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, 21 deletions

diff --git a/rts/sm/Evac.c b/rts/sm/Evac.c
index 76026b0bac..21017a63a0 100644
--- a/rts/sm/Evac.c
+++ b/rts/sm/Evac.c
@@ -626,7 +626,8 @@ loop:
       return;
 
   case WEAK:
-  case STABLE_NAME:
+  case PRIM:
+  case MUT_PRIM:
       copy_tag(p,info,q,sizeW_fromITBL(INFO_PTR_TO_STRUCT(info)),gen,tag);
       return;
 
@@ -721,30 +722,10 @@ loop:
       }
     }
 
-  case TREC_HEADER: 
-      copy(p,info,q,sizeofW(StgTRecHeader),gen);
-      return;
-
-  case TVAR_WATCH_QUEUE:
-      copy(p,info,q,sizeofW(StgTVarWatchQueue),gen);
-      return;
-
-  case TVAR:
-      copy(p,info,q,sizeofW(StgTVar),gen);
-      return;
-    
   case TREC_CHUNK:
       copy(p,info,q,sizeofW(StgTRecChunk),gen);
       return;
 
-  case ATOMIC_INVARIANT:
-      copy(p,info,q,sizeofW(StgAtomicInvariant),gen);
-      return;
-
-  case INVARIANT_CHECK_QUEUE:
-      copy(p,info,q,sizeofW(StgInvariantCheckQueue),gen);
-      return;
-
   default:
     barf("evacuate: strange closure type %d", (int)(INFO_PTR_TO_STRUCT(info)->type));
   }