1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
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
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
|
/*
* Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
* Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
*
* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
*
* Permission is hereby granted to use or copy this program
* for any purpose, provided the above notices are retained on all copies.
* Permission to modify the code and to distribute modified code is granted,
* provided the above notices are retained, and a notice that the code was
* modified is included with the above copyright notice.
*/
/* Boehm, May 19, 1994 1:56 pm PDT */
# include "gc_priv.h"
/*
* We maintain several hash tables of hblks that have had false hits.
* Each contains one bit per hash bucket; If any page in the bucket
* has had a false hit, we assume that all of them have.
* See the definition of page_hash_table in gc_private.h.
* False hits from the stack(s) are much more dangerous than false hits
* from elsewhere, since the former can pin a large object that spans the
* block, eventhough it does not start on the dangerous block.
*/
/*
* Externally callable routines are:
* GC_add_to_black_list_normal
* GC_add_to_black_list_stack
* GC_promote_black_lists
* GC_is_black_listed
*
* All require that the allocator lock is held.
*/
/* Pointers to individual tables. We replace one table by another by */
/* switching these pointers. */
word * GC_old_normal_bl;
/* Nonstack false references seen at last full */
/* collection. */
word * GC_incomplete_normal_bl;
/* Nonstack false references seen since last */
/* full collection. */
word * GC_old_stack_bl;
word * GC_incomplete_stack_bl;
void GC_clear_bl();
void GC_bl_init()
{
# ifndef ALL_INTERIOR_POINTERS
GC_old_normal_bl = (word *)
GC_scratch_alloc((word)(sizeof (page_hash_table)));
GC_incomplete_normal_bl = (word *)GC_scratch_alloc
((word)(sizeof(page_hash_table)));
if (GC_old_normal_bl == 0 || GC_incomplete_normal_bl == 0) {
GC_err_printf0("Insufficient memory for black list\n");
EXIT();
}
GC_clear_bl(GC_old_normal_bl);
GC_clear_bl(GC_incomplete_normal_bl);
# endif
GC_old_stack_bl = (word *)GC_scratch_alloc((word)(sizeof(page_hash_table)));
GC_incomplete_stack_bl = (word *)GC_scratch_alloc
((word)(sizeof(page_hash_table)));
if (GC_old_stack_bl == 0 || GC_incomplete_stack_bl == 0) {
GC_err_printf0("Insufficient memory for black list\n");
EXIT();
}
GC_clear_bl(GC_old_stack_bl);
GC_clear_bl(GC_incomplete_stack_bl);
}
void GC_clear_bl(doomed)
word *doomed;
{
BZERO(doomed, sizeof(page_hash_table));
}
/* Signal the completion of a collection. Turn the incomplete black */
/* lists into new black lists, etc. */
void GC_promote_black_lists()
{
word * very_old_normal_bl = GC_old_normal_bl;
word * very_old_stack_bl = GC_old_stack_bl;
GC_old_normal_bl = GC_incomplete_normal_bl;
GC_old_stack_bl = GC_incomplete_stack_bl;
# ifndef ALL_INTERIOR_POINTERS
GC_clear_bl(very_old_normal_bl);
# endif
GC_clear_bl(very_old_stack_bl);
GC_incomplete_normal_bl = very_old_normal_bl;
GC_incomplete_stack_bl = very_old_stack_bl;
}
# ifndef ALL_INTERIOR_POINTERS
/* P is not a valid pointer reference, but it falls inside */
/* the plausible heap bounds. */
/* Add it to the normal incomplete black list if appropriate. */
void GC_add_to_black_list_normal(p)
word p;
{
if (!(GC_modws_valid_offsets[p & (sizeof(word)-1)])) return;
{
register int index = PHT_HASH(p);
if (HDR(p) == 0 || get_pht_entry_from_index(GC_old_normal_bl, index)) {
# ifdef PRINTBLACKLIST
if (!get_pht_entry_from_index(GC_incomplete_normal_bl, index)) {
GC_printf1("Black listing (normal) 0x%lx\n",
(unsigned long) p);
}
# endif
set_pht_entry_from_index(GC_incomplete_normal_bl, index);
} /* else this is probably just an interior pointer to an allocated */
/* object, and isn't worth black listing. */
}
}
# endif
/* And the same for false pointers from the stack. */
void GC_add_to_black_list_stack(p)
word p;
{
register int index = PHT_HASH(p);
if (HDR(p) == 0 || get_pht_entry_from_index(GC_old_stack_bl, index)) {
# ifdef PRINTBLACKLIST
if (!get_pht_entry_from_index(GC_incomplete_stack_bl, index)) {
GC_printf1("Black listing (stack) 0x%lx\n",
(unsigned long)p);
}
# endif
set_pht_entry_from_index(GC_incomplete_stack_bl, index);
}
}
/*
* Is the block starting at h of size len bytes black listed? If so,
* return the address of the next plausible r such that (r, len) might not
* be black listed. (R may not actually be in the heap. We guarantee only
* that every smaller value of r after h is also black listed.)
* If (h,len) is not black listed, return 0.
* Knows about the structure of the black list hash tables.
*/
struct hblk * GC_is_black_listed(h, len)
struct hblk * h;
word len;
{
register int index = PHT_HASH((word)h);
register word i;
word nblocks = divHBLKSZ(len);
# ifndef ALL_INTERIOR_POINTERS
if (get_pht_entry_from_index(GC_old_normal_bl, index)
|| get_pht_entry_from_index(GC_incomplete_normal_bl, index)) {
return(h+1);
}
# endif
for (i = 0; ; ) {
if (GC_old_stack_bl[divWORDSZ(index)] == 0
&& GC_incomplete_stack_bl[divWORDSZ(index)] == 0) {
/* An easy case */
i += WORDSZ - modWORDSZ(index);
} else {
if (get_pht_entry_from_index(GC_old_stack_bl, index)
|| get_pht_entry_from_index(GC_incomplete_stack_bl, index)) {
return(h+i+1);
}
i++;
}
if (i >= nblocks) break;
index = PHT_HASH((word)(h+i));
}
return(0);
}
|
