FIX #2164: check for ThreadRelocated in isAlive()
[ghc.git] / rts / Weak.c
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"
12 #include "SchedAPI.h"
13 #include "RtsFlags.h"
14 #include "Weak.h"
15 #include "Schedule.h"
16 #include "Prelude.h"
17 #include "RtsAPI.h"
18 #include "Trace.h"
19
20 StgWeak *weak_ptr_list;
21
22 /*
23 * scheduleFinalizers() is called on the list of weak pointers found
24 * to be dead after a garbage collection. It overwrites each object
25 * with DEAD_WEAK, and creates a new thread to run the pending finalizers.
26 *
27 * This function is called just after GC. The weak pointers on the
28 * argument list are those whose keys were found to be not reachable,
29 * however the value and finalizer fields have by now been marked live.
30 * The weak pointer object itself may not be alive - i.e. we may be
31 * looking at either an object in from-space or one in to-space. It
32 * doesn't really matter either way.
33 *
34 * Pre-condition: sched_mutex _not_ held.
35 */
36
37 void
38 scheduleFinalizers(Capability *cap, StgWeak *list)
39 {
40 StgWeak *w;
41 StgTSO *t;
42 StgMutArrPtrs *arr;
43 nat n;
44
45 // count number of finalizers, and kill all the weak pointers first...
46 n = 0;
47 for (w = list; w; w = w->link) {
48
49 // Better not be a DEAD_WEAK at this stage; the garbage
50 // collector removes DEAD_WEAKs from the weak pointer list.
51 ASSERT(w->header.info != &stg_DEAD_WEAK_info);
52
53 if (w->finalizer != &stg_NO_FINALIZER_closure) {
54 n++;
55 }
56
57 #ifdef PROFILING
58 // A weak pointer is inherently used, so we do not need to call
59 // LDV_recordDead().
60 //
61 // Furthermore, when PROFILING is turned on, dead weak
62 // pointers are exactly as large as weak pointers, so there is
63 // no need to fill the slop, either. See stg_DEAD_WEAK_info
64 // in StgMiscClosures.hc.
65 #endif
66 SET_HDR(w, &stg_DEAD_WEAK_info, w->header.prof.ccs);
67 }
68
69 // No finalizers to run?
70 if (n == 0) return;
71
72 debugTrace(DEBUG_weak, "weak: batching %d finalizers", n);
73
74 arr = (StgMutArrPtrs *)allocateLocal(cap, sizeofW(StgMutArrPtrs) + n);
75 TICK_ALLOC_PRIM(sizeofW(StgMutArrPtrs), n, 0);
76 SET_HDR(arr, &stg_MUT_ARR_PTRS_FROZEN_info, CCS_SYSTEM);
77 arr->ptrs = n;
78
79 n = 0;
80 for (w = list; w; w = w->link) {
81 if (w->finalizer != &stg_NO_FINALIZER_closure) {
82 arr->payload[n] = w->finalizer;
83 n++;
84 }
85 }
86
87 t = createIOThread(cap,
88 RtsFlags.GcFlags.initialStkSize,
89 rts_apply(cap,
90 rts_apply(cap,
91 (StgClosure *)runFinalizerBatch_closure,
92 rts_mkInt(cap,n)),
93 (StgClosure *)arr)
94 );
95 scheduleThread(cap,t);
96 }