X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Frts%2FGC.c;h=a4f0c178292ba1c5e2ea80b6178b5603a57e4ff5;hb=6444de585f3d7cd44119eb651629f5b7b7f6eb45;hp=9d25926ecd4866587c5f51d631ced7270ff1be0e;hpb=95ca6bff6fc9918203173b442192d9298ef9757a;p=ghc-hetmet.git

diff --git a/ghc/rts/GC.c b/ghc/rts/GC.c
index 9d25926..a4f0c17 100644
--- a/ghc/rts/GC.c
+++ b/ghc/rts/GC.c
@@ -1,5 +1,4 @@
 /* -----------------------------------------------------------------------------
- * $Id: GC.c,v 1.169 2004/09/03 15:28:20 simonmar Exp $
  *
  * (c) The GHC Team 1998-2003
  *
@@ -12,12 +11,12 @@
 #include "RtsFlags.h"
 #include "RtsUtils.h"
 #include "Apply.h"
+#include "OSThreads.h"
 #include "Storage.h"
 #include "LdvProfile.h"
 #include "Updates.h"
 #include "Stats.h"
 #include "Schedule.h"
-#include "SchedAPI.h"		// for ReverCAFs prototype
 #include "Sanity.h"
 #include "BlockAlloc.h"
 #include "MBlock.h"
@@ -28,6 +27,7 @@
 #include "ParTicky.h"		// ToDo: move into Rts.h
 #include "GCCompact.h"
 #include "Signals.h"
+#include "STM.h"
 #if defined(GRAN) || defined(PAR)
 # include "GranSimRts.h"
 # include "ParallelRts.h"
@@ -47,6 +47,12 @@
 
 #include <string.h>
 
+// Turn off inlining when debugging - it obfuscates things
+#ifdef DEBUG
+# undef  STATIC_INLINE
+# define STATIC_INLINE static
+#endif
+
 /* STATIC OBJECT LIST.
  *
  * During GC:
@@ -149,7 +155,6 @@ static void         mark_root               ( StgClosure **root );
 REGPARM1 static StgClosure * evacuate (StgClosure *q);
 
 static void         zero_static_object_list ( StgClosure* first_static );
-static void         zero_mutable_list       ( StgMutClosure *first );
 
 static rtsBool      traverse_weak_ptr_list  ( void );
 static void         mark_weak_ptr_list      ( StgWeak **list );
@@ -164,7 +169,6 @@ static rtsBool scavenge_one            ( StgPtr p );
 static void    scavenge_large          ( step * );
 static void    scavenge_static         ( void );
 static void    scavenge_mutable_list   ( generation *g );
-static void    scavenge_mut_once_list  ( generation *g );
 
 static void    scavenge_large_bitmap   ( StgPtr p, 
 					 StgLargeBitmap *large_bitmap, 
@@ -266,7 +270,7 @@ gc_alloc_block(step *stp)
    (and all younger generations):
 
      - follow all pointers in the root set.  the root set includes all 
-       mutable objects in all generations (mutable_list and mut_once_list).
+       mutable objects in all generations (mutable_list).
 
      - for each pointer, evacuate the object it points to into either
 
@@ -278,7 +282,7 @@ gc_alloc_block(step *stp)
          When we evacuate an object we attempt to evacuate
          everything it points to into the same generation - this is
          achieved by setting evac_gen to the desired generation.  If
-         we can't do this, then an entry in the mut_once list has to
+         we can't do this, then an entry in the mut list has to
          be made for the cross-generation pointer.
 
        + if the object is already in a generation > N, then leave
@@ -316,6 +320,9 @@ GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
   blockUserSignals();
 #endif
 
+  // tell the STM to discard any cached closures its hoping to re-use
+  stmPreGCHook();
+
   // tell the stats department that we've started a GC 
   stat_startGC();
 
@@ -367,13 +374,6 @@ GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
   static_objects = END_OF_STATIC_LIST;
   scavenged_static_objects = END_OF_STATIC_LIST;
 
-  /* zero the mutable list for the oldest generation (see comment by
-   * zero_mutable_list below).
-   */
-  if (major_gc) { 
-    zero_mutable_list(generations[RtsFlags.GcFlags.generations-1].mut_once_list);
-  }
-
   /* Save the old to-space if we're doing a two-space collection
    */
   if (RtsFlags.GcFlags.generations == 1) {
@@ -391,8 +391,14 @@ GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
   // collecting.
   //
   for (g = 0; g <= N; g++) {
-    generations[g].mut_once_list = END_MUT_LIST;
-    generations[g].mut_list = END_MUT_LIST;
+
+    // throw away the mutable list.  Invariant: the mutable list
+    // always has at least one block; this means we can avoid a check for
+    // NULL in recordMutable().
+    if (g != 0) {
+	freeChain(generations[g].mut_list);
+	generations[g].mut_list = allocBlock();
+    }
 
     for (s = 0; s < generations[g].n_steps; s++) {
 
@@ -435,7 +441,7 @@ GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
 	  bitmap_size = stp->n_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE);
 
 	  if (bitmap_size > 0) {
-	      bitmap_bdescr = allocGroup((nat)BLOCK_ROUND_UP(bitmap_size) 
+	      bitmap_bdescr = allocGroup((lnat)BLOCK_ROUND_UP(bitmap_size) 
 					 / BLOCK_SIZE);
 	      stp->bitmap = bitmap_bdescr;
 	      bitmap = bitmap_bdescr->start;
@@ -515,23 +521,12 @@ GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
     int st;
     for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
       generations[g].saved_mut_list = generations[g].mut_list;
-      generations[g].mut_list = END_MUT_LIST;
-    }
-
-    // Do the mut-once lists first 
-    for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
-      IF_PAR_DEBUG(verbose,
-		   printMutOnceList(&generations[g]));
-      scavenge_mut_once_list(&generations[g]);
-      evac_gen = g;
-      for (st = generations[g].n_steps-1; st >= 0; st--) {
-	scavenge(&generations[g].steps[st]);
-      }
+      generations[g].mut_list = allocBlock(); 
+        // mut_list always has at least one block.
     }
 
     for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
-      IF_PAR_DEBUG(verbose,
-		   printMutableList(&generations[g]));
+      IF_PAR_DEBUG(verbose, printMutableList(&generations[g]));
       scavenge_mutable_list(&generations[g]);
       evac_gen = g;
       for (st = generations[g].n_steps-1; st >= 0; st--) {
@@ -717,6 +712,14 @@ GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
       generations[g].collections++; // for stats 
     }
 
+    // Count the mutable list as bytes "copied" for the purposes of
+    // stats.  Every mutable list is copied during every GC.
+    if (g > 0) {
+	for (bd = generations[g].mut_list; bd != NULL; bd = bd->link) {
+	    copied += (bd->free - bd->start) * sizeof(StgWord);
+	}
+    }
+
     for (s = 0; s < generations[g].n_steps; s++) {
       bdescr *next;
       stp = &generations[g].steps[s];
@@ -981,7 +984,7 @@ GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
 	blocks = RtsFlags.GcFlags.minAllocAreaSize;
       }
     }
-    resizeNursery(blocks);
+    resizeNurseries(blocks);
     
   } else {
     /* Generational collector:
@@ -998,7 +1001,7 @@ GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
        * percentage of g0s0 that was live at the last minor GC.
        */
       if (N == 0) {
-	g0s0_pcnt_kept = (new_blocks * 100) / g0s0->n_blocks;
+	g0s0_pcnt_kept = (new_blocks * 100) / countNurseryBlocks();
       }
 
       /* Estimate a size for the allocation area based on the
@@ -1021,12 +1024,12 @@ GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
 	blocks = RtsFlags.GcFlags.minAllocAreaSize;
       }
       
-      resizeNursery((nat)blocks);
+      resizeNurseries((nat)blocks);
 
     } else {
       // we might have added extra large blocks to the nursery, so
       // resize back to minAllocAreaSize again.
-      resizeNursery(RtsFlags.GcFlags.minAllocAreaSize);
+      resizeNurseries(RtsFlags.GcFlags.minAllocAreaSize);
     }
   }
 
@@ -1238,7 +1241,7 @@ traverse_weak_ptr_list(void)
 	  prev = &old_all_threads;
 	  for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
 	      
-	      (StgClosure *)tmp = isAlive((StgClosure *)t);
+	      tmp = (StgTSO *)isAlive((StgClosure *)t);
 	      
 	      if (tmp != NULL) {
 		  t = tmp;
@@ -1285,7 +1288,7 @@ traverse_weak_ptr_list(void)
 	  StgTSO *t, *tmp, *next;
 	  for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
 	      next = t->global_link;
-	      (StgClosure *)tmp = evacuate((StgClosure *)t);
+	      tmp = (StgTSO *)evacuate((StgClosure *)t);
 	      tmp->global_link = resurrected_threads;
 	      resurrected_threads = tmp;
 	  }
@@ -1324,7 +1327,7 @@ mark_weak_ptr_list ( StgWeak **list )
       // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
       ASSERT(w->header.info == &stg_DEAD_WEAK_info 
 	     || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
-      (StgClosure *)w = evacuate((StgClosure *)w);
+      w = (StgWeak *)evacuate((StgClosure *)w);
       *last_w = w;
       last_w = &(w->link);
   }
@@ -1419,8 +1422,6 @@ mark_root(StgClosure **root)
 STATIC_INLINE void 
 upd_evacuee(StgClosure *p, StgClosure *dest)
 {
-    // Source object must be in from-space:
-    ASSERT((Bdescr((P_)p)->flags & BF_EVACUATED) == 0);
     // not true: (ToDo: perhaps it should be)
     // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
     SET_INFO(p, &stg_EVACUATED_info);
@@ -1586,39 +1587,6 @@ evacuate_large(StgPtr p)
 }
 
 /* -----------------------------------------------------------------------------
-   Adding a MUT_CONS to an older generation.
-
-   This is necessary from time to time when we end up with an
-   old-to-new generation pointer in a non-mutable object.  We defer
-   the promotion until the next GC.
-   -------------------------------------------------------------------------- */
-
-static StgClosure *
-mkMutCons(StgClosure *ptr, generation *gen)
-{
-  StgMutVar *q;
-  step *stp;
-
-  stp = &gen->steps[0];
-
-  /* chain a new block onto the to-space for the destination step if
-   * necessary.
-   */
-  if (stp->hp + sizeofW(StgIndOldGen) >= stp->hpLim) {
-    gc_alloc_block(stp);
-  }
-
-  q = (StgMutVar *)stp->hp;
-  stp->hp += sizeofW(StgMutVar);
-
-  SET_HDR(q,&stg_MUT_CONS_info,CCS_GC);
-  q->var = ptr;
-  recordOldToNewPtrs((StgMutClosure *)q);
-
-  return (StgClosure *)q;
-}
-
-/* -----------------------------------------------------------------------------
    Evacuate
 
    This is called (eventually) for every live object in the system.
@@ -1663,7 +1631,9 @@ mkMutCons(StgClosure *ptr, generation *gen)
 REGPARM1 static StgClosure *
 evacuate(StgClosure *q)
 {
+#if defined(PAR)
   StgClosure *to;
+#endif
   bdescr *bd = NULL;
   step *stp;
   const StgInfoTable *info;
@@ -1714,6 +1684,9 @@ loop:
 	return q;
     }
 
+    /* Object is not already evacuated. */
+    ASSERT((bd->flags & BF_EVACUATED) == 0);
+
     stp = bd->step->to;
   }
 #ifdef DEBUG
@@ -1750,8 +1723,10 @@ loop:
   case CONSTR_1_0:
     return copy(q,sizeofW(StgHeader)+1,stp);
 
-  case THUNK_1_0:		// here because of MIN_UPD_SIZE 
+  case THUNK_1_0:
   case THUNK_0_1:
+    return copy(q,sizeofW(StgThunk)+1,stp);
+
   case THUNK_1_1:
   case THUNK_0_2:
   case THUNK_2_0:
@@ -1762,7 +1737,7 @@ loop:
       stp = bd->step;
     }
 #endif
-    return copy(q,sizeofW(StgHeader)+2,stp);
+    return copy(q,sizeofW(StgThunk)+2,stp);
 
   case FUN_1_1:
   case FUN_0_2:
@@ -1772,8 +1747,10 @@ loop:
   case CONSTR_2_0:
     return copy(q,sizeofW(StgHeader)+2,stp);
 
-  case FUN:
   case THUNK:
+    return copy(q,thunk_sizeW_fromITBL(info),stp);
+
+  case FUN:
   case CONSTR:
   case IND_PERM:
   case IND_OLDGEN_PERM:
@@ -1791,10 +1768,6 @@ loop:
   case BLACKHOLE:
     return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
 
-  case BLACKHOLE_BQ:
-    to = copy(q,BLACKHOLE_sizeW(),stp); 
-    return to;
-
   case THUNK_SELECTOR:
     {
 	StgClosure *p;
@@ -1832,16 +1805,16 @@ loop:
 
   case THUNK_STATIC:
     if (info->srt_bitmap != 0 && major_gc && 
-	THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
-      THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
+	*THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
+      *THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
       static_objects = (StgClosure *)q;
     }
     return q;
 
   case FUN_STATIC:
     if (info->srt_bitmap != 0 && major_gc && 
-	FUN_STATIC_LINK((StgClosure *)q) == NULL) {
-      FUN_STATIC_LINK((StgClosure *)q) = static_objects;
+	*FUN_STATIC_LINK((StgClosure *)q) == NULL) {
+      *FUN_STATIC_LINK((StgClosure *)q) = static_objects;
       static_objects = (StgClosure *)q;
     }
     return q;
@@ -1853,15 +1826,15 @@ loop:
      */
     if (major_gc
 	  && ((StgIndStatic *)q)->saved_info == NULL
- 	  && IND_STATIC_LINK((StgClosure *)q) == NULL) {
-	IND_STATIC_LINK((StgClosure *)q) = static_objects;
+ 	  && *IND_STATIC_LINK((StgClosure *)q) == NULL) {
+	*IND_STATIC_LINK((StgClosure *)q) = static_objects;
 	static_objects = (StgClosure *)q;
     }
     return q;
 
   case CONSTR_STATIC:
-    if (major_gc && STATIC_LINK(info,(StgClosure *)q) == NULL) {
-      STATIC_LINK(info,(StgClosure *)q) = static_objects;
+    if (major_gc && *STATIC_LINK(info,(StgClosure *)q) == NULL) {
+      *STATIC_LINK(info,(StgClosure *)q) = static_objects;
       static_objects = (StgClosure *)q;
     }
     return q;
@@ -1883,13 +1856,18 @@ loop:
   case UPDATE_FRAME:
   case STOP_FRAME:
   case CATCH_FRAME:
+  case CATCH_STM_FRAME:
+  case CATCH_RETRY_FRAME:
+  case ATOMICALLY_FRAME:
     // shouldn't see these 
     barf("evacuate: stack frame at %p\n", q);
 
   case PAP:
-  case AP:
       return copy(q,pap_sizeW((StgPAP*)q),stp);
 
+  case AP:
+      return copy(q,ap_sizeW((StgAP*)q),stp);
+
   case AP_STACK:
       return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
 
@@ -1916,6 +1894,7 @@ loop:
 
   case MUT_ARR_PTRS:
   case MUT_ARR_PTRS_FROZEN:
+  case MUT_ARR_PTRS_FROZEN0:
       // just copy the block 
       return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
 
@@ -1951,7 +1930,7 @@ loop:
     }
 
 #if defined(PAR)
-  case RBH: // cf. BLACKHOLE_BQ
+  case RBH:
     {
       //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
       to = copy(q,BLACKHOLE_sizeW(),stp); 
@@ -1991,6 +1970,18 @@ loop:
     return to;
 #endif
 
+  case TREC_HEADER: 
+    return copy(q,sizeofW(StgTRecHeader),stp);
+
+  case TVAR_WAIT_QUEUE:
+    return copy(q,sizeofW(StgTVarWaitQueue),stp);
+
+  case TVAR:
+    return copy(q,sizeofW(StgTVar),stp);
+    
+  case TREC_CHUNK:
+    return copy(q,sizeofW(StgTRecChunk),stp);
+
   default:
     barf("evacuate: strange closure type %d", (int)(info->type));
   }
@@ -2011,6 +2002,48 @@ loop:
    been BLACKHOLE'd, and should be updated with an indirection or a
    forwarding pointer.  If the return value is NULL, then the selector
    thunk is unchanged.
+
+   ***
+   ToDo: the treatment of THUNK_SELECTORS could be improved in the
+   following way (from a suggestion by Ian Lynagh):
+
+   We can have a chain like this:
+
+      sel_0 --> (a,b)
+                 |
+                 |-----> sel_0 --> (a,b)
+                                    |
+                                    |-----> sel_0 --> ...
+
+   and the depth limit means we don't go all the way to the end of the
+   chain, which results in a space leak.  This affects the recursive
+   call to evacuate() in the THUNK_SELECTOR case in evacuate(): *not*
+   the recursive call to eval_thunk_selector() in
+   eval_thunk_selector().
+
+   We could eliminate the depth bound in this case, in the following
+   way:
+
+      - traverse the chain once to discover the *value* of the 
+        THUNK_SELECTOR.  Mark all THUNK_SELECTORS that we
+        visit on the way as having been visited already (somehow).
+
+      - in a second pass, traverse the chain again updating all
+        THUNK_SEELCTORS that we find on the way with indirections to
+        the value.
+
+      - if we encounter a "marked" THUNK_SELECTOR in a normal 
+        evacuate(), we konw it can't be updated so just evac it.
+
+   Program that illustrates the problem:
+
+	foo [] = ([], [])
+	foo (x:xs) = let (ys, zs) = foo xs
+	             in if x >= 0 then (x:ys, zs) else (ys, x:zs)
+
+	main = bar [1..(100000000::Int)]
+	bar xs = (\(ys, zs) -> print ys >> print zs) (foo xs)
+
    -------------------------------------------------------------------------- */
 
 static inline rtsBool
@@ -2138,10 +2171,10 @@ selector_loop:
 
 	  // check that we don't recurse too much, re-using the
 	  // depth bound also used in evacuate().
-	  thunk_selector_depth++;
-	  if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
+	  if (thunk_selector_depth >= MAX_THUNK_SELECTOR_DEPTH) {
 	      break;
 	  }
+	  thunk_selector_depth++;
 
 	  val = eval_thunk_selector(info->layout.selector_offset, 
 				    (StgSelector *)selectee);
@@ -2187,7 +2220,6 @@ selector_loop:
       case SE_CAF_BLACKHOLE:
       case SE_BLACKHOLE:
       case BLACKHOLE:
-      case BLACKHOLE_BQ:
 #if defined(PAR)
       case RBH:
       case BLOCKED_FETCH:
@@ -2305,7 +2337,7 @@ scavenge_thunk_srt(const StgInfoTable *info)
     StgThunkInfoTable *thunk_info;
 
     thunk_info = itbl_to_thunk_itbl(info);
-    scavenge_srt((StgClosure **)thunk_info->srt, thunk_info->i.srt_bitmap);
+    scavenge_srt((StgClosure **)GET_SRT(thunk_info), thunk_info->i.srt_bitmap);
 }
 
 STATIC_INLINE void
@@ -2314,16 +2346,7 @@ scavenge_fun_srt(const StgInfoTable *info)
     StgFunInfoTable *fun_info;
 
     fun_info = itbl_to_fun_itbl(info);
-    scavenge_srt((StgClosure **)fun_info->f.srt, fun_info->i.srt_bitmap);
-}
-
-STATIC_INLINE void
-scavenge_ret_srt(const StgInfoTable *info)
-{
-    StgRetInfoTable *ret_info;
-
-    ret_info = itbl_to_ret_itbl(info);
-    scavenge_srt((StgClosure **)ret_info->srt, ret_info->i.srt_bitmap);
+    scavenge_srt((StgClosure **)GET_FUN_SRT(fun_info), fun_info->i.srt_bitmap);
 }
 
 /* -----------------------------------------------------------------------------
@@ -2334,7 +2357,7 @@ static void
 scavengeTSO (StgTSO *tso)
 {
     // chase the link field for any TSOs on the same queue 
-    (StgClosure *)tso->link = evacuate((StgClosure *)tso->link);
+    tso->link = (StgTSO *)evacuate((StgClosure *)tso->link);
     if (   tso->why_blocked == BlockedOnMVar
 	|| tso->why_blocked == BlockedOnBlackHole
 	|| tso->why_blocked == BlockedOnException
@@ -2350,6 +2373,9 @@ scavengeTSO (StgTSO *tso)
 	    (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
     }
     
+    // scavange current transaction record
+    tso->trec = (StgTRecHeader *)evacuate((StgClosure *)tso->trec);
+    
     // scavenge this thread's stack 
     scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
 }
@@ -2369,12 +2395,12 @@ scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
     p = (StgPtr)args;
     switch (fun_info->f.fun_type) {
     case ARG_GEN:
-	bitmap = BITMAP_BITS(fun_info->f.bitmap);
-	size = BITMAP_SIZE(fun_info->f.bitmap);
+	bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
+	size = BITMAP_SIZE(fun_info->f.b.bitmap);
 	goto small_bitmap;
     case ARG_GEN_BIG:
-	size = ((StgLargeBitmap *)fun_info->f.bitmap)->size;
-	scavenge_large_bitmap(p, (StgLargeBitmap *)fun_info->f.bitmap, size);
+	size = GET_FUN_LARGE_BITMAP(fun_info)->size;
+	scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
 	p += size;
 	break;
     default:
@@ -2383,7 +2409,7 @@ scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
     small_bitmap:
 	while (size > 0) {
 	    if ((bitmap & 1) == 0) {
-		(StgClosure *)*p = evacuate((StgClosure *)*p);
+		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
 	    }
 	    p++;
 	    bitmap = bitmap >> 1;
@@ -2395,38 +2421,34 @@ scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
 }
 
 STATIC_INLINE StgPtr
-scavenge_PAP (StgPAP *pap)
+scavenge_PAP_payload (StgClosure *fun, StgClosure **payload, StgWord size)
 {
     StgPtr p;
-    StgWord bitmap, size;
+    StgWord bitmap;
     StgFunInfoTable *fun_info;
-
-    pap->fun = evacuate(pap->fun);
-    fun_info = get_fun_itbl(pap->fun);
+    
+    fun_info = get_fun_itbl(fun);
     ASSERT(fun_info->i.type != PAP);
-
-    p = (StgPtr)pap->payload;
-    size = pap->n_args;
+    p = (StgPtr)payload;
 
     switch (fun_info->f.fun_type) {
     case ARG_GEN:
-	bitmap = BITMAP_BITS(fun_info->f.bitmap);
+	bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
 	goto small_bitmap;
     case ARG_GEN_BIG:
-	scavenge_large_bitmap(p, (StgLargeBitmap *)fun_info->f.bitmap, size);
+	scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
 	p += size;
 	break;
     case ARG_BCO:
-	scavenge_large_bitmap((StgPtr)pap->payload, BCO_BITMAP(pap->fun), size);
+	scavenge_large_bitmap((StgPtr)payload, BCO_BITMAP(fun), size);
 	p += size;
 	break;
     default:
 	bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
     small_bitmap:
-	size = pap->n_args;
 	while (size > 0) {
 	    if ((bitmap & 1) == 0) {
-		(StgClosure *)*p = evacuate((StgClosure *)*p);
+		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
 	    }
 	    p++;
 	    bitmap = bitmap >> 1;
@@ -2437,6 +2459,20 @@ scavenge_PAP (StgPAP *pap)
     return p;
 }
 
+STATIC_INLINE StgPtr
+scavenge_PAP (StgPAP *pap)
+{
+    pap->fun = evacuate(pap->fun);
+    return scavenge_PAP_payload (pap->fun, pap->payload, pap->n_args);
+}
+
+STATIC_INLINE StgPtr
+scavenge_AP (StgAP *ap)
+{
+    ap->fun = evacuate(ap->fun);
+    return scavenge_PAP_payload (ap->fun, ap->payload, ap->n_args);
+}
+
 /* -----------------------------------------------------------------------------
    Scavenge a given step until there are no more objects in this step
    to scavenge.
@@ -2485,18 +2521,14 @@ scavenge(step *stp)
     switch (info->type) {
 
     case MVAR:
-	/* treat MVars specially, because we don't want to evacuate the
-	 * mut_link field in the middle of the closure.
-	 */
     { 
 	StgMVar *mvar = ((StgMVar *)p);
 	evac_gen = 0;
-	(StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
-	(StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
-	(StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
+	mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
+	mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
+	mvar->value = evacuate((StgClosure *)mvar->value);
 	evac_gen = saved_evac_gen;
-	recordMutable((StgMutClosure *)mvar);
-	failed_to_evac = rtsFalse; // mutable.
+	failed_to_evac = rtsTrue; // mutable.
 	p += sizeofW(StgMVar);
 	break;
     }
@@ -2510,6 +2542,11 @@ scavenge(step *stp)
 
     case THUNK_2_0:
 	scavenge_thunk_srt(info);
+	((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
+	((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
+	p += sizeofW(StgThunk) + 2;
+	break;
+
     case CONSTR_2_0:
 	((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
 	((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
@@ -2518,8 +2555,8 @@ scavenge(step *stp)
 	
     case THUNK_1_0:
 	scavenge_thunk_srt(info);
-	((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
-	p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE 
+	((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
+	p += sizeofW(StgThunk) + 1;
 	break;
 	
     case FUN_1_0:
@@ -2531,7 +2568,7 @@ scavenge(step *stp)
 	
     case THUNK_0_1:
 	scavenge_thunk_srt(info);
-	p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE 
+	p += sizeofW(StgThunk) + 1;
 	break;
 	
     case FUN_0_1:
@@ -2542,7 +2579,7 @@ scavenge(step *stp)
 	
     case THUNK_0_2:
 	scavenge_thunk_srt(info);
-	p += sizeofW(StgHeader) + 2;
+	p += sizeofW(StgThunk) + 2;
 	break;
 	
     case FUN_0_2:
@@ -2553,8 +2590,8 @@ scavenge(step *stp)
 	
     case THUNK_1_1:
 	scavenge_thunk_srt(info);
-	((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
-	p += sizeofW(StgHeader) + 2;
+	((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
+	p += sizeofW(StgThunk) + 2;
 	break;
 
     case FUN_1_1:
@@ -2569,8 +2606,17 @@ scavenge(step *stp)
 	goto gen_obj;
 
     case THUNK:
+    {
+	StgPtr end;
+
 	scavenge_thunk_srt(info);
-	// fall through 
+	end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
+	for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	}
+	p += info->layout.payload.nptrs;
+	break;
+    }
 	
     gen_obj:
     case CONSTR:
@@ -2582,7 +2628,7 @@ scavenge(step *stp)
 
 	end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
 	for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
-	    (StgClosure *)*p = evacuate((StgClosure *)*p);
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
 	}
 	p += info->layout.payload.nptrs;
 	break;
@@ -2590,10 +2636,10 @@ scavenge(step *stp)
 
     case BCO: {
 	StgBCO *bco = (StgBCO *)p;
-	(StgClosure *)bco->instrs = evacuate((StgClosure *)bco->instrs);
-	(StgClosure *)bco->literals = evacuate((StgClosure *)bco->literals);
-	(StgClosure *)bco->ptrs = evacuate((StgClosure *)bco->ptrs);
-	(StgClosure *)bco->itbls = evacuate((StgClosure *)bco->itbls);
+	bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
+	bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
+	bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
+	bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
 	p += bco_sizeW(bco);
 	break;
     }
@@ -2616,27 +2662,15 @@ scavenge(step *stp)
       }
 	// fall through 
     case IND_OLDGEN_PERM:
-	((StgIndOldGen *)p)->indirectee = 
-	    evacuate(((StgIndOldGen *)p)->indirectee);
-	if (failed_to_evac) {
-	    failed_to_evac = rtsFalse;
-	    recordOldToNewPtrs((StgMutClosure *)p);
-	}
-	p += sizeofW(StgIndOldGen);
+	((StgInd *)p)->indirectee = evacuate(((StgInd *)p)->indirectee);
+	p += sizeofW(StgInd);
 	break;
 
     case MUT_VAR:
 	evac_gen = 0;
 	((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
 	evac_gen = saved_evac_gen;
-	recordMutable((StgMutClosure *)p);
-	failed_to_evac = rtsFalse; // mutable anyhow
-	p += sizeofW(StgMutVar);
-	break;
-
-    case MUT_CONS:
-	// ignore these
-	failed_to_evac = rtsFalse; // mutable anyhow
+	failed_to_evac = rtsTrue; // mutable anyhow
 	p += sizeofW(StgMutVar);
 	break;
 
@@ -2647,17 +2681,6 @@ scavenge(step *stp)
 	p += BLACKHOLE_sizeW();
 	break;
 
-    case BLACKHOLE_BQ:
-    { 
-	StgBlockingQueue *bh = (StgBlockingQueue *)p;
-	(StgClosure *)bh->blocking_queue = 
-	    evacuate((StgClosure *)bh->blocking_queue);
-	recordMutable((StgMutClosure *)bh);
-	failed_to_evac = rtsFalse;
-	p += BLACKHOLE_sizeW();
-	break;
-    }
-
     case THUNK_SELECTOR:
     { 
 	StgSelector *s = (StgSelector *)p;
@@ -2678,10 +2701,13 @@ scavenge(step *stp)
     }
 
     case PAP:
-    case AP:
 	p = scavenge_PAP((StgPAP *)p);
 	break;
 
+    case AP:
+	p = scavenge_AP((StgAP *)p);
+	break;
+
     case ARR_WORDS:
 	// nothing to follow 
 	p += arr_words_sizeW((StgArrWords *)p);
@@ -2695,27 +2721,22 @@ scavenge(step *stp)
 	evac_gen = 0;		// repeatedly mutable 
 	next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
 	for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-	    (StgClosure *)*p = evacuate((StgClosure *)*p);
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
 	}
 	evac_gen = saved_evac_gen;
-	recordMutable((StgMutClosure *)q);
-	failed_to_evac = rtsFalse; // mutable anyhow.
+	failed_to_evac = rtsTrue; // mutable anyhow.
 	break;
     }
 
     case MUT_ARR_PTRS_FROZEN:
+    case MUT_ARR_PTRS_FROZEN0:
 	// follow everything 
     {
 	StgPtr next;
 
-	// Set the mut_link field to NULL, so that we will put this
-	// array back on the mutable list if it is subsequently thawed
-	// by unsafeThaw#.
-	((StgMutArrPtrs*)p)->mut_link = NULL;
-
 	next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
 	for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-	    (StgClosure *)*p = evacuate((StgClosure *)*p);
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
 	}
 	// it's tempting to recordMutable() if failed_to_evac is
 	// false, but that breaks some assumptions (eg. every
@@ -2730,14 +2751,13 @@ scavenge(step *stp)
 	evac_gen = 0;
 	scavengeTSO(tso);
 	evac_gen = saved_evac_gen;
-	recordMutable((StgMutClosure *)tso);
-	failed_to_evac = rtsFalse; // mutable anyhow.
+	failed_to_evac = rtsTrue; // mutable anyhow.
 	p += tso_sizeW(tso);
 	break;
     }
 
 #if defined(PAR)
-    case RBH: // cf. BLACKHOLE_BQ
+    case RBH:
     { 
 #if 0
 	nat size, ptrs, nonptrs, vhs;
@@ -2747,8 +2767,7 @@ scavenge(step *stp)
 	StgRBH *rbh = (StgRBH *)p;
 	(StgClosure *)rbh->blocking_queue = 
 	    evacuate((StgClosure *)rbh->blocking_queue);
-	recordMutable((StgMutClosure *)to);
-	failed_to_evac = rtsFalse;  // mutable anyhow.
+	failed_to_evac = rtsTrue;  // mutable anyhow.
 	IF_DEBUG(gc,
 		 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
 		       p, info_type(p), (StgClosure *)rbh->blocking_queue));
@@ -2766,10 +2785,6 @@ scavenge(step *stp)
 	// follow the link to the rest of the blocking queue 
 	(StgClosure *)bf->link = 
 	    evacuate((StgClosure *)bf->link);
-	if (failed_to_evac) {
-	    failed_to_evac = rtsFalse;
-	    recordMutable((StgMutClosure *)bf);
-	}
 	IF_DEBUG(gc,
 		 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
 		       bf, info_type((StgClosure *)bf), 
@@ -2785,15 +2800,11 @@ scavenge(step *stp)
 	p += sizeofW(StgFetchMe);
 	break; // nothing to do in this case
 
-    case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
+    case FETCH_ME_BQ:
     { 
 	StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
 	(StgClosure *)fmbq->blocking_queue = 
 	    evacuate((StgClosure *)fmbq->blocking_queue);
-	if (failed_to_evac) {
-	    failed_to_evac = rtsFalse;
-	    recordMutable((StgMutClosure *)fmbq);
-	}
 	IF_DEBUG(gc,
 		 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
 		       p, info_type((StgClosure *)p)));
@@ -2802,18 +2813,76 @@ scavenge(step *stp)
     }
 #endif
 
+    case TVAR_WAIT_QUEUE:
+      {
+	StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
+	evac_gen = 0;
+	wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
+	wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
+	wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+	p += sizeofW(StgTVarWaitQueue);
+	break;
+      }
+
+    case TVAR:
+      {
+	StgTVar *tvar = ((StgTVar *) p);
+	evac_gen = 0;
+	tvar->current_value = evacuate((StgClosure*)tvar->current_value);
+	tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+	p += sizeofW(StgTVar);
+	break;
+      }
+
+    case TREC_HEADER:
+      {
+        StgTRecHeader *trec = ((StgTRecHeader *) p);
+        evac_gen = 0;
+	trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
+	trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+	p += sizeofW(StgTRecHeader);
+        break;
+      }
+
+    case TREC_CHUNK:
+      {
+	StgWord i;
+	StgTRecChunk *tc = ((StgTRecChunk *) p);
+	TRecEntry *e = &(tc -> entries[0]);
+	evac_gen = 0;
+	tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
+	for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
+	  e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
+	  e->expected_value = evacuate((StgClosure*)e->expected_value);
+	  e->new_value = evacuate((StgClosure*)e->new_value);
+	}
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+	p += sizeofW(StgTRecChunk);
+	break;
+      }
+
     default:
 	barf("scavenge: unimplemented/strange closure type %d @ %p", 
 	     info->type, p);
     }
 
-    /* If we didn't manage to promote all the objects pointed to by
-     * the current object, then we have to designate this object as
-     * mutable (because it contains old-to-new generation pointers).
+    /*
+     * We need to record the current object on the mutable list if
+     *  (a) It is actually mutable, or 
+     *  (b) It contains pointers to a younger generation.
+     * Case (b) arises if we didn't manage to promote everything that
+     * the current object points to into the current generation.
      */
     if (failed_to_evac) {
 	failed_to_evac = rtsFalse;
-	mkMutCons((StgClosure *)q, &generations[evac_gen]);
+	recordMutableGen((StgClosure *)q, stp->gen);
     }
   }
 
@@ -2850,17 +2919,14 @@ linear_scan:
 	switch (info->type) {
 	    
 	case MVAR:
-	    /* treat MVars specially, because we don't want to evacuate the
-	     * mut_link field in the middle of the closure.
-	     */
 	{
 	    StgMVar *mvar = ((StgMVar *)p);
 	    evac_gen = 0;
-	    (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
-	    (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
-	    (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
+	    mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
+	    mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
+	    mvar->value = evacuate((StgClosure *)mvar->value);
 	    evac_gen = saved_evac_gen;
-	    failed_to_evac = rtsFalse; // mutable.
+	    failed_to_evac = rtsTrue; // mutable.
 	    break;
 	}
 
@@ -2872,6 +2938,10 @@ linear_scan:
 
 	case THUNK_2_0:
 	    scavenge_thunk_srt(info);
+	    ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
+	    ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
+	    break;
+
 	case CONSTR_2_0:
 	    ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
 	    ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
@@ -2886,6 +2956,9 @@ linear_scan:
 	case THUNK_1_0:
 	case THUNK_1_1:
 	    scavenge_thunk_srt(info);
+	    ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
+	    break;
+
 	case CONSTR_1_0:
 	case CONSTR_1_1:
 	    ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
@@ -2910,8 +2983,16 @@ linear_scan:
 	    goto gen_obj;
 
 	case THUNK:
+	{
+	    StgPtr end;
+	    
 	    scavenge_thunk_srt(info);
-	    // fall through 
+	    end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
+	    for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
+		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	    }
+	    break;
+	}
 	
 	gen_obj:
 	case CONSTR:
@@ -2923,17 +3004,17 @@ linear_scan:
 	    
 	    end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
 	    for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
-		(StgClosure *)*p = evacuate((StgClosure *)*p);
+		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
 	    }
 	    break;
 	}
 
 	case BCO: {
 	    StgBCO *bco = (StgBCO *)p;
-	    (StgClosure *)bco->instrs = evacuate((StgClosure *)bco->instrs);
-	    (StgClosure *)bco->literals = evacuate((StgClosure *)bco->literals);
-	    (StgClosure *)bco->ptrs = evacuate((StgClosure *)bco->ptrs);
-	    (StgClosure *)bco->itbls = evacuate((StgClosure *)bco->itbls);
+	    bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
+	    bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
+	    bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
+	    bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
 	    break;
 	}
 
@@ -2945,24 +3026,15 @@ linear_scan:
 
 	case IND_OLDGEN:
 	case IND_OLDGEN_PERM:
-	    ((StgIndOldGen *)p)->indirectee = 
-		evacuate(((StgIndOldGen *)p)->indirectee);
-	    if (failed_to_evac) {
-		recordOldToNewPtrs((StgMutClosure *)p);
-	    }
-	    failed_to_evac = rtsFalse;
+	    ((StgInd *)p)->indirectee = 
+		evacuate(((StgInd *)p)->indirectee);
 	    break;
 
 	case MUT_VAR:
 	    evac_gen = 0;
 	    ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
 	    evac_gen = saved_evac_gen;
-	    failed_to_evac = rtsFalse;
-	    break;
-
-	case MUT_CONS:
-	    // ignore these
-	    failed_to_evac = rtsFalse;
+	    failed_to_evac = rtsTrue;
 	    break;
 
 	case CAF_BLACKHOLE:
@@ -2972,15 +3044,6 @@ linear_scan:
 	case ARR_WORDS:
 	    break;
 
-	case BLACKHOLE_BQ:
-	{ 
-	    StgBlockingQueue *bh = (StgBlockingQueue *)p;
-	    (StgClosure *)bh->blocking_queue = 
-		evacuate((StgClosure *)bh->blocking_queue);
-	    failed_to_evac = rtsFalse;
-	    break;
-	}
-
 	case THUNK_SELECTOR:
 	{ 
 	    StgSelector *s = (StgSelector *)p;
@@ -2999,9 +3062,12 @@ linear_scan:
 	}
 
 	case PAP:
-	case AP:
 	    scavenge_PAP((StgPAP *)p);
 	    break;
+
+	case AP:
+	    scavenge_AP((StgAP *)p);
+	    break;
       
 	case MUT_ARR_PTRS:
 	    // follow everything 
@@ -3011,26 +3077,22 @@ linear_scan:
 	    evac_gen = 0;		// repeatedly mutable 
 	    next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
 	    for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-		(StgClosure *)*p = evacuate((StgClosure *)*p);
+		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
 	    }
 	    evac_gen = saved_evac_gen;
-	    failed_to_evac = rtsFalse; // mutable anyhow.
+	    failed_to_evac = rtsTrue; // mutable anyhow.
 	    break;
 	}
 
 	case MUT_ARR_PTRS_FROZEN:
+	case MUT_ARR_PTRS_FROZEN0:
 	    // follow everything 
 	{
 	    StgPtr next;
 	    
-	    // Set the mut_link field to NULL, so that we will put this
-	    // array on the mutable list if it is subsequently thawed
-	    // by unsafeThaw#.
-	    ((StgMutArrPtrs*)p)->mut_link = NULL;
-
 	    next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
 	    for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-		(StgClosure *)*p = evacuate((StgClosure *)*p);
+		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
 	    }
 	    break;
 	}
@@ -3041,12 +3103,12 @@ linear_scan:
 	    evac_gen = 0;
 	    scavengeTSO(tso);
 	    evac_gen = saved_evac_gen;
-	    failed_to_evac = rtsFalse;
+	    failed_to_evac = rtsTrue;
 	    break;
 	}
 
 #if defined(PAR)
-	case RBH: // cf. BLACKHOLE_BQ
+	case RBH:
 	{ 
 #if 0
 	    nat size, ptrs, nonptrs, vhs;
@@ -3054,10 +3116,9 @@ linear_scan:
 	    StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
 #endif
 	    StgRBH *rbh = (StgRBH *)p;
-	    (StgClosure *)rbh->blocking_queue = 
-		evacuate((StgClosure *)rbh->blocking_queue);
-	    recordMutable((StgMutClosure *)rbh);
-	    failed_to_evac = rtsFalse;  // mutable anyhow.
+	    bh->blocking_queue = 
+		(StgTSO *)evacuate((StgClosure *)bh->blocking_queue);
+	    failed_to_evac = rtsTrue;  // mutable anyhow.
 	    IF_DEBUG(gc,
 		     debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
 			   p, info_type(p), (StgClosure *)rbh->blocking_queue));
@@ -3073,10 +3134,6 @@ linear_scan:
 	    // follow the link to the rest of the blocking queue 
 	    (StgClosure *)bf->link = 
 		evacuate((StgClosure *)bf->link);
-	    if (failed_to_evac) {
-		failed_to_evac = rtsFalse;
-		recordMutable((StgMutClosure *)bf);
-	    }
 	    IF_DEBUG(gc,
 		     debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
 			   bf, info_type((StgClosure *)bf), 
@@ -3090,21 +3147,68 @@ linear_scan:
 	case FETCH_ME:
 	    break; // nothing to do in this case
 
-	case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
+	case FETCH_ME_BQ:
 	{ 
 	    StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
 	    (StgClosure *)fmbq->blocking_queue = 
 		evacuate((StgClosure *)fmbq->blocking_queue);
-	    if (failed_to_evac) {
-		failed_to_evac = rtsFalse;
-		recordMutable((StgMutClosure *)fmbq);
-	    }
 	    IF_DEBUG(gc,
 		     debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
 			   p, info_type((StgClosure *)p)));
 	    break;
 	}
-#endif // PAR
+#endif /* PAR */
+
+	case TVAR_WAIT_QUEUE:
+	  {
+	    StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
+	    evac_gen = 0;
+	    wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
+	    wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
+	    wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
+	    evac_gen = saved_evac_gen;
+	    failed_to_evac = rtsTrue; // mutable
+	    break;
+	  }
+	  
+	case TVAR:
+	  {
+	    StgTVar *tvar = ((StgTVar *) p);
+	    evac_gen = 0;
+	    tvar->current_value = evacuate((StgClosure*)tvar->current_value);
+	    tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
+	    evac_gen = saved_evac_gen;
+	    failed_to_evac = rtsTrue; // mutable
+	    break;
+	  }
+	  
+	case TREC_CHUNK:
+	  {
+	    StgWord i;
+	    StgTRecChunk *tc = ((StgTRecChunk *) p);
+	    TRecEntry *e = &(tc -> entries[0]);
+	    evac_gen = 0;
+	    tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
+	    for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
+	      e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
+	      e->expected_value = evacuate((StgClosure*)e->expected_value);
+	      e->new_value = evacuate((StgClosure*)e->new_value);
+	    }
+	    evac_gen = saved_evac_gen;
+	    failed_to_evac = rtsTrue; // mutable
+	    break;
+	  }
+
+	case TREC_HEADER:
+	  {
+	    StgTRecHeader *trec = ((StgTRecHeader *) p);
+	    evac_gen = 0;
+	    trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
+	    trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
+	    evac_gen = saved_evac_gen;
+	    failed_to_evac = rtsTrue; // mutable
+	    break;
+	  }
 
 	default:
 	    barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p", 
@@ -3113,7 +3217,7 @@ linear_scan:
 
 	if (failed_to_evac) {
 	    failed_to_evac = rtsFalse;
-	    mkMutCons((StgClosure *)q, &generations[evac_gen]);
+	    recordMutableGen((StgClosure *)q, &generations[evac_gen]);
 	}
 	
 	// mark the next bit to indicate "scavenged"
@@ -3180,18 +3284,40 @@ scavenge_one(StgPtr p)
     
     switch (info->type) {
 	
-    case FUN:
-    case FUN_1_0:			// hardly worth specialising these guys
-    case FUN_0_1:
-    case FUN_1_1:
-    case FUN_0_2:
-    case FUN_2_0:
+    case MVAR:
+    { 
+	StgMVar *mvar = ((StgMVar *)p);
+	evac_gen = 0;
+	mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
+	mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
+	mvar->value = evacuate((StgClosure *)mvar->value);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable.
+	break;
+    }
+
     case THUNK:
     case THUNK_1_0:
     case THUNK_0_1:
     case THUNK_1_1:
     case THUNK_0_2:
     case THUNK_2_0:
+    {
+	StgPtr q, end;
+	
+	end = (StgPtr)((StgThunk *)p)->payload + info->layout.payload.ptrs;
+	for (q = (StgPtr)((StgThunk *)p)->payload; q < end; q++) {
+	    *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
+	}
+	break;
+    }
+
+    case FUN:
+    case FUN_1_0:			// hardly worth specialising these guys
+    case FUN_0_1:
+    case FUN_1_1:
+    case FUN_0_2:
+    case FUN_2_0:
     case CONSTR:
     case CONSTR_1_0:
     case CONSTR_0_1:
@@ -3201,17 +3327,23 @@ scavenge_one(StgPtr p)
     case WEAK:
     case FOREIGN:
     case IND_PERM:
-    case IND_OLDGEN_PERM:
     {
 	StgPtr q, end;
 	
 	end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
 	for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
-	    (StgClosure *)*q = evacuate((StgClosure *)*q);
+	    *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
 	}
 	break;
     }
     
+    case MUT_VAR:
+	evac_gen = 0;
+	((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable anyhow
+	break;
+
     case CAF_BLACKHOLE:
     case SE_CAF_BLACKHOLE:
     case SE_BLACKHOLE:
@@ -3225,39 +3357,52 @@ scavenge_one(StgPtr p)
 	break;
     }
     
-    case ARR_WORDS:
-	// nothing to follow 
+    case AP_STACK:
+    {
+	StgAP_STACK *ap = (StgAP_STACK *)p;
+
+	ap->fun = evacuate(ap->fun);
+	scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
+	p = (StgPtr)ap->payload + ap->size;
 	break;
+    }
 
-    case MUT_ARR_PTRS:
-    {
-	// follow everything 
-	StgPtr next;
-      
-	evac_gen = 0;		// repeatedly mutable 
-	recordMutable((StgMutClosure *)p);
+    case PAP:
+	p = scavenge_AP((StgAP *)p);
+	break;
+
+    case AP:
+	p = scavenge_PAP((StgPAP *)p);
+	break;
+
+    case ARR_WORDS:
+	// nothing to follow 
+	break;
+
+    case MUT_ARR_PTRS:
+    {
+	// follow everything 
+	StgPtr next;
+      
+	evac_gen = 0;		// repeatedly mutable 
 	next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
 	for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-	    (StgClosure *)*p = evacuate((StgClosure *)*p);
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
 	}
 	evac_gen = saved_evac_gen;
-	failed_to_evac = rtsFalse;
+	failed_to_evac = rtsTrue;
 	break;
     }
 
     case MUT_ARR_PTRS_FROZEN:
+    case MUT_ARR_PTRS_FROZEN0:
     {
 	// follow everything 
 	StgPtr next;
       
-	// Set the mut_link field to NULL, so that we will put this
-	// array on the mutable list if it is subsequently thawed
-	// by unsafeThaw#.
-	((StgMutArrPtrs*)p)->mut_link = NULL;
-
 	next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
 	for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-	    (StgClosure *)*p = evacuate((StgClosure *)*p);
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
 	}
 	break;
     }
@@ -3268,83 +3413,133 @@ scavenge_one(StgPtr p)
       
 	evac_gen = 0;		// repeatedly mutable 
 	scavengeTSO(tso);
-	recordMutable((StgMutClosure *)tso);
 	evac_gen = saved_evac_gen;
-	failed_to_evac = rtsFalse;
+	failed_to_evac = rtsTrue;
 	break;
     }
   
-    case AP_STACK:
-    {
-	StgAP_STACK *ap = (StgAP_STACK *)p;
-
-	ap->fun = evacuate(ap->fun);
-	scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
-	p = (StgPtr)ap->payload + ap->size;
+#if defined(PAR)
+    case RBH:
+    { 
+#if 0
+	nat size, ptrs, nonptrs, vhs;
+	char str[80];
+	StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
+#endif
+	StgRBH *rbh = (StgRBH *)p;
+	(StgClosure *)rbh->blocking_queue = 
+	    evacuate((StgClosure *)rbh->blocking_queue);
+	failed_to_evac = rtsTrue;  // mutable anyhow.
+	IF_DEBUG(gc,
+		 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
+		       p, info_type(p), (StgClosure *)rbh->blocking_queue));
+	// ToDo: use size of reverted closure here!
 	break;
     }
 
-    case PAP:
-    case AP:
-	p = scavenge_PAP((StgPAP *)p);
-	break;
-
-    case IND_OLDGEN:
-	// This might happen if for instance a MUT_CONS was pointing to a
-	// THUNK which has since been updated.  The IND_OLDGEN will
-	// be on the mutable list anyway, so we don't need to do anything
-	// here.
+    case BLOCKED_FETCH:
+    { 
+	StgBlockedFetch *bf = (StgBlockedFetch *)p;
+	// follow the pointer to the node which is being demanded 
+	(StgClosure *)bf->node = 
+	    evacuate((StgClosure *)bf->node);
+	// follow the link to the rest of the blocking queue 
+	(StgClosure *)bf->link = 
+	    evacuate((StgClosure *)bf->link);
+	IF_DEBUG(gc,
+		 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
+		       bf, info_type((StgClosure *)bf), 
+		       bf->node, info_type(bf->node)));
 	break;
+    }
 
-    default:
-	barf("scavenge_one: strange object %d", (int)(info->type));
-    }    
-
-    no_luck = failed_to_evac;
-    failed_to_evac = rtsFalse;
-    return (no_luck);
-}
-
-/* -----------------------------------------------------------------------------
-   Scavenging mutable lists.
+#ifdef DIST
+    case REMOTE_REF:
+#endif
+    case FETCH_ME:
+	break; // nothing to do in this case
 
-   We treat the mutable list of each generation > N (i.e. all the
-   generations older than the one being collected) as roots.  We also
-   remove non-mutable objects from the mutable list at this point.
-   -------------------------------------------------------------------------- */
+    case FETCH_ME_BQ:
+    { 
+	StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
+	(StgClosure *)fmbq->blocking_queue = 
+	    evacuate((StgClosure *)fmbq->blocking_queue);
+	IF_DEBUG(gc,
+		 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
+		       p, info_type((StgClosure *)p)));
+	break;
+    }
+#endif
 
-static void
-scavenge_mut_once_list(generation *gen)
-{
-  const StgInfoTable *info;
-  StgMutClosure *p, *next, *new_list;
+    case TVAR_WAIT_QUEUE:
+      {
+	StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
+	evac_gen = 0;
+	wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
+	wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
+	wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+	break;
+      }
 
-  p = gen->mut_once_list;
-  new_list = END_MUT_LIST;
-  next = p->mut_link;
+    case TVAR:
+      {
+	StgTVar *tvar = ((StgTVar *) p);
+	evac_gen = 0;
+	tvar->current_value = evacuate((StgClosure*)tvar->current_value);
+	tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+	break;
+      }
 
-  evac_gen = gen->no;
-  failed_to_evac = rtsFalse;
+    case TREC_HEADER:
+      {
+        StgTRecHeader *trec = ((StgTRecHeader *) p);
+        evac_gen = 0;
+	trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
+	trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+        break;
+      }
 
-  for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
+    case TREC_CHUNK:
+      {
+	StgWord i;
+	StgTRecChunk *tc = ((StgTRecChunk *) p);
+	TRecEntry *e = &(tc -> entries[0]);
+	evac_gen = 0;
+	tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
+	for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
+	  e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
+	  e->expected_value = evacuate((StgClosure*)e->expected_value);
+	  e->new_value = evacuate((StgClosure*)e->new_value);
+	}
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+	break;
+      }
 
-    ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
-    info = get_itbl(p);
-    /*
-    if (info->type==RBH)
-      info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
-    */
-    switch(info->type) {
-      
     case IND_OLDGEN:
     case IND_OLDGEN_PERM:
     case IND_STATIC:
-      /* Try to pull the indirectee into this generation, so we can
-       * remove the indirection from the mutable list.  
-       */
-      ((StgIndOldGen *)p)->indirectee = 
-        evacuate(((StgIndOldGen *)p)->indirectee);
-      
+    {
+	/* Careful here: a THUNK can be on the mutable list because
+	 * it contains pointers to young gen objects.  If such a thunk
+	 * is updated, the IND_OLDGEN will be added to the mutable
+	 * list again, and we'll scavenge it twice.  evacuate()
+	 * doesn't check whether the object has already been
+	 * evacuated, so we perform that check here.
+	 */
+	StgClosure *q = ((StgInd *)p)->indirectee;
+	if (HEAP_ALLOCED(q) && Bdescr((StgPtr)q)->flags & BF_EVACUATED) {
+	    break;
+	}
+	((StgInd *)p)->indirectee = evacuate(q);
+    }
+
 #if 0 && defined(DEBUG)
       if (RtsFlags.DebugFlags.gc) 
       /* Debugging code to print out the size of the thing we just
@@ -3370,237 +3565,50 @@ scavenge_mut_once_list(generation *gen)
 	debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
       }
 #endif
-
-      /* failed_to_evac might happen if we've got more than two
-       * generations, we're collecting only generation 0, the
-       * indirection resides in generation 2 and the indirectee is
-       * in generation 1.
-       */
-      if (failed_to_evac) {
-	failed_to_evac = rtsFalse;
-	p->mut_link = new_list;
-	new_list = p;
-      } else {
-	/* the mut_link field of an IND_STATIC is overloaded as the
-	 * static link field too (it just so happens that we don't need
-	 * both at the same time), so we need to NULL it out when
-	 * removing this object from the mutable list because the static
-	 * link fields are all assumed to be NULL before doing a major
-	 * collection. 
-	 */
-	p->mut_link = NULL;
-      }
-      continue;
-
-    case MUT_CONS:
-	/* MUT_CONS is a kind of MUT_VAR, except it that we try to remove
-	 * it from the mutable list if possible by promoting whatever it
-	 * points to.
-	 */
-	if (scavenge_one((StgPtr)((StgMutVar *)p)->var)) {
-	    /* didn't manage to promote everything, so put the
-	     * MUT_CONS back on the list.
-	     */
-	    p->mut_link = new_list;
-	    new_list = p;
-	}
-	continue;
+      break;
 
     default:
-      // shouldn't have anything else on the mutables list 
-      barf("scavenge_mut_once_list: strange object? %d", (int)(info->type));
-    }
-  }
+	barf("scavenge_one: strange object %d", (int)(info->type));
+    }    
 
-  gen->mut_once_list = new_list;
+    no_luck = failed_to_evac;
+    failed_to_evac = rtsFalse;
+    return (no_luck);
 }
 
+/* -----------------------------------------------------------------------------
+   Scavenging mutable lists.
+
+   We treat the mutable list of each generation > N (i.e. all the
+   generations older than the one being collected) as roots.  We also
+   remove non-mutable objects from the mutable list at this point.
+   -------------------------------------------------------------------------- */
 
 static void
 scavenge_mutable_list(generation *gen)
 {
-  const StgInfoTable *info;
-  StgMutClosure *p, *next;
-
-  p = gen->saved_mut_list;
-  next = p->mut_link;
-
-  evac_gen = 0;
-  failed_to_evac = rtsFalse;
-
-  for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
-
-    ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
-    info = get_itbl(p);
-    /*
-    if (info->type==RBH)
-      info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
-    */
-    switch(info->type) {
-      
-    case MUT_ARR_PTRS:
-      // follow everything 
-      p->mut_link = gen->mut_list;
-      gen->mut_list = p;
-      {
-	StgPtr end, q;
-	
-	end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
-	for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
-	  (StgClosure *)*q = evacuate((StgClosure *)*q);
-	}
-	continue;
-      }
-      
-      // Happens if a MUT_ARR_PTRS in the old generation is frozen
-    case MUT_ARR_PTRS_FROZEN:
-      {
-	StgPtr end, q;
-	
-	evac_gen = gen->no;
-	end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
-	for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
-	  (StgClosure *)*q = evacuate((StgClosure *)*q);
-	}
-	evac_gen = 0;
-	// Set the mut_link field to NULL, so that we will put this
-	// array back on the mutable list if it is subsequently thawed
-	// by unsafeThaw#.
-	p->mut_link = NULL;
-	if (failed_to_evac) {
-	    failed_to_evac = rtsFalse;
-	    mkMutCons((StgClosure *)p, gen);
-	}
-	continue;
-      }
-	
-    case MUT_VAR:
-	((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
-	p->mut_link = gen->mut_list;
-	gen->mut_list = p;
-	continue;
-
-    case MVAR:
-      {
-	StgMVar *mvar = (StgMVar *)p;
-	(StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
-	(StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
-	(StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
-	p->mut_link = gen->mut_list;
-	gen->mut_list = p;
-	continue;
-      }
-
-    case TSO:
-      { 
-	StgTSO *tso = (StgTSO *)p;
-
-	scavengeTSO(tso);
-
-	/* Don't take this TSO off the mutable list - it might still
-	 * point to some younger objects (because we set evac_gen to 0
-	 * above). 
-	 */
-	tso->mut_link = gen->mut_list;
-	gen->mut_list = (StgMutClosure *)tso;
-	continue;
-      }
-      
-    case BLACKHOLE_BQ:
-      { 
-	StgBlockingQueue *bh = (StgBlockingQueue *)p;
-	(StgClosure *)bh->blocking_queue = 
-	  evacuate((StgClosure *)bh->blocking_queue);
-	p->mut_link = gen->mut_list;
-	gen->mut_list = p;
-	continue;
-      }
-
-      /* Happens if a BLACKHOLE_BQ in the old generation is updated: 
-       */
-    case IND_OLDGEN:
-    case IND_OLDGEN_PERM:
-      /* Try to pull the indirectee into this generation, so we can
-       * remove the indirection from the mutable list.  
-       */
-      evac_gen = gen->no;
-      ((StgIndOldGen *)p)->indirectee = 
-        evacuate(((StgIndOldGen *)p)->indirectee);
-      evac_gen = 0;
-
-      if (failed_to_evac) {
-	failed_to_evac = rtsFalse;
-	p->mut_link = gen->mut_once_list;
-	gen->mut_once_list = p;
-      } else {
-	p->mut_link = NULL;
-      }
-      continue;
-
-#if defined(PAR)
-    // HWL: check whether all of these are necessary
-
-    case RBH: // cf. BLACKHOLE_BQ
-      { 
-	// nat size, ptrs, nonptrs, vhs;
-	// char str[80];
-	// StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
-	StgRBH *rbh = (StgRBH *)p;
-	(StgClosure *)rbh->blocking_queue = 
-	  evacuate((StgClosure *)rbh->blocking_queue);
-	if (failed_to_evac) {
-	  failed_to_evac = rtsFalse;
-	  recordMutable((StgMutClosure *)rbh);
-	}
-	// ToDo: use size of reverted closure here!
-	p += BLACKHOLE_sizeW(); 
-	break;
-      }
-
-    case BLOCKED_FETCH:
-      { 
-	StgBlockedFetch *bf = (StgBlockedFetch *)p;
-	// follow the pointer to the node which is being demanded 
-	(StgClosure *)bf->node = 
-	  evacuate((StgClosure *)bf->node);
-	// follow the link to the rest of the blocking queue 
-	(StgClosure *)bf->link = 
-	  evacuate((StgClosure *)bf->link);
-	if (failed_to_evac) {
-	  failed_to_evac = rtsFalse;
-	  recordMutable((StgMutClosure *)bf);
-	}
-	p += sizeofW(StgBlockedFetch);
-	break;
-      }
+    bdescr *bd;
+    StgPtr p, q;
 
-#ifdef DIST
-    case REMOTE_REF:
-      barf("scavenge_mutable_list: REMOTE_REF %d", (int)(info->type));
-#endif
-    case FETCH_ME:
-      p += sizeofW(StgFetchMe);
-      break; // nothing to do in this case
+    bd = gen->saved_mut_list;
 
-    case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
-      { 
-	StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
-	(StgClosure *)fmbq->blocking_queue = 
-	  evacuate((StgClosure *)fmbq->blocking_queue);
-	if (failed_to_evac) {
-	  failed_to_evac = rtsFalse;
-	  recordMutable((StgMutClosure *)fmbq);
+    evac_gen = gen->no;
+    for (; bd != NULL; bd = bd->link) {
+	for (q = bd->start; q < bd->free; q++) {
+	    p = (StgPtr)*q;
+	    ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
+	    if (scavenge_one(p)) {
+		/* didn't manage to promote everything, so put the
+		 * object back on the list.
+		 */
+		recordMutableGen((StgClosure *)p,gen);
+	    }
 	}
-	p += sizeofW(StgFetchMeBlockingQueue);
-	break;
-      }
-#endif
-
-    default:
-      // shouldn't have anything else on the mutables list 
-      barf("scavenge_mutable_list: strange object? %d", (int)(info->type));
     }
-  }
+
+    // free the old mut_list
+    freeChain(gen->saved_mut_list);
+    gen->saved_mut_list = NULL;
 }
 
 
@@ -3629,8 +3637,8 @@ scavenge_static(void)
     /* Take this object *off* the static_objects list,
      * and put it on the scavenged_static_objects list.
      */
-    static_objects = STATIC_LINK(info,p);
-    STATIC_LINK(info,p) = scavenged_static_objects;
+    static_objects = *STATIC_LINK(info,p);
+    *STATIC_LINK(info,p) = scavenged_static_objects;
     scavenged_static_objects = p;
     
     switch (info -> type) {
@@ -3641,15 +3649,13 @@ scavenge_static(void)
 	ind->indirectee = evacuate(ind->indirectee);
 
 	/* might fail to evacuate it, in which case we have to pop it
-	 * back on the mutable list (and take it off the
-	 * scavenged_static list because the static link and mut link
-	 * pointers are one and the same).
+	 * back on the mutable list of the oldest generation.  We
+	 * leave it *on* the scavenged_static_objects list, though,
+	 * in case we visit this object again.
 	 */
 	if (failed_to_evac) {
 	  failed_to_evac = rtsFalse;
-	  scavenged_static_objects = IND_STATIC_LINK(p);
-	  ((StgMutClosure *)ind)->mut_link = oldest_gen->mut_once_list;
-	  oldest_gen->mut_once_list = (StgMutClosure *)ind;
+	  recordMutableGen((StgClosure *)p,oldest_gen);
 	}
 	break;
       }
@@ -3669,7 +3675,7 @@ scavenge_static(void)
 	next = (P_)p->payload + info->layout.payload.ptrs;
 	// evacuate the pointers 
 	for (q = (P_)p->payload; q < next; q++) {
-	  (StgClosure *)*q = evacuate((StgClosure *)*q);
+	    *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
 	}
 	break;
       }
@@ -3702,7 +3708,7 @@ scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
     bitmap = large_bitmap->bitmap[b];
     for (i = 0; i < size; ) {
 	if ((bitmap & 1) == 0) {
-	    (StgClosure *)*p = evacuate((StgClosure *)*p);
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
 	}
 	i++;
 	p++;
@@ -3720,7 +3726,7 @@ scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
 {
     while (size > 0) {
 	if ((bitmap & 1) == 0) {
-	    (StgClosure *)*p = evacuate((StgClosure *)*p);
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
 	}
 	p++;
 	bitmap = bitmap >> 1;
@@ -3762,6 +3768,9 @@ scavenge_stack(StgPtr p, StgPtr stack_end)
 	continue;
 
       // small bitmap (< 32 entries, or 64 on a 64-bit machine) 
+    case CATCH_STM_FRAME:
+    case CATCH_RETRY_FRAME:
+    case ATOMICALLY_FRAME:
     case STOP_FRAME:
     case CATCH_FRAME:
     case RET_SMALL:
@@ -3774,7 +3783,7 @@ scavenge_stack(StgPtr p, StgPtr stack_end)
 	p = scavenge_small_bitmap(p, size, bitmap);
 
     follow_srt:
-	scavenge_srt((StgClosure **)info->srt, info->i.srt_bitmap);
+	scavenge_srt((StgClosure **)GET_SRT(info), info->i.srt_bitmap);
 	continue;
 
     case RET_BCO: {
@@ -3782,7 +3791,7 @@ scavenge_stack(StgPtr p, StgPtr stack_end)
 	nat size;
 
 	p++;
-	(StgClosure *)*p = evacuate((StgClosure *)*p);
+	*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
 	bco = (StgBCO *)*p;
 	p++;
 	size = BCO_BITMAP_SIZE(bco);
@@ -3797,9 +3806,9 @@ scavenge_stack(StgPtr p, StgPtr stack_end)
     {
 	nat size;
 
-	size = info->i.layout.large_bitmap->size;
+	size = GET_LARGE_BITMAP(&info->i)->size;
 	p++;
-	scavenge_large_bitmap(p, info->i.layout.large_bitmap, size);
+	scavenge_large_bitmap(p, GET_LARGE_BITMAP(&info->i), size);
 	p += size;
 	// and don't forget to follow the SRT 
 	goto follow_srt;
@@ -3825,7 +3834,7 @@ scavenge_stack(StgPtr p, StgPtr stack_end)
 	
 	// follow the ptr words
 	for (size = RET_DYN_PTRS(dyn); size > 0; size--) {
-	    (StgClosure *)*p = evacuate((StgClosure *)*p);
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
 	    p++;
 	}
 	continue;
@@ -3880,7 +3889,7 @@ scavenge_large(step *stp)
 
     p = bd->start;
     if (scavenge_one(p)) {
-	mkMutCons((StgClosure *)p, stp->gen);
+	recordMutableGen((StgClosure *)p, stp->gen);
     }
   }
 }
@@ -3898,28 +3907,8 @@ zero_static_object_list(StgClosure* first_static)
 
   for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
     info = get_itbl(p);
-    link = STATIC_LINK(info, p);
-    STATIC_LINK(info,p) = NULL;
-  }
-}
-
-/* This function is only needed because we share the mutable link
- * field with the static link field in an IND_STATIC, so we have to
- * zero the mut_link field before doing a major GC, which needs the
- * static link field.  
- *
- * It doesn't do any harm to zero all the mutable link fields on the
- * mutable list.
- */
-
-static void
-zero_mutable_list( StgMutClosure *first )
-{
-  StgMutClosure *next, *c;
-
-  for (c = first; c != END_MUT_LIST; c = next) {
-    next = c->mut_link;
-    c->mut_link = NULL;
+    link = *STATIC_LINK(info, p);
+    *STATIC_LINK(info,p) = NULL;
   }
 }
 
@@ -3932,14 +3921,14 @@ revertCAFs( void )
 {
     StgIndStatic *c;
 
-    for (c = (StgIndStatic *)caf_list; c != NULL; 
+    for (c = (StgIndStatic *)revertible_caf_list; c != NULL; 
 	 c = (StgIndStatic *)c->static_link) 
     {
 	SET_INFO(c, c->saved_info);
 	c->saved_info = NULL;
 	// could, but not necessary: c->static_link = NULL; 
     }
-    caf_list = NULL;
+    revertible_caf_list = NULL;
 }
 
 void
@@ -3952,6 +3941,11 @@ markCAFs( evac_fn evac )
     {
 	evac(&c->indirectee);
     }
+    for (c = (StgIndStatic *)revertible_caf_list; c != NULL; 
+	 c = (StgIndStatic *)c->static_link) 
+    {
+	evac(&c->indirectee);
+    }
 }
 
 /* -----------------------------------------------------------------------------
@@ -4019,7 +4013,7 @@ threadLazyBlackHole(StgTSO *tso)
 {
     StgClosure *frame;
     StgRetInfoTable *info;
-    StgBlockingQueue *bh;
+    StgClosure *bh;
     StgPtr stack_end;
     
     stack_end = &tso->stack[tso->stack_size];
@@ -4032,7 +4026,7 @@ threadLazyBlackHole(StgTSO *tso)
 	switch (info->i.type) {
 	    
 	case UPDATE_FRAME:
-	    bh = (StgBlockingQueue *)((StgUpdateFrame *)frame)->updatee;
+	    bh = ((StgUpdateFrame *)frame)->updatee;
 	    
 	    /* if the thunk is already blackholed, it means we've also
 	     * already blackholed the rest of the thunks on this stack,
@@ -4045,10 +4039,9 @@ threadLazyBlackHole(StgTSO *tso)
 		return;
 	    }
 	    
-	    if (bh->header.info != &stg_BLACKHOLE_BQ_info &&
-		bh->header.info != &stg_CAF_BLACKHOLE_info) {
+	    if (bh->header.info != &stg_CAF_BLACKHOLE_info) {
 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
-		debugBelch("Unexpected lazy BHing required at 0x%04x",(int)bh);
+		debugBelch("Unexpected lazy BHing required at 0x%04x\n",(int)bh);
 #endif
 #ifdef PROFILING
 		// @LDV profiling
@@ -4069,7 +4062,7 @@ threadLazyBlackHole(StgTSO *tso)
 	    
 	    // normal stack frames; do nothing except advance the pointer
 	default:
-	    (StgPtr)frame += stack_frame_sizeW(frame);
+	    frame = (StgClosure *)((StgPtr)frame + stack_frame_sizeW(frame));
 	}
     }
 }
@@ -4150,7 +4143,6 @@ threadSqueezeStack(StgTSO *tso)
 		 * screw us up if we don't check.
 		 */
 		if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
-		    // this wakes the threads up 
 		    UPD_IND_NOLOCK(upd->updatee, updatee);
 		}
 
@@ -4168,11 +4160,10 @@ threadSqueezeStack(StgTSO *tso)
 
 	    // single update frame, or the topmost update frame in a series
 	    else {
-		StgBlockingQueue *bh = (StgBlockingQueue *)upd->updatee;
+		StgClosure *bh = upd->updatee;
 
 		// Do lazy black-holing
 		if (bh->header.info != &stg_BLACKHOLE_info &&
-		    bh->header.info != &stg_BLACKHOLE_BQ_info &&
 		    bh->header.info != &stg_CAF_BLACKHOLE_info) {
 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
 		    debugBelch("Unexpected lazy BHing required at 0x%04x",(int)bh);
@@ -4191,8 +4182,8 @@ threadSqueezeStack(StgTSO *tso)
 			 * same size as a BLACKHOLE in any case.
 			 */
 			if (bh_info->type != THUNK_SELECTOR) {
-			    for (i = np; i < np + nw; i++) {
-				((StgClosure *)bh)->payload[i] = 0;
+			    for (i = 0; i < np + nw; i++) {
+				((StgClosure *)bh)->payload[i] = INVALID_OBJECT;
 			    }
 			}
 		    }
@@ -4273,7 +4264,7 @@ done_traversing:
 	    next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
 
 	    chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
-	    (unsigned char*)sp -= chunk_size;
+	    sp -= chunk_size;
 	    memmove(sp, next_gap_start, chunk_size);
 	}
 
@@ -4303,35 +4294,19 @@ threadPaused(StgTSO *tso)
 
 #if DEBUG
 void
-printMutOnceList(generation *gen)
-{
-  StgMutClosure *p, *next;
-
-  p = gen->mut_once_list;
-  next = p->mut_link;
-
-  debugBelch("@@ Mut once list %p: ", gen->mut_once_list);
-  for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
-    debugBelch("%p (%s), ", 
-	    p, info_type((StgClosure *)p));
-  }
-  debugBelch("\n");
-}
-
-void
 printMutableList(generation *gen)
 {
-  StgMutClosure *p, *next;
+    bdescr *bd;
+    StgPtr p;
 
-  p = gen->mut_list;
-  next = p->mut_link;
+    debugBelch("@@ Mutable list %p: ", gen->mut_list);
 
-  debugBelch("@@ Mutable list %p: ", gen->mut_list);
-  for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
-    debugBelch("%p (%s), ",
-	    p, info_type((StgClosure *)p));
-  }
-  debugBelch("\n");
+    for (bd = gen->mut_list; bd != NULL; bd = bd->link) {
+	for (p = bd->start; p < bd->free; p++) {
+	    debugBelch("%p (%s), ", (void *)*p, info_type((StgClosure *)*p));
+	}
+    }
+    debugBelch("\n");
 }
 
 STATIC_INLINE rtsBool
@@ -4343,9 +4318,10 @@ maybeLarge(StgClosure *closure)
      see scavenge_large */
   return (info->type == MUT_ARR_PTRS ||
 	  info->type == MUT_ARR_PTRS_FROZEN ||
+	  info->type == MUT_ARR_PTRS_FROZEN0 ||
 	  info->type == TSO ||
 	  info->type == ARR_WORDS);
 }
 
   
-#endif // DEBUG
+#endif /* DEBUG */