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 * Copyright 2018 Nexenta Systems, Inc. All rights reserved.
29 */
30
31 /*
32 * This file contains the semaphore operations.
33 */
34
35 #include <sys/param.h>
36 #include <sys/types.h>
37 #include <sys/systm.h>
38 #include <sys/schedctl.h>
39 #include <sys/semaphore.h>
40 #include <sys/sema_impl.h>
41 #include <sys/t_lock.h>
42 #include <sys/thread.h>
43 #include <sys/proc.h>
44 #include <sys/cmn_err.h>
45 #include <sys/debug.h>
46 #include <sys/disp.h>
47 #include <sys/sobject.h>
48 #include <sys/cpuvar.h>
49 #include <sys/sleepq.h>
50 #include <sys/sdt.h>
51
52 static void sema_unsleep(kthread_t *t);
53 static void sema_change_pri(kthread_t *t, pri_t pri, pri_t *t_prip);
54 static kthread_t *sema_owner(ksema_t *);
55
56 /*
57 * The sobj_ops vector exports a set of functions needed when a thread
58 * is asleep on a synchronization object of this type.
59 */
60 static sobj_ops_t sema_sobj_ops = {
61 SOBJ_SEMA, sema_owner, sema_unsleep, sema_change_pri
62 };
63
64 /*
65 * SEMA_BLOCK(sema_impl_t *s, disp_lock_t *lockp)
66 */
67 #define SEMA_BLOCK(s, lockp) \
68 { \
69 kthread_t *tp; \
70 kthread_t **tpp; \
71 pri_t cpri; \
72 klwp_t *lwp = ttolwp(curthread); \
73 ASSERT(THREAD_LOCK_HELD(curthread)); \
74 ASSERT(curthread != CPU->cpu_idle_thread); \
75 ASSERT(CPU_ON_INTR(CPU) == 0); \
76 ASSERT(curthread->t_wchan0 == NULL); \
77 ASSERT(curthread->t_wchan == NULL); \
78 ASSERT(curthread->t_state == TS_ONPROC); \
79 CL_SLEEP(curthread); \
80 THREAD_SLEEP(curthread, lockp); \
81 curthread->t_wchan = (caddr_t)s; \
82 curthread->t_sobj_ops = &sema_sobj_ops; \
83 DTRACE_SCHED(sleep); \
84 if (lwp != NULL) { \
85 lwp->lwp_ru.nvcsw++; \
86 (void) new_mstate(curthread, LMS_SLEEP); \
87 } \
88 cpri = DISP_PRIO(curthread); \
89 tpp = &s->s_slpq; \
90 while ((tp = *tpp) != NULL) { \
91 if (cpri > DISP_PRIO(tp)) \
92 break; \
93 tpp = &tp->t_link; \
94 } \
95 *tpp = curthread; \
96 curthread->t_link = tp; \
97 ASSERT(s->s_slpq != NULL); \
98 }
99
100 /* ARGSUSED */
101 void
sema_init(ksema_t * sp,unsigned count,char * name,ksema_type_t type,void * arg)102 sema_init(ksema_t *sp, unsigned count, char *name, ksema_type_t type, void *arg)
103 {
104 ((sema_impl_t *)sp)->s_count = count;
105 ((sema_impl_t *)sp)->s_slpq = NULL;
106 }
107
108 void
sema_destroy(ksema_t * sp)109 sema_destroy(ksema_t *sp)
110 {
111 ASSERT(((sema_impl_t *)sp)->s_slpq == NULL);
112 }
113
114 /*
115 * Put a thread on the sleep queue for this semaphore.
116 */
117 static void
sema_queue(ksema_t * sp,kthread_t * t)118 sema_queue(ksema_t *sp, kthread_t *t)
119 {
120 kthread_t **tpp;
121 kthread_t *tp;
122 pri_t cpri;
123 sema_impl_t *s;
124
125 ASSERT(THREAD_LOCK_HELD(t));
126 s = (sema_impl_t *)sp;
127 tpp = &s->s_slpq;
128 cpri = DISP_PRIO(t);
129 while ((tp = *tpp) != NULL) {
130 if (cpri > DISP_PRIO(tp))
131 break;
132 tpp = &tp->t_link;
133 }
134 *tpp = t;
135 t->t_link = tp;
136 }
137
138 /*
139 * Remove a thread from the sleep queue for this
140 * semaphore.
141 */
142 static void
sema_dequeue(ksema_t * sp,kthread_t * t)143 sema_dequeue(ksema_t *sp, kthread_t *t)
144 {
145 kthread_t **tpp;
146 kthread_t *tp;
147 sema_impl_t *s;
148
149 ASSERT(THREAD_LOCK_HELD(t));
150 s = (sema_impl_t *)sp;
151 tpp = &s->s_slpq;
152 while ((tp = *tpp) != NULL) {
153 if (tp == t) {
154 *tpp = t->t_link;
155 t->t_link = NULL;
156 return;
157 }
158 tpp = &tp->t_link;
159 }
160 }
161
162 /* ARGSUSED */
163 static kthread_t *
sema_owner(ksema_t * sp)164 sema_owner(ksema_t *sp)
165 {
166 return ((kthread_t *)NULL);
167 }
168
169 /*
170 * Wakeup a thread sleeping on a semaphore, and put it
171 * on the dispatch queue.
172 * Called via SOBJ_UNSLEEP().
173 */
174 static void
sema_unsleep(kthread_t * t)175 sema_unsleep(kthread_t *t)
176 {
177 kthread_t **tpp;
178 kthread_t *tp;
179 sema_impl_t *s;
180
181 ASSERT(THREAD_LOCK_HELD(t));
182 s = (sema_impl_t *)t->t_wchan;
183 tpp = &s->s_slpq;
184 while ((tp = *tpp) != NULL) {
185 if (tp == t) {
186 *tpp = t->t_link;
187 t->t_link = NULL;
188 t->t_sobj_ops = NULL;
189 t->t_wchan = NULL;
190 t->t_wchan0 = NULL;
191 /*
192 * Change thread to transition state and
193 * drop the semaphore sleep queue lock.
194 */
195 THREAD_TRANSITION(t);
196 CL_SETRUN(t);
197 return;
198 }
199 tpp = &tp->t_link;
200 }
201 }
202
203 /*
204 * operations to perform when changing the priority
205 * of a thread asleep on a semaphore.
206 * Called via SOBJ_CHANGE_PRI() and SOBJ_CHANGE_EPRI().
207 */
208 static void
sema_change_pri(kthread_t * t,pri_t pri,pri_t * t_prip)209 sema_change_pri(kthread_t *t, pri_t pri, pri_t *t_prip)
210 {
211 ksema_t *sp;
212
213 if ((sp = (ksema_t *)t->t_wchan) != NULL) {
214 sema_dequeue(sp, t);
215 *t_prip = pri;
216 sema_queue(sp, t);
217 } else
218 panic("sema_change_pri: %p not on sleep queue", (void *)t);
219 }
220
221 /*
222 * the semaphore is granted when the semaphore's
223 * count is greater than zero and blocks when equal
224 * to zero.
225 */
226 void
sema_p(ksema_t * sp)227 sema_p(ksema_t *sp)
228 {
229 sema_impl_t *s;
230 disp_lock_t *sqlp;
231
232 /* no-op during panic */
233 if (panicstr)
234 return;
235
236 s = (sema_impl_t *)sp;
237 sqlp = &SQHASH(s)->sq_lock;
238 disp_lock_enter(sqlp);
239 ASSERT(s->s_count >= 0);
240 while (s->s_count == 0) {
241 thread_lock_high(curthread);
242 SEMA_BLOCK(s, sqlp);
243 thread_unlock_nopreempt(curthread);
244 swtch();
245 disp_lock_enter(sqlp);
246 }
247 s->s_count--;
248 disp_lock_exit(sqlp);
249 }
250
251 /*
252 * similiar to sema_p except that it blocks at an interruptible
253 * priority. if a signal is present then return 1 otherwise 0.
254 */
255 int
sema_p_sig(ksema_t * sp)256 sema_p_sig(ksema_t *sp)
257 {
258 kthread_t *t = curthread;
259 klwp_t *lwp = ttolwp(t);
260 int cancel_pending;
261 int cancelled = 0;
262 sema_impl_t *s;
263 disp_lock_t *sqlp;
264
265 if (lwp == NULL) {
266 sema_p(sp);
267 return (0);
268 }
269
270 cancel_pending = schedctl_cancel_pending();
271 s = (sema_impl_t *)sp;
272 sqlp = &SQHASH(s)->sq_lock;
273 disp_lock_enter(sqlp);
274 ASSERT(s->s_count >= 0);
275 while (s->s_count == 0) {
276 proc_t *p = ttoproc(t);
277 thread_lock_high(t);
278 t->t_flag |= T_WAKEABLE;
279 SEMA_BLOCK(s, sqlp);
280 lwp->lwp_asleep = 1;
281 lwp->lwp_sysabort = 0;
282 thread_unlock_nopreempt(t);
283 if (ISSIG(t, JUSTLOOKING) || MUSTRETURN(p, t) || cancel_pending)
284 setrun(t);
285 swtch();
286 t->t_flag &= ~T_WAKEABLE;
287 if (ISSIG(t, FORREAL) || lwp->lwp_sysabort ||
288 MUSTRETURN(p, t) || (cancelled = cancel_pending) != 0) {
289 kthread_t *sq, *tp;
290 lwp->lwp_asleep = 0;
291 lwp->lwp_sysabort = 0;
292 disp_lock_enter(sqlp);
293 sq = s->s_slpq;
294 /*
295 * in case sema_v and interrupt happen
296 * at the same time, we need to pass the
297 * sema_v to the next thread.
298 */
299 if ((sq != NULL) && (s->s_count > 0)) {
300 tp = sq;
301 ASSERT(THREAD_LOCK_HELD(tp));
302 sq = sq->t_link;
303 tp->t_link = NULL;
304 DTRACE_SCHED1(wakeup, kthread_t *, tp);
305 tp->t_sobj_ops = NULL;
306 tp->t_wchan = NULL;
307 ASSERT(tp->t_state == TS_SLEEP);
308 CL_WAKEUP(tp);
309 s->s_slpq = sq;
310 disp_lock_exit_high(sqlp);
311 thread_unlock(tp);
312 } else {
313 disp_lock_exit(sqlp);
314 }
315 if (cancelled)
316 schedctl_cancel_eintr();
317 return (1);
318 }
319 lwp->lwp_asleep = 0;
320 disp_lock_enter(sqlp);
321 }
322 s->s_count--;
323 disp_lock_exit(sqlp);
324 return (0);
325 }
326
327 /*
328 * the semaphore's count is incremented by one. a blocked thread
329 * is awakened and re-tries to acquire the semaphore.
330 */
331 void
sema_v(ksema_t * sp)332 sema_v(ksema_t *sp)
333 {
334 sema_impl_t *s;
335 kthread_t *sq, *tp;
336 disp_lock_t *sqlp;
337
338 /* no-op during panic */
339 if (panicstr)
340 return;
341
342 s = (sema_impl_t *)sp;
343 sqlp = &SQHASH(s)->sq_lock;
344 disp_lock_enter(sqlp);
345 s->s_count++;
346 sq = s->s_slpq;
347 if (sq != NULL) {
348 tp = sq;
349 ASSERT(THREAD_LOCK_HELD(tp));
350 sq = sq->t_link;
351 tp->t_link = NULL;
352 DTRACE_SCHED1(wakeup, kthread_t *, tp);
353 tp->t_sobj_ops = NULL;
354 tp->t_wchan = NULL;
355 ASSERT(tp->t_state == TS_SLEEP);
356 CL_WAKEUP(tp);
357 s->s_slpq = sq;
358 disp_lock_exit_high(sqlp);
359 thread_unlock(tp);
360 } else {
361 disp_lock_exit(sqlp);
362 }
363 }
364
365 /*
366 * try to acquire the semaphore. if the semaphore is greater than
367 * zero, then the semaphore is granted and returns 1. otherwise
368 * return 0.
369 */
370 int
sema_tryp(ksema_t * sp)371 sema_tryp(ksema_t *sp)
372 {
373 sema_impl_t *s;
374 sleepq_head_t *sqh;
375
376 int gotit = 0;
377
378 /* no-op during panic */
379 if (panicstr)
380 return (1);
381
382 s = (sema_impl_t *)sp;
383 sqh = SQHASH(s);
384 disp_lock_enter(&sqh->sq_lock);
385 if (s->s_count > 0) {
386 s->s_count--;
387 gotit = 1;
388 }
389 disp_lock_exit(&sqh->sq_lock);
390 return (gotit);
391 }
392
393 int
sema_held(ksema_t * sp)394 sema_held(ksema_t *sp)
395 {
396 sema_impl_t *s;
397
398 /* no-op during panic */
399 if (panicstr)
400 return (1);
401
402 s = (sema_impl_t *)sp;
403 return (s->s_count <= 0);
404 }
405