Use message-passing to implement throwTo in the RTS

This replaces some complicated locking schemes with message-passing
in the implementation of throwTo. The benefits are

 - previously it was impossible to guarantee that a throwTo from
   a thread running on one CPU to a thread running on another CPU
   would be noticed, and we had to rely on the GC to pick up these
   forgotten exceptions. This no longer happens.

 - the locking regime is simpler (though the code is about the same
   size)

 - threads can be unblocked from a blocked_exceptions queue without
   having to traverse the whole queue now.  It's a rare case, but
   replaces an O(n) operation with an O(1).

 - generally we move in the direction of sharing less between
   Capabilities (aka HECs), which will become important with other
   changes we have planned.

Also in this patch I replaced several STM-specific closure types with
a generic MUT_PRIM closure type, which allowed a lot of code in the GC
and other places to go away, hence the line-count reduction.  The
message-passing changes resulted in about a net zero line-count
difference.

1 files changed, 2 insertions, 26 deletions

diff --git a/rts/ProfHeap.c b/rts/ProfHeap.c
index 15337d4585..e90051c5e6 100644
--- a/rts/ProfHeap.c
+++ b/rts/ProfHeap.c
@@ -912,7 +912,8 @@ heapCensusChain( Census *census, bdescr *bd )
             case MVAR_CLEAN:
             case MVAR_DIRTY:
 	    case WEAK:
-	    case STABLE_NAME:
+	    case PRIM:
+	    case MUT_PRIM:
 	    case MUT_VAR_CLEAN:
 	    case MUT_VAR_DIRTY:
 		prim = rtsTrue;
@@ -960,31 +961,6 @@ heapCensusChain( Census *census, bdescr *bd )
 		break;
 #endif
 
-	    case TREC_HEADER: 
-		prim = rtsTrue;
-		size = sizeofW(StgTRecHeader);
-		break;
-
-	    case TVAR_WATCH_QUEUE:
-		prim = rtsTrue;
-		size = sizeofW(StgTVarWatchQueue);
-		break;
-		
-	    case INVARIANT_CHECK_QUEUE:
-		prim = rtsTrue;
-		size = sizeofW(StgInvariantCheckQueue);
-		break;
-		
-	    case ATOMIC_INVARIANT:
-		prim = rtsTrue;
-		size = sizeofW(StgAtomicInvariant);
-		break;
-		
-	    case TVAR:
-		prim = rtsTrue;
-		size = sizeofW(StgTVar);
-		break;
-		
 	    case TREC_CHUNK:
 		prim = rtsTrue;
 		size = sizeofW(StgTRecChunk);