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
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
|
// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include "runtime.h"
#include "arch.h"
#include "malloc.h"
enum { debug = 0 };
typedef struct Fin Fin;
struct Fin
{
void (*fn)(void*);
const struct __go_func_type *ft;
};
// Finalizer hash table. Direct hash, linear scan, at most 3/4 full.
// Table size is power of 3 so that hash can be key % max.
// Key[i] == (void*)-1 denotes free but formerly occupied entry
// (doesn't stop the linear scan).
// Key and val are separate tables because the garbage collector
// must be instructed to ignore the pointers in key but follow the
// pointers in val.
typedef struct Fintab Fintab;
struct Fintab
{
Lock;
void **fkey;
Fin *val;
int32 nkey; // number of non-nil entries in key
int32 ndead; // number of dead (-1) entries in key
int32 max; // size of key, val allocations
};
#define TABSZ 17
#define TAB(p) (&fintab[((uintptr)(p)>>3)%TABSZ])
static struct {
Fintab;
uint8 pad[0 /* CacheLineSize - sizeof(Fintab) */];
} fintab[TABSZ];
void
runtime_initfintab()
{
int32 i;
for(i=0; i<TABSZ; i++)
runtime_initlock(&fintab[i]);
}
static void
addfintab(Fintab *t, void *k, void (*fn)(void*), const struct __go_func_type *ft)
{
int32 i, j;
i = (uintptr)k % (uintptr)t->max;
for(j=0; j<t->max; j++) {
if(t->fkey[i] == nil) {
t->nkey++;
goto ret;
}
if(t->fkey[i] == (void*)-1) {
t->ndead--;
goto ret;
}
if(++i == t->max)
i = 0;
}
// cannot happen - table is known to be non-full
runtime_throw("finalizer table inconsistent");
ret:
t->fkey[i] = k;
t->val[i].fn = fn;
t->val[i].ft = ft;
}
static bool
lookfintab(Fintab *t, void *k, bool del, Fin *f)
{
int32 i, j;
if(t->max == 0)
return false;
i = (uintptr)k % (uintptr)t->max;
for(j=0; j<t->max; j++) {
if(t->fkey[i] == nil)
return false;
if(t->fkey[i] == k) {
if(f)
*f = t->val[i];
if(del) {
t->fkey[i] = (void*)-1;
t->val[i].fn = nil;
t->val[i].ft = nil;
t->ndead++;
}
return true;
}
if(++i == t->max)
i = 0;
}
// cannot happen - table is known to be non-full
runtime_throw("finalizer table inconsistent");
return false;
}
static void
resizefintab(Fintab *tab)
{
Fintab newtab;
void *k;
int32 i;
runtime_memclr((byte*)&newtab, sizeof newtab);
newtab.max = tab->max;
if(newtab.max == 0)
newtab.max = 3*3*3;
else if(tab->ndead < tab->nkey/2) {
// grow table if not many dead values.
// otherwise just rehash into table of same size.
newtab.max *= 3;
}
newtab.fkey = runtime_mallocgc(newtab.max*sizeof newtab.fkey[0], FlagNoPointers, 0, 1);
newtab.val = runtime_mallocgc(newtab.max*sizeof newtab.val[0], 0, 0, 1);
for(i=0; i<tab->max; i++) {
k = tab->fkey[i];
if(k != nil && k != (void*)-1)
addfintab(&newtab, k, tab->val[i].fn, tab->val[i].ft);
}
runtime_free(tab->fkey);
runtime_free(tab->val);
tab->fkey = newtab.fkey;
tab->val = newtab.val;
tab->nkey = newtab.nkey;
tab->ndead = newtab.ndead;
tab->max = newtab.max;
}
bool
runtime_addfinalizer(void *p, void (*f)(void*), const struct __go_func_type *ft)
{
Fintab *tab;
byte *base;
bool ret = false;
if(debug) {
if(!runtime_mlookup(p, &base, nil, nil) || p != base)
runtime_throw("addfinalizer on invalid pointer");
}
if(!__sync_bool_compare_and_swap(&m->holds_finlock, 0, 1))
runtime_throw("finalizer deadlock");
tab = TAB(p);
runtime_lock(tab);
if(f == nil) {
if(lookfintab(tab, p, true, nil))
runtime_setblockspecial(p, false);
ret = true;
goto unlock;
}
if(lookfintab(tab, p, false, nil)) {
ret = false;
goto unlock;
}
if(tab->nkey >= tab->max/2+tab->max/4) {
// keep table at most 3/4 full:
// allocate new table and rehash.
resizefintab(tab);
}
addfintab(tab, p, f, ft);
runtime_setblockspecial(p, true);
ret = true;
unlock:
runtime_unlock(tab);
__sync_bool_compare_and_swap(&m->holds_finlock, 1, 0);
if(__sync_bool_compare_and_swap(&m->gcing_for_finlock, 1, 0)) {
__go_run_goroutine_gc(200);
}
return ret;
}
// get finalizer; if del, delete finalizer.
// caller is responsible for updating RefHasFinalizer (special) bit.
bool
runtime_getfinalizer(void *p, bool del, void (**fn)(void*), const struct __go_func_type **ft)
{
Fintab *tab;
bool res;
Fin f;
if(!__sync_bool_compare_and_swap(&m->holds_finlock, 0, 1))
runtime_throw("finalizer deadlock");
tab = TAB(p);
runtime_lock(tab);
res = lookfintab(tab, p, del, &f);
runtime_unlock(tab);
__sync_bool_compare_and_swap(&m->holds_finlock, 1, 0);
if(__sync_bool_compare_and_swap(&m->gcing_for_finlock, 1, 0)) {
__go_run_goroutine_gc(201);
}
if(res==false)
return false;
*fn = f.fn;
*ft = f.ft;
return true;
}
void
runtime_walkfintab(void (*fn)(void*), void (*scan)(byte *, int64))
{
void **key;
void **ekey;
int32 i;
if(!__sync_bool_compare_and_swap(&m->holds_finlock, 0, 1))
runtime_throw("finalizer deadlock");
for(i=0; i<TABSZ; i++) {
runtime_lock(&fintab[i]);
key = fintab[i].fkey;
ekey = key + fintab[i].max;
for(; key < ekey; key++)
if(*key != nil && *key != ((void*)-1))
fn(*key);
scan((byte*)&fintab[i].fkey, sizeof(void*));
scan((byte*)&fintab[i].val, sizeof(void*));
runtime_unlock(&fintab[i]);
}
__sync_bool_compare_and_swap(&m->holds_finlock, 1, 0);
if(__sync_bool_compare_and_swap(&m->gcing_for_finlock, 1, 0)) {
runtime_throw("walkfintab not called from gc");
}
}
|
