micro-opt: replace stmGetEnclosingTRec() with a field access

[ghc-hetmet.git] / rts / RaiseAsync.c

diff --git a/rts/RaiseAsync.c b/rts/RaiseAsync.c
index ee53e0d..a0f78ee 100644 (file)
--- a/rts/RaiseAsync.c
+++ b/rts/RaiseAsync.c
@@ -8,12 +8,12 @@
 
 #include "PosixSource.h"
 #include "Rts.h"
 
 #include "PosixSource.h"
 #include "Rts.h"

+
+#include "sm/Storage.h"

 #include "Threads.h"
 #include "Trace.h"
 #include "RaiseAsync.h"
 #include "Threads.h"
 #include "Trace.h"
 #include "RaiseAsync.h"

-#include "SMP.h"

 #include "Schedule.h"
 #include "Schedule.h"

-#include "LdvProfile.h"

 #include "Updates.h"
 #include "STM.h"
 #include "Sanity.h"
 #include "Updates.h"
 #include "STM.h"
 #include "Sanity.h"

@@ -26,11 +26,11 @@ static void raiseAsync (Capability *cap,
                        StgTSO *tso,
                        StgClosure *exception, 
                        rtsBool stop_at_atomically,
                        StgTSO *tso,
                        StgClosure *exception, 
                        rtsBool stop_at_atomically,

-                       StgPtr stop_here);
+                       StgUpdateFrame *stop_here);

 
 static void removeFromQueues(Capability *cap, StgTSO *tso);
 
 
 static void removeFromQueues(Capability *cap, StgTSO *tso);
 

-static void blockedThrowTo (StgTSO *source, StgTSO *target);
+static void blockedThrowTo (Capability *cap, StgTSO *source, StgTSO *target);

 
 static void performBlockedException (Capability *cap, 
                                     StgTSO *source, StgTSO *target);
 
 static void performBlockedException (Capability *cap, 
                                     StgTSO *source, StgTSO *target);

@@ -55,12 +55,12 @@ static void performBlockedException (Capability *cap,
 void
 throwToSingleThreaded(Capability *cap, StgTSO *tso, StgClosure *exception)
 {
 void
 throwToSingleThreaded(Capability *cap, StgTSO *tso, StgClosure *exception)
 {

-    throwToSingleThreaded_(cap, tso, exception, rtsFalse, NULL);
+    throwToSingleThreaded_(cap, tso, exception, rtsFalse);

 }
 
 void
 throwToSingleThreaded_(Capability *cap, StgTSO *tso, StgClosure *exception, 
 }
 
 void
 throwToSingleThreaded_(Capability *cap, StgTSO *tso, StgClosure *exception, 

-                      rtsBool stop_at_atomically, StgPtr stop_here)
+                      rtsBool stop_at_atomically)

 {
     // Thread already dead?
     if (tso->what_next == ThreadComplete || tso->what_next == ThreadKilled) {
 {
     // Thread already dead?
     if (tso->what_next == ThreadComplete || tso->what_next == ThreadKilled) {

@@ -70,11 +70,11 @@ throwToSingleThreaded_(Capability *cap, StgTSO *tso, StgClosure *exception,
     // Remove it from any blocking queues
     removeFromQueues(cap,tso);
 
     // Remove it from any blocking queues
     removeFromQueues(cap,tso);
 

-    raiseAsync(cap, tso, exception, stop_at_atomically, stop_here);
+    raiseAsync(cap, tso, exception, stop_at_atomically, NULL);

 }
 
 void
 }
 
 void

-suspendComputation(Capability *cap, StgTSO *tso, StgPtr stop_here)
+suspendComputation(Capability *cap, StgTSO *tso, StgUpdateFrame *stop_here)

 {
     // Thread already dead?
     if (tso->what_next == ThreadComplete || tso->what_next == ThreadKilled) {
 {
     // Thread already dead?
     if (tso->what_next == ThreadComplete || tso->what_next == ThreadKilled) {

@@ -152,7 +152,7 @@ throwTo (Capability *cap,   // the Capability we hold
 
     // follow ThreadRelocated links in the target first
     while (target->what_next == ThreadRelocated) {
 
     // follow ThreadRelocated links in the target first
     while (target->what_next == ThreadRelocated) {

-       target = target->link;
+       target = target->_link;

        // No, it might be a WHITEHOLE:
        // ASSERT(get_itbl(target)->type == TSO);
     }
        // No, it might be a WHITEHOLE:
        // ASSERT(get_itbl(target)->type == TSO);
     }

@@ -161,11 +161,7 @@ throwTo (Capability *cap,  // the Capability we hold
               (unsigned long)source->id, (unsigned long)target->id);
 
 #ifdef DEBUG
               (unsigned long)source->id, (unsigned long)target->id);
 
 #ifdef DEBUG

-    if (traceClass(DEBUG_sched)) {
-       debugTraceBegin("throwTo: target");
-       printThreadStatus(target);
-       debugTraceEnd();
-    }
+    traceThreadStatus(DEBUG_sched, target);

 #endif
 
     goto check_target;
 #endif
 
     goto check_target;

@@ -261,10 +257,19 @@ check_target:
            // just moved this TSO.
            if (target->what_next == ThreadRelocated) {
                unlockTSO(target);
            // just moved this TSO.
            if (target->what_next == ThreadRelocated) {
                unlockTSO(target);

-               target = target->link;
+               target = target->_link;

                goto retry;
            }
                goto retry;
            }

-           blockedThrowTo(source,target);
+            // check again for ThreadComplete and ThreadKilled.  This
+            // cooperates with scheduleHandleThreadFinished to ensure
+            // that we never miss any threads that are throwing an
+            // exception to a thread in the process of terminating.
+            if (target->what_next == ThreadComplete
+                || target->what_next == ThreadKilled) {
+               unlockTSO(target);
+                return THROWTO_SUCCESS;
+            }
+           blockedThrowTo(cap,source,target);

            *out = target;
            return THROWTO_BLOCKED;
        }
            *out = target;
            return THROWTO_BLOCKED;
        }

@@ -294,7 +299,7 @@ check_target:
        info = lockClosure((StgClosure *)mvar);
 
        if (target->what_next == ThreadRelocated) {
        info = lockClosure((StgClosure *)mvar);
 
        if (target->what_next == ThreadRelocated) {

-           target = target->link;
+           target = target->_link;

            unlockClosure((StgClosure *)mvar,info);
            goto retry;
        }
            unlockClosure((StgClosure *)mvar,info);
            goto retry;
        }

@@ -309,12 +314,12 @@ check_target:
        if ((target->flags & TSO_BLOCKEX) &&
            ((target->flags & TSO_INTERRUPTIBLE) == 0)) {
            lockClosure((StgClosure *)target);
        if ((target->flags & TSO_BLOCKEX) &&
            ((target->flags & TSO_INTERRUPTIBLE) == 0)) {
            lockClosure((StgClosure *)target);

-           blockedThrowTo(source,target);
+           blockedThrowTo(cap,source,target);

            unlockClosure((StgClosure *)mvar, info);
            *out = target;
            return THROWTO_BLOCKED; // caller releases TSO
        } else {
            unlockClosure((StgClosure *)mvar, info);
            *out = target;
            return THROWTO_BLOCKED; // caller releases TSO
        } else {

-           removeThreadFromMVarQueue(mvar, target);
+           removeThreadFromMVarQueue(cap, mvar, target);

            raiseAsync(cap, target, exception, rtsFalse, NULL);
            unblockOne(cap, target);
            unlockClosure((StgClosure *)mvar, info);
            raiseAsync(cap, target, exception, rtsFalse, NULL);
            unblockOne(cap, target);
            unlockClosure((StgClosure *)mvar, info);

@@ -333,12 +338,12 @@ check_target:
 
        if (target->flags & TSO_BLOCKEX) {
            lockTSO(target);
 
        if (target->flags & TSO_BLOCKEX) {
            lockTSO(target);

-           blockedThrowTo(source,target);
+           blockedThrowTo(cap,source,target);

            RELEASE_LOCK(&sched_mutex);
            *out = target;
            return THROWTO_BLOCKED; // caller releases TSO
        } else {
            RELEASE_LOCK(&sched_mutex);
            *out = target;
            return THROWTO_BLOCKED; // caller releases TSO
        } else {

-           removeThreadFromQueue(&blackhole_queue, target);
+           removeThreadFromQueue(cap, &blackhole_queue, target);

            raiseAsync(cap, target, exception, rtsFalse, NULL);
            unblockOne(cap, target);
            RELEASE_LOCK(&sched_mutex);
            raiseAsync(cap, target, exception, rtsFalse, NULL);
            unblockOne(cap, target);
            RELEASE_LOCK(&sched_mutex);

@@ -373,12 +378,12 @@ check_target:
            goto retry;
        }
        if (target->what_next == ThreadRelocated) {
            goto retry;
        }
        if (target->what_next == ThreadRelocated) {

-           target = target->link;
+           target = target->_link;

            unlockTSO(target2);
            goto retry;
        }
        if (target2->what_next == ThreadRelocated) {
            unlockTSO(target2);
            goto retry;
        }
        if (target2->what_next == ThreadRelocated) {

-           target->block_info.tso = target2->link;
+           target->block_info.tso = target2->_link;

            unlockTSO(target2);
            goto retry;
        }
            unlockTSO(target2);
            goto retry;
        }

@@ -397,12 +402,12 @@ check_target:
        if ((target->flags & TSO_BLOCKEX) &&
            ((target->flags & TSO_INTERRUPTIBLE) == 0)) {
            lockTSO(target);
        if ((target->flags & TSO_BLOCKEX) &&
            ((target->flags & TSO_INTERRUPTIBLE) == 0)) {
            lockTSO(target);

-           blockedThrowTo(source,target);
+           blockedThrowTo(cap,source,target);

            unlockTSO(target2);
            *out = target;
            return THROWTO_BLOCKED;
        } else {
            unlockTSO(target2);
            *out = target;
            return THROWTO_BLOCKED;
        } else {

-           removeThreadFromQueue(&target2->blocked_exceptions, target);
+           removeThreadFromQueue(cap, &target2->blocked_exceptions, target);

            raiseAsync(cap, target, exception, rtsFalse, NULL);
            unblockOne(cap, target);
            unlockTSO(target2);
            raiseAsync(cap, target, exception, rtsFalse, NULL);
            unblockOne(cap, target);
            unlockTSO(target2);

@@ -415,11 +420,12 @@ check_target:
        // Unblocking BlockedOnSTM threads requires the TSO to be
        // locked; see STM.c:unpark_tso().
        if (target->why_blocked != BlockedOnSTM) {
        // Unblocking BlockedOnSTM threads requires the TSO to be
        // locked; see STM.c:unpark_tso().
        if (target->why_blocked != BlockedOnSTM) {

+           unlockTSO(target);

            goto retry;
        }
        if ((target->flags & TSO_BLOCKEX) &&
            ((target->flags & TSO_INTERRUPTIBLE) == 0)) {
            goto retry;
        }
        if ((target->flags & TSO_BLOCKEX) &&
            ((target->flags & TSO_INTERRUPTIBLE) == 0)) {

-           blockedThrowTo(source,target);
+           blockedThrowTo(cap,source,target);

            *out = target;
            return THROWTO_BLOCKED;
        } else {
            *out = target;
            return THROWTO_BLOCKED;
        } else {

@@ -436,7 +442,12 @@ check_target:
        // thread is blocking exceptions, and block on its
        // blocked_exception queue.
        lockTSO(target);
        // thread is blocking exceptions, and block on its
        // blocked_exception queue.
        lockTSO(target);

-       blockedThrowTo(source,target);
+       if (target->why_blocked != BlockedOnCCall &&
+           target->why_blocked != BlockedOnCCall_NoUnblockExc) {
+           unlockTSO(target);
+            goto retry;
+       }
+       blockedThrowTo(cap,source,target);

        *out = target;
        return THROWTO_BLOCKED;
 
        *out = target;
        return THROWTO_BLOCKED;
 

@@ -449,7 +460,7 @@ check_target:
 #endif
        if ((target->flags & TSO_BLOCKEX) &&
            ((target->flags & TSO_INTERRUPTIBLE) == 0)) {
 #endif
        if ((target->flags & TSO_BLOCKEX) &&
            ((target->flags & TSO_INTERRUPTIBLE) == 0)) {

-           blockedThrowTo(source,target);
+           blockedThrowTo(cap,source,target);

            return THROWTO_BLOCKED;
        } else {
            removeFromQueues(cap,target);
            return THROWTO_BLOCKED;
        } else {
            removeFromQueues(cap,target);

@@ -469,12 +480,12 @@ check_target:
 // complex to achieve as there's no single lock on a TSO; see
 // throwTo()).
 static void
 // complex to achieve as there's no single lock on a TSO; see
 // throwTo()).
 static void

-blockedThrowTo (StgTSO *source, StgTSO *target)
+blockedThrowTo (Capability *cap, StgTSO *source, StgTSO *target)

 {
     debugTrace(DEBUG_sched, "throwTo: blocking on thread %lu", (unsigned long)target->id);
 {
     debugTrace(DEBUG_sched, "throwTo: blocking on thread %lu", (unsigned long)target->id);

-    source->link = target->blocked_exceptions;
+    setTSOLink(cap, source, target->blocked_exceptions);

     target->blocked_exceptions = source;
     target->blocked_exceptions = source;

-    dirtyTSO(target); // we modified the blocked_exceptions queue
+    dirty_TSO(cap,target); // we modified the blocked_exceptions queue

     
     source->block_info.tso = target;
     write_barrier(); // throwTo_exception *must* be visible if BlockedOnException is.
     
     source->block_info.tso = target;
     write_barrier(); // throwTo_exception *must* be visible if BlockedOnException is.

@@ -512,6 +523,15 @@ maybePerformBlockedException (Capability *cap, StgTSO *tso)
 {
     StgTSO *source;
     
 {
     StgTSO *source;
     

+    if (tso->what_next == ThreadComplete || tso->what_next == ThreadFinished) {
+        if (tso->blocked_exceptions != END_TSO_QUEUE) {
+            awakenBlockedExceptionQueue(cap,tso);
+            return 1;
+        } else {
+            return 0;
+        }
+    }
+

     if (tso->blocked_exceptions != END_TSO_QUEUE && 
         (tso->flags & TSO_BLOCKEX) != 0) {
         debugTrace(DEBUG_sched, "throwTo: thread %lu has blocked exceptions but is inside block", (unsigned long)tso->id);
     if (tso->blocked_exceptions != END_TSO_QUEUE && 
         (tso->flags & TSO_BLOCKEX) != 0) {
         debugTrace(DEBUG_sched, "throwTo: thread %lu has blocked exceptions but is inside block", (unsigned long)tso->id);

@@ -543,15 +563,16 @@ maybePerformBlockedException (Capability *cap, StgTSO *tso)
     return 0;
 }
 
     return 0;
 }
 

+// awakenBlockedExceptionQueue(): Just wake up the whole queue of
+// blocked exceptions and let them try again.
+

 void
 awakenBlockedExceptionQueue (Capability *cap, StgTSO *tso)
 {
 void
 awakenBlockedExceptionQueue (Capability *cap, StgTSO *tso)
 {

-    if (tso->blocked_exceptions != END_TSO_QUEUE) {
-       lockTSO(tso);
-       awakenBlockedQueue(cap, tso->blocked_exceptions);
-       tso->blocked_exceptions = END_TSO_QUEUE;
-       unlockTSO(tso);
-    }
+    lockTSO(tso);
+    awakenBlockedQueue(cap, tso->blocked_exceptions);
+    tso->blocked_exceptions = END_TSO_QUEUE;
+    unlockTSO(tso);

 }    
 
 static void
 }    
 
 static void

@@ -575,161 +596,11 @@ performBlockedException (Capability *cap, StgTSO *source, StgTSO *target)
 
    This is for use when we raise an exception in another thread, which
    may be blocked.
 
    This is for use when we raise an exception in another thread, which
    may be blocked.

-   This has nothing to do with the UnblockThread event in GranSim. -- HWL
-   -------------------------------------------------------------------------- */
-
-#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
-      long live polymorphism!
-
-  Locks: sched_mutex is held upon entry and exit.
-
-*/
-static void
-removeFromQueues(Capability *cap, StgTSO *tso)
-{
-  StgBlockingQueueElement *t, **last;
-
-  switch (tso->why_blocked) {
-
-  case NotBlocked:
-    return;  /* not blocked */
-
-  case BlockedOnSTM:
-    // Be careful: nothing to do here!  We tell the scheduler that the thread
-    // is runnable and we leave it to the stack-walking code to abort the 
-    // transaction while unwinding the stack.  We should perhaps have a debugging
-    // test to make sure that this really happens and that the 'zombie' transaction
-    // does not get committed.
-    goto done;
-
-  case BlockedOnMVar:
-    ASSERT(get_itbl(tso->block_info.closure)->type == MVAR);
-    {
-      StgBlockingQueueElement *last_tso = END_BQ_QUEUE;
-      StgMVar *mvar = (StgMVar *)(tso->block_info.closure);
-
-      last = (StgBlockingQueueElement **)&mvar->head;
-      for (t = (StgBlockingQueueElement *)mvar->head; 
-          t != END_BQ_QUEUE; 
-          last = &t->link, last_tso = t, t = t->link) {
-       if (t == (StgBlockingQueueElement *)tso) {
-         *last = (StgBlockingQueueElement *)tso->link;
-         if (mvar->tail == tso) {
-           mvar->tail = (StgTSO *)last_tso;
-         }
-         goto done;
-       }
-      }
-      barf("removeFromQueues (MVAR): TSO not found");
-    }
-
-  case BlockedOnBlackHole:
-    ASSERT(get_itbl(tso->block_info.closure)->type == BLACKHOLE_BQ);
-    {
-      StgBlockingQueue *bq = (StgBlockingQueue *)(tso->block_info.closure);
-
-      last = &bq->blocking_queue;
-      for (t = bq->blocking_queue; 
-          t != END_BQ_QUEUE; 
-          last = &t->link, t = t->link) {
-       if (t == (StgBlockingQueueElement *)tso) {
-         *last = (StgBlockingQueueElement *)tso->link;
-         goto done;
-       }
-      }
-      barf("removeFromQueues (BLACKHOLE): TSO not found");
-    }
-
-  case BlockedOnException:
-    {
-      StgTSO *target  = tso->block_info.tso;

 
 

-      ASSERT(get_itbl(target)->type == TSO);
-
-      while (target->what_next == ThreadRelocated) {
-         target = target2->link;
-         ASSERT(get_itbl(target)->type == TSO);
-      }
-
-      last = (StgBlockingQueueElement **)&target->blocked_exceptions;
-      for (t = (StgBlockingQueueElement *)target->blocked_exceptions; 
-          t != END_BQ_QUEUE; 
-          last = &t->link, t = t->link) {
-       ASSERT(get_itbl(t)->type == TSO);
-       if (t == (StgBlockingQueueElement *)tso) {
-         *last = (StgBlockingQueueElement *)tso->link;
-         goto done;
-       }
-      }
-      barf("removeFromQueues (Exception): TSO not found");
-    }
-
-  case BlockedOnRead:
-  case BlockedOnWrite:
-#if defined(mingw32_HOST_OS)
-  case BlockedOnDoProc:
-#endif
-    {
-      /* take TSO off blocked_queue */
-      StgBlockingQueueElement *prev = NULL;
-      for (t = (StgBlockingQueueElement *)blocked_queue_hd; t != END_BQ_QUEUE; 
-          prev = t, t = t->link) {
-       if (t == (StgBlockingQueueElement *)tso) {
-         if (prev == NULL) {
-           blocked_queue_hd = (StgTSO *)t->link;
-           if ((StgBlockingQueueElement *)blocked_queue_tl == t) {
-             blocked_queue_tl = END_TSO_QUEUE;
-           }
-         } else {
-           prev->link = t->link;
-           if ((StgBlockingQueueElement *)blocked_queue_tl == t) {
-             blocked_queue_tl = (StgTSO *)prev;
-           }
-         }
-#if defined(mingw32_HOST_OS)
-         /* (Cooperatively) signal that the worker thread should abort
-          * the request.
-          */
-         abandonWorkRequest(tso->block_info.async_result->reqID);
-#endif
-         goto done;
-       }
-      }
-      barf("removeFromQueues (I/O): TSO not found");
-    }
-
-  case BlockedOnDelay:
-    {
-      /* take TSO off sleeping_queue */
-      StgBlockingQueueElement *prev = NULL;
-      for (t = (StgBlockingQueueElement *)sleeping_queue; t != END_BQ_QUEUE; 
-          prev = t, t = t->link) {
-       if (t == (StgBlockingQueueElement *)tso) {
-         if (prev == NULL) {
-           sleeping_queue = (StgTSO *)t->link;
-         } else {
-           prev->link = t->link;
-         }
-         goto done;
-       }
-      }
-      barf("removeFromQueues (delay): TSO not found");
-    }
-
-  default:
-    barf("removeFromQueues: %d", tso->why_blocked);
-  }
+   Precondition: we have exclusive access to the TSO, via the same set
+   of conditions as throwToSingleThreaded() (c.f.).
+   -------------------------------------------------------------------------- */

 
 

- done:
-  tso->link = END_TSO_QUEUE;
-  tso->why_blocked = NotBlocked;
-  tso->block_info.closure = NULL;
-  pushOnRunQueue(cap,tso);
-}
-#else

 static void
 removeFromQueues(Capability *cap, StgTSO *tso)
 {
 static void
 removeFromQueues(Capability *cap, StgTSO *tso)
 {

@@ -748,11 +619,11 @@ removeFromQueues(Capability *cap, StgTSO *tso)
     goto done;
 
   case BlockedOnMVar:
     goto done;
 
   case BlockedOnMVar:

-      removeThreadFromMVarQueue((StgMVar *)tso->block_info.closure, tso);
+      removeThreadFromMVarQueue(cap, (StgMVar *)tso->block_info.closure, tso);

       goto done;
 
   case BlockedOnBlackHole:
       goto done;
 
   case BlockedOnBlackHole:

-      removeThreadFromQueue(&blackhole_queue, tso);
+      removeThreadFromQueue(cap, &blackhole_queue, tso);

       goto done;
 
   case BlockedOnException:
       goto done;
 
   case BlockedOnException:

@@ -765,10 +636,10 @@ removeFromQueues(Capability *cap, StgTSO *tso)
       // ASSERT(get_itbl(target)->type == TSO);
 
       while (target->what_next == ThreadRelocated) {
       // ASSERT(get_itbl(target)->type == TSO);
 
       while (target->what_next == ThreadRelocated) {

-         target = target->link;
+         target = target->_link;

       }
       
       }
       

-      removeThreadFromQueue(&target->blocked_exceptions, tso);
+      removeThreadFromQueue(cap, &target->blocked_exceptions, tso);

       goto done;
     }
 
       goto done;
     }
 

@@ -778,7 +649,7 @@ removeFromQueues(Capability *cap, StgTSO *tso)
 #if defined(mingw32_HOST_OS)
   case BlockedOnDoProc:
 #endif
 #if defined(mingw32_HOST_OS)
   case BlockedOnDoProc:
 #endif

-      removeThreadFromDeQueue(&blocked_queue_hd, &blocked_queue_tl, tso);
+      removeThreadFromDeQueue(cap, &blocked_queue_hd, &blocked_queue_tl, tso);

 #if defined(mingw32_HOST_OS)
       /* (Cooperatively) signal that the worker thread should abort
        * the request.
 #if defined(mingw32_HOST_OS)
       /* (Cooperatively) signal that the worker thread should abort
        * the request.

@@ -788,7 +659,7 @@ removeFromQueues(Capability *cap, StgTSO *tso)
       goto done;
 
   case BlockedOnDelay:
       goto done;
 
   case BlockedOnDelay:

-       removeThreadFromQueue(&sleeping_queue, tso);
+        removeThreadFromQueue(cap, &sleeping_queue, tso);

        goto done;
 #endif
 
        goto done;
 #endif
 

@@ -797,18 +668,8 @@ removeFromQueues(Capability *cap, StgTSO *tso)
   }
 
  done:
   }
 
  done:

-  tso->link = END_TSO_QUEUE;
-  tso->why_blocked = NotBlocked;
-  tso->block_info.closure = NULL;
-  appendToRunQueue(cap,tso);
-
-  // We might have just migrated this TSO to our Capability:
-  if (tso->bound) {
-      tso->bound->cap = cap;
-  }
-  tso->cap = cap;
+  unblockOne(cap, tso);

 }
 }

-#endif

 
 /* -----------------------------------------------------------------------------
  * raiseAsync()
 
 /* -----------------------------------------------------------------------------
  * raiseAsync()

@@ -849,10 +710,11 @@ removeFromQueues(Capability *cap, StgTSO *tso)
 
 static void
 raiseAsync(Capability *cap, StgTSO *tso, StgClosure *exception, 
 
 static void
 raiseAsync(Capability *cap, StgTSO *tso, StgClosure *exception, 

-          rtsBool stop_at_atomically, StgPtr stop_here)
+          rtsBool stop_at_atomically, StgUpdateFrame *stop_here)

 {
     StgRetInfoTable *info;
     StgPtr sp, frame;
 {
     StgRetInfoTable *info;
     StgPtr sp, frame;

+    StgClosure *updatee;

     nat i;
 
     debugTrace(DEBUG_sched,
     nat i;
 
     debugTrace(DEBUG_sched,

@@ -861,7 +723,7 @@ raiseAsync(Capability *cap, StgTSO *tso, StgClosure *exception,
 #if defined(PROFILING)
     /* 
      * Debugging tool: on raising an  exception, show where we are.
 #if defined(PROFILING)
     /* 
      * Debugging tool: on raising an  exception, show where we are.

-     * See also Exception.cmm:raisezh_fast.
+     * See also Exception.cmm:stg_raisezh.

      * This wasn't done for asynchronous exceptions originally; see #1450 
      */
     if (RtsFlags.ProfFlags.showCCSOnException)
      * This wasn't done for asynchronous exceptions originally; see #1450 
      */
     if (RtsFlags.ProfFlags.showCCSOnException)

@@ -871,7 +733,7 @@ raiseAsync(Capability *cap, StgTSO *tso, StgClosure *exception,
 #endif
 
     // mark it dirty; we're about to change its stack.
 #endif
 
     // mark it dirty; we're about to change its stack.

-    dirtyTSO(tso);
+    dirty_TSO(cap, tso);

 
     sp = tso->sp;
     
 
     sp = tso->sp;
     

@@ -879,6 +741,12 @@ raiseAsync(Capability *cap, StgTSO *tso, StgClosure *exception,
     // layers should deal with that.
     ASSERT(tso->what_next != ThreadComplete && tso->what_next != ThreadKilled);
 
     // layers should deal with that.
     ASSERT(tso->what_next != ThreadComplete && tso->what_next != ThreadKilled);
 

+    if (stop_here != NULL) {
+        updatee = stop_here->updatee;
+    } else {
+        updatee = NULL;
+    }
+

     // The stack freezing code assumes there's a closure pointer on
     // the top of the stack, so we have to arrange that this is the case...
     //
     // The stack freezing code assumes there's a closure pointer on
     // the top of the stack, so we have to arrange that this is the case...
     //

@@ -890,7 +758,7 @@ raiseAsync(Capability *cap, StgTSO *tso, StgClosure *exception,
     }
 
     frame = sp + 1;
     }
 
     frame = sp + 1;

-    while (stop_here == NULL || frame < stop_here) {
+    while (stop_here == NULL || frame < (StgPtr)stop_here) {

 
        // 1. Let the top of the stack be the "current closure"
        //
 
        // 1. Let the top of the stack be the "current closure"
        //

@@ -944,21 +812,20 @@ raiseAsync(Capability *cap, StgTSO *tso, StgClosure *exception,
            //       printObj((StgClosure *)ap);
            //  );
 
            //       printObj((StgClosure *)ap);
            //  );
 

-           // Replace the updatee with an indirection
-           //
-           // Warning: if we're in a loop, more than one update frame on
-           // the stack may point to the same object.  Be careful not to
-           // overwrite an IND_OLDGEN in this case, because we'll screw
-           // up the mutable lists.  To be on the safe side, don't
-           // overwrite any kind of indirection at all.  See also
-           // threadSqueezeStack in GC.c, where we have to make a similar
-           // check.
-           //
-           if (!closure_IND(((StgUpdateFrame *)frame)->updatee)) {
-               // revert the black hole
-               UPD_IND_NOLOCK(((StgUpdateFrame *)frame)->updatee,
-                              (StgClosure *)ap);
-           }
+            if (((StgUpdateFrame *)frame)->updatee == updatee) {
+                // If this update frame points to the same closure as
+                // the update frame further down the stack
+                // (stop_here), then don't perform the update.  We
+                // want to keep the blackhole in this case, so we can
+                // detect and report the loop (#2783).
+                ap = (StgAP_STACK*)updatee;
+            } else {
+                // Perform the update
+                // TODO: this may waste some work, if the thunk has
+                // already been updated by another thread.
+                UPD_IND(((StgUpdateFrame *)frame)->updatee, (StgClosure *)ap);
+            }
+

            sp += sizeofW(StgUpdateFrame) - 1;
            sp[0] = (W_)ap; // push onto stack
            frame = sp + 1;
            sp += sizeofW(StgUpdateFrame) - 1;
            sp[0] = (W_)ap; // push onto stack
            frame = sp + 1;

@@ -1017,25 +884,26 @@ raiseAsync(Capability *cap, StgTSO *tso, StgClosure *exception,
            
        case ATOMICALLY_FRAME:
            if (stop_at_atomically) {
            
        case ATOMICALLY_FRAME:
            if (stop_at_atomically) {

-               ASSERT(stmGetEnclosingTRec(tso->trec) == NO_TREC);
+               ASSERT(tso->trec->enclosing_trec == NO_TREC);

                stmCondemnTransaction(cap, tso -> trec);
                stmCondemnTransaction(cap, tso -> trec);

-#ifdef REG_R1
-               tso->sp = frame;
-#else
-               // R1 is not a register: the return convention for IO in
-               // this case puts the return value on the stack, so we
-               // need to set up the stack to return to the atomically
-               // frame properly...

                tso->sp = frame - 2;
                tso->sp = frame - 2;

-               tso->sp[1] = (StgWord) &stg_NO_FINALIZER_closure; // why not?
-               tso->sp[0] = (StgWord) &stg_ut_1_0_unreg_info;
-#endif
+                // The ATOMICALLY_FRAME expects to be returned a
+                // result from the transaction, which it stores in the
+                // stack frame.  Hence we arrange to return a dummy
+                // result, so that the GC doesn't get upset (#3578).
+                // Perhaps a better way would be to have a different
+                // ATOMICALLY_FRAME instance for condemned
+                // transactions, but I don't fully understand the
+                // interaction with STM invariants.
+                tso->sp[1] = (W_)&stg_NO_TREC_closure;
+                tso->sp[0] = (W_)&stg_gc_unpt_r1_info;

                tso->what_next = ThreadRunGHC;
                return;
            }
            // Not stop_at_atomically... fall through and abort the
            // transaction.
            
                tso->what_next = ThreadRunGHC;
                return;
            }
            // Not stop_at_atomically... fall through and abort the
            // transaction.
            

+       case CATCH_STM_FRAME:

        case CATCH_RETRY_FRAME:
            // IF we find an ATOMICALLY_FRAME then we abort the
            // current transaction and propagate the exception.  In
        case CATCH_RETRY_FRAME:
            // IF we find an ATOMICALLY_FRAME then we abort the
            // current transaction and propagate the exception.  In

@@ -1046,7 +914,7 @@ raiseAsync(Capability *cap, StgTSO *tso, StgClosure *exception,
 
                {
             StgTRecHeader *trec = tso -> trec;
 
                {
             StgTRecHeader *trec = tso -> trec;

-            StgTRecHeader *outer = stmGetEnclosingTRec(trec);
+            StgTRecHeader *outer = trec -> enclosing_trec;

            debugTrace(DEBUG_stm, 
                       "found atomically block delivering async exception");
             stmAbortTransaction(cap, trec);
            debugTrace(DEBUG_stm, 
                       "found atomically block delivering async exception");
             stmAbortTransaction(cap, trec);