Weak.c 3.69 KB
Newer Older
1
/* -----------------------------------------------------------------------------
2 3
 *
 * (c) The GHC Team, 1998-1999
4
 *
5
 * Weak pointers / finalizers
6 7 8
 *
 * ---------------------------------------------------------------------------*/

9
#include "PosixSource.h"
10
#include "Rts.h"
11
#include "RtsUtils.h"
sof's avatar
sof committed
12
#include "SchedAPI.h"
13 14
#include "RtsFlags.h"
#include "Weak.h"
sof's avatar
sof committed
15
#include "Schedule.h"
16
#include "Prelude.h"
sof's avatar
sof committed
17
#include "RtsAPI.h"
Simon Marlow's avatar
Simon Marlow committed
18
#include "Trace.h"
19

20 21 22
// ForeignPtrs with C finalizers rely on weak pointers inside weak_ptr_list
// to always be in the same order.

23 24
StgWeak *weak_ptr_list;

25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51
void
runCFinalizer(StgVoid *fn, StgVoid *ptr, StgVoid *env, StgWord flag)
{
    if (flag)
	((void (*)(void *, void *))fn)(env, ptr);
    else
	((void (*)(void *))fn)(ptr);
}

void
runAllCFinalizers(StgWeak *list)
{
    StgWeak *w;

    for (w = list; w; w = w->link) {
	StgArrWords *farr;

	farr = (StgArrWords *)UNTAG_CLOSURE(w->cfinalizer);

	if ((StgClosure *)farr != &stg_NO_FINALIZER_closure)
	    runCFinalizer((StgVoid *)farr->payload[0],
	                  (StgVoid *)farr->payload[1],
	                  (StgVoid *)farr->payload[2],
	                  farr->payload[3]);
    }
}

52
/*
53
 * scheduleFinalizers() is called on the list of weak pointers found
54
 * to be dead after a garbage collection.  It overwrites each object
55
 * with DEAD_WEAK, and creates a new thread to run the pending finalizers.
56 57 58 59 60 61 62
 *
 * 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.
sof's avatar
sof committed
63 64
 *
 * Pre-condition: sched_mutex _not_ held.
65 66 67
 */

void
68
scheduleFinalizers(Capability *cap, StgWeak *list)
69
{
70 71 72 73 74
    StgWeak *w;
    StgTSO *t;
    StgMutArrPtrs *arr;
    nat n;

75
    // count number of finalizers, and kill all the weak pointers first...
76 77
    n = 0;
    for (w = list; w; w = w->link) { 
78
	StgArrWords *farr;
79 80 81 82 83 84

	// 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) {
85
	    n++;
86 87
	}

88 89 90 91 92 93 94 95
	farr = (StgArrWords *)UNTAG_CLOSURE(w->cfinalizer);

	if ((StgClosure *)farr != &stg_NO_FINALIZER_closure)
	    runCFinalizer((StgVoid *)farr->payload[0],
	                  (StgVoid *)farr->payload[1],
	                  (StgVoid *)farr->payload[2],
	                  farr->payload[3]);

96 97 98 99 100 101 102 103 104 105
#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);
106
    }
107
	
108
    // No finalizers to run?
109 110
    if (n == 0) return;

Simon Marlow's avatar
Simon Marlow committed
111
    debugTrace(DEBUG_weak, "weak: batching %d finalizers", n);
112

113
    arr = (StgMutArrPtrs *)allocateLocal(cap, sizeofW(StgMutArrPtrs) + n);
114
    TICK_ALLOC_PRIM(sizeofW(StgMutArrPtrs), n, 0);
115
    SET_HDR(arr, &stg_MUT_ARR_PTRS_FROZEN_info, CCS_SYSTEM);
116 117
    arr->ptrs = n;

118 119 120
    n = 0;
    for (w = list; w; w = w->link) {
	if (w->finalizer != &stg_NO_FINALIZER_closure) {
121 122 123 124 125
	    arr->payload[n] = w->finalizer;
	    n++;
	}
    }

126 127 128 129
    t = createIOThread(cap, 
		       RtsFlags.GcFlags.initialStkSize, 
		       rts_apply(cap,
			   rts_apply(cap,
130
			       (StgClosure *)runFinalizerBatch_closure,
131
			       rts_mkInt(cap,n)), 
132 133
			   (StgClosure *)arr)
	);
134
    scheduleThread(cap,t);
135
}