small updates

[ghc-hetmet.git] / ghc / includes / Closures.h

diff --git a/ghc/includes/Closures.h b/ghc/includes/Closures.h
index f9bfeb4..3df208c 100644 (file)
--- a/ghc/includes/Closures.h
+++ b/ghc/includes/Closures.h
@@ -36,9 +36,15 @@ typedef struct {
 
 /* -----------------------------------------------------------------------------
    The SMP header
-
-   In SMP mode, we have an extra word of padding in a thunk's header.
-   (Note: thunks only; other closures do not have this padding word).
+   
+   A thunk has a padding word to take the updated value.  This is so
+   that the update doesn't overwrite the payload, so we can avoid
+   needing to lock the thunk during entry and update.
+   
+   Note: this doesn't apply to THUNK_STATICs, which have no payload.
+
+   Note: we leave this padding word in all ways, rather than just SMP,
+   so that we don't have to recompile all our libraries for SMP.
    -------------------------------------------------------------------------- */
 
 typedef struct {
@@ -62,13 +68,6 @@ typedef struct {
 #endif
 } StgHeader;
 
-/*
- * In SMP mode, a thunk has a padding word to take the updated value.
- * This is so that the update doesn't overwrite the payload, so we can
- * avoid needing to lock the thunk during entry and update.
- *
- * Note: this doesn't apply to THUNK_STATICs, which have no payload.
- */
 typedef struct {
     const struct _StgInfoTable* info;
 #ifdef PROFILING
@@ -77,11 +76,11 @@ typedef struct {
 #ifdef GRAN
     StgGranHeader         gran;
 #endif
-#ifdef SMP
     StgSMPThunkHeader     smp;
-#endif
 } StgThunkHeader;
 
+#define THUNK_EXTRA_HEADER_W (sizeofW(StgThunkHeader)-sizeofW(StgHeader))
+
 /* -----------------------------------------------------------------------------
    Closure Types
 
@@ -339,6 +338,11 @@ typedef struct {
  *   - In StgTRecHeader, it might be worthwhile having separate chunks
  *     of read-only and read-write locations.  This would save a
  *     new_value field in the read-only locations.
+ *
+ *   - In StgAtomicallyFrame, we could combine the waiting bit into
+ *     the header (maybe a different info tbl for a waiting transaction).
+ *     This means we can specialise the code for the atomically frame
+ *     (it immediately switches on frame->waiting anyway).
  */
 
 typedef struct StgTVarWaitQueue_ {
@@ -352,8 +356,8 @@ typedef struct {
   StgHeader                  header;
   StgClosure                *volatile current_value;
   StgTVarWaitQueue          *volatile first_wait_queue_entry;
-#if defined(SMP)
-  struct StgTRecHeader_     *volatile last_update_by;
+#if defined(THREADED_RTS)
+  StgInt                     volatile num_updates;
 #endif
 } StgTVar;
 
@@ -363,12 +367,12 @@ typedef struct {
   StgTVar                   *tvar;
   StgClosure                *expected_value;
   StgClosure                *new_value; 
-#if defined(SMP)
-  struct StgTRecHeader_     *saw_update_by;
+#if defined(THREADED_RTS)
+  StgInt                     num_updates;
 #endif
 } TRecEntry;
 
-#define TREC_CHUNK_NUM_ENTRIES 256
+#define TREC_CHUNK_NUM_ENTRIES 16
 
 typedef struct StgTRecChunk_ {
   StgHeader                  header;
@@ -394,7 +398,6 @@ typedef struct StgTRecHeader_ {
 
 typedef struct {
     StgHeader   header;
-    StgBool     waiting;
     StgClosure *code;
 } StgAtomicallyFrame;