FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_kobj.c
1 /*-
2 * Copyright (c) 2000,2003 Doug Rabson
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD: releng/11.2/sys/kern/subr_kobj.c 318274 2017-05-14 14:21:09Z marius $");
29
30 #include <sys/param.h>
31 #include <sys/kernel.h>
32 #include <sys/kobj.h>
33 #include <sys/lock.h>
34 #include <sys/malloc.h>
35 #include <sys/mutex.h>
36 #include <sys/sysctl.h>
37 #ifndef TEST
38 #include <sys/systm.h>
39 #endif
40
41 #ifdef TEST
42 #include "usertest.h"
43 #endif
44
45 static MALLOC_DEFINE(M_KOBJ, "kobj", "Kernel object structures");
46
47 #ifdef KOBJ_STATS
48
49 u_int kobj_lookup_hits;
50 u_int kobj_lookup_misses;
51
52 SYSCTL_UINT(_kern, OID_AUTO, kobj_hits, CTLFLAG_RD,
53 &kobj_lookup_hits, 0, "");
54 SYSCTL_UINT(_kern, OID_AUTO, kobj_misses, CTLFLAG_RD,
55 &kobj_lookup_misses, 0, "");
56
57 #endif
58
59 static struct mtx kobj_mtx;
60 static int kobj_mutex_inited;
61 static int kobj_next_id = 1;
62
63 #define KOBJ_LOCK() mtx_lock(&kobj_mtx)
64 #define KOBJ_UNLOCK() mtx_unlock(&kobj_mtx)
65 #define KOBJ_ASSERT(what) mtx_assert(&kobj_mtx, what);
66
67 SYSCTL_INT(_kern, OID_AUTO, kobj_methodcount, CTLFLAG_RD,
68 &kobj_next_id, 0, "");
69
70 static void
71 kobj_init_mutex(void *arg)
72 {
73 if (!kobj_mutex_inited) {
74 mtx_init(&kobj_mtx, "kobj", NULL, MTX_DEF);
75 kobj_mutex_inited = 1;
76 }
77 }
78
79 SYSINIT(kobj, SI_SUB_LOCK, SI_ORDER_ANY, kobj_init_mutex, NULL);
80
81 /*
82 * This method structure is used to initialise new caches. Since the
83 * desc pointer is NULL, it is guaranteed never to match any read
84 * descriptors.
85 */
86 static const struct kobj_method null_method = {
87 0, 0,
88 };
89
90 int
91 kobj_error_method(void)
92 {
93
94 return ENXIO;
95 }
96
97 static void
98 kobj_class_compile_common(kobj_class_t cls, kobj_ops_t ops)
99 {
100 kobj_method_t *m;
101 int i;
102
103 /*
104 * Don't do anything if we are already compiled.
105 */
106 if (cls->ops)
107 return;
108
109 /*
110 * First register any methods which need it.
111 */
112 for (i = 0, m = cls->methods; m->desc; i++, m++) {
113 if (m->desc->id == 0)
114 m->desc->id = kobj_next_id++;
115 }
116
117 /*
118 * Then initialise the ops table.
119 */
120 for (i = 0; i < KOBJ_CACHE_SIZE; i++)
121 ops->cache[i] = &null_method;
122 ops->cls = cls;
123 cls->ops = ops;
124 }
125
126 void
127 kobj_class_compile(kobj_class_t cls)
128 {
129 kobj_ops_t ops;
130
131 KOBJ_ASSERT(MA_NOTOWNED);
132
133 /*
134 * Allocate space for the compiled ops table.
135 */
136 ops = malloc(sizeof(struct kobj_ops), M_KOBJ, M_NOWAIT);
137 if (!ops)
138 panic("%s: out of memory", __func__);
139
140 KOBJ_LOCK();
141
142 /*
143 * We may have lost a race for kobj_class_compile here - check
144 * to make sure someone else hasn't already compiled this
145 * class.
146 */
147 if (cls->ops) {
148 KOBJ_UNLOCK();
149 free(ops, M_KOBJ);
150 return;
151 }
152
153 kobj_class_compile_common(cls, ops);
154 KOBJ_UNLOCK();
155 }
156
157 void
158 kobj_class_compile_static(kobj_class_t cls, kobj_ops_t ops)
159 {
160
161 KASSERT(kobj_mutex_inited == 0,
162 ("%s: only supported during early cycles", __func__));
163
164 /*
165 * Increment refs to make sure that the ops table is not freed.
166 */
167 cls->refs++;
168 kobj_class_compile_common(cls, ops);
169 }
170
171 static kobj_method_t*
172 kobj_lookup_method_class(kobj_class_t cls, kobjop_desc_t desc)
173 {
174 kobj_method_t *methods = cls->methods;
175 kobj_method_t *ce;
176
177 for (ce = methods; ce && ce->desc; ce++) {
178 if (ce->desc == desc) {
179 return ce;
180 }
181 }
182
183 return NULL;
184 }
185
186 static kobj_method_t*
187 kobj_lookup_method_mi(kobj_class_t cls,
188 kobjop_desc_t desc)
189 {
190 kobj_method_t *ce;
191 kobj_class_t *basep;
192
193 ce = kobj_lookup_method_class(cls, desc);
194 if (ce)
195 return ce;
196
197 basep = cls->baseclasses;
198 if (basep) {
199 for (; *basep; basep++) {
200 ce = kobj_lookup_method_mi(*basep, desc);
201 if (ce)
202 return ce;
203 }
204 }
205
206 return NULL;
207 }
208
209 kobj_method_t*
210 kobj_lookup_method(kobj_class_t cls,
211 kobj_method_t **cep,
212 kobjop_desc_t desc)
213 {
214 kobj_method_t *ce;
215
216 ce = kobj_lookup_method_mi(cls, desc);
217 if (!ce)
218 ce = &desc->deflt;
219 if (cep)
220 *cep = ce;
221 return ce;
222 }
223
224 void
225 kobj_class_free(kobj_class_t cls)
226 {
227 void* ops = NULL;
228
229 KOBJ_ASSERT(MA_NOTOWNED);
230 KOBJ_LOCK();
231
232 /*
233 * Protect against a race between kobj_create and
234 * kobj_delete.
235 */
236 if (cls->refs == 0) {
237 /*
238 * For now we don't do anything to unregister any methods
239 * which are no longer used.
240 */
241
242 /*
243 * Free memory and clean up.
244 */
245 ops = cls->ops;
246 cls->ops = NULL;
247 }
248
249 KOBJ_UNLOCK();
250
251 if (ops)
252 free(ops, M_KOBJ);
253 }
254
255 kobj_t
256 kobj_create(kobj_class_t cls,
257 struct malloc_type *mtype,
258 int mflags)
259 {
260 kobj_t obj;
261
262 /*
263 * Allocate and initialise the new object.
264 */
265 obj = malloc(cls->size, mtype, mflags | M_ZERO);
266 if (!obj)
267 return NULL;
268 kobj_init(obj, cls);
269
270 return obj;
271 }
272
273 static void
274 kobj_init_common(kobj_t obj, kobj_class_t cls)
275 {
276
277 obj->ops = cls->ops;
278 cls->refs++;
279 }
280
281 void
282 kobj_init(kobj_t obj, kobj_class_t cls)
283 {
284 KOBJ_ASSERT(MA_NOTOWNED);
285 retry:
286 KOBJ_LOCK();
287
288 /*
289 * Consider compiling the class' method table.
290 */
291 if (!cls->ops) {
292 /*
293 * kobj_class_compile doesn't want the lock held
294 * because of the call to malloc - we drop the lock
295 * and re-try.
296 */
297 KOBJ_UNLOCK();
298 kobj_class_compile(cls);
299 goto retry;
300 }
301
302 kobj_init_common(obj, cls);
303
304 KOBJ_UNLOCK();
305 }
306
307 void
308 kobj_init_static(kobj_t obj, kobj_class_t cls)
309 {
310
311 KASSERT(kobj_mutex_inited == 0,
312 ("%s: only supported during early cycles", __func__));
313
314 kobj_init_common(obj, cls);
315 }
316
317 void
318 kobj_delete(kobj_t obj, struct malloc_type *mtype)
319 {
320 kobj_class_t cls = obj->ops->cls;
321 int refs;
322
323 /*
324 * Consider freeing the compiled method table for the class
325 * after its last instance is deleted. As an optimisation, we
326 * should defer this for a short while to avoid thrashing.
327 */
328 KOBJ_ASSERT(MA_NOTOWNED);
329 KOBJ_LOCK();
330 cls->refs--;
331 refs = cls->refs;
332 KOBJ_UNLOCK();
333
334 if (!refs)
335 kobj_class_free(cls);
336
337 obj->ops = NULL;
338 if (mtype)
339 free(obj, mtype);
340 }
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