[project @ 2005-04-04 13:51:26 by simonmar]
authorsimonmar <unknown>
Mon, 4 Apr 2005 13:51:26 +0000 (13:51 +0000)
committersimonmar <unknown>
Mon, 4 Apr 2005 13:51:26 +0000 (13:51 +0000)
Big cleanup of the scheduler.

The main idea here was to extract as much stuff as possible from the
scheduler loop into seprate functions, so as to better expose the
control structure of the scheduler.  Now, the scheduler loop is down
to some 300+ lines; there's some more code that could be extracted,
but I think it looks pretty good now.

This work is partly due to an initial cleanup by the GRAN/PAR folks,
heavily re-worked by me.

ghc/rts/Schedule.c

index e2e1db2..206531d 100644 (file)
@@ -9,7 +9,7 @@
  *
  * WAY  Name     CPP flag  What's it for
  * --------------------------------------
- * mp   GUM      PAR          Parallel execution on a distrib. memory machine
+ * mp   GUM      PARALLEL_HASKELL          Parallel execution on a distrib. memory machine
  * s    SMP      SMP          Parallel execution on a shared memory machine
  * mg   GranSim  GRAN         Simulation of parallel execution
  * md   GUM/GdH  DIST         Distributed execution (based on GUM)
 #include "RtsUtils.h"
 #include "RtsFlags.h"
 #include "BlockAlloc.h"
+#include "OSThreads.h"
 #include "Storage.h"
 #include "StgRun.h"
 #include "Hooks.h"
 #define COMPILING_SCHEDULER
 #include "Schedule.h"
 #include "StgMiscClosures.h"
-#include "Storage.h"
 #include "Interpreter.h"
 #include "Exception.h"
 #include "Printer.h"
@@ -65,7 +65,7 @@
 #include "Proftimer.h"
 #include "ProfHeap.h"
 #endif
-#if defined(GRAN) || defined(PAR)
+#if defined(GRAN) || defined(PARALLEL_HASKELL)
 # include "GranSimRts.h"
 # include "GranSim.h"
 # include "ParallelRts.h"
@@ -76,7 +76,6 @@
 #endif
 #include "Sparks.h"
 #include "Capability.h"
-#include "OSThreads.h"
 #include  "Task.h"
 
 #ifdef HAVE_SYS_TYPES_H
 #include <errno.h>
 #endif
 
+// Turn off inlining when debugging - it obfuscates things
+#ifdef DEBUG
+# undef  STATIC_INLINE
+# define STATIC_INLINE static
+#endif
+
 #ifdef THREADED_RTS
 #define USED_IN_THREADED_RTS
 #else
  */
 StgMainThread *main_threads = NULL;
 
-/* Thread queues.
- * Locks required: sched_mutex.
- */
 #if defined(GRAN)
 
 StgTSO* ActiveTSO = NULL; /* for assigning system costs; GranSim-Light only */
@@ -136,6 +138,9 @@ StgTSO *ccalling_threadss[MAX_PROC];
 
 #else /* !GRAN */
 
+/* Thread queues.
+ * Locks required: sched_mutex.
+ */
 StgTSO *run_queue_hd = NULL;
 StgTSO *run_queue_tl = NULL;
 StgTSO *blocked_queue_hd = NULL;
@@ -155,8 +160,6 @@ StgTSO *all_threads = NULL;
  */
 static StgTSO *suspended_ccalling_threads;
 
-static StgTSO *threadStackOverflow(StgTSO *tso);
-
 /* KH: The following two flags are shared memory locations.  There is no need
        to lock them, since they are only unset at the end of a scheduler
        operation.
@@ -171,7 +174,7 @@ rtsBool interrupted = rtsFalse;
 /* If this flag is set, we are running Haskell code.  Used to detect
  * uses of 'foreign import unsafe' that should be 'safe'.
  */
-rtsBool in_haskell = rtsFalse;
+static rtsBool in_haskell = rtsFalse;
 
 /* Next thread ID to allocate.
  * Locks required: thread_id_mutex
@@ -208,6 +211,10 @@ StgTSO *CurrentTSO;
  */
 StgTSO dummy_tso;
 
+# if defined(SMP)
+static Condition gc_pending_cond = INIT_COND_VAR;
+# endif
+
 static rtsBool ready_to_gc;
 
 /*
@@ -217,13 +224,6 @@ static rtsBool ready_to_gc;
  */
 static rtsBool shutting_down_scheduler = rtsFalse;
 
-void            addToBlockedQueue ( StgTSO *tso );
-
-static void     schedule          ( StgMainThread *mainThread, Capability *initialCapability );
-       void     interruptStgRts   ( void );
-
-static void     raiseAsync_(StgTSO *tso, StgClosure *exception, rtsBool stop_at_atomically);
-
 #if defined(RTS_SUPPORTS_THREADS)
 /* ToDo: carefully document the invariants that go together
  *       with these synchronisation objects.
@@ -233,7 +233,7 @@ Mutex     term_mutex        = INIT_MUTEX_VAR;
 
 #endif /* RTS_SUPPORTS_THREADS */
 
-#if defined(PAR)
+#if defined(PARALLEL_HASKELL)
 StgTSO *LastTSO;
 rtsTime TimeOfLastYield;
 rtsBool emitSchedule = rtsTrue;
@@ -250,7 +250,64 @@ static char *whatNext_strs[] = {
 };
 #endif
 
-#if defined(PAR)
+/* -----------------------------------------------------------------------------
+ * static function prototypes
+ * -------------------------------------------------------------------------- */
+
+#if defined(RTS_SUPPORTS_THREADS)
+static void taskStart(void);
+#endif
+
+static void schedule( StgMainThread *mainThread USED_WHEN_RTS_SUPPORTS_THREADS,
+                     Capability *initialCapability );
+
+//
+// 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);
+static void scheduleHandleInterrupt(void);
+static void scheduleStartSignalHandlers(void);
+static void scheduleCheckBlockedThreads(void);
+static void scheduleDetectDeadlock(void);
+#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(void);
+static rtsBool scheduleHandleHeapOverflow( Capability *cap, StgTSO *t );
+static void scheduleHandleStackOverflow( StgTSO *t);
+static rtsBool scheduleHandleYield( StgTSO *t, nat prev_what_next );
+static void scheduleHandleThreadBlocked( StgTSO *t );
+static rtsBool scheduleHandleThreadFinished( StgMainThread *mainThread, 
+                                            Capability *cap, StgTSO *t );
+static void scheduleDoHeapProfile(void);
+static void scheduleDoGC(void);
+
+static void unblockThread(StgTSO *tso);
+static SchedulerStatus waitThread_(/*out*/StgMainThread* m,
+                                  Capability *initialCapability
+                                  );
+static void scheduleThread_ (StgTSO* tso);
+static void AllRoots(evac_fn evac);
+
+static StgTSO *threadStackOverflow(StgTSO *tso);
+
+static void raiseAsync_(StgTSO *tso, StgClosure *exception, 
+                       rtsBool stop_at_atomically);
+
+static void printThreadBlockage(StgTSO *tso);
+static void printThreadStatus(StgTSO *tso);
+
+#if defined(PARALLEL_HASKELL)
 StgTSO * createSparkThread(rtsSpark spark);
 StgTSO * activateSpark (rtsSpark spark);  
 #endif
@@ -262,7 +319,6 @@ StgTSO * activateSpark (rtsSpark spark);
 #if defined(RTS_SUPPORTS_THREADS)
 static rtsBool startingWorkerThread = rtsFalse;
 
-static void taskStart(void);
 static void
 taskStart(void)
 {
@@ -284,15 +340,35 @@ startSchedulerTaskIfNecessary(void)
       // just because the last one hasn't yet reached the
       // "waiting for capability" state
       startingWorkerThread = rtsTrue;
-      if(!startTask(taskStart))
-      {
-        startingWorkerThread = rtsFalse;
+      if (!startTask(taskStart)) {
+         startingWorkerThread = rtsFalse;
       }
     }
   }
 }
 #endif
 
+/* -----------------------------------------------------------------------------
+ * Putting a thread on the run queue: different scheduling policies
+ * -------------------------------------------------------------------------- */
+
+STATIC_INLINE void
+addToRunQueue( StgTSO *t )
+{
+#if defined(PARALLEL_HASKELL)
+    if (RtsFlags.ParFlags.doFairScheduling) { 
+       // this does round-robin scheduling; good for concurrency
+       APPEND_TO_RUN_QUEUE(t);
+    } else {
+       // this does unfair scheduling; good for parallelism
+       PUSH_ON_RUN_QUEUE(t);
+    }
+#else
+    // this does round-robin scheduling; good for concurrency
+    APPEND_TO_RUN_QUEUE(t);
+#endif
+}
+    
 /* ---------------------------------------------------------------------------
    Main scheduling loop.
 
@@ -328,6 +404,7 @@ startSchedulerTaskIfNecessary(void)
      This is not the ugliest code you could imagine, but it's bloody close.
 
    ------------------------------------------------------------------------ */
+
 static void
 schedule( StgMainThread *mainThread USED_WHEN_RTS_SUPPORTS_THREADS,
           Capability *initialCapability )
@@ -337,9 +414,7 @@ schedule( StgMainThread *mainThread USED_WHEN_RTS_SUPPORTS_THREADS,
   StgThreadReturnCode ret;
 #if defined(GRAN)
   rtsEvent *event;
-#elif defined(PAR)
-  StgSparkPool *pool;
-  rtsSpark spark;
+#elif defined(PARALLEL_HASKELL)
   StgTSO *tso;
   GlobalTaskId pe;
   rtsBool receivedFinish = rtsFalse;
@@ -347,64 +422,58 @@ schedule( StgMainThread *mainThread USED_WHEN_RTS_SUPPORTS_THREADS,
   nat tp_size, sp_size; // stats only
 # endif
 #endif
-  rtsBool was_interrupted = rtsFalse;
   nat prev_what_next;
   
   // Pre-condition: sched_mutex is held.
   // We might have a capability, passed in as initialCapability.
   cap = initialCapability;
 
-#if defined(RTS_SUPPORTS_THREADS)
-  //
-  // in the threaded case, the capability is either passed in via the
-  // initialCapability parameter, or initialized inside the scheduler
-  // loop 
-  //
-  IF_DEBUG(scheduler,
-          sched_belch("### NEW SCHEDULER LOOP (main thr: %p, cap: %p)",
-                      mainThread, initialCapability);
-      );
-#else
+#if !defined(RTS_SUPPORTS_THREADS)
   // simply initialise it in the non-threaded case
   grabCapability(&cap);
 #endif
 
-#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);
-
-  IF_DEBUG(gran,
-          debugBelch("GRAN: Init CurrentTSO (in schedule) = %p\n", CurrentTSO);
-          G_TSO(CurrentTSO, 5));
-
-  if (RtsFlags.GranFlags.Light) {
-    /* Save current time; GranSim Light only */
-    CurrentTSO->gran.clock = CurrentTime[CurrentProc];
-  }      
+  IF_DEBUG(scheduler,
+          sched_belch("### NEW SCHEDULER LOOP (main thr: %p, cap: %p)",
+                      mainThread, initialCapability);
+      );
 
-  event = get_next_event();
+  schedulePreLoop();
 
-  while (event!=(rtsEvent*)NULL) {
-    /* Choose the processor with the next event */
-    CurrentProc = event->proc;
-    CurrentTSO = event->tso;
+  // -----------------------------------------------------------
+  // Scheduler loop starts here:
 
-#elif defined(PAR)
+#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 (!receivedFinish) {    /* set by processMessages */
-                               /* when receiving PP_FINISH message         */ 
+  while (TERMINATION_CONDITION) {
 
-#else // everything except GRAN and PAR
+#if defined(GRAN)
+      /* Choose the processor with the next event */
+      CurrentProc = event->proc;
+      CurrentTSO = event->tso;
+#endif
 
-  while (1) {
+      IF_DEBUG(scheduler, printAllThreads());
 
+#if defined(SMP)
+      // 
+      // Wait until GC has completed, if necessary.
+      //
+      if (ready_to_gc) {
+         if (cap != NULL) {
+             releaseCapability(cap);
+             IF_DEBUG(scheduler,sched_belch("waiting for GC"));
+             waitCondition( &gc_pending_cond, &sched_mutex );
+         }
+      }
 #endif
 
-     IF_DEBUG(scheduler, printAllThreads());
-
 #if defined(RTS_SUPPORTS_THREADS)
       // Yield the capability to higher-priority tasks if necessary.
       //
@@ -431,161 +500,459 @@ schedule( StgMainThread *mainThread USED_WHEN_RTS_SUPPORTS_THREADS,
          stg_exit(1);
     }
 
+    scheduleHandleInterrupt();
+
+#if defined(not_yet) && defined(SMP)
     //
-    // If we're interrupted (the user pressed ^C, or some other
-    // termination condition occurred), kill all the currently running
-    // threads.
+    // Top up the run queue from our spark pool.  We try to make the
+    // number of threads in the run queue equal to the number of
+    // free capabilities.
     //
-    if (interrupted) {
-       IF_DEBUG(scheduler, sched_belch("interrupted"));
-       interrupted = rtsFalse;
-       was_interrupted = rtsTrue;
-#if defined(RTS_SUPPORTS_THREADS)
-       // In the threaded RTS, deadlock detection doesn't work,
-       // so just exit right away.
-       errorBelch("interrupted");
-       releaseCapability(cap);
-       RELEASE_LOCK(&sched_mutex);
-       shutdownHaskellAndExit(EXIT_SUCCESS);
-#else
-       deleteAllThreads();
-#endif
+    {
+       StgClosure *spark;
+       if (EMPTY_RUN_QUEUE()) {
+           spark = findSpark(rtsFalse);
+           if (spark == NULL) {
+               break; /* no more sparks in the pool */
+           } else {
+               createSparkThread(spark);         
+               IF_DEBUG(scheduler,
+                        sched_belch("==^^ turning spark of closure %p into a thread",
+                                    (StgClosure *)spark));
+           }
+       }
     }
+#endif // SMP
 
-#if defined(RTS_USER_SIGNALS)
-    // check for signals each time around the scheduler
-    if (signals_pending()) {
-      RELEASE_LOCK(&sched_mutex); /* ToDo: kill */
-      startSignalHandlers();
-      ACQUIRE_LOCK(&sched_mutex);
-    }
-#endif
+    scheduleStartSignalHandlers();
 
+    scheduleCheckBlockedThreads();
+
+    scheduleDetectDeadlock();
+
+    // 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.
     //
-    // 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 ( !EMPTY_QUEUE(blocked_queue_hd) || !EMPTY_QUEUE(sleeping_queue) )
-    {
-#if defined(RTS_SUPPORTS_THREADS)
-       // We shouldn't be here...
-       barf("schedule: awaitEvent() in threaded RTS");
+    // win32: might be here due to awaitEvent() being abandoned
+    // as a result of a console event having been delivered.
+    if ( EMPTY_RUN_QUEUE() ) {
+#if !defined(RTS_SUPPORTS_THREADS) && !defined(mingw32_HOST_OS)
+       ASSERT(interrupted);
 #endif
-       awaitEvent( EMPTY_RUN_QUEUE() );
+       continue; // nothing to do
     }
-    // we can be interrupted while waiting for I/O...
-    if (interrupted) continue;
 
-    /* 
-     * Detect deadlock: when we have no threads to run, there are no
-     * threads waiting on I/O or sleeping, and all the other tasks are
-     * waiting for work, we must have a deadlock of some description.
-     *
-     * We first try to find threads blocked on themselves (ie. black
-     * holes), and generate NonTermination exceptions where necessary.
-     *
-     * If no threads are black holed, we have a deadlock situation, so
-     * inform all the main threads.
-     */
-#if !defined(PAR) && !defined(RTS_SUPPORTS_THREADS)
-    if (   EMPTY_THREAD_QUEUES() )
-    {
-       IF_DEBUG(scheduler, sched_belch("deadlocked, forcing major GC..."));
+#if defined(PARALLEL_HASKELL)
+    scheduleSendPendingMessages();
+    if (EMPTY_RUN_QUEUE() && scheduleActivateSpark()) 
+       continue;
 
-       // 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.
-       GarbageCollect(GetRoots,rtsTrue);
-       if ( !EMPTY_RUN_QUEUE() ) { goto not_deadlocked; }
+#if defined(SPARKS)
+    ASSERT(next_fish_to_send_at==0);  // i.e. no delayed fishes left!
+#endif
 
-#if defined(RTS_USER_SIGNALS)
-       /* If we have user-installed signal handlers, then wait
-        * for signals to arrive rather then bombing out with a
-        * deadlock.
-        */
-       if ( anyUserHandlers() ) {
-           IF_DEBUG(scheduler, 
-                    sched_belch("still deadlocked, waiting for signals..."));
+    /* If we still have no work we need to send a FISH to get a spark
+       from another PE */
+    if (EMPTY_RUN_QUEUE()) {
+       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
 
-           awaitUserSignals();
+#if defined(GRAN)
+    scheduleProcessEvent(event);
+#endif
 
-           // we might be interrupted...
-           if (interrupted) { continue; }
+    // 
+    // Get a thread to run
+    //
+    ASSERT(run_queue_hd != END_TSO_QUEUE);
+    POP_RUN_QUEUE(t);
 
-           if (signals_pending()) {
-               RELEASE_LOCK(&sched_mutex);
-               startSignalHandlers();
-               ACQUIRE_LOCK(&sched_mutex);
-           }
-           ASSERT(!EMPTY_RUN_QUEUE());
-           goto not_deadlocked;
-       }
+#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
 
-       /* Probably a real deadlock.  Send the current main thread the
-        * Deadlock exception (or in the SMP build, send *all* main
-        * threads the deadlock exception, since none of them can make
-        * progress).
-        */
+#if defined(RTS_SUPPORTS_THREADS)
+    // Check whether we can run this thread in the current task.
+    // If not, we have to pass our capability to the right task.
+    {
+      StgMainThread *m = t->main;
+      
+      if(m)
+      {
+       if(m == mainThread)
        {
-           StgMainThread *m;
-           m = main_threads;
-           switch (m->tso->why_blocked) {
-           case BlockedOnBlackHole:
-           case BlockedOnException:
-           case BlockedOnMVar:
-               raiseAsync(m->tso, (StgClosure *)NonTermination_closure);
-               break;
-           default:
-               barf("deadlock: main thread blocked in a strange way");
-           }
+         IF_DEBUG(scheduler,
+           sched_belch("### Running thread %d in bound thread", t->id));
+         // yes, the Haskell thread is bound to the current native thread
+       }
+       else
+       {
+         IF_DEBUG(scheduler,
+           sched_belch("### thread %d bound to another OS thread", t->id));
+         // no, bound to a different Haskell thread: pass to that thread
+         PUSH_ON_RUN_QUEUE(t);
+         passCapability(&m->bound_thread_cond);
+         continue;
+       }
+      }
+      else
+      {
+       if(mainThread != NULL)
+        // The thread we want to run is bound.
+       {
+         IF_DEBUG(scheduler,
+           sched_belch("### this OS thread cannot run thread %d", t->id));
+         // no, the current native thread is bound to a different
+         // Haskell thread, so pass it to any worker thread
+         PUSH_ON_RUN_QUEUE(t);
+         passCapabilityToWorker();
+         continue; 
        }
+      }
     }
-  not_deadlocked:
-
-#elif defined(RTS_SUPPORTS_THREADS)
-    // ToDo: add deadlock detection in threaded RTS
-#elif defined(PAR)
-    // ToDo: add deadlock detection in GUM (similar to SMP) -- HWL
 #endif
 
-#if defined(RTS_SUPPORTS_THREADS) || defined(mingw32_HOST_OS)
-    /* win32: might be back here due to awaitEvent() being abandoned
-     * as a result of a console event having been delivered.
+    cap->r.rCurrentTSO = t;
+    
+    /* context switches are now initiated by the timer signal, unless
+     * the user specified "context switch as often as possible", with
+     * +RTS -C0
      */
-    if ( EMPTY_RUN_QUEUE() ) {
-       continue; // nothing to do
-    }
-#endif
+    if ((RtsFlags.ConcFlags.ctxtSwitchTicks == 0
+        && (run_queue_hd != END_TSO_QUEUE
+            || blocked_queue_hd != END_TSO_QUEUE
+            || sleeping_queue != END_TSO_QUEUE)))
+       context_switch = 1;
 
-#if defined(GRAN)
-    if (RtsFlags.GranFlags.Light)
-      GranSimLight_enter_system(event, &ActiveTSO); // adjust ActiveTSO etc
+run_thread:
 
-    /* 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();
+    RELEASE_LOCK(&sched_mutex);
 
-    IF_DEBUG(gran, debugBelch("GRAN: switch by event-type\n"));
+    IF_DEBUG(scheduler, sched_belch("-->> running thread %ld %s ...", 
+                             (long)t->id, whatNext_strs[t->what_next]));
 
-    /* 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 defined(PROFILING)
+    startHeapProfTimer();
+#endif
+
+    /* +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */
+    /* Run the current thread 
+     */
+    prev_what_next = t->what_next;
+
+    errno = t->saved_errno;
+    in_haskell = rtsTrue;
+
+    switch (prev_what_next) {
+
+    case ThreadKilled:
+    case ThreadComplete:
+       /* Thread already finished, return to scheduler. */
+       ret = ThreadFinished;
+       break;
+
+    case ThreadRunGHC:
+       ret = StgRun((StgFunPtr) stg_returnToStackTop, &cap->r);
+       break;
+
+    case ThreadInterpret:
+       ret = interpretBCO(cap);
+       break;
+
+    default:
+      barf("schedule: invalid what_next field");
+    }
+
+    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;
+
+    // And save the current errno in this thread.
+    t->saved_errno = errno;
+
+    /* +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */
+    
+    /* Costs for the scheduler are assigned to CCS_SYSTEM */
+#if defined(PROFILING)
+    stopHeapProfTimer();
+    CCCS = CCS_SYSTEM;
+#endif
+    
+    ACQUIRE_LOCK(&sched_mutex);
+    
+#if defined(RTS_SUPPORTS_THREADS)
+    IF_DEBUG(scheduler,debugBelch("sched (task %p): ", osThreadId()););
+#elif !defined(GRAN) && !defined(PARALLEL_HASKELL)
+    IF_DEBUG(scheduler,debugBelch("sched: "););
+#endif
+    
+    schedulePostRunThread();
+
+    switch (ret) {
+    case HeapOverflow:
+       ready_to_gc = scheduleHandleHeapOverflow(cap,t);
+       break;
+
+    case StackOverflow:
+       scheduleHandleStackOverflow(t);
+       break;
+
+    case ThreadYielding:
+       if (scheduleHandleYield(t, prev_what_next)) {
+            // shortcut for switching between compiler/interpreter:
+           goto run_thread; 
+       }
+       break;
+
+    case ThreadBlocked:
+       scheduleHandleThreadBlocked(t);
+       threadPaused(t);
+       break;
+
+    case ThreadFinished:
+       if (scheduleHandleThreadFinished(mainThread, cap, t)) return;;
+       break;
+
+    default:
+      barf("schedule: invalid thread return code %d", (int)ret);
+    }
+
+    scheduleDoHeapProfile();
+    scheduleDoGC();
+  } /* end of while() */
+
+  IF_PAR_DEBUG(verbose,
+              debugBelch("== Leaving schedule() after having received Finish\n"));
+}
+
+/* ----------------------------------------------------------------------------
+ * Setting up the scheduler loop
+ * ASSUMES: sched_mutex
+ * ------------------------------------------------------------------------- */
+
+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);
+    
+    IF_DEBUG(gran,
+            debugBelch("GRAN: Init CurrentTSO (in schedule) = %p\n", 
+                       CurrentTSO);
+            G_TSO(CurrentTSO, 5));
+    
+    if (RtsFlags.GranFlags.Light) {
+       /* Save current time; GranSim Light only */
+       CurrentTSO->gran.clock = CurrentTime[CurrentProc];
+    }      
+#endif
+}
+
+/* ----------------------------------------------------------------------------
+ * Deal with the interrupt flag
+ * ASSUMES: sched_mutex
+ * ------------------------------------------------------------------------- */
+
+static
+void scheduleHandleInterrupt(void)
+{
+    //
+    // Test for interruption.  If interrupted==rtsTrue, then either
+    // we received a keyboard interrupt (^C), or the scheduler is
+    // trying to shut down all the tasks (shutting_down_scheduler) in
+    // the threaded RTS.
+    //
+    if (interrupted) {
+       if (shutting_down_scheduler) {
+           IF_DEBUG(scheduler, sched_belch("shutting down"));
+#if defined(RTS_SUPPORTS_THREADS)
+           shutdownThread();
+#endif
+       } else {
+           IF_DEBUG(scheduler, sched_belch("interrupted"));
+           deleteAllThreads();
+       }
+    }
+}
+
+/* ----------------------------------------------------------------------------
+ * Start any pending signal handlers
+ * ASSUMES: sched_mutex
+ * ------------------------------------------------------------------------- */
+
+static void
+scheduleStartSignalHandlers(void)
+{
+#if defined(RTS_USER_SIGNALS)
+    if (signals_pending()) {
+      RELEASE_LOCK(&sched_mutex); /* ToDo: kill */
+      startSignalHandlers();
+      ACQUIRE_LOCK(&sched_mutex);
+    }
+#endif
+}
+
+/* ----------------------------------------------------------------------------
+ * Check for blocked threads that can be woken up.
+ * ASSUMES: sched_mutex
+ * ------------------------------------------------------------------------- */
+
+static void
+scheduleCheckBlockedThreads(void)
+{
+    //
+    // 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 ( !EMPTY_QUEUE(blocked_queue_hd) || !EMPTY_QUEUE(sleeping_queue) )
+    {
+#if defined(RTS_SUPPORTS_THREADS)
+       // We shouldn't be here...
+       barf("schedule: awaitEvent() in threaded RTS");
+#endif
+       awaitEvent( EMPTY_RUN_QUEUE() );
+    }
+}
+
+/* ----------------------------------------------------------------------------
+ * Detect deadlock conditions and attempt to resolve them.
+ * ASSUMES: sched_mutex
+ * ------------------------------------------------------------------------- */
+
+static void
+scheduleDetectDeadlock(void)
+{
+    /* 
+     * Detect deadlock: when we have no threads to run, there are no
+     * threads waiting on I/O or sleeping, and all the other tasks are
+     * waiting for work, we must have a deadlock of some description.
+     *
+     * We first try to find threads blocked on themselves (ie. black
+     * holes), and generate NonTermination exceptions where necessary.
+     *
+     * If no threads are black holed, we have a deadlock situation, so
+     * inform all the main threads.
+     */
+#if !defined(PARALLEL_HASKELL) && !defined(RTS_SUPPORTS_THREADS)
+    if ( EMPTY_THREAD_QUEUES() )
+    {
+       IF_DEBUG(scheduler, sched_belch("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.
+       GarbageCollect(GetRoots,rtsTrue);
+       if ( !EMPTY_RUN_QUEUE() ) return;
+
+#if defined(RTS_USER_SIGNALS)
+       /* If we have user-installed signal handlers, then wait
+        * for signals to arrive rather then bombing out with a
+        * deadlock.
+        */
+       if ( anyUserHandlers() ) {
+           IF_DEBUG(scheduler, 
+                    sched_belch("still deadlocked, waiting for signals..."));
+
+           awaitUserSignals();
+
+           if (signals_pending()) {
+               RELEASE_LOCK(&sched_mutex);
+               startSignalHandlers();
+               ACQUIRE_LOCK(&sched_mutex);
+           }
+
+           // either we have threads to run, or we were interrupted:
+           ASSERT(!EMPTY_RUN_QUEUE() || interrupted);
+       }
+#endif
+
+       /* Probably a real deadlock.  Send the current main thread the
+        * Deadlock exception (or in the SMP build, send *all* main
+        * threads the deadlock exception, since none of them can make
+        * progress).
+        */
+       {
+           StgMainThread *m;
+           m = main_threads;
+           switch (m->tso->why_blocked) {
+           case BlockedOnBlackHole:
+           case BlockedOnException:
+           case BlockedOnMVar:
+               raiseAsync(m->tso, (StgClosure *)NonTermination_closure);
+               return;
+           default:
+               barf("deadlock: main thread blocked in a strange way");
+           }
+       }
+    }
+
+#elif defined(RTS_SUPPORTS_THREADS)
+    // ToDo: add deadlock detection in threaded RTS
+#elif defined(PARALLEL_HASKELL)
+    // ToDo: add deadlock detection in GUM (similar to SMP) -- HWL
+#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",
@@ -696,18 +1063,54 @@ schedule( StgMainThread *mainThread USED_WHEN_RTS_SUPPORTS_THREADS,
             DumpGranEvent(GR_SCHEDULE, t));
 
     procStatus[CurrentProc] = Busy;
+}
+#endif // GRAN
 
-#elif defined(PAR)
+/* ----------------------------------------------------------------------------
+ * 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(EMPTY_RUN_QUEUE());
+/* 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.
+*/
 
-    /* ToDo: phps merge with spark activation above */
-    /* check whether we have local work and send requests if we have none */
-    if (EMPTY_RUN_QUEUE()) {  /* no runnable threads */
       /* :-[  no local threads => look out for local sparks */
       /* the spark pool for the current PE */
-      pool = &(MainRegTable.rSparks); // generalise to cap = &MainRegTable
+      pool = &(cap.r.rSparks); // JB: cap = (old) MainCap
       if (advisory_thread_count < RtsFlags.ParFlags.maxThreads &&
          pool->hd < pool->tl) {
        /* 
@@ -719,29 +1122,73 @@ schedule( StgMainThread *mainThread USED_WHEN_RTS_SUPPORTS_THREADS,
         * thread... 
         */
 
-       spark = findSpark(rtsFalse);                /* get a spark */
-       if (spark != (rtsSpark) NULL) {
-         tso = activateSpark(spark);       /* turn the spark into a thread */
-         IF_PAR_DEBUG(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 */
-           debugBelch("==^^ failed to activate spark\n");
-           goto next_thread;
-         }               /* otherwise fall through & pick-up new tso */
-       } else {
-         IF_PAR_DEBUG(verbose,
-                      debugBelch("==^^ no local sparks (spark pool contains only NFs: %d)\n", 
-                            spark_queue_len(pool)));
-         goto next_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(EMPTY_RUN_QUEUE());
+
+  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);
 
-      /* If we still have no work we need to send a FISH to get a spark
-        from another PE 
-      */
-      if (EMPTY_RUN_QUEUE()) {
       /* =8-[  no local sparks => look for work on other PEs */
        /*
         * We really have absolutely no work.  Send out a fish
@@ -751,48 +1198,106 @@ schedule( StgMainThread *mainThread USED_WHEN_RTS_SUPPORTS_THREADS,
         * we're hoping to see.  (Of course, we still have to
         * respond to other types of messages.)
         */
-       TIME now = msTime() /*CURRENT_TIME*/;
+       rtsTime now = msTime() /*CURRENT_TIME*/;
        IF_PAR_DEBUG(verbose, 
                     debugBelch("--  now=%ld\n", now));
-       IF_PAR_DEBUG(verbose,
-                    if (outstandingFishes < RtsFlags.ParFlags.maxFishes &&
-                        (last_fish_arrived_at!=0 &&
-                         last_fish_arrived_at+RtsFlags.ParFlags.fishDelay > now)) {
-                      debugBelch("--$$ delaying FISH until %ld (last fish %ld, delay %ld, now %ld)\n",
-                            last_fish_arrived_at+RtsFlags.ParFlags.fishDelay,
-                            last_fish_arrived_at,
-                            RtsFlags.ParFlags.fishDelay, now);
-                    });
-       
+       IF_PAR_DEBUG(fish, // verbose,
+            if (outstandingFishes < RtsFlags.ParFlags.maxFishes &&
+                (last_fish_arrived_at!=0 &&
+                 last_fish_arrived_at+delay > now)) {
+              debugBelch("--$$ <%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 &&
-           (last_fish_arrived_at==0 ||
-            (last_fish_arrived_at+RtsFlags.ParFlags.fishDelay <= now))) {
-         /* outstandingFishes is set in sendFish, processFish;
-            avoid flooding system with fishes via delay */
-         pe = choosePE();
-         sendFish(pe, mytid, 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++;
-         }
-       }
-      
-       receivedFinish = processMessages();
-       goto next_thread;
+           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();
       }
-    } else if (PacketsWaiting()) {  /* Look for incoming messages */
-      receivedFinish = processMessages();
-    }
+      now = msTime();
+    } while (!*receivedFinish || now<next_fish_to_send_at);
+    // JB: This means the fish could become obsolete, if we receive
+    // work. Better check for work again? 
+    // last line: while (!receivedFinish || !haveWork || now<...)
+    // next line: if (receivedFinish || haveWork )
+
+    if (*receivedFinish) // no need to send a FISH if we are finishing anyway
+      return rtsFalse;  // NB: this will leave scheduler loop
+                       // immediately after return!
+                         
+    IF_PAR_DEBUG(fish, // verbose,
+              debugBelch("--$$ <%llu> sent delayed fish (%d processMessages); active/total threads=%d/%d\n",now,iq,run_queue_len(),advisory_thread_count));
 
-    /* Now we are sure that we have some work available */
-    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_DEBUG(sanity,checkTSO(t));
+    // 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)
@@ -801,25 +1306,20 @@ schedule( StgMainThread *mainThread USED_WHEN_RTS_SUPPORTS_THREADS,
     CurrentTSO = t;
     */
     /* the spark pool for the current PE */
-    pool = &(MainRegTable.rSparks); // generalise to cap = &MainRegTable
+    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 1
-    if (0 && RtsFlags.ParFlags.ParStats.Full && 
-       t && LastTSO && t->id != LastTSO->id && 
-       LastTSO->why_blocked == NotBlocked && 
-       LastTSO->what_next != ThreadComplete) {
-      // if previously scheduled TSO not blocked we have to record the context switch
-      DumpVeryRawGranEvent(TimeOfLastYield, CURRENT_PROC, CURRENT_PROC,
-                          GR_DESCHEDULE, LastTSO, (StgClosure *)NULL, 0, 0);
-    }
+    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 && 
-       (emitSchedule /* forced emit */ ||
-        (t && LastTSO && t->id != LastTSO->id))) {
+       (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 
@@ -827,137 +1327,24 @@ schedule( StgMainThread *mainThread USED_WHEN_RTS_SUPPORTS_THREADS,
             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
-#else /* !GRAN && !PAR */
-  
-    // grab a thread from the run queue
-    ASSERT(run_queue_hd != END_TSO_QUEUE);
-    POP_RUN_QUEUE(t);
-
-    // 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
 
-#ifdef THREADED_RTS
-    {
-      StgMainThread *m = t->main;
-      
-      if(m)
-      {
-       if(m == mainThread)
-       {
-         IF_DEBUG(scheduler,
-           sched_belch("### Running thread %d in bound thread", t->id));
-         // yes, the Haskell thread is bound to the current native thread
-       }
-       else
-       {
-         IF_DEBUG(scheduler,
-           sched_belch("### thread %d bound to another OS thread", t->id));
-         // no, bound to a different Haskell thread: pass to that thread
-         PUSH_ON_RUN_QUEUE(t);
-         passCapability(&m->bound_thread_cond);
-         continue;
-       }
-      }
-      else
-      {
-       if(mainThread != NULL)
-        // The thread we want to run is bound.
-       {
-         IF_DEBUG(scheduler,
-           sched_belch("### this OS thread cannot run thread %d", t->id));
-         // no, the current native thread is bound to a different
-         // Haskell thread, so pass it to any worker thread
-         PUSH_ON_RUN_QUEUE(t);
-         passCapabilityToWorker();
-         continue; 
-       }
-      }
-    }
-#endif
-
-    cap->r.rCurrentTSO = t;
-    
-    /* context switches are now initiated by the timer signal, unless
-     * the user specified "context switch as often as possible", with
-     * +RTS -C0
-     */
-    if ((RtsFlags.ConcFlags.ctxtSwitchTicks == 0
-        && (run_queue_hd != END_TSO_QUEUE
-            || blocked_queue_hd != END_TSO_QUEUE
-            || sleeping_queue != END_TSO_QUEUE)))
-       context_switch = 1;
-
-run_thread:
-
-    RELEASE_LOCK(&sched_mutex);
-
-    IF_DEBUG(scheduler, sched_belch("-->> running thread %ld %s ...", 
-                             (long)t->id, whatNext_strs[t->what_next]));
-
-#ifdef PROFILING
-    startHeapProfTimer();
-#endif
-
-    /* +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */
-    /* Run the current thread 
-     */
-    prev_what_next = t->what_next;
-
-    errno = t->saved_errno;
-    in_haskell = rtsTrue;
-
-    switch (prev_what_next) {
-
-    case ThreadKilled:
-    case ThreadComplete:
-       /* Thread already finished, return to scheduler. */
-       ret = ThreadFinished;
-       break;
-
-    case ThreadRunGHC:
-       ret = StgRun((StgFunPtr) stg_returnToStackTop, &cap->r);
-       break;
-
-    case ThreadInterpret:
-       ret = interpretBCO(cap);
-       break;
-
-    default:
-      barf("schedule: invalid what_next field");
-    }
-
-    in_haskell = rtsFalse;
-
-    // The TSO might have moved, so find the new location:
-    t = cap->r.rCurrentTSO;
-
-    // And save the current errno in this thread.
-    t->saved_errno = errno;
+/* ----------------------------------------------------------------------------
+ * After running a thread...
+ * ASSUMES: sched_mutex
+ * ------------------------------------------------------------------------- */
 
-    /* +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */
-    
-    /* Costs for the scheduler are assigned to CCS_SYSTEM */
-#ifdef PROFILING
-    stopHeapProfTimer();
-    CCCS = CCS_SYSTEM;
-#endif
-    
-    ACQUIRE_LOCK(&sched_mutex);
-    
-#ifdef RTS_SUPPORTS_THREADS
-    IF_DEBUG(scheduler,debugBelch("sched (task %p): ", osThreadId()););
-#elif !defined(GRAN) && !defined(PAR)
-    IF_DEBUG(scheduler,debugBelch("sched: "););
-#endif
-    
+static void
+schedulePostRunThread(void)
+{
 #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
@@ -966,221 +1353,52 @@ run_thread:
     TimeOfLastYield = CURRENT_TIME;
 #endif
 
-    switch (ret) {
+  /* some statistics gathering in the parallel case */
+
+#if defined(GRAN) || defined(PAR) || defined(EDEN)
+  switch (ret) {
     case HeapOverflow:
-#if defined(GRAN)
+# if defined(GRAN)
       IF_DEBUG(gran, DumpGranEvent(GR_DESCHEDULE, t));
-      globalGranStats.tot_heapover++;
-#elif defined(PAR)
-      globalParStats.tot_heapover++;
-#endif
-
-      // 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;
-         nat blocks;
-         
-         blocks = (nat)BLOCK_ROUND_UP(cap->r.rHpAlloc) / BLOCK_SIZE;
-
-         IF_DEBUG(scheduler,debugBelch("--<< thread %ld (%s) stopped: requesting a large block (size %d)\n", 
-                                  (long)t->id, whatNext_strs[t->what_next], blocks));
-
-         // don't do this if it would push us over the
-         // alloc_blocks_lim limit; we'll GC first.
-         if (alloc_blocks + blocks < alloc_blocks_lim) {
-
-             alloc_blocks += blocks;
-             bd = allocGroup( 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 {
-                 ASSERT(g0s0->blocks == cap->r.rCurrentNursery &&
-                        g0s0->blocks == cap->r.rNursery);
-                 cap->r.rNursery = g0s0->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 = g0s0;
-                     x->gen_no = 0;
-                     x->flags = 0;
-                 }
-             }
-
-             // don't forget to update the block count in g0s0.
-             g0s0->n_blocks += blocks;
-             // This assert can be a killer if the app is doing lots
-             // of large block allocations.
-             ASSERT(countBlocks(g0s0->blocks) == g0s0->n_blocks);
-
-             // 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.
-             PUSH_ON_RUN_QUEUE(t);
-             break;
-         }
-      }
-
-      /* make all the running tasks block on a condition variable,
-       * maybe set context_switch and wait till they all pile in,
-       * then have them wait on a GC condition variable.
-       */
-      IF_DEBUG(scheduler,debugBelch("--<< thread %ld (%s) stopped: HeapOverflow\n", 
-                              (long)t->id, whatNext_strs[t->what_next]));
-      threadPaused(t);
-#if defined(GRAN)
-      ASSERT(!is_on_queue(t,CurrentProc));
-#elif defined(PAR)
-      /* 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
-      
-      ready_to_gc = rtsTrue;
-      PUSH_ON_RUN_QUEUE(t);
-      /* actual GC is done at the end of the while loop */
+      globalGranStats.tot_heapover++;
+# elif defined(PAR)
+      globalParStats.tot_heapover++;
+# endif
       break;
-      
-    case StackOverflow:
-#if defined(GRAN)
+
+     case StackOverflow:
+# if defined(GRAN)
       IF_DEBUG(gran, 
               DumpGranEvent(GR_DESCHEDULE, t));
       globalGranStats.tot_stackover++;
-#elif defined(PAR)
+# elif defined(PAR)
       // IF_DEBUG(par, 
       // DumpGranEvent(GR_DESCHEDULE, t);
       globalParStats.tot_stackover++;
-#endif
-      IF_DEBUG(scheduler,debugBelch("--<< thread %ld (%s) stopped, StackOverflow\n", 
-                              (long)t->id, whatNext_strs[t->what_next]));
-      /* just adjust the stack for this thread, then pop it back
-       * on the run queue.
-       */
-      threadPaused(t);
-      { 
-       /* enlarge the stack */
-       StgTSO *new_t = threadStackOverflow(t);
-       
-       /* This TSO has moved, so update any pointers to it from the
-        * main thread stack.  It better not be on any other queues...
-        * (it shouldn't be).
-        */
-       if (t->main != NULL) {
-           t->main->tso = new_t;
-       }
-       PUSH_ON_RUN_QUEUE(new_t);
-      }
+# endif
       break;
 
     case ThreadYielding:
-      // 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;
-
-#if defined(GRAN)
+# if defined(GRAN)
       IF_DEBUG(gran, 
               DumpGranEvent(GR_DESCHEDULE, t));
       globalGranStats.tot_yields++;
-#elif defined(PAR)
+# elif defined(PAR)
       // IF_DEBUG(par, 
       // DumpGranEvent(GR_DESCHEDULE, t);
       globalParStats.tot_yields++;
-#endif
-      /* 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.
-       */
-      IF_DEBUG(scheduler,
-               if (t->what_next != prev_what_next) {
-                  debugBelch("--<< thread %ld (%s) stopped to switch evaluators\n", 
-                        (long)t->id, whatNext_strs[t->what_next]);
-               } else {
-                   debugBelch("--<< thread %ld (%s) stopped, yielding\n",
-                        (long)t->id, whatNext_strs[t->what_next]);
-               }
-               );
-
-      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) {
-         goto run_thread;
-      }
-
-      threadPaused(t);
-
-#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
-
-#if defined(PAR)
-      if (RtsFlags.ParFlags.doFairScheduling) { 
-       /* this does round-robin scheduling; good for concurrency */
-       APPEND_TO_RUN_QUEUE(t);
-      } else {
-       /* this does unfair scheduling; good for parallelism */
-       PUSH_ON_RUN_QUEUE(t);
-      }
-#else
-      // this does round-robin scheduling; good for concurrency
-      APPEND_TO_RUN_QUEUE(t);
-#endif
-
-#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 /* GRAN */
-      break;
+# endif
+      break; 
 
     case ThreadBlocked:
-#if defined(GRAN)
+# 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));
+              debugBelch("--<< 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, 
@@ -1196,69 +1414,346 @@ run_thread:
            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,
+# elif defined(PAR)
+//++PAR++  blockThread() writes the event (change?)
+# endif
+    break;
+
+  case ThreadFinished:
+    break;
+
+  default:
+    barf("parGlobalStats: unknown return code");
+    break;
+    }
+#endif
+}
 
-                  if (t->block_info.closure!=(StgClosure*)NULL) 
-                    print_bq(t->block_info.closure));
+/* -----------------------------------------------------------------------------
+ * Handle a thread that returned to the scheduler with ThreadHeepOverflow
+ * ASSUMES: sched_mutex
+ * -------------------------------------------------------------------------- */
 
-      /* Send a fetch (if BlockedOnGA) and dump event to log file */
-      blockThread(t);
+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;
+       nat blocks;
+       
+       blocks = (nat)BLOCK_ROUND_UP(cap->r.rHpAlloc) / BLOCK_SIZE;
+       
+       IF_DEBUG(scheduler,
+                debugBelch("--<< thread %ld (%s) stopped: requesting a large block (size %d)\n", 
+                           (long)t->id, whatNext_strs[t->what_next], blocks));
+       
+       // don't do this if it would push us over the
+       // alloc_blocks_lim limit; we'll GC first.
+       if (alloc_blocks + blocks < alloc_blocks_lim) {
+           
+           alloc_blocks += blocks;
+           bd = allocGroup( 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 {
+               ASSERT(g0s0->blocks == cap->r.rCurrentNursery &&
+                      g0s0->blocks == cap->r.rNursery);
+               cap->r.rNursery = g0s0->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 = g0s0;
+                   x->gen_no = 0;
+                   x->flags = 0;
+               }
+           }
+           
+           // don't forget to update the block count in g0s0.
+           g0s0->n_blocks += blocks;
+           // This assert can be a killer if the app is doing lots
+           // of large block allocations.
+           ASSERT(countBlocks(g0s0->blocks) == g0s0->n_blocks);
+           
+           // 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.
+           PUSH_ON_RUN_QUEUE(t);
+           return rtsFalse;  /* not actually GC'ing */
+       }
+    }
+    
+    /* make all the running tasks block on a condition variable,
+     * maybe set context_switch and wait till they all pile in,
+     * then have them wait on a GC condition variable.
+     */
+    IF_DEBUG(scheduler,
+            debugBelch("--<< thread %ld (%s) stopped: HeapOverflow\n", 
+                       (long)t->id, whatNext_strs[t->what_next]));
+    threadPaused(t);
+#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
+      
+    PUSH_ON_RUN_QUEUE(t);
+    return rtsTrue;
+    /* actual GC is done at the end of the while loop in schedule() */
+}
 
-      /* whatever we schedule next, we must log that schedule */
-      emitSchedule = rtsTrue;
+/* -----------------------------------------------------------------------------
+ * Handle a thread that returned to the scheduler with ThreadStackOverflow
+ * ASSUMES: sched_mutex
+ * -------------------------------------------------------------------------- */
+
+static void
+scheduleHandleStackOverflow( StgTSO *t)
+{
+    IF_DEBUG(scheduler,debugBelch("--<< thread %ld (%s) stopped, StackOverflow\n", 
+                                 (long)t->id, whatNext_strs[t->what_next]));
+    /* just adjust the stack for this thread, then pop it back
+     * on the run queue.
+     */
+    threadPaused(t);
+    { 
+       /* enlarge the stack */
+       StgTSO *new_t = threadStackOverflow(t);
+       
+       /* This TSO has moved, so update any pointers to it from the
+        * main thread stack.  It better not be on any other queues...
+        * (it shouldn't be).
+        */
+       if (t->main != NULL) {
+           t->main->tso = new_t;
+       }
+       PUSH_ON_RUN_QUEUE(new_t);
+    }
+}
+
+/* -----------------------------------------------------------------------------
+ * Handle a thread that returned to the scheduler with ThreadYielding
+ * ASSUMES: sched_mutex
+ * -------------------------------------------------------------------------- */
+
+static rtsBool
+scheduleHandleYield( 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.
+     */
+    IF_DEBUG(scheduler,
+            if (t->what_next != prev_what_next) {
+                debugBelch("--<< thread %ld (%s) stopped to switch evaluators\n", 
+                           (long)t->id, whatNext_strs[t->what_next]);
+            } else {
+                debugBelch("--<< thread %ld (%s) stopped, yielding\n",
+                           (long)t->id, whatNext_strs[t->what_next]);
+            }
+       );
+    
+    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;
+    }
+    
+    threadPaused(t);
+    
+#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(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
+ * ASSUMES: sched_mutex
+ * -------------------------------------------------------------------------- */
 
+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 */
       /* don't need to do anything.  Either the thread is blocked on
        * I/O, in which case we'll have called addToBlockedQueue
        * previously, or it's blocked on an MVar or Blackhole, in which
        * case it'll be on the relevant queue already.
        */
-      ASSERT(t->why_blocked != NotBlocked);
-      IF_DEBUG(scheduler,
-              debugBelch("--<< thread %d (%s) stopped: ", 
-                      t->id, whatNext_strs[t->what_next]);
-              printThreadBlockage(t);
-              debugBelch("\n"));
-
-      /* Only for dumping event to log file 
-        ToDo: do I need this in GranSim, too?
-      blockThread(t);
-      */
+    ASSERT(t->why_blocked != NotBlocked);
+    IF_DEBUG(scheduler,
+            debugBelch("--<< thread %d (%s) stopped: ", 
+                       t->id, whatNext_strs[t->what_next]);
+            printThreadBlockage(t);
+            debugBelch("\n"));
+    
+    /* Only for dumping event to log file 
+       ToDo: do I need this in GranSim, too?
+       blockThread(t);
+    */
 #endif
-      threadPaused(t);
-      break;
+}
+
+/* -----------------------------------------------------------------------------
+ * Handle a thread that returned to the scheduler with ThreadFinished
+ * ASSUMES: sched_mutex
+ * -------------------------------------------------------------------------- */
+
+static rtsBool
+scheduleHandleThreadFinished( StgMainThread *mainThread
+                             USED_WHEN_RTS_SUPPORTS_THREADS,
+                             Capability *cap,
+                             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.
+     */
+    IF_DEBUG(scheduler,debugBelch("--++ thread %d (%s) finished\n", 
+                                 t->id, whatNext_strs[t->what_next]));
 
-    case ThreadFinished:
-      /* Need to check whether this was a main thread, and if so, signal
-       * the task that started it with the return value.  If we have no
-       * more main threads, we probably need to stop all the tasks until
-       * we get a new one.
-       */
-      /* We also end up here if the thread kills itself with an
-       * uncaught exception, see Exception.hc.
-       */
-      IF_DEBUG(scheduler,debugBelch("--++ thread %d (%s) finished\n", 
-                              t->id, whatNext_strs[t->what_next]));
 #if defined(GRAN)
       endThread(t, CurrentProc); // clean-up the thread
-#elif defined(PAR)
+#elif defined(PARALLEL_HASKELL)
       /* For now all are advisory -- HWL */
       //if(t->priority==AdvisoryPriority) ??
-      advisory_thread_count--;
+      advisory_thread_count--; // JB: Caution with this counter, buggy!
       
-# ifdef DIST
+# 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 */);
-#endif
+
+      //  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 main
@@ -1291,7 +1786,7 @@ run_thread:
              if (mainThread->ret) {
                  *(mainThread->ret) = NULL;
              }
-             if (was_interrupted) {
+             if (interrupted) {
                  mainThread->stat = Interrupted;
              } else {
                  mainThread->stat = Killed;
@@ -1309,7 +1804,7 @@ run_thread:
              mainThread->link->prev = NULL;
          }
          releaseCapability(cap);
-         return;
+         return rtsTrue; // tells schedule() to return
       }
 
 #ifdef RTS_SUPPORTS_THREADS
@@ -1325,12 +1820,16 @@ run_thread:
          APPEND_TO_RUN_QUEUE(t);
       }
 #endif
-      break;
+      return rtsFalse;
+}
 
-    default:
-      barf("schedule: invalid thread return code %d", (int)ret);
-    }
+/* -----------------------------------------------------------------------------
+ * Perform a heap census, if PROFILING
+ * -------------------------------------------------------------------------- */
 
+static void
+scheduleDoHeapProfile(void)
+{
 #ifdef PROFILING
     // When we have +RTS -i0 and we're heap profiling, do a census at
     // every GC.  This lets us get repeatable runs for debugging.
@@ -1343,65 +1842,71 @@ run_thread:
        ready_to_gc = rtsFalse; // we already GC'd
     }
 #endif
+}
+
+/* -----------------------------------------------------------------------------
+ * Perform a garbage collection if necessary
+ * ASSUMES: sched_mutex
+ * -------------------------------------------------------------------------- */
+
+static void
+scheduleDoGC(void)
+{
+    StgTSO *t;
 
-    if (ready_to_gc) {
-      /* Kick any transactions which are invalid back to their atomically frames.
-       * When next scheduled they will try to commit, this commit will fail and
-       * they will retry. */
-      for (t = all_threads; t != END_TSO_QUEUE; t = t -> link) {
-        if (t -> what_next != ThreadRelocated && t -> trec != NO_TREC && t -> why_blocked == NotBlocked) {
-          if (!stmValidateTransaction (t -> trec)) {
-            IF_DEBUG(stm, sched_belch("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.
-           raiseAsync_(t, NULL, rtsTrue);
-            
+#ifdef SMP
+    // The last task to stop actually gets to do the GC.  The rest
+    // of the tasks release their capabilities and wait gc_pending_cond.
+    if (ready_to_gc && allFreeCapabilities())
+#else
+    if (ready_to_gc)
+#endif
+    {
+       /* Kick any transactions which are invalid back to their
+        * atomically frames.  When next scheduled they will try to
+        * commit, this commit will fail and they will retry.
+        */
+       for (t = all_threads; t != END_TSO_QUEUE; t = t -> link) {
+           if (t -> what_next != ThreadRelocated && t -> trec != NO_TREC && t -> why_blocked == NotBlocked) {
+               if (!stmValidateTransaction (t -> trec)) {
+                   IF_DEBUG(stm, sched_belch("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.
+                   raiseAsync_(t, NULL, rtsTrue);
+                   
 #ifdef REG_R1
-           ASSERT(get_itbl((StgClosure *)t->sp)->type == ATOMICALLY_FRAME);
+                   ASSERT(get_itbl((StgClosure *)t->sp)->type == ATOMICALLY_FRAME);
 #endif
-          }
-        }
-      }
+               }
+           }
+       }
 
-      /* 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.
-       */
+       /* 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(RTS_SUPPORTS_THREADS)
-      IF_DEBUG(scheduler,sched_belch("doing GC"));
+       IF_DEBUG(scheduler,sched_belch("doing GC"));
+#endif
+       GarbageCollect(GetRoots,rtsFalse);
+       ready_to_gc = rtsFalse;
+#if defined(SMP)
+       broadcastCondition(&gc_pending_cond);
 #endif
-      GarbageCollect(GetRoots,rtsFalse);
-      ready_to_gc = rtsFalse;
 #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));
+       /* 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 */
     }
-
-#if defined(GRAN)
-  next_thread:
-    IF_GRAN_DEBUG(unused,
-                 print_eventq(EventHd));
-
-    event = get_next_event();
-#elif defined(PAR)
-  next_thread:
-    /* ToDo: wait for next message to arrive rather than busy wait */
-#endif /* GRAN */
-
-  } /* end of while(1) */
-
-  IF_PAR_DEBUG(verbose,
-              debugBelch("== Leaving schedule() after having received Finish\n"));
 }
 
 /* ---------------------------------------------------------------------------
@@ -1650,12 +2155,6 @@ resumeThread( StgInt tok )
   return &cap->r;
 }
 
-
-/* ---------------------------------------------------------------------------
- * Static functions
- * ------------------------------------------------------------------------ */
-static void unblockThread(StgTSO *tso);
-
 /* ---------------------------------------------------------------------------
  * Comparing Thread ids.
  *
@@ -1728,7 +2227,7 @@ createThread(nat size)
     nat stack_size;
 
     /* First check whether we should create a thread at all */
-#if defined(PAR)
+#if defined(PARALLEL_HASKELL)
   /* check that no more than RtsFlags.ParFlags.maxThreads threads are created */
   if (advisory_thread_count >= RtsFlags.ParFlags.maxThreads) {
     threadsIgnored++;
@@ -1799,7 +2298,7 @@ createThread(nat size)
 #if defined(GRAN) 
   if (RtsFlags.GranFlags.GranSimStats.Full) 
     DumpGranEvent(GR_START,tso);
-#elif defined(PAR)
+#elif defined(PARALLEL_HASKELL)
   if (RtsFlags.ParFlags.ParStats.Full) 
     DumpGranEvent(GR_STARTQ,tso);
   /* HACk to avoid SCHEDULE 
@@ -1839,7 +2338,7 @@ createThread(nat size)
     tso->gran.clock  = 0;
 
   IF_DEBUG(gran,printTSO(tso));
-#elif defined(PAR)
+#elif defined(PARALLEL_HASKELL)
 # if defined(DEBUG)
   tso->par.magic = TSO_MAGIC; // debugging only
 # endif
@@ -1863,7 +2362,7 @@ createThread(nat size)
   globalGranStats.threads_created_on_PE[CurrentProc]++;
   globalGranStats.tot_sq_len += spark_queue_len(CurrentProc);
   globalGranStats.tot_sq_probes++;
-#elif defined(PAR)
+#elif defined(PARALLEL_HASKELL)
   // collect parallel global statistics (currently done together with GC stats)
   if (RtsFlags.ParFlags.ParStats.Global &&
       RtsFlags.GcFlags.giveStats > NO_GC_STATS) {
@@ -1876,13 +2375,13 @@ createThread(nat size)
   IF_GRAN_DEBUG(pri,
                sched_belch("==__ schedule: Created TSO %d (%p);",
                      CurrentProc, tso, tso->id));
-#elif defined(PAR)
-    IF_PAR_DEBUG(verbose,
-                sched_belch("==__ schedule: Created TSO %d (%p); %d threads active",
-                      (long)tso->id, tso, advisory_thread_count));
+#elif defined(PARALLEL_HASKELL)
+  IF_PAR_DEBUG(verbose,
+              sched_belch("==__ schedule: Created TSO %d (%p); %d threads active",
+                          (long)tso->id, tso, advisory_thread_count));
 #else
   IF_DEBUG(scheduler,sched_belch("created thread %ld, stack size = %lx words", 
-                               (long)tso->id, (long)tso->stack_size));
+                                (long)tso->id, (long)tso->stack_size));
 #endif    
   return tso;
 }
@@ -1892,9 +2391,10 @@ createThread(nat size)
    all parallel thread creation calls should fall through the following routine.
 */
 StgTSO *
-createSparkThread(rtsSpark spark) 
+createThreadFromSpark(rtsSpark spark) 
 { StgTSO *tso;
   ASSERT(spark != (rtsSpark)NULL);
+// JB: TAKE CARE OF THIS COUNTER! BUGGY
   if (advisory_thread_count >= RtsFlags.ParFlags.maxThreads) 
   { threadsIgnored++;
     barf("{createSparkThread}Daq ghuH: refusing to create another thread; no more than %d threads allowed (currently %d)",
@@ -1910,8 +2410,8 @@ createSparkThread(rtsSpark spark)
     tso->priority = AdvisoryPriority;
 #endif
     pushClosure(tso,spark);
-    PUSH_ON_RUN_QUEUE(tso);
-    advisory_thread_count++;    
+    addToRunQueue(tso);
+    advisory_thread_count++;  // JB: TAKE CARE OF THIS COUNTER! BUGGY
   }
   return tso;
 }
@@ -1921,7 +2421,7 @@ createSparkThread(rtsSpark spark)
   Turn a spark into a thread.
   ToDo: fix for SMP (needs to acquire SCHED_MUTEX!)
 */
-#if defined(PAR)
+#if 0
 StgTSO *
 activateSpark (rtsSpark spark) 
 {
@@ -1930,9 +2430,9 @@ activateSpark (rtsSpark spark)
   tso = createSparkThread(spark);
   if (RtsFlags.ParFlags.ParStats.Full) {   
     //ASSERT(run_queue_hd == END_TSO_QUEUE); // I think ...
-    IF_PAR_DEBUG(verbose,
-                debugBelch("==^^ activateSpark: turning spark of closure %p (%s) into a thread\n",
-                      (StgClosure *)spark, info_type((StgClosure *)spark)));
+      IF_PAR_DEBUG(verbose,
+                  debugBelch("==^^ activateSpark: turning spark of closure %p (%s) into a thread\n",
+                             (StgClosure *)spark, info_type((StgClosure *)spark)));
   }
   // ToDo: fwd info on local/global spark to thread -- HWL
   // tso->gran.exported =  spark->exported;
@@ -1943,11 +2443,6 @@ activateSpark (rtsSpark spark)
 }
 #endif
 
-static SchedulerStatus waitThread_(/*out*/StgMainThread* m,
-                                  Capability *initialCapability
-                                  );
-
-
 /* ---------------------------------------------------------------------------
  * scheduleThread()
  *
@@ -1958,9 +2453,7 @@ static SchedulerStatus waitThread_(/*out*/StgMainThread* m,
  * on this thread's stack before the scheduler is invoked.
  * ------------------------------------------------------------------------ */
 
-static void scheduleThread_ (StgTSO* tso);
-
-void
+static void
 scheduleThread_(StgTSO *tso)
 {
   // The thread goes at the *end* of the run-queue, to avoid possible
@@ -2095,7 +2588,7 @@ initScheduler(void)
     startTaskManager(0,taskStart);
 #endif
 
-#if /* defined(SMP) ||*/ defined(PAR)
+#if /* defined(SMP) ||*/ defined(PARALLEL_HASKELL)
   initSparkPools();
 #endif
 
@@ -2108,6 +2601,7 @@ exitScheduler( void )
 #if defined(RTS_SUPPORTS_THREADS)
   stopTaskManager();
 #endif
+  interrupted = rtsTrue;
   shutting_down_scheduler = rtsTrue;
 }
 
@@ -2120,8 +2614,7 @@ exitScheduler( void )
    ToDo: no support for two-space collection at the moment???
    ------------------------------------------------------------------------- */
 
-static
-SchedulerStatus
+static SchedulerStatus
 waitThread_(StgMainThread* m, Capability *initialCapability)
 {
   SchedulerStatus stat;
@@ -2220,7 +2713,7 @@ GetRoots( evac_fn evac )
       evac((StgClosure **)&suspended_ccalling_threads);
   }
 
-#if defined(PAR) || defined(GRAN)
+#if defined(PARALLEL_HASKELL) || defined(GRAN)
   markSparkQueue(evac);
 #endif
 
@@ -2370,7 +2863,7 @@ STATIC_INLINE void
 unblockCount ( StgBlockingQueueElement *bqe, StgClosure *node )
 {
 }
-#elif defined(PAR)
+#elif defined(PARALLEL_HASKELL)
 STATIC_INLINE void
 unblockCount ( StgBlockingQueueElement *bqe, StgClosure *node )
 {
@@ -2443,7 +2936,7 @@ unblockOneLocked(StgBlockingQueueElement *bqe, StgClosure *node)
     IF_DEBUG(scheduler,debugBelch("-- Waking up thread %ld (%p)\n", 
                             tso->id, tso));
 }
-#elif defined(PAR)
+#elif defined(PARALLEL_HASKELL)
 static StgBlockingQueueElement *
 unblockOneLocked(StgBlockingQueueElement *bqe, StgClosure *node)
 {
@@ -2489,7 +2982,7 @@ unblockOneLocked(StgBlockingQueueElement *bqe, StgClosure *node)
   return next;
 }
 
-#else /* !GRAN && !PAR */
+#else /* !GRAN && !PARALLEL_HASKELL */
 static StgTSO *
 unblockOneLocked(StgTSO *tso)
 {
@@ -2507,7 +3000,7 @@ unblockOneLocked(StgTSO *tso)
 }
 #endif
 
-#if defined(GRAN) || defined(PAR)
+#if defined(GRAN) || defined(PARALLEL_HASKELL)
 INLINE_ME StgBlockingQueueElement *
 unblockOne(StgBlockingQueueElement *bqe, StgClosure *node)
 {
@@ -2609,7 +3102,7 @@ awakenBlockedQueue(StgBlockingQueueElement *q, StgClosure *node)
                debugBelch("## BQ Stats of %p: [%d entries] %s\n",
                        node, len, (bqe!=END_BQ_QUEUE) ? "RBH" : ""));
 }
-#elif defined(PAR)
+#elif defined(PARALLEL_HASKELL)
 void 
 awakenBlockedQueue(StgBlockingQueueElement *q, StgClosure *node)
 {
@@ -2641,7 +3134,7 @@ awakenBlockedQueue(StgBlockingQueueElement *q, StgClosure *node)
   RELEASE_LOCK(&sched_mutex);
 }
 
-#else   /* !GRAN && !PAR */
+#else   /* !GRAN && !PARALLEL_HASKELL */
 
 void
 awakenBlockedQueueNoLock(StgTSO *tso)
@@ -2682,7 +3175,7 @@ interruptStgRts(void)
    This has nothing to do with the UnblockThread event in GranSim. -- HWL
    -------------------------------------------------------------------------- */
 
-#if defined(GRAN) || defined(PAR)
+#if defined(GRAN) || defined(PARALLEL_HASKELL)
 /*
   NB: only the type of the blocking queue is different in GranSim and GUM
       the operations on the queue-elements are the same
@@ -3432,8 +3925,7 @@ resurrectThreads( StgTSO *threads )
  *  at the Haskell source code level, so enable outside of DEBUG. --sof 7/02]
    ------------------------------------------------------------------------- */
 
-static
-void
+static void
 printThreadBlockage(StgTSO *tso)
 {
   switch (tso->why_blocked) {
@@ -3464,7 +3956,7 @@ printThreadBlockage(StgTSO *tso)
   case NotBlocked:
     debugBelch("is not blocked");
     break;
-#if defined(PAR)
+#if defined(PARALLEL_HASKELL)
   case BlockedOnGA:
     debugBelch("is blocked on global address; local FM_BQ is %p (%s)",
            tso->block_info.closure, info_type(tso->block_info.closure));
@@ -3489,8 +3981,7 @@ printThreadBlockage(StgTSO *tso)
   }
 }
 
-static
-void
+static void
 printThreadStatus(StgTSO *tso)
 {
   switch (tso->what_next) {
@@ -3516,7 +4007,7 @@ printAllThreads(void)
                       time_string, rtsFalse/*no commas!*/);
 
   debugBelch("all threads at [%s]:\n", time_string);
-# elif defined(PAR)
+# elif defined(PARALLEL_HASKELL)
   char time_string[TIME_STR_LEN], node_str[NODE_STR_LEN];
   ullong_format_string(CURRENT_TIME,
                       time_string, rtsFalse/*no commas!*/);
@@ -3544,7 +4035,7 @@ printAllThreads(void)
 /* 
    Print a whole blocking queue attached to node (debugging only).
 */
-# if defined(PAR)
+# if defined(PARALLEL_HASKELL)
 void 
 print_bq (StgClosure *node)
 {
@@ -3692,7 +4183,7 @@ print_bq (StgClosure *node)
 }
 # endif
 
-#if defined(PAR)
+#if defined(PARALLEL_HASKELL)
 static nat
 run_queue_len(void)
 {
@@ -3715,7 +4206,7 @@ sched_belch(char *s, ...)
   va_start(ap,s);
 #ifdef RTS_SUPPORTS_THREADS
   debugBelch("sched (task %p): ", osThreadId());
-#elif defined(PAR)
+#elif defined(PARALLEL_HASKELL)
   debugBelch("== ");
 #else
   debugBelch("sched: ");