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/* -----------------------------------------------------------------------------
* $Id: Weak.c,v 1.31 2003/10/24 09:00:59 simonmar Exp $
*
* (c) The GHC Team, 1998-1999
*
* Weak pointers / finalizers
*
* ---------------------------------------------------------------------------*/
#include "PosixSource.h"
#define COMPILING_RTS_MAIN
#include "Rts.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;
/*
* 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
finalizeWeakPointersNow(void)
{
StgWeak *w;
rts_lock();
while ((w = weak_ptr_list)) {
weak_ptr_list = w->link;
if (w->header.info != &stg_DEAD_WEAK_info) {
w->header.info = &stg_DEAD_WEAK_info;
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();
}
/*
* 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 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
scheduleFinalizers(StgWeak *list)
{
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
SET_HDR(w, &stg_DEAD_WEAK_info, w->header.prof.ccs);
}
// No finalizers to run?
if (n == 0) return;
IF_DEBUG(weak,fprintf(stderr,"weak: batching %d finalizers\n", n));
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;
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);
}
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