1 /* -----------------------------------------------------------------------------
2 * $Id: Weak.c,v 1.33 2004/09/03 15:28:59 simonmar Exp $
4 * (c) The GHC Team, 1998-1999
6 * Weak pointers / finalizers
8 * ---------------------------------------------------------------------------*/
10 #include "PosixSource.h"
11 #define COMPILING_RTS_MAIN
22 StgWeak *weak_ptr_list;
25 * finalizeWeakPointersNow() is called just before the system is shut
26 * down. It runs the finalizer for each weak pointer still in the
29 * Careful here - rts_evalIO might cause a garbage collection, which
30 * might change weak_ptr_list. Must re-load weak_ptr_list each time
35 finalizeWeakPointersNow(void)
40 while ((w = weak_ptr_list)) {
41 weak_ptr_list = w->link;
42 if (w->header.info != &stg_DEAD_WEAK_info) {
43 SET_HDR(w, &stg_DEAD_WEAK_info, w->header.prof.ccs);
44 IF_DEBUG(weak,debugBelch("Finalising weak pointer at %p -> %p\n", w, w->key));
45 if (w->finalizer != &stg_NO_FINALIZER_closure) {
46 rts_evalLazyIO(w->finalizer,NULL);
56 * scheduleFinalizers() is called on the list of weak pointers found
57 * to be dead after a garbage collection. It overwrites each object
58 * with DEAD_WEAK, and creates a new thread to run the pending finalizers.
60 * This function is called just after GC. The weak pointers on the
61 * argument list are those whose keys were found to be not reachable,
62 * however the value and finalizer fields have by now been marked live.
63 * The weak pointer object itself may not be alive - i.e. we may be
64 * looking at either an object in from-space or one in to-space. It
65 * doesn't really matter either way.
67 * Pre-condition: sched_mutex _not_ held.
71 scheduleFinalizers(StgWeak *list)
78 // count number of finalizers, and kill all the weak pointers first...
80 for (w = list; w; w = w->link) {
82 // Better not be a DEAD_WEAK at this stage; the garbage
83 // collector removes DEAD_WEAKs from the weak pointer list.
84 ASSERT(w->header.info != &stg_DEAD_WEAK_info);
86 if (w->finalizer != &stg_NO_FINALIZER_closure) {
91 // A weak pointer is inherently used, so we do not need to call
94 // Furthermore, when PROFILING is turned on, dead weak
95 // pointers are exactly as large as weak pointers, so there is
96 // no need to fill the slop, either. See stg_DEAD_WEAK_info
97 // in StgMiscClosures.hc.
99 SET_HDR(w, &stg_DEAD_WEAK_info, w->header.prof.ccs);
102 // No finalizers to run?
105 IF_DEBUG(weak,debugBelch("weak: batching %d finalizers\n", n));
107 arr = (StgMutArrPtrs *)allocate(sizeofW(StgMutArrPtrs) + n);
108 TICK_ALLOC_PRIM(sizeofW(StgMutArrPtrs), n, 0);
109 SET_HDR(arr, &stg_MUT_ARR_PTRS_FROZEN_info, CCS_SYSTEM);
110 arr->mut_link = NULL;
114 for (w = list; w; w = w->link) {
115 if (w->finalizer != &stg_NO_FINALIZER_closure) {
116 arr->payload[n] = w->finalizer;
121 t = createIOThread(RtsFlags.GcFlags.initialStkSize,
124 (StgClosure *)runFinalizerBatch_closure,