FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_kobj.c
1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2000,2003 Doug Rabson
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include <sys/cdefs.h>
30 __FBSDID("$FreeBSD$");
31
32 #include <sys/param.h>
33 #include <sys/kernel.h>
34 #include <sys/kobj.h>
35 #include <sys/lock.h>
36 #include <sys/malloc.h>
37 #include <sys/mutex.h>
38 #include <sys/sysctl.h>
39 #ifndef TEST
40 #include <sys/systm.h>
41 #endif
42
43 #ifdef TEST
44 #include "usertest.h"
45 #endif
46
47 static MALLOC_DEFINE(M_KOBJ, "kobj", "Kernel object structures");
48
49 #ifdef KOBJ_STATS
50
51 u_int kobj_lookup_hits;
52 u_int kobj_lookup_misses;
53
54 SYSCTL_UINT(_kern, OID_AUTO, kobj_hits, CTLFLAG_RD,
55 &kobj_lookup_hits, 0, "");
56 SYSCTL_UINT(_kern, OID_AUTO, kobj_misses, CTLFLAG_RD,
57 &kobj_lookup_misses, 0, "");
58
59 #endif
60
61 static struct mtx kobj_mtx;
62 static int kobj_mutex_inited;
63 static int kobj_next_id = 1;
64
65 #define KOBJ_LOCK() mtx_lock(&kobj_mtx)
66 #define KOBJ_UNLOCK() mtx_unlock(&kobj_mtx)
67 #define KOBJ_ASSERT(what) mtx_assert(&kobj_mtx, what);
68
69 SYSCTL_INT(_kern, OID_AUTO, kobj_methodcount, CTLFLAG_RD,
70 &kobj_next_id, 0,
71 "Number of kernel object methods registered");
72
73 static void
74 kobj_init_mutex(void *arg)
75 {
76 if (!kobj_mutex_inited) {
77 mtx_init(&kobj_mtx, "kobj", NULL, MTX_DEF);
78 kobj_mutex_inited = 1;
79 }
80 }
81
82 SYSINIT(kobj, SI_SUB_LOCK, SI_ORDER_ANY, kobj_init_mutex, NULL);
83
84 /*
85 * This method structure is used to initialise new caches. Since the
86 * desc pointer is NULL, it is guaranteed never to match any read
87 * descriptors.
88 */
89 static const struct kobj_method null_method = {
90 0, 0,
91 };
92
93 int
94 kobj_error_method(void)
95 {
96
97 return ENXIO;
98 }
99
100 static void
101 kobj_class_compile_common(kobj_class_t cls, kobj_ops_t ops)
102 {
103 kobj_method_t *m;
104 int i;
105
106 /*
107 * Don't do anything if we are already compiled.
108 */
109 if (cls->ops)
110 return;
111
112 /*
113 * First register any methods which need it.
114 */
115 for (m = cls->methods; m->desc; m++) {
116 if (m->desc->id == 0)
117 m->desc->id = kobj_next_id++;
118 }
119
120 /*
121 * Then initialise the ops table.
122 */
123 for (i = 0; i < KOBJ_CACHE_SIZE; i++)
124 ops->cache[i] = &null_method;
125 ops->cls = cls;
126 cls->ops = ops;
127 }
128
129 static int
130 kobj_class_compile1(kobj_class_t cls, int mflags)
131 {
132 kobj_ops_t ops;
133
134 KOBJ_ASSERT(MA_NOTOWNED);
135
136 ops = malloc(sizeof(struct kobj_ops), M_KOBJ, mflags);
137 if (ops == NULL)
138 return (ENOMEM);
139
140 /*
141 * We may have lost a race for kobj_class_compile here - check
142 * to make sure someone else hasn't already compiled this
143 * class.
144 */
145 KOBJ_LOCK();
146 if (cls->ops) {
147 KOBJ_UNLOCK();
148 free(ops, M_KOBJ);
149 return (0);
150 }
151 kobj_class_compile_common(cls, ops);
152 KOBJ_UNLOCK();
153 return (0);
154 }
155
156 void
157 kobj_class_compile(kobj_class_t cls)
158 {
159 int error __diagused;
160
161 error = kobj_class_compile1(cls, M_WAITOK);
162 KASSERT(error == 0, ("kobj_class_compile1 returned %d", error));
163 }
164
165 void
166 kobj_class_compile_static(kobj_class_t cls, kobj_ops_t ops)
167 {
168
169 KASSERT(kobj_mutex_inited == 0,
170 ("%s: only supported during early cycles", __func__));
171
172 /*
173 * Increment refs to make sure that the ops table is not freed.
174 */
175 cls->refs++;
176 kobj_class_compile_common(cls, ops);
177 }
178
179 static kobj_method_t*
180 kobj_lookup_method_class(kobj_class_t cls, kobjop_desc_t desc)
181 {
182 kobj_method_t *methods = cls->methods;
183 kobj_method_t *ce;
184
185 for (ce = methods; ce && ce->desc; ce++) {
186 if (ce->desc == desc) {
187 return ce;
188 }
189 }
190
191 return NULL;
192 }
193
194 static kobj_method_t*
195 kobj_lookup_method_mi(kobj_class_t cls,
196 kobjop_desc_t desc)
197 {
198 kobj_method_t *ce;
199 kobj_class_t *basep;
200
201 ce = kobj_lookup_method_class(cls, desc);
202 if (ce)
203 return ce;
204
205 basep = cls->baseclasses;
206 if (basep) {
207 for (; *basep; basep++) {
208 ce = kobj_lookup_method_mi(*basep, desc);
209 if (ce)
210 return ce;
211 }
212 }
213
214 return NULL;
215 }
216
217 kobj_method_t*
218 kobj_lookup_method(kobj_class_t cls,
219 kobj_method_t **cep,
220 kobjop_desc_t desc)
221 {
222 kobj_method_t *ce;
223
224 ce = kobj_lookup_method_mi(cls, desc);
225 if (!ce)
226 ce = &desc->deflt;
227 if (cep)
228 *cep = ce;
229 return ce;
230 }
231
232 void
233 kobj_class_free(kobj_class_t cls)
234 {
235 void* ops = NULL;
236
237 KOBJ_ASSERT(MA_NOTOWNED);
238 KOBJ_LOCK();
239
240 /*
241 * Protect against a race between kobj_create and
242 * kobj_delete.
243 */
244 if (cls->refs == 0) {
245 /*
246 * For now we don't do anything to unregister any methods
247 * which are no longer used.
248 */
249
250 /*
251 * Free memory and clean up.
252 */
253 ops = cls->ops;
254 cls->ops = NULL;
255 }
256
257 KOBJ_UNLOCK();
258
259 if (ops)
260 free(ops, M_KOBJ);
261 }
262
263 static void
264 kobj_init_common(kobj_t obj, kobj_class_t cls)
265 {
266
267 obj->ops = cls->ops;
268 cls->refs++;
269 }
270
271 static int
272 kobj_init1(kobj_t obj, kobj_class_t cls, int mflags)
273 {
274 int error;
275
276 KOBJ_LOCK();
277 while (cls->ops == NULL) {
278 /*
279 * kobj_class_compile doesn't want the lock held
280 * because of the call to malloc - we drop the lock
281 * and re-try.
282 */
283 KOBJ_UNLOCK();
284 error = kobj_class_compile1(cls, mflags);
285 if (error != 0)
286 return (error);
287 KOBJ_LOCK();
288 }
289 kobj_init_common(obj, cls);
290 KOBJ_UNLOCK();
291 return (0);
292 }
293
294 kobj_t
295 kobj_create(kobj_class_t cls, struct malloc_type *mtype, int mflags)
296 {
297 kobj_t obj;
298
299 obj = malloc(cls->size, mtype, mflags | M_ZERO);
300 if (obj == NULL)
301 return (NULL);
302 if (kobj_init1(obj, cls, mflags) != 0) {
303 free(obj, mtype);
304 return (NULL);
305 }
306 return (obj);
307 }
308
309 void
310 kobj_init(kobj_t obj, kobj_class_t cls)
311 {
312 int error;
313
314 error = kobj_init1(obj, cls, M_NOWAIT);
315 if (error != 0)
316 panic("kobj_init1 failed: error %d", error);
317 }
318
319 void
320 kobj_init_static(kobj_t obj, kobj_class_t cls)
321 {
322
323 KASSERT(kobj_mutex_inited == 0,
324 ("%s: only supported during early cycles", __func__));
325
326 kobj_init_common(obj, cls);
327 }
328
329 void
330 kobj_delete(kobj_t obj, struct malloc_type *mtype)
331 {
332 kobj_class_t cls = obj->ops->cls;
333 int refs;
334
335 /*
336 * Consider freeing the compiled method table for the class
337 * after its last instance is deleted. As an optimisation, we
338 * should defer this for a short while to avoid thrashing.
339 */
340 KOBJ_ASSERT(MA_NOTOWNED);
341 KOBJ_LOCK();
342 cls->refs--;
343 refs = cls->refs;
344 KOBJ_UNLOCK();
345
346 if (!refs)
347 kobj_class_free(cls);
348
349 obj->ops = NULL;
350 if (mtype)
351 free(obj, mtype);
352 }
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