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 /*
28 * This file contains the semaphore operations.
29 */
30
31 #include <sys/param.h>
32 #include <sys/types.h>
33 #include <sys/systm.h>
34 #include <sys/schedctl.h>
35 #include <sys/semaphore.h>
36 #include <sys/sema_impl.h>
37 #include <sys/t_lock.h>
38 #include <sys/thread.h>
39 #include <sys/proc.h>
40 #include <sys/cmn_err.h>
41 #include <sys/debug.h>
42 #include <sys/disp.h>
43 #include <sys/sobject.h>
44 #include <sys/cpuvar.h>
45 #include <sys/sleepq.h>
46 #include <sys/sdt.h>
47
48 static void sema_unsleep(kthread_t *t);
49 static void sema_change_pri(kthread_t *t, pri_t pri, pri_t *t_prip);
50 static kthread_t *sema_owner(ksema_t *);
51
52 /*
53 * The sobj_ops vector exports a set of functions needed when a thread
54 * is asleep on a synchronization object of this type.
55 */
56 static sobj_ops_t sema_sobj_ops = {
57 SOBJ_SEMA, sema_owner, sema_unsleep, sema_change_pri
58 };
59
60 /*
61 * SEMA_BLOCK(sema_impl_t *s, disp_lock_t *lockp)
62 */
63 #define SEMA_BLOCK(s, lockp) \
64 { \
65 kthread_t *tp; \
66 kthread_t **tpp; \
67 pri_t cpri; \
68 klwp_t *lwp = ttolwp(curthread); \
69 ASSERT(THREAD_LOCK_HELD(curthread)); \
70 ASSERT(curthread != CPU->cpu_idle_thread); \
71 ASSERT(CPU_ON_INTR(CPU) == 0); \
72 ASSERT(curthread->t_wchan0 == NULL); \
73 ASSERT(curthread->t_wchan == NULL); \
74 ASSERT(curthread->t_state == TS_ONPROC); \
75 CL_SLEEP(curthread); \
76 THREAD_SLEEP(curthread, lockp); \
77 curthread->t_wchan = (caddr_t)s; \
78 curthread->t_sobj_ops = &sema_sobj_ops; \
79 DTRACE_SCHED(sleep); \
80 if (lwp != NULL) { \
81 lwp->lwp_ru.nvcsw++; \
82 (void) new_mstate(curthread, LMS_SLEEP); \
83 } \
84 cpri = DISP_PRIO(curthread); \
85 tpp = &s->s_slpq; \
86 while ((tp = *tpp) != NULL) { \
87 if (cpri > DISP_PRIO(tp)) \
88 break; \
89 tpp = &tp->t_link; \
90 } \
91 *tpp = curthread; \
92 curthread->t_link = tp; \
93 ASSERT(s->s_slpq != NULL); \
94 }
95
96 /* ARGSUSED */
97 void
98 sema_init(ksema_t *sp, unsigned count, char *name, ksema_type_t type, void *arg)
99 {
100 ((sema_impl_t *)sp)->s_count = count;
101 ((sema_impl_t *)sp)->s_slpq = NULL;
102 }
103
104 void
105 sema_destroy(ksema_t *sp)
106 {
107 ASSERT(((sema_impl_t *)sp)->s_slpq == NULL);
108 }
109
110 /*
111 * Put a thread on the sleep queue for this semaphore.
112 */
113 static void
114 sema_queue(ksema_t *sp, kthread_t *t)
115 {
116 kthread_t **tpp;
117 kthread_t *tp;
118 pri_t cpri;
119 sema_impl_t *s;
120
121 ASSERT(THREAD_LOCK_HELD(t));
122 s = (sema_impl_t *)sp;
123 tpp = &s->s_slpq;
124 cpri = DISP_PRIO(t);
125 while ((tp = *tpp) != NULL) {
126 if (cpri > DISP_PRIO(tp))
127 break;
128 tpp = &tp->t_link;
129 }
130 *tpp = t;
131 t->t_link = tp;
132 }
133
134 /*
135 * Remove a thread from the sleep queue for this
136 * semaphore.
137 */
138 static void
139 sema_dequeue(ksema_t *sp, kthread_t *t)
140 {
141 kthread_t **tpp;
142 kthread_t *tp;
143 sema_impl_t *s;
144
145 ASSERT(THREAD_LOCK_HELD(t));
146 s = (sema_impl_t *)sp;
147 tpp = &s->s_slpq;
148 while ((tp = *tpp) != NULL) {
149 if (tp == t) {
150 *tpp = t->t_link;
151 t->t_link = NULL;
152 return;
153 }
154 tpp = &tp->t_link;
155 }
156 }
157
158 /* ARGSUSED */
159 static kthread_t *
160 sema_owner(ksema_t *sp)
161 {
162 return ((kthread_t *)NULL);
163 }
164
165 /*
166 * Wakeup a thread sleeping on a semaphore, and put it
167 * on the dispatch queue.
168 * Called via SOBJ_UNSLEEP().
169 */
170 static void
171 sema_unsleep(kthread_t *t)
172 {
173 kthread_t **tpp;
174 kthread_t *tp;
175 sema_impl_t *s;
176
177 ASSERT(THREAD_LOCK_HELD(t));
178 s = (sema_impl_t *)t->t_wchan;
179 tpp = &s->s_slpq;
180 while ((tp = *tpp) != NULL) {
181 if (tp == t) {
182 *tpp = t->t_link;
183 t->t_link = NULL;
184 t->t_sobj_ops = NULL;
185 t->t_wchan = NULL;
186 t->t_wchan0 = NULL;
187 /*
188 * Change thread to transition state and
189 * drop the semaphore sleep queue lock.
190 */
191 THREAD_TRANSITION(t);
192 CL_SETRUN(t);
193 return;
194 }
195 tpp = &tp->t_link;
196 }
197 }
198
199 /*
200 * operations to perform when changing the priority
201 * of a thread asleep on a semaphore.
202 * Called via SOBJ_CHANGE_PRI() and SOBJ_CHANGE_EPRI().
203 */
204 static void
205 sema_change_pri(kthread_t *t, pri_t pri, pri_t *t_prip)
206 {
207 ksema_t *sp;
208
209 if ((sp = (ksema_t *)t->t_wchan) != NULL) {
210 sema_dequeue(sp, t);
211 *t_prip = pri;
212 sema_queue(sp, t);
213 } else
214 panic("sema_change_pri: %p not on sleep queue", (void *)t);
215 }
216
217 /*
218 * the semaphore is granted when the semaphore's
219 * count is greater than zero and blocks when equal
220 * to zero.
221 */
222 void
223 sema_p(ksema_t *sp)
224 {
225 sema_impl_t *s;
226 disp_lock_t *sqlp;
227
228 s = (sema_impl_t *)sp;
229 sqlp = &SQHASH(s)->sq_lock;
230 disp_lock_enter(sqlp);
231 ASSERT(s->s_count >= 0);
232 if (panicstr) {
233 disp_lock_exit(sqlp);
234 return;
235 }
236 while (s->s_count == 0) {
237 thread_lock_high(curthread);
238 SEMA_BLOCK(s, sqlp);
239 thread_unlock_nopreempt(curthread);
240 swtch();
241 disp_lock_enter(sqlp);
242 }
243 s->s_count--;
244 disp_lock_exit(sqlp);
245 }
246
247 /*
248 * similiar to sema_p except that it blocks at an interruptible
249 * priority. if a signal is present then return 1 otherwise 0.
250 */
251 int
252 sema_p_sig(ksema_t *sp)
253 {
254 kthread_t *t = curthread;
255 klwp_t *lwp = ttolwp(t);
256 int cancel_pending;
257 int cancelled = 0;
258 sema_impl_t *s;
259 disp_lock_t *sqlp;
260
261 if (lwp == NULL) {
262 sema_p(sp);
263 return (0);
264 }
265
266 cancel_pending = schedctl_cancel_pending();
267 s = (sema_impl_t *)sp;
268 sqlp = &SQHASH(s)->sq_lock;
269 disp_lock_enter(sqlp);
270 ASSERT(s->s_count >= 0);
271 while (s->s_count == 0) {
272 proc_t *p = ttoproc(t);
273 thread_lock_high(t);
274 t->t_flag |= T_WAKEABLE;
275 SEMA_BLOCK(s, sqlp);
276 lwp->lwp_asleep = 1;
277 lwp->lwp_sysabort = 0;
278 thread_unlock_nopreempt(t);
279 if (ISSIG(t, JUSTLOOKING) || MUSTRETURN(p, t) || cancel_pending)
280 setrun(t);
281 swtch();
282 t->t_flag &= ~T_WAKEABLE;
283 if (ISSIG(t, FORREAL) || lwp->lwp_sysabort ||
284 MUSTRETURN(p, t) || (cancelled = cancel_pending) != 0) {
285 kthread_t *sq, *tp;
286 lwp->lwp_asleep = 0;
287 lwp->lwp_sysabort = 0;
288 disp_lock_enter(sqlp);
289 sq = s->s_slpq;
290 /*
291 * in case sema_v and interrupt happen
292 * at the same time, we need to pass the
293 * sema_v to the next thread.
294 */
295 if ((sq != NULL) && (s->s_count > 0)) {
296 tp = sq;
297 ASSERT(THREAD_LOCK_HELD(tp));
298 sq = sq->t_link;
299 tp->t_link = NULL;
300 DTRACE_SCHED1(wakeup, kthread_t *, tp);
301 tp->t_sobj_ops = NULL;
302 tp->t_wchan = NULL;
303 ASSERT(tp->t_state == TS_SLEEP);
304 CL_WAKEUP(tp);
305 s->s_slpq = sq;
306 disp_lock_exit_high(sqlp);
307 thread_unlock(tp);
308 } else {
309 disp_lock_exit(sqlp);
310 }
311 if (cancelled)
312 schedctl_cancel_eintr();
313 return (1);
314 }
315 lwp->lwp_asleep = 0;
316 disp_lock_enter(sqlp);
317 }
318 s->s_count--;
319 disp_lock_exit(sqlp);
320 return (0);
321 }
322
323 /*
324 * the semaphore's count is incremented by one. a blocked thread
325 * is awakened and re-tries to acquire the semaphore.
326 */
327 void
328 sema_v(ksema_t *sp)
329 {
330 sema_impl_t *s;
331 kthread_t *sq, *tp;
332 disp_lock_t *sqlp;
333
334 s = (sema_impl_t *)sp;
335 sqlp = &SQHASH(s)->sq_lock;
336 disp_lock_enter(sqlp);
337 if (panicstr) {
338 disp_lock_exit(sqlp);
339 return;
340 }
341 s->s_count++;
342 sq = s->s_slpq;
343 if (sq != NULL) {
344 tp = sq;
345 ASSERT(THREAD_LOCK_HELD(tp));
346 sq = sq->t_link;
347 tp->t_link = NULL;
348 DTRACE_SCHED1(wakeup, kthread_t *, tp);
349 tp->t_sobj_ops = NULL;
350 tp->t_wchan = NULL;
351 ASSERT(tp->t_state == TS_SLEEP);
352 CL_WAKEUP(tp);
353 s->s_slpq = sq;
354 disp_lock_exit_high(sqlp);
355 thread_unlock(tp);
356 } else {
357 disp_lock_exit(sqlp);
358 }
359 }
360
361 /*
362 * try to acquire the semaphore. if the semaphore is greater than
363 * zero, then the semaphore is granted and returns 1. otherwise
364 * return 0.
365 */
366 int
367 sema_tryp(ksema_t *sp)
368 {
369 sema_impl_t *s;
370 sleepq_head_t *sqh;
371
372 int gotit = 0;
373
374 s = (sema_impl_t *)sp;
375 sqh = SQHASH(s);
376 disp_lock_enter(&sqh->sq_lock);
377 if (panicstr) {
378 disp_lock_exit(sqlp);
379 return (1);
380 }
381 if (s->s_count > 0) {
382 s->s_count--;
383 gotit = 1;
384 }
385 disp_lock_exit(&sqh->sq_lock);
386 return (gotit);
387 }
388
389 int
390 sema_held(ksema_t *sp)
391 {
392 sema_impl_t *s;
393
394
395 s = (sema_impl_t *)sp;
396 if (panicstr)
397 return (1);
398 else
399 return (s->s_count <= 0);
400 }