sys/kern/subr_taskqueue.c

   1 /*-
   2  * Copyright (c) 2000 Doug Rabson
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24  * SUCH DAMAGE.
  25  */
  26
  27 #include <sys/cdefs.h>
  28 __FBSDID("$FreeBSD$");
  29
  30 #include <sys/param.h>
  31 #include <sys/systm.h>
  32 #include <sys/bus.h>
  33 #include <sys/interrupt.h>
  34 #include <sys/kernel.h>
  35 #include <sys/kthread.h>
  36 #include <sys/limits.h>
  37 #include <sys/lock.h>
  38 #include <sys/malloc.h>
  39 #include <sys/mutex.h>
  40 #include <sys/proc.h>
  41 #include <sys/sched.h>
  42 #include <sys/taskqueue.h>
  43 #include <sys/unistd.h>
  44 #include <machine/stdarg.h>
  45
  46 static MALLOC_DEFINE(M_TASKQUEUE, "taskqueue", "Task Queues");
  47 static void     *taskqueue_giant_ih;
  48 static void     *taskqueue_ih;
  49
  50 struct taskqueue_busy {
  51         struct task     *tb_running;
  52         TAILQ_ENTRY(taskqueue_busy) tb_link;
  53 };
  54
  55 struct taskqueue {
  56         STAILQ_HEAD(, task)     tq_queue;
  57         taskqueue_enqueue_fn    tq_enqueue;
  58         void                    *tq_context;
  59         TAILQ_HEAD(, taskqueue_busy) tq_active;
  60         struct mtx              tq_mutex;
  61         struct thread           **tq_threads;
  62         int                     tq_tcount;
  63         int                     tq_spin;
  64         int                     tq_flags;
  65         int                     tq_callouts;
  66         taskqueue_callback_fn   tq_callbacks[TASKQUEUE_NUM_CALLBACKS];
  67         void                    *tq_cb_contexts[TASKQUEUE_NUM_CALLBACKS];
  68 };
  69
  70 #define TQ_FLAGS_ACTIVE         (1 << 0)
  71 #define TQ_FLAGS_BLOCKED        (1 << 1)
  72 #define TQ_FLAGS_PENDING        (1 << 2)
  73
  74 #define DT_CALLOUT_ARMED        (1 << 0)
  75
  76 #define TQ_LOCK(tq)                                                     \
  77         do {                                                            \
  78                 if ((tq)->tq_spin)                                      \
  79                         mtx_lock_spin(&(tq)->tq_mutex);                 \
  80                 else                                                    \
  81                         mtx_lock(&(tq)->tq_mutex);                      \
  82         } while (0)
  83 #define TQ_ASSERT_LOCKED(tq)    mtx_assert(&(tq)->tq_mutex, MA_OWNED)
  84
  85 #define TQ_UNLOCK(tq)                                                   \
  86         do {                                                            \
  87                 if ((tq)->tq_spin)                                      \
  88                         mtx_unlock_spin(&(tq)->tq_mutex);               \
  89                 else                                                    \
  90                         mtx_unlock(&(tq)->tq_mutex);                    \
  91         } while (0)
  92 #define TQ_ASSERT_UNLOCKED(tq)  mtx_assert(&(tq)->tq_mutex, MA_NOTOWNED)
  93
  94 void
  95 _timeout_task_init(struct taskqueue *queue, struct timeout_task *timeout_task,
  96     int priority, task_fn_t func, void *context)
  97 {
  98
  99         TASK_INIT(&timeout_task->t, priority, func, context);
 100         callout_init_mtx(&timeout_task->c, &queue->tq_mutex, 0);
 101         timeout_task->q = queue;
 102         timeout_task->f = 0;
 103 }
 104
 105 static __inline int
 106 TQ_SLEEP(struct taskqueue *tq, void *p, struct mtx *m, int pri, const char *wm,
 107     int t)
 108 {
 109         if (tq->tq_spin)
 110                 return (msleep_spin(p, m, wm, t));
 111         return (msleep(p, m, pri, wm, t));
 112 }
 113
 114 static struct taskqueue *
 115 _taskqueue_create(const char *name __unused, int mflags,
 116                  taskqueue_enqueue_fn enqueue, void *context,
 117                  int mtxflags, const char *mtxname)
 118 {
 119         struct taskqueue *queue;
 120
 121         queue = malloc(sizeof(struct taskqueue), M_TASKQUEUE, mflags | M_ZERO);
 122         if (!queue)
 123                 return NULL;
 124
 125         STAILQ_INIT(&queue->tq_queue);
 126         TAILQ_INIT(&queue->tq_active);
 127         queue->tq_enqueue = enqueue;
 128         queue->tq_context = context;
 129         queue->tq_spin = (mtxflags & MTX_SPIN) != 0;
 130         queue->tq_flags |= TQ_FLAGS_ACTIVE;
 131         mtx_init(&queue->tq_mutex, mtxname, NULL, mtxflags);
 132
 133         return queue;
 134 }
 135
 136 struct taskqueue *
 137 taskqueue_create(const char *name, int mflags,
 138                  taskqueue_enqueue_fn enqueue, void *context)
 139 {
 140         return _taskqueue_create(name, mflags, enqueue, context,
 141                         MTX_DEF, "taskqueue");
 142 }
 143
 144 void
 145 taskqueue_set_callback(struct taskqueue *queue,
 146     enum taskqueue_callback_type cb_type, taskqueue_callback_fn callback,
 147     void *context)
 148 {
 149
 150         KASSERT(((cb_type >= TASKQUEUE_CALLBACK_TYPE_MIN) &&
 151             (cb_type <= TASKQUEUE_CALLBACK_TYPE_MAX)),
 152             ("Callback type %d not valid, must be %d-%d", cb_type,
 153             TASKQUEUE_CALLBACK_TYPE_MIN, TASKQUEUE_CALLBACK_TYPE_MAX));
 154         KASSERT((queue->tq_callbacks[cb_type] == NULL),
 155             ("Re-initialization of taskqueue callback?"));
 156
 157         queue->tq_callbacks[cb_type] = callback;
 158         queue->tq_cb_contexts[cb_type] = context;
 159 }
 160
 161 /*
 162  * Signal a taskqueue thread to terminate.
 163  */
 164 static void
 165 taskqueue_terminate(struct thread **pp, struct taskqueue *tq)
 166 {
 167
 168         while (tq->tq_tcount > 0 || tq->tq_callouts > 0) {
 169                 wakeup(tq);
 170                 TQ_SLEEP(tq, pp, &tq->tq_mutex, PWAIT, "taskqueue_destroy", 0);
 171         }
 172 }
 173
 174 void
 175 taskqueue_free(struct taskqueue *queue)
 176 {
 177
 178         TQ_LOCK(queue);
 179         queue->tq_flags &= ~TQ_FLAGS_ACTIVE;
 180         taskqueue_terminate(queue->tq_threads, queue);
 181         KASSERT(TAILQ_EMPTY(&queue->tq_active), ("Tasks still running?"));
 182         KASSERT(queue->tq_callouts == 0, ("Armed timeout tasks"));
 183         mtx_destroy(&queue->tq_mutex);
 184         free(queue->tq_threads, M_TASKQUEUE);
 185         free(queue, M_TASKQUEUE);
 186 }
 187
 188 static int
 189 taskqueue_enqueue_locked(struct taskqueue *queue, struct task *task)
 190 {
 191         struct task *ins;
 192         struct task *prev;
 193
 194         /*
 195          * Count multiple enqueues.
 196          */
 197         if (task->ta_pending) {
 198                 if (task->ta_pending < USHRT_MAX)
 199                         task->ta_pending++;
 200                 return (0);
 201         }
 202
 203         /*
 204          * Optimise the case when all tasks have the same priority.
 205          */
 206         prev = STAILQ_LAST(&queue->tq_queue, task, ta_link);
 207         if (!prev || prev->ta_priority >= task->ta_priority) {
 208                 STAILQ_INSERT_TAIL(&queue->tq_queue, task, ta_link);
 209         } else {
 210                 prev = NULL;
 211                 for (ins = STAILQ_FIRST(&queue->tq_queue); ins;
 212                      prev = ins, ins = STAILQ_NEXT(ins, ta_link))
 213                         if (ins->ta_priority < task->ta_priority)
 214                                 break;
 215
 216                 if (prev)
 217                         STAILQ_INSERT_AFTER(&queue->tq_queue, prev, task, ta_link);
 218                 else
 219                         STAILQ_INSERT_HEAD(&queue->tq_queue, task, ta_link);
 220         }
 221
 222         task->ta_pending = 1;
 223         if ((queue->tq_flags & TQ_FLAGS_BLOCKED) == 0)
 224                 queue->tq_enqueue(queue->tq_context);
 225         else
 226                 queue->tq_flags |= TQ_FLAGS_PENDING;
 227
 228         return (0);
 229 }
 230 int
 231 taskqueue_enqueue(struct taskqueue *queue, struct task *task)
 232 {
 233         int res;
 234
 235         TQ_LOCK(queue);
 236         res = taskqueue_enqueue_locked(queue, task);
 237         TQ_UNLOCK(queue);
 238
 239         return (res);
 240 }
 241
 242 static void
 243 taskqueue_timeout_func(void *arg)
 244 {
 245         struct taskqueue *queue;
 246         struct timeout_task *timeout_task;
 247
 248         timeout_task = arg;
 249         queue = timeout_task->q;
 250         KASSERT((timeout_task->f & DT_CALLOUT_ARMED) != 0, ("Stray timeout"));
 251         timeout_task->f &= ~DT_CALLOUT_ARMED;
 252         queue->tq_callouts--;
 253         taskqueue_enqueue_locked(timeout_task->q, &timeout_task->t);
 254 }
 255
 256 int
 257 taskqueue_enqueue_timeout(struct taskqueue *queue,
 258     struct timeout_task *timeout_task, int ticks)
 259 {
 260         int res;
 261
 262         TQ_LOCK(queue);
 263         KASSERT(timeout_task->q == NULL || timeout_task->q == queue,
 264             ("Migrated queue"));
 265         KASSERT(!queue->tq_spin, ("Timeout for spin-queue"));
 266         timeout_task->q = queue;
 267         res = timeout_task->t.ta_pending;
 268         if (ticks == 0) {
 269                 taskqueue_enqueue_locked(queue, &timeout_task->t);
 270         } else {
 271                 if ((timeout_task->f & DT_CALLOUT_ARMED) != 0) {
 272                         res++;
 273                 } else {
 274                         queue->tq_callouts++;
 275                         timeout_task->f |= DT_CALLOUT_ARMED;
 276                         if (ticks < 0)
 277                                 ticks = -ticks; /* Ignore overflow. */
 278                 }
 279                 if (ticks > 0) {
 280                         callout_reset(&timeout_task->c, ticks,
 281                             taskqueue_timeout_func, timeout_task);
 282                 }
 283         }
 284         TQ_UNLOCK(queue);
 285         return (res);
 286 }
 287
 288 void
 289 taskqueue_block(struct taskqueue *queue)
 290 {
 291
 292         TQ_LOCK(queue);
 293         queue->tq_flags |= TQ_FLAGS_BLOCKED;
 294         TQ_UNLOCK(queue);
 295 }
 296
 297 void
 298 taskqueue_unblock(struct taskqueue *queue)
 299 {
 300
 301         TQ_LOCK(queue);
 302         queue->tq_flags &= ~TQ_FLAGS_BLOCKED;
 303         if (queue->tq_flags & TQ_FLAGS_PENDING) {
 304                 queue->tq_flags &= ~TQ_FLAGS_PENDING;
 305                 queue->tq_enqueue(queue->tq_context);
 306         }
 307         TQ_UNLOCK(queue);
 308 }
 309
 310 static void
 311 taskqueue_run_locked(struct taskqueue *queue)
 312 {
 313         struct taskqueue_busy tb;
 314         struct task *task;
 315         int pending;
 316
 317         TQ_ASSERT_LOCKED(queue);
 318         tb.tb_running = NULL;
 319         TAILQ_INSERT_TAIL(&queue->tq_active, &tb, tb_link);
 320
 321         while (STAILQ_FIRST(&queue->tq_queue)) {
 322                 /*
 323                  * Carefully remove the first task from the queue and
 324                  * zero its pending count.
 325                  */
 326                 task = STAILQ_FIRST(&queue->tq_queue);
 327                 STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
 328                 pending = task->ta_pending;
 329                 task->ta_pending = 0;
 330                 tb.tb_running = task;
 331                 TQ_UNLOCK(queue);
 332
 333                 task->ta_func(task->ta_context, pending);
 334
 335                 TQ_LOCK(queue);
 336                 tb.tb_running = NULL;
 337                 wakeup(task);
 338         }
 339         TAILQ_REMOVE(&queue->tq_active, &tb, tb_link);
 340 }
 341
 342 void
 343 taskqueue_run(struct taskqueue *queue)
 344 {
 345
 346         TQ_LOCK(queue);
 347         taskqueue_run_locked(queue);
 348         TQ_UNLOCK(queue);
 349 }
 350
 351 static int
 352 task_is_running(struct taskqueue *queue, struct task *task)
 353 {
 354         struct taskqueue_busy *tb;
 355
 356         TQ_ASSERT_LOCKED(queue);
 357         TAILQ_FOREACH(tb, &queue->tq_active, tb_link) {
 358                 if (tb->tb_running == task)
 359                         return (1);
 360         }
 361         return (0);
 362 }
 363
 364 static int
 365 taskqueue_cancel_locked(struct taskqueue *queue, struct task *task,
 366     u_int *pendp)
 367 {
 368
 369         if (task->ta_pending > 0)
 370                 STAILQ_REMOVE(&queue->tq_queue, task, task, ta_link);
 371         if (pendp != NULL)
 372                 *pendp = task->ta_pending;
 373         task->ta_pending = 0;
 374         return (task_is_running(queue, task) ? EBUSY : 0);
 375 }
 376
 377 int
 378 taskqueue_cancel(struct taskqueue *queue, struct task *task, u_int *pendp)
 379 {
 380         u_int pending;
 381         int error;
 382
 383         TQ_LOCK(queue);
 384         pending = task->ta_pending;
 385         error = taskqueue_cancel_locked(queue, task, pendp);
 386         TQ_UNLOCK(queue);
 387
 388         return (error);
 389 }
 390
 391 int
 392 taskqueue_cancel_timeout(struct taskqueue *queue,
 393     struct timeout_task *timeout_task, u_int *pendp)
 394 {
 395         u_int pending, pending1;
 396         int error;
 397
 398         TQ_LOCK(queue);
 399         pending = !!callout_stop(&timeout_task->c);
 400         error = taskqueue_cancel_locked(queue, &timeout_task->t, &pending1);
 401         if ((timeout_task->f & DT_CALLOUT_ARMED) != 0) {
 402                 timeout_task->f &= ~DT_CALLOUT_ARMED;
 403                 queue->tq_callouts--;
 404         }
 405         TQ_UNLOCK(queue);
 406
 407         if (pendp != NULL)
 408                 *pendp = pending + pending1;
 409         return (error);
 410 }
 411
 412 void
 413 taskqueue_drain(struct taskqueue *queue, struct task *task)
 414 {
 415
 416         if (!queue->tq_spin)
 417                 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, __func__);
 418
 419         TQ_LOCK(queue);
 420         while (task->ta_pending != 0 || task_is_running(queue, task))
 421                 TQ_SLEEP(queue, task, &queue->tq_mutex, PWAIT, "-", 0);
 422         TQ_UNLOCK(queue);
 423 }
 424
 425 void
 426 taskqueue_drain_timeout(struct taskqueue *queue,
 427     struct timeout_task *timeout_task)
 428 {
 429
 430         callout_drain(&timeout_task->c);
 431         taskqueue_drain(queue, &timeout_task->t);
 432 }
 433
 434 static void
 435 taskqueue_swi_enqueue(void *context)
 436 {
 437         swi_sched(taskqueue_ih, 0);
 438 }
 439
 440 static void
 441 taskqueue_swi_run(void *dummy)
 442 {
 443         taskqueue_run(taskqueue_swi);
 444 }
 445
 446 static void
 447 taskqueue_swi_giant_enqueue(void *context)
 448 {
 449         swi_sched(taskqueue_giant_ih, 0);
 450 }
 451
 452 static void
 453 taskqueue_swi_giant_run(void *dummy)
 454 {
 455         taskqueue_run(taskqueue_swi_giant);
 456 }
 457
 458 int
 459 taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
 460                         const char *name, ...)
 461 {
 462         va_list ap;
 463         struct thread *td;
 464         struct taskqueue *tq;
 465         int i, error;
 466         char ktname[MAXCOMLEN + 1];
 467
 468         if (count <= 0)
 469                 return (EINVAL);
 470
 471         tq = *tqp;
 472
 473         va_start(ap, name);
 474         vsnprintf(ktname, sizeof(ktname), name, ap);
 475         va_end(ap);
 476
 477         tq->tq_threads = malloc(sizeof(struct thread *) * count, M_TASKQUEUE,
 478             M_NOWAIT | M_ZERO);
 479         if (tq->tq_threads == NULL) {
 480                 printf("%s: no memory for %s threads\n", __func__, ktname);
 481                 return (ENOMEM);
 482         }
 483
 484         for (i = 0; i < count; i++) {
 485                 if (count == 1)
 486                         error = kthread_add(taskqueue_thread_loop, tqp, NULL,
 487                             &tq->tq_threads[i], RFSTOPPED, 0, "%s", ktname);
 488                 else
 489                         error = kthread_add(taskqueue_thread_loop, tqp, NULL,
 490                             &tq->tq_threads[i], RFSTOPPED, 0,
 491                             "%s_%d", ktname, i);
 492                 if (error) {
 493                         /* should be ok to continue, taskqueue_free will dtrt */
 494                         printf("%s: kthread_add(%s): error %d", __func__,
 495                             ktname, error);
 496                         tq->tq_threads[i] = NULL;               /* paranoid */
 497                 } else
 498                         tq->tq_tcount++;
 499         }
 500         for (i = 0; i < count; i++) {
 501                 if (tq->tq_threads[i] == NULL)
 502                         continue;
 503                 td = tq->tq_threads[i];
 504                 thread_lock(td);
 505                 sched_prio(td, pri);
 506                 sched_add(td, SRQ_BORING);
 507                 thread_unlock(td);
 508         }
 509
 510         return (0);
 511 }
 512
 513 static inline void
 514 taskqueue_run_callback(struct taskqueue *tq,
 515     enum taskqueue_callback_type cb_type)
 516 {
 517         taskqueue_callback_fn tq_callback;
 518
 519         TQ_ASSERT_UNLOCKED(tq);
 520         tq_callback = tq->tq_callbacks[cb_type];
 521         if (tq_callback != NULL)
 522                 tq_callback(tq->tq_cb_contexts[cb_type]);
 523 }
 524
 525 void
 526 taskqueue_thread_loop(void *arg)
 527 {
 528         struct taskqueue **tqp, *tq;
 529
 530         tqp = arg;
 531         tq = *tqp;
 532         taskqueue_run_callback(tq, TASKQUEUE_CALLBACK_TYPE_INIT);
 533         TQ_LOCK(tq);
 534         while ((tq->tq_flags & TQ_FLAGS_ACTIVE) != 0) {
 535                 taskqueue_run_locked(tq);
 536                 /*
 537                  * Because taskqueue_run() can drop tq_mutex, we need to
 538                  * check if the TQ_FLAGS_ACTIVE flag wasn't removed in the
 539                  * meantime, which means we missed a wakeup.
 540                  */
 541                 if ((tq->tq_flags & TQ_FLAGS_ACTIVE) == 0)
 542                         break;
 543                 TQ_SLEEP(tq, tq, &tq->tq_mutex, 0, "-", 0);
 544         }
 545         taskqueue_run_locked(tq);
 546
 547         /*
 548          * This thread is on its way out, so just drop the lock temporarily
 549          * in order to call the shutdown callback.  This allows the callback
 550          * to look at the taskqueue, even just before it dies.
 551          */
 552         TQ_UNLOCK(tq);
 553         taskqueue_run_callback(tq, TASKQUEUE_CALLBACK_TYPE_SHUTDOWN);
 554         TQ_LOCK(tq);
 555
 556         /* rendezvous with thread that asked us to terminate */
 557         tq->tq_tcount--;
 558         wakeup_one(tq->tq_threads);
 559         TQ_UNLOCK(tq);
 560         kthread_exit();
 561 }
 562
 563 void
 564 taskqueue_thread_enqueue(void *context)
 565 {
 566         struct taskqueue **tqp, *tq;
 567
 568         tqp = context;
 569         tq = *tqp;
 570
 571         TQ_ASSERT_LOCKED(tq);
 572         wakeup_one(tq);
 573 }
 574
 575 TASKQUEUE_DEFINE(swi, taskqueue_swi_enqueue, NULL,
 576                  swi_add(NULL, "task queue", taskqueue_swi_run, NULL, SWI_TQ,
 577                      INTR_MPSAFE, &taskqueue_ih));
 578
 579 TASKQUEUE_DEFINE(swi_giant, taskqueue_swi_giant_enqueue, NULL,
 580                  swi_add(NULL, "Giant taskq", taskqueue_swi_giant_run,
 581                      NULL, SWI_TQ_GIANT, 0, &taskqueue_giant_ih));
 582
 583 TASKQUEUE_DEFINE_THREAD(thread);
 584
 585 struct taskqueue *
 586 taskqueue_create_fast(const char *name, int mflags,
 587                  taskqueue_enqueue_fn enqueue, void *context)
 588 {
 589         return _taskqueue_create(name, mflags, enqueue, context,
 590                         MTX_SPIN, "fast_taskqueue");
 591 }
 592
 593 /* NB: for backwards compatibility */
 594 int
 595 taskqueue_enqueue_fast(struct taskqueue *queue, struct task *task)
 596 {
 597         return taskqueue_enqueue(queue, task);
 598 }
 599
 600 static void     *taskqueue_fast_ih;
 601
 602 static void
 603 taskqueue_fast_enqueue(void *context)
 604 {
 605         swi_sched(taskqueue_fast_ih, 0);
 606 }
 607
 608 static void
 609 taskqueue_fast_run(void *dummy)
 610 {
 611         taskqueue_run(taskqueue_fast);
 612 }
 613
 614 TASKQUEUE_FAST_DEFINE(fast, taskqueue_fast_enqueue, NULL,
 615         swi_add(NULL, "fast taskq", taskqueue_fast_run, NULL,
 616         SWI_TQ_FAST, INTR_MPSAFE, &taskqueue_fast_ih));
 617
 618 int
 619 taskqueue_member(struct taskqueue *queue, struct thread *td)
 620 {
 621         int i, j, ret = 0;
 622
 623         for (i = 0, j = 0; ; i++) {
 624                 if (queue->tq_threads[i] == NULL)
 625                         continue;
 626                 if (queue->tq_threads[i] == td) {
 627                         ret = 1;
 628                         break;
 629                 }
 630                 if (++j >= queue->tq_tcount)
 631                         break;
 632         }
 633         return (ret);
 634 }