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
|
// SPDX-License-Identifier: GPL-3.0-or-later
#include "rrdengine.h"
struct page_cache_descr *rrdeng_create_pg_cache_descr(struct rrdengine_instance *ctx)
{
struct page_cache_descr *pg_cache_descr;
pg_cache_descr = mallocz(sizeof(*pg_cache_descr));
rrd_stat_atomic_add(&ctx->stats.page_cache_descriptors, 1);
pg_cache_descr->page = NULL;
pg_cache_descr->flags = 0;
pg_cache_descr->prev = pg_cache_descr->next = NULL;
pg_cache_descr->refcnt = 0;
pg_cache_descr->waiters = 0;
fatal_assert(0 == uv_cond_init(&pg_cache_descr->cond));
fatal_assert(0 == uv_mutex_init(&pg_cache_descr->mutex));
return pg_cache_descr;
}
void rrdeng_destroy_pg_cache_descr(struct rrdengine_instance *ctx, struct page_cache_descr *pg_cache_descr)
{
uv_cond_destroy(&pg_cache_descr->cond);
uv_mutex_destroy(&pg_cache_descr->mutex);
freez(pg_cache_descr);
rrd_stat_atomic_add(&ctx->stats.page_cache_descriptors, -1);
}
/* also allocates page cache descriptor if missing */
void rrdeng_page_descr_mutex_lock(struct rrdengine_instance *ctx, struct rrdeng_page_descr *descr)
{
unsigned long old_state, old_users, new_state, ret_state;
struct page_cache_descr *pg_cache_descr = NULL;
uint8_t we_locked;
we_locked = 0;
while (1) { /* spin */
old_state = descr->pg_cache_descr_state;
old_users = old_state >> PG_CACHE_DESCR_SHIFT;
if (unlikely(we_locked)) {
fatal_assert(old_state & PG_CACHE_DESCR_LOCKED);
new_state = (1 << PG_CACHE_DESCR_SHIFT) | PG_CACHE_DESCR_ALLOCATED;
ret_state = ulong_compare_and_swap(&descr->pg_cache_descr_state, old_state, new_state);
if (old_state == ret_state) {
/* success */
break;
}
continue; /* spin */
}
if (old_state & PG_CACHE_DESCR_LOCKED) {
fatal_assert(0 == old_users);
continue; /* spin */
}
if (0 == old_state) {
/* no page cache descriptor has been allocated */
if (NULL == pg_cache_descr) {
pg_cache_descr = rrdeng_create_pg_cache_descr(ctx);
}
new_state = PG_CACHE_DESCR_LOCKED;
ret_state = ulong_compare_and_swap(&descr->pg_cache_descr_state, 0, new_state);
if (0 == ret_state) {
we_locked = 1;
descr->pg_cache_descr = pg_cache_descr;
pg_cache_descr->descr = descr;
pg_cache_descr = NULL; /* make sure we don't free pg_cache_descr */
/* retry */
continue;
}
continue; /* spin */
}
/* page cache descriptor is already allocated */
if (unlikely(!(old_state & PG_CACHE_DESCR_ALLOCATED))) {
fatal("Invalid page cache descriptor locking state:%#lX", old_state);
}
new_state = (old_users + 1) << PG_CACHE_DESCR_SHIFT;
new_state |= old_state & PG_CACHE_DESCR_FLAGS_MASK;
ret_state = ulong_compare_and_swap(&descr->pg_cache_descr_state, old_state, new_state);
if (old_state == ret_state) {
/* success */
break;
}
/* spin */
}
if (pg_cache_descr) {
rrdeng_destroy_pg_cache_descr(ctx, pg_cache_descr);
}
pg_cache_descr = descr->pg_cache_descr;
uv_mutex_lock(&pg_cache_descr->mutex);
}
void rrdeng_page_descr_mutex_unlock(struct rrdengine_instance *ctx, struct rrdeng_page_descr *descr)
{
unsigned long old_state, new_state, ret_state, old_users;
struct page_cache_descr *pg_cache_descr, *delete_pg_cache_descr = NULL;
uint8_t we_locked;
uv_mutex_unlock(&descr->pg_cache_descr->mutex);
we_locked = 0;
while (1) { /* spin */
old_state = descr->pg_cache_descr_state;
old_users = old_state >> PG_CACHE_DESCR_SHIFT;
if (unlikely(we_locked)) {
fatal_assert(0 == old_users);
ret_state = ulong_compare_and_swap(&descr->pg_cache_descr_state, old_state, 0);
if (old_state == ret_state) {
/* success */
rrdeng_destroy_pg_cache_descr(ctx, delete_pg_cache_descr);
return;
}
continue; /* spin */
}
if (old_state & PG_CACHE_DESCR_LOCKED) {
fatal_assert(0 == old_users);
continue; /* spin */
}
fatal_assert(old_state & PG_CACHE_DESCR_ALLOCATED);
pg_cache_descr = descr->pg_cache_descr;
/* caller is the only page cache descriptor user and there are no pending references on the page */
if ((old_state & PG_CACHE_DESCR_DESTROY) && (1 == old_users) &&
!pg_cache_descr->flags && !pg_cache_descr->refcnt) {
fatal_assert(!pg_cache_descr->waiters);
new_state = PG_CACHE_DESCR_LOCKED;
ret_state = ulong_compare_and_swap(&descr->pg_cache_descr_state, old_state, new_state);
if (old_state == ret_state) {
we_locked = 1;
delete_pg_cache_descr = pg_cache_descr;
descr->pg_cache_descr = NULL;
/* retry */
continue;
}
continue; /* spin */
}
fatal_assert(old_users > 0);
new_state = (old_users - 1) << PG_CACHE_DESCR_SHIFT;
new_state |= old_state & PG_CACHE_DESCR_FLAGS_MASK;
ret_state = ulong_compare_and_swap(&descr->pg_cache_descr_state, old_state, new_state);
if (old_state == ret_state) {
/* success */
break;
}
/* spin */
}
}
/*
* Tries to deallocate page cache descriptor. If it fails, it postpones deallocation by setting the
* PG_CACHE_DESCR_DESTROY flag which will be eventually cleared by a different context after doing
* the deallocation.
*/
void rrdeng_try_deallocate_pg_cache_descr(struct rrdengine_instance *ctx, struct rrdeng_page_descr *descr)
{
unsigned long old_state, new_state, ret_state, old_users;
struct page_cache_descr *pg_cache_descr = NULL;
uint8_t just_locked, can_free, must_unlock;
just_locked = 0;
can_free = 0;
must_unlock = 0;
while (1) { /* spin */
old_state = descr->pg_cache_descr_state;
old_users = old_state >> PG_CACHE_DESCR_SHIFT;
if (unlikely(just_locked)) {
fatal_assert(0 == old_users);
must_unlock = 1;
just_locked = 0;
/* Try deallocate if there are no pending references on the page */
if (!pg_cache_descr->flags && !pg_cache_descr->refcnt) {
fatal_assert(!pg_cache_descr->waiters);
descr->pg_cache_descr = NULL;
can_free = 1;
/* success */
continue;
}
continue; /* spin */
}
if (unlikely(must_unlock)) {
fatal_assert(0 == old_users);
if (can_free) {
/* success */
new_state = 0;
} else {
new_state = old_state | PG_CACHE_DESCR_DESTROY;
new_state &= ~PG_CACHE_DESCR_LOCKED;
}
ret_state = ulong_compare_and_swap(&descr->pg_cache_descr_state, old_state, new_state);
if (old_state == ret_state) {
/* unlocked */
if (can_free)
rrdeng_destroy_pg_cache_descr(ctx, pg_cache_descr);
return;
}
continue; /* spin */
}
if (!(old_state & PG_CACHE_DESCR_ALLOCATED)) {
/* don't do anything */
return;
}
if (old_state & PG_CACHE_DESCR_LOCKED) {
fatal_assert(0 == old_users);
continue; /* spin */
}
/* caller is the only page cache descriptor user */
if (0 == old_users) {
new_state = old_state | PG_CACHE_DESCR_LOCKED;
ret_state = ulong_compare_and_swap(&descr->pg_cache_descr_state, old_state, new_state);
if (old_state == ret_state) {
just_locked = 1;
pg_cache_descr = descr->pg_cache_descr;
/* retry */
continue;
}
continue; /* spin */
}
if (old_state & PG_CACHE_DESCR_DESTROY) {
/* don't do anything */
return;
}
/* plant PG_CACHE_DESCR_DESTROY so that other contexts eventually free the page cache descriptor */
new_state = old_state | PG_CACHE_DESCR_DESTROY;
ret_state = ulong_compare_and_swap(&descr->pg_cache_descr_state, old_state, new_state);
if (old_state == ret_state) {
/* success */
return;
}
/* spin */
}
}
|
