)", (long)tso->id, tso, (long)tso->stack_size, (long)tso->max_stack_size); IF_DEBUG(gc, /* If we're debugging, just print out the top of the stack */ printStackChunk(tso->sp, stg_min(tso->stack+tso->stack_size, tso->sp+64))); // Send this thread the StackOverflow exception unlockTSO(tso); throwToSingleThreaded(cap, tso, (StgClosure *)stackOverflow_closure); return tso; } /* Try to double the current stack size. If that takes us over the * maximum stack size for this thread, then use the maximum instead. * Finally round up so the TSO ends up as a whole number of blocks. */ new_stack_size = stg_min(tso->stack_size * 2, tso->max_stack_size); new_tso_size = (lnat)BLOCK_ROUND_UP(new_stack_size * sizeof(W_) + TSO_STRUCT_SIZE)/sizeof(W_); new_tso_size = round_to_mblocks(new_tso_size); /* Be MBLOCK-friendly */ new_stack_size = new_tso_size - TSO_STRUCT_SIZEW; debugTrace(DEBUG_sched, "increasing stack size from %ld words to %d.", (long)tso->stack_size, new_stack_size); dest = (StgTSO *)allocateLocal(cap,new_tso_size); TICK_ALLOC_TSO(new_stack_size,0); /* copy the TSO block and the old stack into the new area */ memcpy(dest,tso,TSO_STRUCT_SIZE); stack_words = tso->stack + tso->stack_size - tso->sp; new_sp = (P_)dest + new_tso_size - stack_words; memcpy(new_sp, tso->sp, stack_words * sizeof(W_)); /* relocate the stack pointers... */ dest->sp = new_sp; dest->stack_size = new_stack_size; /* Mark the old TSO as relocated. We have to check for relocated * TSOs in the garbage collector and any primops that deal with TSOs. * * It's important to set the sp value to just beyond the end * of the stack, so we don't attempt to scavenge any part of the * dead TSO's stack. */ tso->what_next = ThreadRelocated; setTSOLink(cap,tso,dest); tso->sp = (P_)&(tso->stack[tso->stack_size]); tso->why_blocked = NotBlocked; IF_PAR_DEBUG(verbose, debugBelch("@@ threadStackOverflow of TSO %d (now at %p): stack size increased to %ld\n", tso->id, tso, tso->stack_size); /* If we're debugging, just print out the top of the stack */ printStackChunk(tso->sp, stg_min(tso->stack+tso->stack_size, tso->sp+64))); unlockTSO(dest); unlockTSO(tso); IF_DEBUG(sanity,checkTSO(dest)); #if 0 IF_DEBUG(scheduler,printTSO(dest)); #endif return dest; } static StgTSO * threadStackUnderflow (Task *task STG_UNUSED, StgTSO *tso) { bdescr *bd, *new_bd; lnat new_tso_size_w, tso_size_w; StgTSO *new_tso; tso_size_w = tso_sizeW(tso); if (tso_size_w < MBLOCK_SIZE_W || (nat)(tso->stack + tso->stack_size - tso->sp) > tso->stack_size / 4) { return tso; } // don't allow throwTo() to modify the blocked_exceptions queue // while we are moving the TSO: lockClosure((StgClosure *)tso); new_tso_size_w = round_to_mblocks(tso_size_w/2); debugTrace(DEBUG_sched, "thread %ld: reducing TSO size from %lu words to %lu", tso->id, tso_size_w, new_tso_size_w); bd = Bdescr((StgPtr)tso); new_bd = splitLargeBlock(bd, new_tso_size_w / BLOCK_SIZE_W); new_bd->free = bd->free; bd->free = bd->start + TSO_STRUCT_SIZEW; new_tso = (StgTSO *)new_bd->start; memcpy(new_tso,tso,TSO_STRUCT_SIZE); new_tso->stack_size = new_tso_size_w - TSO_STRUCT_SIZEW; tso->what_next = ThreadRelocated; tso->_link = new_tso; // no write barrier reqd: same generation // The TSO attached to this Task may have moved, so update the // pointer to it. if (task->tso == tso) { task->tso = new_tso; } unlockTSO(new_tso); unlockTSO(tso); IF_DEBUG(sanity,checkTSO(new_tso)); return new_tso; } /* --------------------------------------------------------------------------- Interrupt execution - usually called inside a signal handler so it mustn't do anything fancy. ------------------------------------------------------------------------ */ void interruptStgRts(void) { sched_state = SCHED_INTERRUPTING; context_switch = 1; wakeUpRts(); } /* ----------------------------------------------------------------------------- Wake up the RTS This function causes at least one OS thread to wake up and run the scheduler loop. It is invoked when the RTS might be deadlocked, or an external event has arrived that may need servicing (eg. a keyboard interrupt). In the single-threaded RTS we don't do anything here; we only have one thread anyway, and the event that caused us to want to wake up will have interrupted any blocking system call in progress anyway. -------------------------------------------------------------------------- */ void wakeUpRts(void) { #if defined(THREADED_RTS) // This forces the IO Manager thread to wakeup, which will // in turn ensure that some OS thread wakes up and runs the // scheduler loop, which will cause a GC and deadlock check. ioManagerWakeup(); #endif } /* ----------------------------------------------------------------------------- * checkBlackHoles() * * Check the blackhole_queue for threads that can be woken up. We do * this periodically: before every GC, and whenever the run queue is * empty. * * An elegant solution might be to just wake up all the blocked * threads with awakenBlockedQueue occasionally: they'll go back to * sleep again if the object is still a BLACKHOLE. Unfortunately this * doesn't give us a way to tell whether we've actually managed to * wake up any threads, so we would be busy-waiting. * * -------------------------------------------------------------------------- */ static rtsBool checkBlackHoles (Capability *cap) { StgTSO **prev, *t; rtsBool any_woke_up = rtsFalse; StgHalfWord type; // blackhole_queue is global: ASSERT_LOCK_HELD(&sched_mutex); debugTrace(DEBUG_sched, "checking threads blocked on black holes"); // ASSUMES: sched_mutex prev = &blackhole_queue; t = blackhole_queue; while (t != END_TSO_QUEUE) { ASSERT(t->why_blocked == BlockedOnBlackHole); type = get_itbl(UNTAG_CLOSURE(t->block_info.closure))->type; if (type != BLACKHOLE && type != CAF_BLACKHOLE) { IF_DEBUG(sanity,checkTSO(t)); t = unblockOne(cap, t); // urk, the threads migrate to the current capability // here, but we'd like to keep them on the original one. *prev = t; any_woke_up = rtsTrue; } else { prev = &t->_link; t = t->_link; } } return any_woke_up; } /* ----------------------------------------------------------------------------- Deleting threads This is used for interruption (^C) and forking, and corresponds to raising an exception but without letting the thread catch the exception. -------------------------------------------------------------------------- */ static void deleteThread (Capability *cap, StgTSO *tso) { // NOTE: must only be called on a TSO that we have exclusive // access to, because we will call throwToSingleThreaded() below. // The TSO must be on the run queue of the Capability we own, or // we must own all Capabilities. if (tso->why_blocked != BlockedOnCCall && tso->why_blocked != BlockedOnCCall_NoUnblockExc) { throwToSingleThreaded(cap,tso,NULL); } } #ifdef FORKPROCESS_PRIMOP_SUPPORTED static void deleteThread_(Capability *cap, StgTSO *tso) { // for forkProcess only: // like deleteThread(), but we delete threads in foreign calls, too. if (tso->why_blocked == BlockedOnCCall || tso->why_blocked == BlockedOnCCall_NoUnblockExc) { unblockOne(cap,tso); tso->what_next = ThreadKilled; } else { deleteThread(cap,tso); } } #endif /* ----------------------------------------------------------------------------- raiseExceptionHelper This function is called by the raise# primitve, just so that we can move some of the tricky bits of raising an exception from C-- into C. Who knows, it might be a useful re-useable thing here too. -------------------------------------------------------------------------- */ StgWord raiseExceptionHelper (StgRegTable *reg, StgTSO *tso, StgClosure *exception) { Capability *cap = regTableToCapability(reg); StgThunk *raise_closure = NULL; StgPtr p, next; StgRetInfoTable *info; // // This closure represents the expression 'raise# E' where E // is the exception raise. It is used to overwrite all the // thunks which are currently under evaluataion. // // OLD COMMENT (we don't have MIN_UPD_SIZE now): // LDV profiling: stg_raise_info has THUNK as its closure // type. Since a THUNK takes at least MIN_UPD_SIZE words in its // payload, MIN_UPD_SIZE is more approprate than 1. It seems that // 1 does not cause any problem unless profiling is performed. // However, when LDV profiling goes on, we need to linearly scan // small object pool, where raise_closure is stored, so we should // use MIN_UPD_SIZE. // // raise_closure = (StgClosure *)RET_STGCALL1(P_,allocate, // sizeofW(StgClosure)+1); // // // Walk up the stack, looking for the catch frame. On the way, // we update any closures pointed to from update frames with the // raise closure that we just built. // p = tso->sp; while(1) { info = get_ret_itbl((StgClosure *)p); next = p + stack_frame_sizeW((StgClosure *)p); switch (info->i.type) { case UPDATE_FRAME: // Only create raise_closure if we need to. if (raise_closure == NULL) { raise_closure = (StgThunk *)allocateLocal(cap,sizeofW(StgThunk)+1); SET_HDR(raise_closure, &stg_raise_info, CCCS); raise_closure->payload[0] = exception; } UPD_IND(((StgUpdateFrame *)p)->updatee,(StgClosure *)raise_closure); p = next; continue; case ATOMICALLY_FRAME: debugTrace(DEBUG_stm, "found ATOMICALLY_FRAME at %p", p); tso->sp = p; return ATOMICALLY_FRAME; case CATCH_FRAME: tso->sp = p; return CATCH_FRAME; case CATCH_STM_FRAME: debugTrace(DEBUG_stm, "found CATCH_STM_FRAME at %p", p); tso->sp = p; return CATCH_STM_FRAME; case STOP_FRAME: tso->sp = p; return STOP_FRAME; case CATCH_RETRY_FRAME: default: p = next; continue; } } } /* ----------------------------------------------------------------------------- findRetryFrameHelper This function is called by the retry# primitive. It traverses the stack leaving tso->sp referring to the frame which should handle the retry. This should either be a CATCH_RETRY_FRAME (if the retry# is within an orElse#) or should be a ATOMICALLY_FRAME (if the retry# reaches the top level). We skip CATCH_STM_FRAMEs (aborting and rolling back the nested tx that they create) because retries are not considered to be exceptions, despite the similar implementation. We should not expect to see CATCH_FRAME or STOP_FRAME because those should not be created within memory transactions. -------------------------------------------------------------------------- */ StgWord findRetryFrameHelper (StgTSO *tso) { StgPtr p, next; StgRetInfoTable *info; p = tso -> sp; while (1) { info = get_ret_itbl((StgClosure *)p); next = p + stack_frame_sizeW((StgClosure *)p); switch (info->i.type) { case ATOMICALLY_FRAME: debugTrace(DEBUG_stm, "found ATOMICALLY_FRAME at %p during retry", p); tso->sp = p; return ATOMICALLY_FRAME; case CATCH_RETRY_FRAME: debugTrace(DEBUG_stm, "found CATCH_RETRY_FRAME at %p during retrry", p); tso->sp = p; return CATCH_RETRY_FRAME; case CATCH_STM_FRAME: { StgTRecHeader *trec = tso -> trec; StgTRecHeader *outer = stmGetEnclosingTRec(trec); debugTrace(DEBUG_stm, "found CATCH_STM_FRAME at %p during retry", p); debugTrace(DEBUG_stm, "trec=%p outer=%p", trec, outer); stmAbortTransaction(tso -> cap, trec); stmFreeAbortedTRec(tso -> cap, trec); tso -> trec = outer; p = next; continue; } default: ASSERT(info->i.type != CATCH_FRAME); ASSERT(info->i.type != STOP_FRAME); p = next; continue; } } } /* ----------------------------------------------------------------------------- resurrectThreads is called after garbage collection on the list of threads found to be garbage. Each of these threads will be woken up and sent a signal: BlockedOnDeadMVar if the thread was blocked on an MVar, or NonTermination if the thread was blocked on a Black Hole. Locks: assumes we hold *all* the capabilities. -------------------------------------------------------------------------- */ void resurrectThreads (StgTSO *threads) { StgTSO *tso, *next; Capability *cap; step *step; for (tso = threads; tso != END_TSO_QUEUE; tso = next) { next = tso->global_link; step = Bdescr((P_)tso)->step; tso->global_link = step->threads; step->threads = tso; debugTrace(DEBUG_sched, "resurrecting thread %lu", (unsigned long)tso->id); // Wake up the thread on the Capability it was last on cap = tso->cap; switch (tso->why_blocked) { case BlockedOnMVar: case BlockedOnException: /* Called by GC - sched_mutex lock is currently held. */ throwToSingleThreaded(cap, tso, (StgClosure *)BlockedOnDeadMVar_closure); break; case BlockedOnBlackHole: throwToSingleThreaded(cap, tso, (StgClosure *)nonTermination_closure); break; case BlockedOnSTM: throwToSingleThreaded(cap, tso, (StgClosure *)BlockedIndefinitely_closure); break; case NotBlocked: /* This might happen if the thread was blocked on a black hole * belonging to a thread that we've just woken up (raiseAsync * can wake up threads, remember...). */ continue; default: barf("resurrectThreads: thread blocked in a strange way"); } } } /* ----------------------------------------------------------------------------- performPendingThrowTos is called after garbage collection, and passed a list of threads that were found to have pending throwTos (tso->blocked_exceptions was not empty), and were blocked. Normally this doesn't happen, because we would deliver the exception directly if the target thread is blocked, but there are small windows where it might occur on a multiprocessor (see throwTo()). NB. we must be holding all the capabilities at this point, just like resurrectThreads(). -------------------------------------------------------------------------- */ void performPendingThrowTos (StgTSO *threads) { StgTSO *tso, *next; Capability *cap; step *step; for (tso = threads; tso != END_TSO_QUEUE; tso = next) { next = tso->global_link; step = Bdescr((P_)tso)->step; tso->global_link = step->threads; step->threads = tso; debugTrace(DEBUG_sched, "performing blocked throwTo to thread %lu", (unsigned long)tso->id); cap = tso->cap; maybePerformBlockedException(cap, tso); } }