Fix a very rare crash in GHCi
[ghc-hetmet.git] / rts / sm / Scav.c
index 1b671a0..d01442b 100644 (file)
@@ -46,17 +46,6 @@ static void scavenge_large_bitmap (StgPtr p,
    Scavenge a TSO.
    -------------------------------------------------------------------------- */
 
-STATIC_INLINE void
-scavenge_TSO_link (StgTSO *tso)
-{
-    // 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);
-    }
-}
-
 static void
 scavengeTSO (StgTSO *tso)
 {
@@ -80,14 +69,9 @@ scavengeTSO (StgTSO *tso)
     saved_eager = gct->eager_promotion;
     gct->eager_promotion = rtsFalse;
 
-    if (   tso->why_blocked == BlockedOnMVar
-       || tso->why_blocked == BlockedOnBlackHole
-       || tso->why_blocked == BlockedOnMsgWakeup
-       || tso->why_blocked == BlockedOnMsgThrowTo
-       ) {
-       evacuate(&tso->block_info.closure);
-    }
+
     evacuate((StgClosure **)&tso->blocked_exceptions);
+    evacuate((StgClosure **)&tso->bq);
     
     // scavange current transaction record
     evacuate((StgClosure **)&tso->trec);
@@ -95,17 +79,30 @@ scavengeTSO (StgTSO *tso)
     // scavenge this thread's stack 
     scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
 
-    if (gct->failed_to_evac) {
-        tso->dirty = 1;
-        scavenge_TSO_link(tso);
+    tso->dirty = gct->failed_to_evac;
+
+    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
+
+    if (tso->dirty == 0 && gct->failed_to_evac) {
+        tso->flags |= TSO_LINK_DIRTY;
     } else {
-        tso->dirty = 0;
-        scavenge_TSO_link(tso);
-        if (gct->failed_to_evac) {
-            tso->flags |= TSO_LINK_DIRTY;
-        } else {
-            tso->flags &= ~TSO_LINK_DIRTY;
-        }
+        tso->flags &= ~TSO_LINK_DIRTY;
     }
 
     gct->eager_promotion = saved_eager;
@@ -332,7 +329,7 @@ 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)
@@ -553,23 +550,7 @@ scavenge_block (bdescr *bd)
     }
 
     case IND_PERM:
-      if (bd->gen_no != 0) {
-#ifdef PROFILING
-        // @LDV profiling
-        // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an 
-        // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
-        LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
-#endif        
-        // 
-        // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
-        //
-       SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
-
-        // We pretend that p has just been created.
-        LDV_RECORD_CREATE((StgClosure *)p);
-      }
-       // fall through 
-    case IND_OLDGEN_PERM:
+    case BLACKHOLE:
        evacuate(&((StgInd *)p)->indirectee);
        p += sizeofW(StgInd);
        break;
@@ -588,10 +569,25 @@ scavenge_block (bdescr *bd)
        p += sizeofW(StgMutVar);
        break;
 
-    case CAF_BLACKHOLE:
-    case BLACKHOLE:
-       p += BLACKHOLE_sizeW();
-       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;
+    }
 
     case THUNK_SELECTOR:
     { 
@@ -882,8 +878,8 @@ scavenge_mark_stack(void)
            // no "old" generation.
            break;
 
-       case IND_OLDGEN:
-       case IND_OLDGEN_PERM:
+       case IND:
+        case BLACKHOLE:
            evacuate(&((StgInd *)p)->indirectee);
            break;
 
@@ -901,8 +897,25 @@ scavenge_mark_stack(void)
            break;
        }
 
-       case CAF_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;
 
@@ -1122,10 +1135,25 @@ scavenge_one(StgPtr p)
        break;
     }
 
-    case CAF_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;
@@ -1237,8 +1265,7 @@ scavenge_one(StgPtr p)
         // 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 IND_OLDGEN:
-    case IND_OLDGEN_PERM:
+    case BLACKHOLE:
     case IND_STATIC:
        evacuate(&((StgInd *)p)->indirectee);
 
@@ -1300,7 +1327,7 @@ scavenge_mutable_list(bdescr *bd, 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:
@@ -1356,7 +1383,14 @@ scavenge_mutable_list(bdescr *bd, generation *gen)
                     // this assertion would be invalid:
                     // ASSERT(tso->flags & TSO_LINK_DIRTY);
 
-                    scavenge_TSO_link(tso);
+                    evacuate((StgClosure **)&tso->_link);
+                    if (   tso->why_blocked == BlockedOnMVar
+                        || tso->why_blocked == BlockedOnBlackHole
+                        || tso->why_blocked == BlockedOnMsgThrowTo
+                        || tso->why_blocked == NotBlocked
+                        ) {
+                        evacuate((StgClosure **)&tso->block_info.prev);
+                    }
                     if (gct->failed_to_evac) {
                         recordMutableGen_GC((StgClosure *)p,gen->no);
                         gct->failed_to_evac = rtsFalse;
@@ -1500,23 +1534,21 @@ 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;
-       }
+        }            
     }
 }
 
@@ -1576,10 +1608,12 @@ 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
@@ -1590,22 +1624,17 @@ scavenge_stack(StgPtr p, StgPtr stack_end)
         // the updatee is never a THUNK_SELECTOR and we're ok.
         // NB. this is a new invariant: blackholing is not optional.
     {
-        nat type;
-        const StgInfoTable *i;
-        StgClosure *updatee;
-
-        updatee = ((StgUpdateFrame *)p)->updatee;
-        i = updatee->header.info;
-        if (!IS_FORWARDING_PTR(i)) {
-            type = get_itbl(updatee)->type;
-            if (type == IND) {
-                updatee->header.info = &stg_IND_PERM_info;
-            } else if (type == IND_OLDGEN) {
-                updatee->header.info = &stg_IND_OLDGEN_PERM_info;
-            }            
+        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;
         }
-        evacuate(&((StgUpdateFrame *)p)->updatee);
-        ASSERT(GET_CLOSURE_TAG(((StgUpdateFrame *)p)->updatee) == 0);
+        ASSERT(v->header.info != &stg_TSO_info);
         p += sizeofW(StgUpdateFrame);
         continue;
     }