kernel/os/semaphore.c

   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
 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
 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
 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
 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 *
 164 sema_owner(ksema_t *sp)
 165 {
 166         return (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
 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
 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
 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
 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
 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
 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
 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 }