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
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
|
/* $OpenBSD: kern_srp.c,v 1.13 2020/12/06 19:18:30 cheloha Exp $ */
/*
* Copyright (c) 2014 Jonathan Matthew <jmatthew@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/timeout.h>
#include <sys/srp.h>
#include <sys/atomic.h>
void srp_v_gc_start(struct srp_gc *, struct srp *, void *);
void
srpl_rc_init(struct srpl_rc *rc, void (*ref)(void *, void *),
void (*unref)(void *, void *), void *cookie)
{
rc->srpl_ref = ref;
srp_gc_init(&rc->srpl_gc, unref, cookie);
}
void
srp_gc_init(struct srp_gc *srp_gc, void (*dtor)(void *, void *), void *cookie)
{
srp_gc->srp_gc_dtor = dtor;
srp_gc->srp_gc_cookie = cookie;
refcnt_init(&srp_gc->srp_gc_refcnt);
}
void
srp_init(struct srp *srp)
{
srp->ref = NULL;
}
void *
srp_swap_locked(struct srp *srp, void *nv)
{
void *ov;
/*
* this doesn't have to be as careful as the caller has already
* prevented concurrent updates, eg. by holding the kernel lock.
* can't be mixed with non-locked updates though.
*/
ov = srp->ref;
srp->ref = nv;
return (ov);
}
void
srp_update_locked(struct srp_gc *srp_gc, struct srp *srp, void *v)
{
if (v != NULL)
refcnt_take(&srp_gc->srp_gc_refcnt);
v = srp_swap_locked(srp, v);
if (v != NULL)
srp_v_gc_start(srp_gc, srp, v);
}
void *
srp_get_locked(struct srp *srp)
{
return (srp->ref);
}
void
srp_gc_finalize(struct srp_gc *srp_gc)
{
refcnt_finalize(&srp_gc->srp_gc_refcnt, "srpfini");
}
#ifdef MULTIPROCESSOR
#include <machine/cpu.h>
#include <sys/pool.h>
struct srp_gc_ctx {
struct srp_gc *srp_gc;
struct timeout tick;
struct srp_hazard hzrd;
};
int srp_v_referenced(struct srp *, void *);
void srp_v_gc(void *);
struct pool srp_gc_ctx_pool;
void
srp_startup(void)
{
pool_init(&srp_gc_ctx_pool, sizeof(struct srp_gc_ctx), 0,
IPL_SOFTCLOCK, PR_WAITOK, "srpgc", NULL);
}
int
srp_v_referenced(struct srp *srp, void *v)
{
struct cpu_info *ci;
CPU_INFO_ITERATOR cii;
u_int i;
struct srp_hazard *hzrd;
CPU_INFO_FOREACH(cii, ci) {
for (i = 0; i < nitems(ci->ci_srp_hazards); i++) {
hzrd = &ci->ci_srp_hazards[i];
if (hzrd->sh_p != srp)
continue;
membar_consumer();
if (hzrd->sh_v != v)
continue;
return (1);
}
}
return (0);
}
void
srp_v_dtor(struct srp_gc *srp_gc, void *v)
{
(*srp_gc->srp_gc_dtor)(srp_gc->srp_gc_cookie, v);
refcnt_rele_wake(&srp_gc->srp_gc_refcnt);
}
void
srp_v_gc_start(struct srp_gc *srp_gc, struct srp *srp, void *v)
{
struct srp_gc_ctx *ctx;
if (!srp_v_referenced(srp, v)) {
/* we win */
srp_v_dtor(srp_gc, v);
return;
}
/* in use, try later */
ctx = pool_get(&srp_gc_ctx_pool, PR_WAITOK);
ctx->srp_gc = srp_gc;
ctx->hzrd.sh_p = srp;
ctx->hzrd.sh_v = v;
timeout_set(&ctx->tick, srp_v_gc, ctx);
timeout_add(&ctx->tick, 1);
}
void
srp_v_gc(void *x)
{
struct srp_gc_ctx *ctx = x;
if (srp_v_referenced(ctx->hzrd.sh_p, ctx->hzrd.sh_v)) {
/* oh well, try again later */
timeout_add(&ctx->tick, 1);
return;
}
srp_v_dtor(ctx->srp_gc, ctx->hzrd.sh_v);
pool_put(&srp_gc_ctx_pool, ctx);
}
void *
srp_swap(struct srp *srp, void *v)
{
return (atomic_swap_ptr(&srp->ref, v));
}
void
srp_update(struct srp_gc *srp_gc, struct srp *srp, void *v)
{
if (v != NULL)
refcnt_take(&srp_gc->srp_gc_refcnt);
v = srp_swap(srp, v);
if (v != NULL)
srp_v_gc_start(srp_gc, srp, v);
}
static inline void *
srp_v(struct srp_hazard *hzrd, struct srp *srp)
{
void *v;
hzrd->sh_p = srp;
/*
* ensure we update this cpu's hazard pointer to a value that's still
* current after the store finishes, otherwise the gc task may already
* be destroying it
*/
do {
v = srp->ref;
hzrd->sh_v = v;
membar_consumer();
} while (__predict_false(v != srp->ref));
return (v);
}
void *
srp_enter(struct srp_ref *sr, struct srp *srp)
{
struct cpu_info *ci = curcpu();
struct srp_hazard *hzrd;
u_int i;
for (i = 0; i < nitems(ci->ci_srp_hazards); i++) {
hzrd = &ci->ci_srp_hazards[i];
if (hzrd->sh_p == NULL) {
sr->hz = hzrd;
return (srp_v(hzrd, srp));
}
}
panic("%s: not enough srp hazard records", __func__);
/* NOTREACHED */
return (NULL);
}
void *
srp_follow(struct srp_ref *sr, struct srp *srp)
{
return (srp_v(sr->hz, srp));
}
void
srp_leave(struct srp_ref *sr)
{
sr->hz->sh_p = NULL;
}
static inline int
srp_referenced(void *v)
{
struct cpu_info *ci;
CPU_INFO_ITERATOR cii;
u_int i;
struct srp_hazard *hzrd;
CPU_INFO_FOREACH(cii, ci) {
for (i = 0; i < nitems(ci->ci_srp_hazards); i++) {
hzrd = &ci->ci_srp_hazards[i];
if (hzrd->sh_p != NULL && hzrd->sh_v == v)
return (1);
}
}
return (0);
}
void
srp_finalize(void *v, const char *wmesg)
{
while (srp_referenced(v))
tsleep_nsec(v, PWAIT, wmesg, MSEC_TO_NSEC(1));
}
#else /* MULTIPROCESSOR */
void
srp_startup(void)
{
}
void
srp_v_gc_start(struct srp_gc *srp_gc, struct srp *srp, void *v)
{
(*srp_gc->srp_gc_dtor)(srp_gc->srp_gc_cookie, v);
refcnt_rele_wake(&srp_gc->srp_gc_refcnt);
}
#endif /* MULTIPROCESSOR */
|