1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 */
26
27 #pragma ident "%Z%%M% %I% %E% SMI"
28
29 /*
30 * This file contains the semaphore operations.
31 */
32
33 #include <sys/param.h>
34 #include <sys/types.h>
35 #include <sys/systm.h>
36 #include <sys/schedctl.h>
37 #include <sys/semaphore.h>
38 #include <sys/sema_impl.h>
39 #include <sys/t_lock.h>
40 #include <sys/thread.h>
41 #include <sys/proc.h>
42 #include <sys/cmn_err.h>
43 #include <sys/debug.h>
44 #include <sys/disp.h>
45 #include <sys/sobject.h>
46 #include <sys/cpuvar.h>
47 #include <sys/sleepq.h>
48 #include <sys/sdt.h>
49
50 static void sema_unsleep(kthread_t *t);
51 static void sema_change_pri(kthread_t *t, pri_t pri, pri_t *t_prip);
52 static kthread_t *sema_owner(ksema_t *);
53
54 /*
55 * The sobj_ops vector exports a set of functions needed when a thread
56 * is asleep on a synchronization object of this type.
57 */
58 static sobj_ops_t sema_sobj_ops = {
59 SOBJ_SEMA, sema_owner, sema_unsleep, sema_change_pri
60 };
61
62 /*
63 * SEMA_BLOCK(sema_impl_t *s, disp_lock_t *lockp)
64 */
65 #define SEMA_BLOCK(s, lockp) \
66 { \
67 kthread_t *tp; \
68 kthread_t **tpp; \
69 pri_t cpri; \
70 klwp_t *lwp = ttolwp(curthread); \
71 ASSERT(THREAD_LOCK_HELD(curthread)); \
72 ASSERT(curthread != CPU->cpu_idle_thread); \
73 ASSERT(CPU_ON_INTR(CPU) == 0); \
74 ASSERT(curthread->t_wchan0 == NULL); \
75 ASSERT(curthread->t_wchan == NULL); \
76 ASSERT(curthread->t_state == TS_ONPROC); \
77 CL_SLEEP(curthread); \
78 THREAD_SLEEP(curthread, lockp); \
79 curthread->t_wchan = (caddr_t)s; \
80 curthread->t_sobj_ops = &sema_sobj_ops; \
81 DTRACE_SCHED(sleep); \
82 if (lwp != NULL) { \
83 lwp->lwp_ru.nvcsw++; \
84 (void) new_mstate(curthread, LMS_SLEEP); \
85 } \
86 cpri = DISP_PRIO(curthread); \
87 tpp = &s->s_slpq; \
88 while ((tp = *tpp) != NULL) { \
89 if (cpri > DISP_PRIO(tp)) \
90 break; \
91 tpp = &tp->t_link; \
92 } \
93 *tpp = curthread; \
94 curthread->t_link = tp; \
95 ASSERT(s->s_slpq != NULL); \
96 }
97
98 /* ARGSUSED */
99 void
100 sema_init(ksema_t *sp, unsigned count, char *name, ksema_type_t type, void *arg)
101 {
102 ((sema_impl_t *)sp)->s_count = count;
103 ((sema_impl_t *)sp)->s_slpq = NULL;
104 }
105
106 void
107 sema_destroy(ksema_t *sp)
108 {
109 ASSERT(((sema_impl_t *)sp)->s_slpq == NULL);
110 }
111
112 /*
113 * Put a thread on the sleep queue for this semaphore.
114 */
115 static void
116 sema_queue(ksema_t *sp, kthread_t *t)
117 {
118 kthread_t **tpp;
119 kthread_t *tp;
120 pri_t cpri;
121 sema_impl_t *s;
122
123 ASSERT(THREAD_LOCK_HELD(t));
124 s = (sema_impl_t *)sp;
125 tpp = &s->s_slpq;
126 cpri = DISP_PRIO(t);
127 while ((tp = *tpp) != NULL) {
128 if (cpri > DISP_PRIO(tp))
129 break;
130 tpp = &tp->t_link;
131 }
132 *tpp = t;
133 t->t_link = tp;
134 }
135
136 /*
137 * Remove a thread from the sleep queue for this
138 * semaphore.
139 */
140 static void
141 sema_dequeue(ksema_t *sp, kthread_t *t)
142 {
143 kthread_t **tpp;
144 kthread_t *tp;
145 sema_impl_t *s;
146
147 ASSERT(THREAD_LOCK_HELD(t));
148 s = (sema_impl_t *)sp;
149 tpp = &s->s_slpq;
150 while ((tp = *tpp) != NULL) {
151 if (tp == t) {
152 *tpp = t->t_link;
153 t->t_link = NULL;
154 return;
155 }
156 tpp = &tp->t_link;
157 }
158 }
159
160 /* ARGSUSED */
161 static kthread_t *
162 sema_owner(ksema_t *sp)
163 {
164 return ((kthread_t *)NULL);
165 }
166
167 /*
168 * Wakeup a thread sleeping on a semaphore, and put it
169 * on the dispatch queue.
170 * Called via SOBJ_UNSLEEP().
171 */
172 static void
173 sema_unsleep(kthread_t *t)
174 {
175 kthread_t **tpp;
176 kthread_t *tp;
177 sema_impl_t *s;
178
179 ASSERT(THREAD_LOCK_HELD(t));
180 s = (sema_impl_t *)t->t_wchan;
181 tpp = &s->s_slpq;
182 while ((tp = *tpp) != NULL) {
183 if (tp == t) {
184 *tpp = t->t_link;
185 t->t_link = NULL;
186 t->t_sobj_ops = NULL;
187 t->t_wchan = NULL;
188 t->t_wchan0 = NULL;
189 /*
190 * Change thread to transition state and
191 * drop the semaphore sleep queue lock.
192 */
193 THREAD_TRANSITION(t);
194 CL_SETRUN(t);
195 return;
196 }
197 tpp = &tp->t_link;
198 }
199 }
200
201 /*
202 * operations to perform when changing the priority
203 * of a thread asleep on a semaphore.
204 * Called via SOBJ_CHANGE_PRI() and SOBJ_CHANGE_EPRI().
205 */
206 static void
207 sema_change_pri(kthread_t *t, pri_t pri, pri_t *t_prip)
208 {
209 ksema_t *sp;
210
211 if ((sp = (ksema_t *)t->t_wchan) != NULL) {
212 sema_dequeue(sp, t);
213 *t_prip = pri;
214 sema_queue(sp, t);
215 } else
216 panic("sema_change_pri: %p not on sleep queue", (void *)t);
217 }
218
219 /*
220 * the semaphore is granted when the semaphore's
221 * count is greater than zero and blocks when equal
222 * to zero.
223 */
224 void
225 sema_p(ksema_t *sp)
226 {
227 sema_impl_t *s;
228 disp_lock_t *sqlp;
229
230 s = (sema_impl_t *)sp;
231 sqlp = &SQHASH(s)->sq_lock;
232 disp_lock_enter(sqlp);
233 ASSERT(s->s_count >= 0);
234 while (s->s_count == 0) {
235 if (panicstr) {
236 disp_lock_exit(sqlp);
237 return;
238 }
239 thread_lock_high(curthread);
240 SEMA_BLOCK(s, sqlp);
241 thread_unlock_nopreempt(curthread);
242 swtch();
243 disp_lock_enter(sqlp);
244 }
245 s->s_count--;
246 disp_lock_exit(sqlp);
247 }
248
249 /*
250 * similiar to sema_p except that it blocks at an interruptible
251 * priority. if a signal is present then return 1 otherwise 0.
252 */
253 int
254 sema_p_sig(ksema_t *sp)
255 {
256 kthread_t *t = curthread;
257 klwp_t *lwp = ttolwp(t);
258 int cancel_pending;
259 int cancelled = 0;
260 sema_impl_t *s;
261 disp_lock_t *sqlp;
262
263 if (lwp == NULL) {
264 sema_p(sp);
265 return (0);
266 }
267
268 cancel_pending = schedctl_cancel_pending();
269 s = (sema_impl_t *)sp;
270 sqlp = &SQHASH(s)->sq_lock;
271 disp_lock_enter(sqlp);
272 ASSERT(s->s_count >= 0);
273 while (s->s_count == 0) {
274 proc_t *p = ttoproc(t);
275 thread_lock_high(t);
276 t->t_flag |= T_WAKEABLE;
277 SEMA_BLOCK(s, sqlp);
278 lwp->lwp_asleep = 1;
279 lwp->lwp_sysabort = 0;
280 thread_unlock_nopreempt(t);
281 if (ISSIG(t, JUSTLOOKING) || MUSTRETURN(p, t) || cancel_pending)
282 setrun(t);
283 swtch();
284 t->t_flag &= ~T_WAKEABLE;
285 if (ISSIG(t, FORREAL) || lwp->lwp_sysabort ||
286 MUSTRETURN(p, t) || (cancelled = cancel_pending) != 0) {
287 kthread_t *sq, *tp;
288 lwp->lwp_asleep = 0;
289 lwp->lwp_sysabort = 0;
290 disp_lock_enter(sqlp);
291 sq = s->s_slpq;
292 /*
293 * in case sema_v and interrupt happen
294 * at the same time, we need to pass the
295 * sema_v to the next thread.
296 */
297 if ((sq != NULL) && (s->s_count > 0)) {
298 tp = sq;
299 ASSERT(THREAD_LOCK_HELD(tp));
300 sq = sq->t_link;
301 tp->t_link = NULL;
302 DTRACE_SCHED1(wakeup, kthread_t *, tp);
303 tp->t_sobj_ops = NULL;
304 tp->t_wchan = NULL;
305 ASSERT(tp->t_state == TS_SLEEP);
306 CL_WAKEUP(tp);
307 s->s_slpq = sq;
308 disp_lock_exit_high(sqlp);
309 thread_unlock(tp);
310 } else {
311 disp_lock_exit(sqlp);
312 }
313 if (cancelled)
314 schedctl_cancel_eintr();
315 return (1);
316 }
317 lwp->lwp_asleep = 0;
318 disp_lock_enter(sqlp);
319 }
320 s->s_count--;
321 disp_lock_exit(sqlp);
322 return (0);
323 }
324
325 /*
326 * the semaphore's count is incremented by one. a blocked thread
327 * is awakened and re-tries to acquire the semaphore.
328 */
329 void
330 sema_v(ksema_t *sp)
331 {
332 sema_impl_t *s;
333 kthread_t *sq, *tp;
334 disp_lock_t *sqlp;
335
336 s = (sema_impl_t *)sp;
337 sqlp = &SQHASH(s)->sq_lock;
338 disp_lock_enter(sqlp);
339 if (panicstr) {
340 disp_lock_exit(sqlp);
341 return;
342 }
343 s->s_count++;
344 sq = s->s_slpq;
345 if (sq != NULL) {
346 tp = sq;
347 ASSERT(THREAD_LOCK_HELD(tp));
348 sq = sq->t_link;
349 tp->t_link = NULL;
350 DTRACE_SCHED1(wakeup, kthread_t *, tp);
351 tp->t_sobj_ops = NULL;
352 tp->t_wchan = NULL;
353 ASSERT(tp->t_state == TS_SLEEP);
354 CL_WAKEUP(tp);
355 s->s_slpq = sq;
356 disp_lock_exit_high(sqlp);
357 thread_unlock(tp);
358 } else {
359 disp_lock_exit(sqlp);
360 }
361 }
362
363 /*
364 * try to acquire the semaphore. if the semaphore is greater than
365 * zero, then the semaphore is granted and returns 1. otherwise
366 * return 0.
367 */
368 int
369 sema_tryp(ksema_t *sp)
370 {
371 sema_impl_t *s;
372 sleepq_head_t *sqh;
373
374 int gotit = 0;
375
376 s = (sema_impl_t *)sp;
377 sqh = SQHASH(s);
378 disp_lock_enter(&sqh->sq_lock);
379 if (s->s_count > 0) {
380 s->s_count--;
381 gotit = 1;
382 }
383 disp_lock_exit(&sqh->sq_lock);
384 return (gotit);
385 }
386
387 int
388 sema_held(ksema_t *sp)
389 {
390 sema_impl_t *s;
391
392
393 s = (sema_impl_t *)sp;
394 if (panicstr)
395 return (1);
396 else
397 return (s->s_count <= 0);
398 }