X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=rts%2Fsm%2FScav.c;h=9ac152af5371604aaff6c4363db57aac0e42d9d5;hp=b7bd7f384b71d07c4d515f11ca93ec0f993d46b3;hb=bef3da1e26639303fccbf26c312d2833eedb486e;hpb=dbbf15c0f141357aa49b583286174867baadb821

diff --git a/rts/sm/Scav.c b/rts/sm/Scav.c
index b7bd7f3..9ac152a 100644
--- a/rts/sm/Scav.c
+++ b/rts/sm/Scav.c
@@ -1,6 +1,6 @@
 /* -----------------------------------------------------------------------------
  *
- * (c) The GHC Team 1998-2006
+ * (c) The GHC Team 1998-2008
  *
  * Generational garbage collector: scavenging functions
  *
@@ -11,19 +11,22 @@
  *
  * ---------------------------------------------------------------------------*/
 
+#include "PosixSource.h"
 #include "Rts.h"
-#include "RtsFlags.h"
+
 #include "Storage.h"
-#include "MBlock.h"
 #include "GC.h"
+#include "GCThread.h"
 #include "GCUtils.h"
 #include "Compact.h"
+#include "MarkStack.h"
 #include "Evac.h"
 #include "Scav.h"
 #include "Apply.h"
 #include "Trace.h"
-#include "LdvProfile.h"
 #include "Sanity.h"
+#include "Capability.h"
+#include "LdvProfile.h"
 
 static void scavenge_stack (StgPtr p, StgPtr stack_end);
 
@@ -31,6 +34,235 @@ static void scavenge_large_bitmap (StgPtr p,
 				   StgLargeBitmap *large_bitmap, 
 				   nat size );
 
+#if defined(THREADED_RTS) && !defined(PARALLEL_GC)
+# define evacuate(a) evacuate1(a)
+# define scavenge_loop(a) scavenge_loop1(a)
+# define scavenge_block(a) scavenge_block1(a)
+# define scavenge_mutable_list(bd,g) scavenge_mutable_list1(bd,g)
+# define scavenge_capability_mut_lists(cap) scavenge_capability_mut_Lists1(cap)
+#endif
+
+/* -----------------------------------------------------------------------------
+   Scavenge a TSO.
+   -------------------------------------------------------------------------- */
+
+static void
+scavengeTSO (StgTSO *tso)
+{
+    rtsBool saved_eager;
+
+    debugTrace(DEBUG_gc,"scavenging thread %d",(int)tso->id);
+
+    // update the pointer from the Task.
+    if (tso->bound != NULL) {
+        tso->bound->tso = tso;
+    }
+
+    saved_eager = gct->eager_promotion;
+    gct->eager_promotion = rtsFalse;
+
+    evacuate((StgClosure **)&tso->blocked_exceptions);
+    evacuate((StgClosure **)&tso->bq);
+    
+    // scavange current transaction record
+    evacuate((StgClosure **)&tso->trec);
+
+    evacuate((StgClosure **)&tso->stackobj);
+
+    evacuate((StgClosure **)&tso->_link);
+    if (   tso->why_blocked == BlockedOnMVar
+	|| tso->why_blocked == BlockedOnBlackHole
+	|| tso->why_blocked == BlockedOnMsgThrowTo
+        || tso->why_blocked == NotBlocked
+	) {
+	evacuate(&tso->block_info.closure);
+    }
+#ifdef THREADED_RTS
+    // in the THREADED_RTS, block_info.closure must always point to a
+    // valid closure, because we assume this in throwTo().  In the
+    // non-threaded RTS it might be a FD (for
+    // BlockedOnRead/BlockedOnWrite) or a time value (BlockedOnDelay)
+    else {
+        tso->block_info.closure = (StgClosure *)END_TSO_QUEUE;
+    }
+#endif
+
+    tso->dirty = gct->failed_to_evac;
+
+    gct->eager_promotion = saved_eager;
+}
+
+/* -----------------------------------------------------------------------------
+   Mutable arrays of pointers
+   -------------------------------------------------------------------------- */
+
+static StgPtr scavenge_mut_arr_ptrs (StgMutArrPtrs *a)
+{
+    lnat m;
+    rtsBool any_failed;
+    StgPtr p, q;
+
+    any_failed = rtsFalse;
+    p = (StgPtr)&a->payload[0];
+    for (m = 0; (int)m < (int)mutArrPtrsCards(a->ptrs) - 1; m++)
+    {
+        q = p + (1 << MUT_ARR_PTRS_CARD_BITS);
+        for (; p < q; p++) {
+            evacuate((StgClosure**)p);
+        }
+        if (gct->failed_to_evac) {
+            any_failed = rtsTrue;
+            *mutArrPtrsCard(a,m) = 1;
+            gct->failed_to_evac = rtsFalse;
+        } else {
+            *mutArrPtrsCard(a,m) = 0;
+        }
+    }
+
+    q = (StgPtr)&a->payload[a->ptrs];
+    if (p < q) {
+        for (; p < q; p++) {
+            evacuate((StgClosure**)p);
+        }
+        if (gct->failed_to_evac) {
+            any_failed = rtsTrue;
+            *mutArrPtrsCard(a,m) = 1;
+            gct->failed_to_evac = rtsFalse;
+        } else {
+            *mutArrPtrsCard(a,m) = 0;
+        }
+    }
+
+    gct->failed_to_evac = any_failed;
+    return (StgPtr)a + mut_arr_ptrs_sizeW(a);
+}
+    
+// scavenge only the marked areas of a MUT_ARR_PTRS
+static StgPtr scavenge_mut_arr_ptrs_marked (StgMutArrPtrs *a)
+{
+    lnat m;
+    StgPtr p, q;
+    rtsBool any_failed;
+
+    any_failed = rtsFalse;
+    for (m = 0; m < mutArrPtrsCards(a->ptrs); m++)
+    {
+        if (*mutArrPtrsCard(a,m) != 0) {
+            p = (StgPtr)&a->payload[m << MUT_ARR_PTRS_CARD_BITS];
+            q = stg_min(p + (1 << MUT_ARR_PTRS_CARD_BITS),
+                        (StgPtr)&a->payload[a->ptrs]);
+            for (; p < q; p++) {
+                evacuate((StgClosure**)p);
+            }
+            if (gct->failed_to_evac) {
+                any_failed = rtsTrue;
+                gct->failed_to_evac = rtsFalse;
+            } else {
+                *mutArrPtrsCard(a,m) = 0;
+            }
+        }
+    }
+
+    gct->failed_to_evac = any_failed;
+    return (StgPtr)a + mut_arr_ptrs_sizeW(a);
+}
+
+/* -----------------------------------------------------------------------------
+   Blocks of function args occur on the stack (at the top) and
+   in PAPs.
+   -------------------------------------------------------------------------- */
+
+STATIC_INLINE StgPtr
+scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
+{
+    StgPtr p;
+    StgWord bitmap;
+    nat size;
+
+    p = (StgPtr)args;
+    switch (fun_info->f.fun_type) {
+    case ARG_GEN:
+	bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
+	size = BITMAP_SIZE(fun_info->f.b.bitmap);
+	goto small_bitmap;
+    case ARG_GEN_BIG:
+	size = GET_FUN_LARGE_BITMAP(fun_info)->size;
+	scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
+	p += size;
+	break;
+    default:
+	bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
+	size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
+    small_bitmap:
+	while (size > 0) {
+	    if ((bitmap & 1) == 0) {
+		evacuate((StgClosure **)p);
+	    }
+	    p++;
+	    bitmap = bitmap >> 1;
+	    size--;
+	}
+	break;
+    }
+    return p;
+}
+
+STATIC_INLINE GNUC_ATTR_HOT StgPtr
+scavenge_PAP_payload (StgClosure *fun, StgClosure **payload, StgWord size)
+{
+    StgPtr p;
+    StgWord bitmap;
+    StgFunInfoTable *fun_info;
+    
+    fun_info = get_fun_itbl(UNTAG_CLOSURE(fun));
+    ASSERT(fun_info->i.type != PAP);
+    p = (StgPtr)payload;
+
+    switch (fun_info->f.fun_type) {
+    case ARG_GEN:
+	bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
+	goto small_bitmap;
+    case ARG_GEN_BIG:
+	scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
+	p += size;
+	break;
+    case ARG_BCO:
+	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:
+	while (size > 0) {
+	    if ((bitmap & 1) == 0) {
+		evacuate((StgClosure **)p);
+	    }
+	    p++;
+	    bitmap = bitmap >> 1;
+	    size--;
+	}
+	break;
+    }
+    return p;
+}
+
+STATIC_INLINE GNUC_ATTR_HOT StgPtr
+scavenge_PAP (StgPAP *pap)
+{
+    evacuate(&pap->fun);
+    return scavenge_PAP_payload (pap->fun, pap->payload, pap->n_args);
+}
+
+STATIC_INLINE StgPtr
+scavenge_AP (StgAP *ap)
+{
+    evacuate(&ap->fun);
+    return scavenge_PAP_payload (ap->fun, ap->payload, ap->n_args);
+}
+
+/* -----------------------------------------------------------------------------
+   Scavenge SRTs
+   -------------------------------------------------------------------------- */
 
 /* Similar to scavenge_large_bitmap(), but we don't write back the
  * pointers we get back from evacuate().
@@ -65,7 +297,7 @@ scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
  * srt field in the info table.  That's ok, because we'll
  * never dereference it.
  */
-STATIC_INLINE void
+STATIC_INLINE GNUC_ATTR_HOT void
 scavenge_srt (StgClosure **srt, nat srt_bitmap)
 {
   nat bitmap;
@@ -81,7 +313,7 @@ scavenge_srt (StgClosure **srt, nat srt_bitmap)
 
   while (bitmap != 0) {
       if ((bitmap & 1) != 0) {
-#if defined(__PIC__) && defined(mingw32_TARGET_OS)
+#if defined(__PIC__) && defined(mingw32_HOST_OS)
 	  // Special-case to handle references to closures hiding out in DLLs, since
 	  // double indirections required to get at those. The code generator knows
 	  // which is which when generating the SRT, so it stores the (indirect)
@@ -91,7 +323,7 @@ scavenge_srt (StgClosure **srt, nat srt_bitmap)
 	  // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
 	  // closure that's fixed at link-time, and no extra magic is required.
 	  if ( (unsigned long)(*srt) & 0x1 ) {
-	      evacuate(stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
+	      evacuate( (StgClosure**) ((unsigned long) (*srt) & ~0x1));
 	  } else {
 	      evacuate(p);
 	  }
@@ -105,7 +337,7 @@ scavenge_srt (StgClosure **srt, nat srt_bitmap)
 }
 
 
-STATIC_INLINE void
+STATIC_INLINE GNUC_ATTR_HOT void
 scavenge_thunk_srt(const StgInfoTable *info)
 {
     StgThunkInfoTable *thunk_info;
@@ -116,7 +348,7 @@ scavenge_thunk_srt(const StgInfoTable *info)
     scavenge_srt((StgClosure **)GET_SRT(thunk_info), thunk_info->i.srt_bitmap);
 }
 
-STATIC_INLINE void
+STATIC_INLINE GNUC_ATTR_HOT void
 scavenge_fun_srt(const StgInfoTable *info)
 {
     StgFunInfoTable *fun_info;
@@ -128,148 +360,385 @@ scavenge_fun_srt(const StgInfoTable *info)
 }
 
 /* -----------------------------------------------------------------------------
-   Scavenge a TSO.
+   Scavenge a block from the given scan pointer up to bd->free.
+
+   evac_gen_no is set by the caller to be either zero (for a step in a
+   generation < N) or G where G is the generation of the step being
+   scavenged.  
+
+   We sometimes temporarily change evac_gen_no back to zero if we're
+   scavenging a mutable object where eager promotion isn't such a good
+   idea.  
    -------------------------------------------------------------------------- */
 
-static void
-scavengeTSO (StgTSO *tso)
+static GNUC_ATTR_HOT void
+scavenge_block (bdescr *bd)
 {
-    rtsBool saved_eager;
+  StgPtr p, q;
+  StgInfoTable *info;
+  rtsBool saved_eager_promotion;
+  gen_workspace *ws;
+
+  debugTrace(DEBUG_gc, "scavenging block %p (gen %d) @ %p",
+	     bd->start, bd->gen_no, bd->u.scan);
+
+  gct->scan_bd = bd;
+  gct->evac_gen_no = bd->gen_no;
+  saved_eager_promotion = gct->eager_promotion;
+  gct->failed_to_evac = rtsFalse;
+
+  ws = &gct->gens[bd->gen->no];
 
-    if (tso->what_next == ThreadRelocated) {
-        // the only way this can happen is if the old TSO was on the
-        // mutable list.  We might have other links to this defunct
-        // TSO, so we must update its link field.
-        evacuate((StgClosure**)&tso->_link);
-        return;
+  p = bd->u.scan;
+  
+  // we might be evacuating into the very object that we're
+  // scavenging, so we have to check the real bd->free pointer each
+  // time around the loop.
+  while (p < bd->free || (bd == ws->todo_bd && p < ws->todo_free)) {
+
+      ASSERT(bd->link == NULL);
+    ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
+    info = get_itbl((StgClosure *)p);
+    
+    ASSERT(gct->thunk_selector_depth == 0);
+
+    q = p;
+    switch (info->type) {
+
+    case MVAR_CLEAN:
+    case MVAR_DIRTY:
+    { 
+	StgMVar *mvar = ((StgMVar *)p);
+	gct->eager_promotion = rtsFalse;
+	evacuate((StgClosure **)&mvar->head);
+	evacuate((StgClosure **)&mvar->tail);
+	evacuate((StgClosure **)&mvar->value);
+	gct->eager_promotion = saved_eager_promotion;
+
+	if (gct->failed_to_evac) {
+	    mvar->header.info = &stg_MVAR_DIRTY_info;
+	} else {
+	    mvar->header.info = &stg_MVAR_CLEAN_info;
+	}
+	p += sizeofW(StgMVar);
+	break;
     }
 
-    saved_eager = gct->eager_promotion;
-    gct->eager_promotion = rtsFalse;
+    case FUN_2_0:
+	scavenge_fun_srt(info);
+	evacuate(&((StgClosure *)p)->payload[1]);
+	evacuate(&((StgClosure *)p)->payload[0]);
+	p += sizeofW(StgHeader) + 2;
+	break;
 
-    if (   tso->why_blocked == BlockedOnMVar
-	|| tso->why_blocked == BlockedOnBlackHole
-	|| tso->why_blocked == BlockedOnException
-	) {
-	evacuate(&tso->block_info.closure);
+    case THUNK_2_0:
+	scavenge_thunk_srt(info);
+	evacuate(&((StgThunk *)p)->payload[1]);
+	evacuate(&((StgThunk *)p)->payload[0]);
+	p += sizeofW(StgThunk) + 2;
+	break;
+
+    case CONSTR_2_0:
+	evacuate(&((StgClosure *)p)->payload[1]);
+	evacuate(&((StgClosure *)p)->payload[0]);
+	p += sizeofW(StgHeader) + 2;
+	break;
+	
+    case THUNK_1_0:
+	scavenge_thunk_srt(info);
+	evacuate(&((StgThunk *)p)->payload[0]);
+	p += sizeofW(StgThunk) + 1;
+	break;
+	
+    case FUN_1_0:
+	scavenge_fun_srt(info);
+    case CONSTR_1_0:
+	evacuate(&((StgClosure *)p)->payload[0]);
+	p += sizeofW(StgHeader) + 1;
+	break;
+	
+    case THUNK_0_1:
+	scavenge_thunk_srt(info);
+	p += sizeofW(StgThunk) + 1;
+	break;
+	
+    case FUN_0_1:
+	scavenge_fun_srt(info);
+    case CONSTR_0_1:
+	p += sizeofW(StgHeader) + 1;
+	break;
+	
+    case THUNK_0_2:
+	scavenge_thunk_srt(info);
+	p += sizeofW(StgThunk) + 2;
+	break;
+	
+    case FUN_0_2:
+	scavenge_fun_srt(info);
+    case CONSTR_0_2:
+	p += sizeofW(StgHeader) + 2;
+	break;
+	
+    case THUNK_1_1:
+	scavenge_thunk_srt(info);
+	evacuate(&((StgThunk *)p)->payload[0]);
+	p += sizeofW(StgThunk) + 2;
+	break;
+
+    case FUN_1_1:
+	scavenge_fun_srt(info);
+    case CONSTR_1_1:
+	evacuate(&((StgClosure *)p)->payload[0]);
+	p += sizeofW(StgHeader) + 2;
+	break;
+	
+    case FUN:
+	scavenge_fun_srt(info);
+	goto gen_obj;
+
+    case THUNK:
+    {
+	StgPtr end;
+
+	scavenge_thunk_srt(info);
+	end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
+	for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
+	    evacuate((StgClosure **)p);
+	}
+	p += info->layout.payload.nptrs;
+	break;
     }
-    evacuate((StgClosure **)&tso->blocked_exceptions);
-    
-    // We don't always chase the link field: TSOs on the blackhole
-    // queue are not automatically alive, so the link field is a
-    // "weak" pointer in that case.
-    if (tso->why_blocked != BlockedOnBlackHole) {
-	evacuate((StgClosure **)&tso->link);
+	
+    gen_obj:
+    case CONSTR:
+    case WEAK:
+    case PRIM:
+    {
+	StgPtr end;
+
+	end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
+	for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
+	    evacuate((StgClosure **)p);
+	}
+	p += info->layout.payload.nptrs;
+	break;
     }
 
-    // scavange current transaction record
-    evacuate((StgClosure **)&tso->trec);
-    
-    // scavenge this thread's stack 
-    scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
+    case BCO: {
+	StgBCO *bco = (StgBCO *)p;
+	evacuate((StgClosure **)&bco->instrs);
+	evacuate((StgClosure **)&bco->literals);
+	evacuate((StgClosure **)&bco->ptrs);
+	p += bco_sizeW(bco);
+	break;
+    }
 
-    if (gct->failed_to_evac) {
-        tso->flags |= TSO_DIRTY;
-    } else {
-        tso->flags &= ~TSO_DIRTY;
+    case IND_PERM:
+    case BLACKHOLE:
+	evacuate(&((StgInd *)p)->indirectee);
+	p += sizeofW(StgInd);
+	break;
+
+    case MUT_VAR_CLEAN:
+    case MUT_VAR_DIRTY:
+	gct->eager_promotion = rtsFalse;
+	evacuate(&((StgMutVar *)p)->var);
+	gct->eager_promotion = saved_eager_promotion;
+
+	if (gct->failed_to_evac) {
+	    ((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
+	} else {
+	    ((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
+	}
+	p += sizeofW(StgMutVar);
+	break;
+
+    case BLOCKING_QUEUE:
+    {
+        StgBlockingQueue *bq = (StgBlockingQueue *)p;
+        
+	gct->eager_promotion = rtsFalse;
+        evacuate(&bq->bh);
+        evacuate((StgClosure**)&bq->owner);
+        evacuate((StgClosure**)&bq->queue);
+        evacuate((StgClosure**)&bq->link);
+	gct->eager_promotion = saved_eager_promotion;
+
+	if (gct->failed_to_evac) {
+	    bq->header.info = &stg_BLOCKING_QUEUE_DIRTY_info;
+	} else {
+	    bq->header.info = &stg_BLOCKING_QUEUE_CLEAN_info;
+	}
+        p += sizeofW(StgBlockingQueue);
+        break;
     }
 
-    gct->eager_promotion = saved_eager;
-}
+    case THUNK_SELECTOR:
+    { 
+	StgSelector *s = (StgSelector *)p;
+	evacuate(&s->selectee);
+	p += THUNK_SELECTOR_sizeW();
+	break;
+    }
 
-/* -----------------------------------------------------------------------------
-   Blocks of function args occur on the stack (at the top) and
-   in PAPs.
-   -------------------------------------------------------------------------- */
+    // A chunk of stack saved in a heap object
+    case AP_STACK:
+    {
+	StgAP_STACK *ap = (StgAP_STACK *)p;
 
-STATIC_INLINE StgPtr
-scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
-{
-    StgPtr p;
-    StgWord bitmap;
-    nat size;
+	evacuate(&ap->fun);
+	scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
+	p = (StgPtr)ap->payload + ap->size;
+	break;
+    }
 
-    p = (StgPtr)args;
-    switch (fun_info->f.fun_type) {
-    case ARG_GEN:
-	bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
-	size = BITMAP_SIZE(fun_info->f.b.bitmap);
-	goto small_bitmap;
-    case ARG_GEN_BIG:
-	size = GET_FUN_LARGE_BITMAP(fun_info)->size;
-	scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
-	p += size;
+    case PAP:
+	p = scavenge_PAP((StgPAP *)p);
 	break;
-    default:
-	bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
-	size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
-    small_bitmap:
-	while (size > 0) {
-	    if ((bitmap & 1) == 0) {
-		evacuate((StgClosure **)p);
-	    }
-	    p++;
-	    bitmap = bitmap >> 1;
-	    size--;
+
+    case AP:
+	p = scavenge_AP((StgAP *)p);
+	break;
+
+    case ARR_WORDS:
+	// nothing to follow 
+	p += arr_words_sizeW((StgArrWords *)p);
+	break;
+
+    case MUT_ARR_PTRS_CLEAN:
+    case MUT_ARR_PTRS_DIRTY:
+    {
+        // We don't eagerly promote objects pointed to by a mutable
+        // array, but if we find the array only points to objects in
+        // the same or an older generation, we mark it "clean" and
+        // avoid traversing it during minor GCs.
+        gct->eager_promotion = rtsFalse;
+
+        p = scavenge_mut_arr_ptrs((StgMutArrPtrs*)p);
+
+	if (gct->failed_to_evac) {
+	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
+	} else {
+	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
 	}
+
+	gct->eager_promotion = saved_eager_promotion;
+	gct->failed_to_evac = rtsTrue; // always put it on the mutable list.
 	break;
     }
-    return p;
-}
 
-STATIC_INLINE StgPtr
-scavenge_PAP_payload (StgClosure *fun, StgClosure **payload, StgWord size)
-{
-    StgPtr p;
-    StgWord bitmap;
-    StgFunInfoTable *fun_info;
-    
-    fun_info = get_fun_itbl(UNTAG_CLOSURE(fun));
-    ASSERT(fun_info->i.type != PAP);
-    p = (StgPtr)payload;
+    case MUT_ARR_PTRS_FROZEN:
+    case MUT_ARR_PTRS_FROZEN0:
+	// follow everything 
+    {
+        p = scavenge_mut_arr_ptrs((StgMutArrPtrs*)p);
 
-    switch (fun_info->f.fun_type) {
-    case ARG_GEN:
-	bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
-	goto small_bitmap;
-    case ARG_GEN_BIG:
-	scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
-	p += size;
+	// If we're going to put this object on the mutable list, then
+	// set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
+	if (gct->failed_to_evac) {
+            ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
+	} else {
+	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
+	}
 	break;
-    case ARG_BCO:
-	scavenge_large_bitmap((StgPtr)payload, BCO_BITMAP(fun), size);
-	p += size;
+    }
+
+    case TSO:
+    { 
+        scavengeTSO((StgTSO *)p);
+        p += sizeofW(StgTSO);
+	break;
+    }
+
+    case STACK:
+    {
+        StgStack *stack = (StgStack*)p;
+
+        gct->eager_promotion = rtsFalse;
+
+        scavenge_stack(stack->sp, stack->stack + stack->stack_size);
+        stack->dirty = gct->failed_to_evac;
+        p += stack_sizeW(stack);
+
+        gct->eager_promotion = saved_eager_promotion;
+        break;
+    }
+
+    case MUT_PRIM:
+      {
+	StgPtr end;
+
+	gct->eager_promotion = rtsFalse;
+
+	end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
+	for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
+	    evacuate((StgClosure **)p);
+	}
+	p += info->layout.payload.nptrs;
+
+	gct->eager_promotion = saved_eager_promotion;
+	gct->failed_to_evac = rtsTrue; // mutable
+	break;
+      }
+
+    case TREC_CHUNK:
+      {
+	StgWord i;
+	StgTRecChunk *tc = ((StgTRecChunk *) p);
+	TRecEntry *e = &(tc -> entries[0]);
+	gct->eager_promotion = rtsFalse;
+	evacuate((StgClosure **)&tc->prev_chunk);
+	for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
+	  evacuate((StgClosure **)&e->tvar);
+	  evacuate((StgClosure **)&e->expected_value);
+	  evacuate((StgClosure **)&e->new_value);
+	}
+	gct->eager_promotion = saved_eager_promotion;
+	gct->failed_to_evac = rtsTrue; // mutable
+	p += sizeofW(StgTRecChunk);
 	break;
+      }
+
     default:
-	bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
-    small_bitmap:
-	while (size > 0) {
-	    if ((bitmap & 1) == 0) {
-		evacuate((StgClosure **)p);
-	    }
-	    p++;
-	    bitmap = bitmap >> 1;
-	    size--;
+	barf("scavenge: unimplemented/strange closure type %d @ %p", 
+	     info->type, p);
+    }
+
+    /*
+     * 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 (gct->failed_to_evac) {
+	gct->failed_to_evac = rtsFalse;
+	if (bd->gen_no > 0) {
+	    recordMutableGen_GC((StgClosure *)q, bd->gen_no);
 	}
-	break;
     }
-    return p;
-}
+  }
 
-STATIC_INLINE StgPtr
-scavenge_PAP (StgPAP *pap)
-{
-    evacuate(&pap->fun);
-    return scavenge_PAP_payload (pap->fun, pap->payload, pap->n_args);
-}
+  if (p > bd->free)  {
+      gct->copied += ws->todo_free - bd->free;
+      bd->free = p;
+  }
 
-STATIC_INLINE StgPtr
-scavenge_AP (StgAP *ap)
-{
-    evacuate(&ap->fun);
-    return scavenge_PAP_payload (ap->fun, ap->payload, ap->n_args);
-}
+  debugTrace(DEBUG_gc, "   scavenged %ld bytes",
+             (unsigned long)((bd->free - bd->u.scan) * sizeof(W_)));
+
+  // update stats: this is a block that has been scavenged
+  gct->scanned += bd->free - bd->u.scan;
+  bd->u.scan = bd->free;
 
+  if (bd != ws->todo_bd) {
+      // we're not going to evac any more objects into
+      // this block, so push it now.
+      push_scanned_block(bd, ws);
+  }
+
+  gct->scan_bd = NULL;
+}
 /* -----------------------------------------------------------------------------
    Scavenge everything on the mark stack.
 
@@ -283,26 +752,22 @@ scavenge_mark_stack(void)
 {
     StgPtr p, q;
     StgInfoTable *info;
-    step *saved_evac_step;
+    rtsBool saved_eager_promotion;
 
-    gct->evac_step = &oldest_gen->steps[0];
-    saved_evac_step = gct->evac_step;
+    gct->evac_gen_no = oldest_gen->no;
+    saved_eager_promotion = gct->eager_promotion;
 
-linear_scan:
-    while (!mark_stack_empty()) {
-	p = pop_mark_stack();
+    while ((p = pop_mark_stack())) {
 
 	ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
 	info = get_itbl((StgClosure *)p);
 	
 	q = p;
-        switch (((volatile StgWord *)info)[1] & 0xffff) {
+        switch (info->type) {
 	    
         case MVAR_CLEAN:
         case MVAR_DIRTY:
         { 
-            rtsBool saved_eager_promotion = gct->eager_promotion;
-            
             StgMVar *mvar = ((StgMVar *)p);
             gct->eager_promotion = rtsFalse;
             evacuate((StgClosure **)&mvar->head);
@@ -385,7 +850,7 @@ linear_scan:
 	gen_obj:
 	case CONSTR:
 	case WEAK:
-	case STABLE_NAME:
+	case PRIM:
 	{
 	    StgPtr end;
 	    
@@ -410,15 +875,13 @@ linear_scan:
 	    // no "old" generation.
 	    break;
 
-	case IND_OLDGEN:
-	case IND_OLDGEN_PERM:
+	case IND:
+        case BLACKHOLE:
 	    evacuate(&((StgInd *)p)->indirectee);
 	    break;
 
 	case MUT_VAR_CLEAN:
 	case MUT_VAR_DIRTY: {
-	    rtsBool saved_eager_promotion = gct->eager_promotion;
-	    
 	    gct->eager_promotion = rtsFalse;
 	    evacuate(&((StgMutVar *)p)->var);
 	    gct->eager_promotion = saved_eager_promotion;
@@ -431,10 +894,25 @@ linear_scan:
 	    break;
 	}
 
-	case CAF_BLACKHOLE:
-	case SE_CAF_BLACKHOLE:
-	case SE_BLACKHOLE:
-	case BLACKHOLE:
+        case BLOCKING_QUEUE:
+        {
+            StgBlockingQueue *bq = (StgBlockingQueue *)p;
+            
+            gct->eager_promotion = rtsFalse;
+            evacuate(&bq->bh);
+            evacuate((StgClosure**)&bq->owner);
+            evacuate((StgClosure**)&bq->queue);
+            evacuate((StgClosure**)&bq->link);
+            gct->eager_promotion = saved_eager_promotion;
+            
+            if (gct->failed_to_evac) {
+                bq->header.info = &stg_BLOCKING_QUEUE_DIRTY_info;
+            } else {
+                bq->header.info = &stg_BLOCKING_QUEUE_CLEAN_info;
+            }
+            break;
+        }
+
 	case ARR_WORDS:
 	    break;
 
@@ -467,27 +945,21 @@ linear_scan:
 	case MUT_ARR_PTRS_DIRTY:
 	    // follow everything 
 	{
-	    StgPtr next;
-	    rtsBool saved_eager;
-
 	    // We don't eagerly promote objects pointed to by a mutable
 	    // array, but if we find the array only points to objects in
 	    // the same or an older generation, we mark it "clean" and
 	    // avoid traversing it during minor GCs.
-	    saved_eager = gct->eager_promotion;
 	    gct->eager_promotion = rtsFalse;
-	    next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
-	    for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-		evacuate((StgClosure **)p);
-	    }
-	    gct->eager_promotion = saved_eager;
 
-	    if (gct->failed_to_evac) {
-		((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
-	    } else {
-		((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
-	    }
+            scavenge_mut_arr_ptrs((StgMutArrPtrs *)p);
+
+            if (gct->failed_to_evac) {
+                ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
+            } else {
+                ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
+            }
 
+	    gct->eager_promotion = saved_eager_promotion;
 	    gct->failed_to_evac = rtsTrue; // mutable anyhow.
 	    break;
 	}
@@ -496,12 +968,9 @@ linear_scan:
 	case MUT_ARR_PTRS_FROZEN0:
 	    // follow everything 
 	{
-	    StgPtr next, q = p;
+	    StgPtr q = p;
 	    
-	    next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
-	    for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-		evacuate((StgClosure **)p);
-	    }
+            scavenge_mut_arr_ptrs((StgMutArrPtrs *)p);
 
 	    // If we're going to put this object on the mutable list, then
 	    // set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
@@ -516,85 +985,55 @@ linear_scan:
 	case TSO:
 	{ 
             scavengeTSO((StgTSO*)p);
-	    gct->failed_to_evac = rtsTrue; // always on the mutable list
 	    break;
 	}
 
-	case TVAR_WATCH_QUEUE:
-	  {
-	    StgTVarWatchQueue *wq = ((StgTVarWatchQueue *) p);
-	    gct->evac_step = 0;
-            evacuate((StgClosure **)&wq->closure);
-	    evacuate((StgClosure **)&wq->next_queue_entry);
-	    evacuate((StgClosure **)&wq->prev_queue_entry);
-	    gct->evac_step = saved_evac_step;
-	    gct->failed_to_evac = rtsTrue; // mutable
-	    break;
-	  }
-	  
-	case TVAR:
-	  {
-	    StgTVar *tvar = ((StgTVar *) p);
-	    gct->evac_step = 0;
-	    evacuate((StgClosure **)&tvar->current_value);
-	    evacuate((StgClosure **)&tvar->first_watch_queue_entry);
-	    gct->evac_step = saved_evac_step;
-	    gct->failed_to_evac = rtsTrue; // mutable
-	    break;
-	  }
-	  
+        case STACK:
+        {
+            StgStack *stack = (StgStack*)p;
+
+            gct->eager_promotion = rtsFalse;
+
+            scavenge_stack(stack->sp, stack->stack + stack->stack_size);
+            stack->dirty = gct->failed_to_evac;
+
+            gct->eager_promotion = saved_eager_promotion;
+            break;
+        }
+
+        case MUT_PRIM:
+        {
+            StgPtr end;
+            
+            gct->eager_promotion = rtsFalse;
+            
+            end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
+            for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
+                evacuate((StgClosure **)p);
+            }
+            
+            gct->eager_promotion = saved_eager_promotion;
+            gct->failed_to_evac = rtsTrue; // mutable
+            break;
+        }
+
 	case TREC_CHUNK:
 	  {
 	    StgWord i;
 	    StgTRecChunk *tc = ((StgTRecChunk *) p);
 	    TRecEntry *e = &(tc -> entries[0]);
-	    gct->evac_step = 0;
+	    gct->eager_promotion = rtsFalse;
 	    evacuate((StgClosure **)&tc->prev_chunk);
 	    for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
 	      evacuate((StgClosure **)&e->tvar);
 	      evacuate((StgClosure **)&e->expected_value);
 	      evacuate((StgClosure **)&e->new_value);
 	    }
-	    gct->evac_step = saved_evac_step;
-	    gct->failed_to_evac = rtsTrue; // mutable
-	    break;
-	  }
-
-	case TREC_HEADER:
-	  {
-	    StgTRecHeader *trec = ((StgTRecHeader *) p);
-	    gct->evac_step = 0;
-	    evacuate((StgClosure **)&trec->enclosing_trec);
-	    evacuate((StgClosure **)&trec->current_chunk);
-  	    evacuate((StgClosure **)&trec->invariants_to_check);
-	    gct->evac_step = saved_evac_step;
+	    gct->eager_promotion = saved_eager_promotion;
 	    gct->failed_to_evac = rtsTrue; // mutable
 	    break;
 	  }
 
-        case ATOMIC_INVARIANT:
-          {
-            StgAtomicInvariant *invariant = ((StgAtomicInvariant *) p);
-            gct->evac_step = 0;
-	    evacuate(&invariant->code);
-    	    evacuate((StgClosure **)&invariant->last_execution);
-	    gct->evac_step = saved_evac_step;
-	    gct->failed_to_evac = rtsTrue; // mutable
-            break;
-          }
-
-        case INVARIANT_CHECK_QUEUE:
-          {
-            StgInvariantCheckQueue *queue = ((StgInvariantCheckQueue *) p);
-            gct->evac_step = 0;
-    	    evacuate((StgClosure **)&queue->invariant);
-	    evacuate((StgClosure **)&queue->my_execution);
-            evacuate((StgClosure **)&queue->next_queue_entry);
-	    gct->evac_step = saved_evac_step;
-	    gct->failed_to_evac = rtsTrue; // mutable
-            break;
-          }
-
 	default:
 	    barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p", 
 		 info->type, p);
@@ -602,53 +1041,11 @@ linear_scan:
 
 	if (gct->failed_to_evac) {
 	    gct->failed_to_evac = rtsFalse;
-	    if (gct->evac_step) {
-		recordMutableGen_GC((StgClosure *)q, gct->evac_step->gen);
-	    }
-	}
-	
-	// mark the next bit to indicate "scavenged"
-	mark(q+1, Bdescr(q));
-
-    } // while (!mark_stack_empty())
-
-    // start a new linear scan if the mark stack overflowed at some point
-    if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
-	debugTrace(DEBUG_gc, "scavenge_mark_stack: starting linear scan");
-	mark_stack_overflowed = rtsFalse;
-	oldgen_scan_bd = oldest_gen->steps[0].old_blocks;
-	oldgen_scan = oldgen_scan_bd->start;
-    }
-
-    if (oldgen_scan_bd) {
-	// push a new thing on the mark stack
-    loop:
-	// find a closure that is marked but not scavenged, and start
-	// from there.
-	while (oldgen_scan < oldgen_scan_bd->free 
-	       && !is_marked(oldgen_scan,oldgen_scan_bd)) {
-	    oldgen_scan++;
-	}
-
-	if (oldgen_scan < oldgen_scan_bd->free) {
-
-	    // already scavenged?
-	    if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
-		oldgen_scan += sizeofW(StgHeader) + MIN_PAYLOAD_SIZE;
-		goto loop;
+            if (gct->evac_gen_no) {
+                recordMutableGen_GC((StgClosure *)q, gct->evac_gen_no);
 	    }
-	    push_mark_stack(oldgen_scan);
-	    // ToDo: bump the linear scan by the actual size of the object
-	    oldgen_scan += sizeofW(StgHeader) + MIN_PAYLOAD_SIZE;
-	    goto linear_scan;
-	}
-
-	oldgen_scan_bd = oldgen_scan_bd->link;
-	if (oldgen_scan_bd != NULL) {
-	    oldgen_scan = oldgen_scan_bd->start;
-	    goto loop;
 	}
-    }
+    } // while (p = pop_mark_stack())
 }
 
 /* -----------------------------------------------------------------------------
@@ -663,9 +1060,11 @@ static rtsBool
 scavenge_one(StgPtr p)
 {
     const StgInfoTable *info;
-    step *saved_evac_step = gct->evac_step;
     rtsBool no_luck;
+    rtsBool saved_eager_promotion;
     
+    saved_eager_promotion = gct->eager_promotion;
+
     ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
     info = get_itbl((StgClosure *)p);
     
@@ -674,8 +1073,6 @@ scavenge_one(StgPtr p)
     case MVAR_CLEAN:
     case MVAR_DIRTY:
     { 
-	rtsBool saved_eager_promotion = gct->eager_promotion;
-
 	StgMVar *mvar = ((StgMVar *)p);
 	gct->eager_promotion = rtsFalse;
 	evacuate((StgClosure **)&mvar->head);
@@ -720,6 +1117,7 @@ scavenge_one(StgPtr p)
     case CONSTR_0_2:
     case CONSTR_2_0:
     case WEAK:
+    case PRIM:
     case IND_PERM:
     {
 	StgPtr q, end;
@@ -734,7 +1132,6 @@ scavenge_one(StgPtr p)
     case MUT_VAR_CLEAN:
     case MUT_VAR_DIRTY: {
 	StgPtr q = p;
-	rtsBool saved_eager_promotion = gct->eager_promotion;
 
 	gct->eager_promotion = rtsFalse;
 	evacuate(&((StgMutVar *)p)->var);
@@ -748,12 +1145,25 @@ scavenge_one(StgPtr p)
 	break;
     }
 
-    case CAF_BLACKHOLE:
-    case SE_CAF_BLACKHOLE:
-    case SE_BLACKHOLE:
-    case BLACKHOLE:
-	break;
-	
+    case BLOCKING_QUEUE:
+    {
+        StgBlockingQueue *bq = (StgBlockingQueue *)p;
+        
+        gct->eager_promotion = rtsFalse;
+        evacuate(&bq->bh);
+        evacuate((StgClosure**)&bq->owner);
+        evacuate((StgClosure**)&bq->queue);
+        evacuate((StgClosure**)&bq->link);
+        gct->eager_promotion = saved_eager_promotion;
+        
+        if (gct->failed_to_evac) {
+            bq->header.info = &stg_BLOCKING_QUEUE_DIRTY_info;
+        } else {
+            bq->header.info = &stg_BLOCKING_QUEUE_CLEAN_info;
+        }
+        break;
+    }
+
     case THUNK_SELECTOR:
     { 
 	StgSelector *s = (StgSelector *)p;
@@ -786,28 +1196,21 @@ scavenge_one(StgPtr p)
     case MUT_ARR_PTRS_CLEAN:
     case MUT_ARR_PTRS_DIRTY:
     {
-	StgPtr next, q;
-	rtsBool saved_eager;
-
 	// We don't eagerly promote objects pointed to by a mutable
 	// array, but if we find the array only points to objects in
 	// the same or an older generation, we mark it "clean" and
 	// avoid traversing it during minor GCs.
-	saved_eager = gct->eager_promotion;
 	gct->eager_promotion = rtsFalse;
-	q = p;
-	next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
-	for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-	    evacuate((StgClosure **)p);
-	}
-	gct->eager_promotion = saved_eager;
+
+        scavenge_mut_arr_ptrs((StgMutArrPtrs *)p);
 
 	if (gct->failed_to_evac) {
-	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
+	    ((StgClosure *)p)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
 	} else {
-	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
+	    ((StgClosure *)p)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
 	}
 
+	gct->eager_promotion = saved_eager_promotion;
 	gct->failed_to_evac = rtsTrue;
 	break;
     }
@@ -816,19 +1219,14 @@ scavenge_one(StgPtr p)
     case MUT_ARR_PTRS_FROZEN0:
     {
 	// follow everything 
-	StgPtr next, q=p;
-      
-	next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
-	for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-	    evacuate((StgClosure **)p);
-	}
-
+        scavenge_mut_arr_ptrs((StgMutArrPtrs *)p);
+        
 	// If we're going to put this object on the mutable list, then
 	// set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
 	if (gct->failed_to_evac) {
-	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
+	    ((StgClosure *)p)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
 	} else {
-	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
+	    ((StgClosure *)p)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
 	}
 	break;
     }
@@ -836,102 +1234,63 @@ scavenge_one(StgPtr p)
     case TSO:
     {
 	scavengeTSO((StgTSO*)p);
-	gct->failed_to_evac = rtsTrue; // always on the mutable list
 	break;
     }
   
-    case TVAR_WATCH_QUEUE:
-      {
-	StgTVarWatchQueue *wq = ((StgTVarWatchQueue *) p);
-	gct->evac_step = 0;
-        evacuate((StgClosure **)&wq->closure);
-        evacuate((StgClosure **)&wq->next_queue_entry);
-        evacuate((StgClosure **)&wq->prev_queue_entry);
-	gct->evac_step = saved_evac_step;
-	gct->failed_to_evac = rtsTrue; // mutable
-	break;
-      }
+    case STACK:
+    {
+        StgStack *stack = (StgStack*)p;
 
-    case TVAR:
-      {
-	StgTVar *tvar = ((StgTVar *) p);
-	gct->evac_step = 0;
-	evacuate((StgClosure **)&tvar->current_value);
-        evacuate((StgClosure **)&tvar->first_watch_queue_entry);
-	gct->evac_step = saved_evac_step;
+        gct->eager_promotion = rtsFalse;
+
+        scavenge_stack(stack->sp, stack->stack + stack->stack_size);
+        stack->dirty = gct->failed_to_evac;
+
+        gct->eager_promotion = saved_eager_promotion;
+        break;
+    }
+
+    case MUT_PRIM:
+    {
+	StgPtr end;
+        
+	gct->eager_promotion = rtsFalse;
+        
+	end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
+	for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
+	    evacuate((StgClosure **)p);
+	}
+
+	gct->eager_promotion = saved_eager_promotion;
 	gct->failed_to_evac = rtsTrue; // mutable
 	break;
-      }
 
-    case TREC_HEADER:
-      {
-        StgTRecHeader *trec = ((StgTRecHeader *) p);
-        gct->evac_step = 0;
-	evacuate((StgClosure **)&trec->enclosing_trec);
-	evacuate((StgClosure **)&trec->current_chunk);
-        evacuate((StgClosure **)&trec->invariants_to_check);
-	gct->evac_step = saved_evac_step;
-	gct->failed_to_evac = rtsTrue; // mutable
-        break;
-      }
+    }
 
     case TREC_CHUNK:
       {
 	StgWord i;
 	StgTRecChunk *tc = ((StgTRecChunk *) p);
 	TRecEntry *e = &(tc -> entries[0]);
-	gct->evac_step = 0;
+	gct->eager_promotion = rtsFalse;
 	evacuate((StgClosure **)&tc->prev_chunk);
 	for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
 	  evacuate((StgClosure **)&e->tvar);
 	  evacuate((StgClosure **)&e->expected_value);
 	  evacuate((StgClosure **)&e->new_value);
 	}
-	gct->evac_step = saved_evac_step;
+	gct->eager_promotion = saved_eager_promotion;
 	gct->failed_to_evac = rtsTrue; // mutable
 	break;
       }
 
-    case ATOMIC_INVARIANT:
-    {
-      StgAtomicInvariant *invariant = ((StgAtomicInvariant *) p);
-      gct->evac_step = 0;
-      evacuate(&invariant->code);
-      evacuate((StgClosure **)&invariant->last_execution);
-      gct->evac_step = saved_evac_step;
-      gct->failed_to_evac = rtsTrue; // mutable
-      break;
-    }
-
-    case INVARIANT_CHECK_QUEUE:
-    {
-      StgInvariantCheckQueue *queue = ((StgInvariantCheckQueue *) p);
-      gct->evac_step = 0;
-      evacuate((StgClosure **)&queue->invariant);
-      evacuate((StgClosure **)&queue->my_execution);
-      evacuate((StgClosure **)&queue->next_queue_entry);
-      gct->evac_step = saved_evac_step;
-      gct->failed_to_evac = rtsTrue; // mutable
-      break;
-    }
-
-    case IND_OLDGEN:
-    case IND_OLDGEN_PERM:
+    case IND:
+        // IND can happen, for example, when the interpreter allocates
+        // a gigantic AP closure (more than one block), which ends up
+        // on the large-object list and then gets updated.  See #3424.
+    case BLACKHOLE:
     case IND_STATIC:
-    {
-	/* 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;
-	}
 	evacuate(&((StgInd *)p)->indirectee);
-    }
 
 #if 0 && defined(DEBUG)
       if (RtsFlags.DebugFlags.gc) 
@@ -939,21 +1298,21 @@ scavenge_one(StgPtr p)
        * promoted 
        */
       { 
-	StgPtr start = gen->steps[0].scan;
-	bdescr *start_bd = gen->steps[0].scan_bd;
+	StgPtr start = gen->scan;
+	bdescr *start_bd = gen->scan_bd;
 	nat size = 0;
-	scavenge(&gen->steps[0]);
-	if (start_bd != gen->steps[0].scan_bd) {
+	scavenge(&gen);
+	if (start_bd != gen->scan_bd) {
 	  size += (P_)BLOCK_ROUND_UP(start) - start;
 	  start_bd = start_bd->link;
-	  while (start_bd != gen->steps[0].scan_bd) {
+	  while (start_bd != gen->scan_bd) {
 	    size += BLOCK_SIZE_W;
 	    start_bd = start_bd->link;
 	  }
-	  size += gen->steps[0].scan -
-	    (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
+	  size += gen->scan -
+	    (P_)BLOCK_ROUND_DOWN(gen->scan);
 	} else {
-	  size = gen->steps[0].scan - start;
+	  size = gen->scan - start;
 	}
 	debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
       }
@@ -978,14 +1337,13 @@ scavenge_one(StgPtr p)
    -------------------------------------------------------------------------- */
 
 void
-scavenge_mutable_list(generation *gen)
+scavenge_mutable_list(bdescr *bd, generation *gen)
 {
-    bdescr *bd;
     StgPtr p, q;
+    nat gen_no;
 
-    bd = gen->saved_mut_list;
-
-    gct->evac_step = &gen->steps[0];
+    gen_no = gen->no;
+    gct->evac_gen_no = gen_no;
     for (; bd != NULL; bd = bd->link) {
 	for (q = bd->start; q < bd->free; q++) {
 	    p = (StgPtr)*q;
@@ -994,7 +1352,7 @@ scavenge_mutable_list(generation *gen)
 #ifdef DEBUG	    
 	    switch (get_itbl((StgClosure *)p)->type) {
 	    case MUT_VAR_CLEAN:
-		barf("MUT_VAR_CLEAN on mutable list");
+                // can happen due to concurrent writeMutVars
 	    case MUT_VAR_DIRTY:
 		mutlist_MUTVARS++; break;
 	    case MUT_ARR_PTRS_CLEAN:
@@ -1015,42 +1373,61 @@ scavenge_mutable_list(generation *gen)
 	    // definitely doesn't point into a young generation.
 	    // Clean objects don't need to be scavenged.  Some clean
 	    // objects (MUT_VAR_CLEAN) are not kept on the mutable
-	    // list at all; others, such as MUT_ARR_PTRS_CLEAN and
-	    // TSO, are always on the mutable list.
+	    // list at all; others, such as TSO
+	    // are always on the mutable list.
 	    //
 	    switch (get_itbl((StgClosure *)p)->type) {
 	    case MUT_ARR_PTRS_CLEAN:
-		recordMutableGen_GC((StgClosure *)p,gen);
+                recordMutableGen_GC((StgClosure *)p,gen_no);
 		continue;
-	    case TSO: {
-		StgTSO *tso = (StgTSO *)p;
-		if ((tso->flags & TSO_DIRTY) == 0) {
-		    // A clean TSO: we don't have to traverse its
-		    // stack.  However, we *do* follow the link field:
-		    // we don't want to have to mark a TSO dirty just
-		    // because we put it on a different queue.
-		    if (tso->why_blocked != BlockedOnBlackHole) {
-			evacuate((StgClosure **)&tso->link);
-		    }
-		    recordMutableGen_GC((StgClosure *)p,gen);
-		    continue;
-		}
-	    }
-	    default:
+	    case MUT_ARR_PTRS_DIRTY:
+            {
+                rtsBool saved_eager_promotion;
+                saved_eager_promotion = gct->eager_promotion;
+                gct->eager_promotion = rtsFalse;
+
+                scavenge_mut_arr_ptrs_marked((StgMutArrPtrs *)p);
+
+                if (gct->failed_to_evac) {
+                    ((StgClosure *)p)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
+                } else {
+                    ((StgClosure *)p)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
+                }
+
+                gct->eager_promotion = saved_eager_promotion;
+                gct->failed_to_evac = rtsFalse;
+                recordMutableGen_GC((StgClosure *)p,gen_no);
+		continue;
+            }
+            default:
 		;
 	    }
 
 	    if (scavenge_one(p)) {
 		// didn't manage to promote everything, so put the
 		// object back on the list.
-		recordMutableGen_GC((StgClosure *)p,gen);
+                recordMutableGen_GC((StgClosure *)p,gen_no);
 	    }
 	}
     }
+}
 
-    // free the old mut_list
-    freeChain_sync(gen->saved_mut_list);
-    gen->saved_mut_list = NULL;
+void
+scavenge_capability_mut_lists (Capability *cap)
+{
+    nat g;
+
+    /* Mutable lists from each generation > N
+     * we want to *scavenge* these roots, not evacuate them: they're not
+     * going to move in this GC.
+     * Also do them in reverse generation order, for the usual reason:
+     * namely to reduce the likelihood of spurious old->new pointers.
+     */
+    for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
+        scavenge_mutable_list(cap->saved_mut_lists[g], &generations[g]);
+        freeChain_sync(cap->saved_mut_lists[g]);
+        cap->saved_mut_lists[g] = NULL;
+    }
 }
 
 /* -----------------------------------------------------------------------------
@@ -1071,7 +1448,7 @@ scavenge_static(void)
 
   /* Always evacuate straight to the oldest generation for static
    * objects */
-  gct->evac_step = &oldest_gen->steps[0];
+  gct->evac_gen_no = oldest_gen->no;
 
   /* keep going until we've scavenged all the objects on the linked
      list... */
@@ -1116,7 +1493,7 @@ scavenge_static(void)
 	 */
 	if (gct->failed_to_evac) {
 	  gct->failed_to_evac = rtsFalse;
-	  recordMutableGen_GC((StgClosure *)p,oldest_gen);
+	  recordMutableGen_GC((StgClosure *)p,oldest_gen->no);
 	}
 	break;
       }
@@ -1156,23 +1533,21 @@ scavenge_static(void)
 static void
 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
 {
-    nat i, b;
+    nat i, j, b;
     StgWord bitmap;
     
     b = 0;
-    bitmap = large_bitmap->bitmap[b];
-    for (i = 0; i < size; ) {
-	if ((bitmap & 1) == 0) {
-	    evacuate((StgClosure **)p);
-	}
-	i++;
-	p++;
-	if (i % BITS_IN(W_) == 0) {
-	    b++;
-	    bitmap = large_bitmap->bitmap[b];
-	} else {
+
+    for (i = 0; i < size; b++) {
+        bitmap = large_bitmap->bitmap[b];
+        j = stg_min(size-i, BITS_IN(W_));
+        i += j;
+        for (; j > 0; j--, p++) {
+            if ((bitmap & 1) == 0) {
+                evacuate((StgClosure **)p);
+            }
 	    bitmap = bitmap >> 1;
-	}
+        }            
     }
 }
 
@@ -1232,29 +1607,42 @@ scavenge_stack(StgPtr p, StgPtr stack_end)
 	// before GC, but that seems like overkill.
 	//
 	// Scavenging this update frame as normal would be disastrous;
-	// the updatee would end up pointing to the value.  So we turn
-	// the indirection into an IND_PERM, so that evacuate will
-	// copy the indirection into the old generation instead of
-	// discarding it.
+	// the updatee would end up pointing to the value.  So we
+	// check whether the value after evacuation is a BLACKHOLE,
+	// and if not, we change the update frame to an stg_enter
+	// frame that simply returns the value.  Hence, blackholing is
+        // compulsory (otherwise we would have to check for thunks
+        // too).
+        //
+        // Note [upd-black-hole]
+        // One slight hiccup is that the THUNK_SELECTOR machinery can
+        // overwrite the updatee with an IND.  In parallel GC, this
+        // could even be happening concurrently, so we can't check for
+        // the IND.  Fortunately if we assume that blackholing is
+        // happening (either lazy or eager), then we can be sure that
+        // the updatee is never a THUNK_SELECTOR and we're ok.
+        // NB. this is a new invariant: blackholing is not optional.
     {
-        nat type;
-        type = get_itbl(((StgUpdateFrame *)p)->updatee)->type;
-	if (type == IND) {
-	    ((StgUpdateFrame *)p)->updatee->header.info = 
-		(StgInfoTable *)&stg_IND_PERM_info;
-	} else if (type == IND_OLDGEN) {
-	    ((StgUpdateFrame *)p)->updatee->header.info = 
-		(StgInfoTable *)&stg_IND_OLDGEN_PERM_info;
-        }            
-	evacuate(&((StgUpdateFrame *)p)->updatee);
-	p += sizeofW(StgUpdateFrame);
-	continue;
+        StgUpdateFrame *frame = (StgUpdateFrame *)p;
+        StgClosure *v;
+
+        evacuate(&frame->updatee);
+        v = frame->updatee;
+        if (GET_CLOSURE_TAG(v) != 0 ||
+            (get_itbl(v)->type != BLACKHOLE)) {
+            // blackholing is compulsory, see above.
+            frame->header.info = (const StgInfoTable*)&stg_enter_checkbh_info;
+        }
+        ASSERT(v->header.info != &stg_TSO_info);
+        p += sizeofW(StgUpdateFrame);
+        continue;
     }
 
       // small bitmap (< 32 entries, or 64 on a 64-bit machine) 
     case CATCH_STM_FRAME:
     case CATCH_RETRY_FRAME:
     case ATOMICALLY_FRAME:
+    case UNDERFLOW_FRAME:
     case STOP_FRAME:
     case CATCH_FRAME:
     case RET_SMALL:
@@ -1343,19 +1731,19 @@ scavenge_stack(StgPtr p, StgPtr stack_end)
 /*-----------------------------------------------------------------------------
   scavenge the large object list.
 
-  evac_step set by caller; similar games played with evac_step as with
+  evac_gen set by caller; similar games played with evac_gen as with
   scavenge() - see comment at the top of scavenge().  Most large
-  objects are (repeatedly) mutable, so most of the time evac_step will
+  objects are (repeatedly) mutable, so most of the time evac_gen will
   be zero.
   --------------------------------------------------------------------------- */
 
 static void
-scavenge_large (step_workspace *ws)
+scavenge_large (gen_workspace *ws)
 {
     bdescr *bd;
     StgPtr p;
 
-    gct->evac_step = ws->step;
+    gct->evac_gen_no = ws->gen->no;
 
     bd = ws->todo_large_objects;
     
@@ -1367,33 +1755,27 @@ scavenge_large (step_workspace *ws)
 	// the front when evacuating.
 	ws->todo_large_objects = bd->link;
 	
-	ACQUIRE_SPIN_LOCK(&ws->step->sync_large_objects);
-	dbl_link_onto(bd, &ws->step->scavenged_large_objects);
-	ws->step->n_scavenged_large_blocks += bd->blocks;
-	RELEASE_SPIN_LOCK(&ws->step->sync_large_objects);
+	ACQUIRE_SPIN_LOCK(&ws->gen->sync_large_objects);
+	dbl_link_onto(bd, &ws->gen->scavenged_large_objects);
+	ws->gen->n_scavenged_large_blocks += bd->blocks;
+	RELEASE_SPIN_LOCK(&ws->gen->sync_large_objects);
 	
 	p = bd->start;
 	if (scavenge_one(p)) {
-	    if (ws->step->gen_no > 0) {
-		recordMutableGen_GC((StgClosure *)p, ws->step->gen);
+	    if (ws->gen->no > 0) {
+		recordMutableGen_GC((StgClosure *)p, ws->gen->no);
 	    }
 	}
+
+        // stats
+        gct->scanned += closure_sizeW((StgClosure*)p);
     }
 }
 
 /* ----------------------------------------------------------------------------
-   Scavenge a block
-   ------------------------------------------------------------------------- */
-
-#define PARALLEL_GC
-#include "Scav.c-inc"
-#undef PARALLEL_GC
-#include "Scav.c-inc"
-
-/* ----------------------------------------------------------------------------
    Look for work to do.
 
-   We look for the oldest step that has either a todo block that can
+   We look for the oldest gen that has either a todo block that can
    be scanned, or a block of work on the global queue that we can
    scan.
 
@@ -1412,8 +1794,8 @@ scavenge_large (step_workspace *ws)
 static rtsBool
 scavenge_find_work (void)
 {
-    int s;
-    step_workspace *ws;
+    int g;
+    gen_workspace *ws;
     rtsBool did_something, did_anything;
     bdescr *bd;
 
@@ -1423,49 +1805,20 @@ scavenge_find_work (void)
 
 loop:
     did_something = rtsFalse;
-    for (s = total_steps-1; s >= 0; s--) {
-        if (s == 0 && RtsFlags.GcFlags.generations > 1) { 
-            continue; 
-        }
-        ws = &gct->steps[s];
-
-        if (ws->todo_bd != NULL)
-        {
-            ws->todo_bd->free = ws->todo_free;
-        }
-        
-        // If we have a todo block and no scan block, start
-        // scanning the todo block.
-        if (ws->scan_bd == NULL && ws->todo_bd != NULL)
-        {
-            ws->scan_bd = ws->todo_bd;
-        }
+    for (g = RtsFlags.GcFlags.generations-1; g >= 0; g--) {
+        ws = &gct->gens[g];
         
+        gct->scan_bd = NULL;
+
         // If we have a scan block with some work to do,
         // scavenge everything up to the free pointer.
-        if (ws->scan_bd != NULL && ws->scan_bd->u.scan < ws->scan_bd->free)
+        if (ws->todo_bd->u.scan < ws->todo_free)
         {
-            if (n_gc_threads == 1) {
-                scavenge_block1(ws->scan_bd);
-            } else {
-                scavenge_block(ws->scan_bd);
-            }
+            scavenge_block(ws->todo_bd);
             did_something = rtsTrue;
-        }
-        
-        if (ws->scan_bd != NULL && ws->scan_bd != ws->todo_bd)
-        {
-            ASSERT(ws->scan_bd->u.scan == ws->scan_bd->free);
-            // we're not going to evac any more objects into
-            // this block, so push it now.
-            push_scanned_block(ws->scan_bd, ws);
-            ws->scan_bd = NULL;
-            // we might be able to scan the todo block now.
-            did_something = rtsTrue; 
+            break;
         }
 
-        if (did_something) break;
-
         // If we have any large objects to scavenge, do them now.
         if (ws->todo_large_objects) {
             scavenge_large(ws);
@@ -1473,17 +1826,8 @@ loop:
             break;
         }
 
-        if ((bd = grab_todo_block(ws)) != NULL) {
-            // no need to assign this to ws->scan_bd, we're going
-            // to scavenge the whole thing and then push it on
-            // our scavd list.  This saves pushing out the
-            // scan_bd block, which might be partial.
-            if (n_gc_threads == 1) {
-                scavenge_block1(bd);
-            } else {
-                scavenge_block(bd);
-            }
-            push_scanned_block(bd, ws);
+        if ((bd = grab_local_todo_block(ws)) != NULL) {
+            scavenge_block(bd);
             did_something = rtsTrue;
             break;
         }
@@ -1493,6 +1837,25 @@ loop:
         did_anything = rtsTrue;
         goto loop;
     }
+
+#if defined(THREADED_RTS)
+    if (work_stealing) {
+        // look for work to steal
+        for (g = RtsFlags.GcFlags.generations-1; g >= 0; g--) {
+            if ((bd = steal_todo_block(g)) != NULL) {
+                scavenge_block(bd);
+                did_something = rtsTrue;
+                break;
+            }
+        }
+
+        if (did_something) {
+            did_anything = rtsTrue;
+            goto loop;
+        }
+    }
+#endif
+
     // only return when there is no more work to do
 
     return did_anything;
@@ -1517,8 +1880,7 @@ loop:
     }
     
     // scavenge objects in compacted generation
-    if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
-	(mark_stack_bdescr != NULL && !mark_stack_empty())) {
+    if (mark_stack_bd != NULL && !mark_stack_empty()) {
 	scavenge_mark_stack();
 	work_to_do = rtsTrue;
     }
@@ -1533,35 +1895,3 @@ loop:
     if (work_to_do) goto loop;
 }
 
-rtsBool
-any_work (void)
-{
-    int s;
-    step_workspace *ws;
-
-    gct->any_work++;
-
-    write_barrier();
-
-    // scavenge objects in compacted generation
-    if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
-	(mark_stack_bdescr != NULL && !mark_stack_empty())) {
-	return rtsTrue;
-    }
-    
-    // Check for global work in any step.  We don't need to check for
-    // local work, because we have already exited scavenge_loop(),
-    // which means there is no local work for this thread.
-    for (s = total_steps-1; s >= 0; s--) {
-        if (s == 0 && RtsFlags.GcFlags.generations > 1) { 
-            continue; 
-        }
-        ws = &gct->steps[s];
-        if (ws->todo_large_objects) return rtsTrue;
-        if (ws->step->todos) return rtsTrue;
-    }
-
-    gct->no_work++;
-
-    return rtsFalse;
-}