[project @ 2004-08-13 13:04:50 by simonmar]

[ghc-hetmet.git] / ghc / rts / Weak.c

diff --git a/ghc/rts/Weak.c b/ghc/rts/Weak.c
index 9cd70eb..ccb9eb2 100644 (file)
--- a/ghc/rts/Weak.c
+++ b/ghc/rts/Weak.c
@@ -1,74 +1,128 @@
 /* -----------------------------------------------------------------------------
- * $Id: Weak.c,v 1.3 1999/01/13 17:25:49 simonm Exp $
+ * $Id: Weak.c,v 1.32 2004/08/13 13:11:13 simonmar Exp $
  *
- * Weak pointers / finalisers
+ * (c) The GHC Team, 1998-1999
+ *
+ * Weak pointers / finalizers
  *
  * ---------------------------------------------------------------------------*/
 
+#include "PosixSource.h"
+#define COMPILING_RTS_MAIN
 #include "Rts.h"
-#include "RtsAPI.h"
+#include "SchedAPI.h"
 #include "RtsFlags.h"
 #include "Weak.h"
 #include "Storage.h"
+#include "Schedule.h"
+#include "Prelude.h"
+#include "RtsAPI.h"
 
 StgWeak *weak_ptr_list;
 
 /*
- * finaliseWeakPointersNow() is called just before the system is shut
- * down.  It runs the finaliser for each weak pointer still in the
+ * finalizeWeakPointersNow() is called just before the system is shut
+ * down.  It runs the finalizer for each weak pointer still in the
  * system.
+ *
+ * Careful here - rts_evalIO might cause a garbage collection, which
+ * might change weak_ptr_list.  Must re-load weak_ptr_list each time
+ * around the loop.
  */
 
 void
-finaliseWeakPointersNow(void)
+finalizeWeakPointersNow(void)
 {
   StgWeak *w;
-
-  for (w = weak_ptr_list; w; w = w->link) {
-    IF_DEBUG(weak,fprintf(stderr,"Finalising weak pointer at %p\n", w));
-    w->header.info = &DEAD_WEAK_info;
-    rts_evalIO(w->finaliser,NULL);
+  
+  rts_lock();
+  while ((w = weak_ptr_list)) {
+    weak_ptr_list = w->link;
+    if (w->header.info != &stg_DEAD_WEAK_info) {
+       SET_HDR(w, &stg_DEAD_WEAK_info, w->header.prof.ccs);
+       IF_DEBUG(weak,fprintf(stderr,"Finalising weak pointer at %p -> %p\n", w, w->key));
+       if (w->finalizer != &stg_NO_FINALIZER_closure) {
+           rts_evalLazyIO(w->finalizer,NULL);
+           rts_unlock();
+           rts_lock();
+       }
+    }
   }
+  rts_unlock();
 } 
 
 /*
- * scheduleFinalisers() is called on the list of weak pointers found
+ * scheduleFinalizers() is called on the list of weak pointers found
  * to be dead after a garbage collection.  It overwrites each object
- * with DEAD_WEAK, and creates a new thread for the finaliser.
+ * with DEAD_WEAK, and creates a new thread to run the pending finalizers.
+ *
+ * This function is called just after GC.  The weak pointers on the
+ * argument list are those whose keys were found to be not reachable,
+ * however the value and finalizer fields have by now been marked live.
+ * The weak pointer object itself may not be alive - i.e. we may be
+ * looking at either an object in from-space or one in to-space.  It
+ * doesn't really matter either way.
+ *
+ * Pre-condition: sched_mutex _not_ held.
  */
 
 void
-scheduleFinalisers(StgWeak *list)
+scheduleFinalizers(StgWeak *list)
 {
-  StgWeak *w;
-  
-  for (w = list; w; w = w->link) {
-    IF_DEBUG(weak,fprintf(stderr,"Finalising weak pointer at %p\n", w));
-#ifdef INTERPRETER
-    createGenThread(RtsFlags.GcFlags.initialStkSize, w->finaliser);
-#else
-    createIOThread(RtsFlags.GcFlags.initialStkSize, w->finaliser);
+    StgWeak *w;
+    StgTSO *t;
+    StgMutArrPtrs *arr;
+    nat n;
+
+    // count number of finalizers, and kill all the weak pointers first...
+    n = 0;
+    for (w = list; w; w = w->link) { 
+
+       // Better not be a DEAD_WEAK at this stage; the garbage
+       // collector removes DEAD_WEAKs from the weak pointer list.
+       ASSERT(w->header.info != &stg_DEAD_WEAK_info);
+
+       if (w->finalizer != &stg_NO_FINALIZER_closure) {
+           n++;
+       }
+
+#ifdef PROFILING
+        // A weak pointer is inherently used, so we do not need to call
+        // LDV_recordDead().
+       //
+        // Furthermore, when PROFILING is turned on, dead weak
+        // pointers are exactly as large as weak pointers, so there is
+        // no need to fill the slop, either.  See stg_DEAD_WEAK_info
+        // in StgMiscClosures.hc.
 #endif
-    w->header.info = &DEAD_WEAK_info;
+       SET_HDR(w, &stg_DEAD_WEAK_info, w->header.prof.ccs);
+    }
+       
+    // No finalizers to run?
+    if (n == 0) return;
 
-    /* need to fill the slop with zeros if we're sanity checking */
-    IF_DEBUG(sanity, {
-      nat dw_size = sizeW_fromITBL(get_itbl(w));
-      memset((P_)w + dw_size, 0, (sizeofW(StgWeak) - dw_size) * sizeof(W_));
-    });
-  }
-}
+    IF_DEBUG(weak,fprintf(stderr,"weak: batching %d finalizers\n", n));
 
-void
-markWeakList(void)
-{
-  StgWeak *w, **last_w;
+    arr = (StgMutArrPtrs *)allocate(sizeofW(StgMutArrPtrs) + n);
+    TICK_ALLOC_PRIM(sizeofW(StgMutArrPtrs), n, 0);
+    SET_HDR(arr, &stg_MUT_ARR_PTRS_FROZEN_info, CCS_SYSTEM);
+    arr->mut_link = NULL;
+    arr->ptrs = n;
 
-  last_w = &weak_ptr_list;
-  for (w = weak_ptr_list; w; w = w->link) {
-    w = (StgWeak *)MarkRoot((StgClosure *)w);
-    *last_w = w;
-    last_w = &(w->link);
-  }
-}
+    n = 0;
+    for (w = list; w; w = w->link) {
+       if (w->finalizer != &stg_NO_FINALIZER_closure) {
+           arr->payload[n] = w->finalizer;
+           n++;
+       }
+    }
 
+    t = createIOThread(RtsFlags.GcFlags.initialStkSize, 
+                      rts_apply(
+                          rts_apply(
+                              (StgClosure *)runFinalizerBatch_closure,
+                              rts_mkInt(n)), 
+                          (StgClosure *)arr)
+       );
+    scheduleThread(t);
+}