The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_taskqueue.c

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    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/lock.h>
   37 #include <sys/malloc.h>
   38 #include <sys/mutex.h>
   39 #include <sys/proc.h>
   40 #include <sys/sched.h>
   41 #include <sys/taskqueue.h>
   42 #include <sys/unistd.h>
   43 #include <machine/stdarg.h>
   44 
   45 static MALLOC_DEFINE(M_TASKQUEUE, "taskqueue", "Task Queues");
   46 static void     *taskqueue_giant_ih;
   47 static void     *taskqueue_ih;
   48 static STAILQ_HEAD(taskqueue_list, taskqueue) taskqueue_queues;
   49 static struct mtx taskqueue_queues_mutex;
   50 
   51 struct taskqueue {
   52         STAILQ_ENTRY(taskqueue) tq_link;
   53         STAILQ_HEAD(, task)     tq_queue;
   54         const char              *tq_name;
   55         taskqueue_enqueue_fn    tq_enqueue;
   56         void                    *tq_context;
   57         struct task             *tq_running;
   58         struct mtx              tq_mutex;
   59         struct proc             **tq_pproc;
   60         int                     tq_pcount;
   61         int                     tq_spin;
   62         int                     tq_flags;
   63 };
   64 
   65 #define TQ_FLAGS_ACTIVE         (1 << 0)
   66 
   67 static __inline void
   68 TQ_LOCK(struct taskqueue *tq)
   69 {
   70         if (tq->tq_spin)
   71                 mtx_lock_spin(&tq->tq_mutex);
   72         else
   73                 mtx_lock(&tq->tq_mutex);
   74 }
   75 
   76 static __inline void
   77 TQ_UNLOCK(struct taskqueue *tq)
   78 {
   79         if (tq->tq_spin)
   80                 mtx_unlock_spin(&tq->tq_mutex);
   81         else
   82                 mtx_unlock(&tq->tq_mutex);
   83 }
   84 
   85 static void     init_taskqueue_list(void *data);
   86 
   87 static __inline int
   88 TQ_SLEEP(struct taskqueue *tq, void *p, struct mtx *m, int pri, const char *wm,
   89     int t)
   90 {
   91         if (tq->tq_spin)
   92                 return (msleep_spin(p, m, wm, t));
   93         return (msleep(p, m, pri, wm, t));
   94 }
   95 
   96 static void
   97 init_taskqueue_list(void *data __unused)
   98 {
   99 
  100         mtx_init(&taskqueue_queues_mutex, "taskqueue list", NULL, MTX_DEF);
  101         STAILQ_INIT(&taskqueue_queues);
  102 }
  103 SYSINIT(taskqueue_list, SI_SUB_INTRINSIC, SI_ORDER_ANY, init_taskqueue_list,
  104     NULL);
  105 
  106 static struct taskqueue *
  107 _taskqueue_create(const char *name, int mflags,
  108                  taskqueue_enqueue_fn enqueue, void *context,
  109                  int mtxflags, const char *mtxname)
  110 {
  111         struct taskqueue *queue;
  112 
  113         queue = malloc(sizeof(struct taskqueue), M_TASKQUEUE, mflags | M_ZERO);
  114         if (!queue)
  115                 return 0;
  116 
  117         STAILQ_INIT(&queue->tq_queue);
  118         queue->tq_name = name;
  119         queue->tq_enqueue = enqueue;
  120         queue->tq_context = context;
  121         queue->tq_spin = (mtxflags & MTX_SPIN) != 0;
  122         queue->tq_flags |= TQ_FLAGS_ACTIVE;
  123         mtx_init(&queue->tq_mutex, mtxname, NULL, mtxflags);
  124 
  125         mtx_lock(&taskqueue_queues_mutex);
  126         STAILQ_INSERT_TAIL(&taskqueue_queues, queue, tq_link);
  127         mtx_unlock(&taskqueue_queues_mutex);
  128 
  129         return queue;
  130 }
  131 
  132 struct taskqueue *
  133 taskqueue_create(const char *name, int mflags,
  134                  taskqueue_enqueue_fn enqueue, void *context,
  135                  struct proc **pp)
  136 {
  137         (void) pp;
  138         return _taskqueue_create(name, mflags, enqueue, context,
  139                         MTX_DEF, "taskqueue");
  140 }
  141 
  142 /*
  143  * Signal a taskqueue thread to terminate.
  144  */
  145 static void
  146 taskqueue_terminate(struct proc **pp, struct taskqueue *tq)
  147 {
  148 
  149         while (tq->tq_pcount > 0) {
  150                 wakeup(tq);
  151                 TQ_SLEEP(tq, pp, &tq->tq_mutex, PWAIT, "taskqueue_destroy", 0);
  152         }
  153 }
  154 
  155 void
  156 taskqueue_free(struct taskqueue *queue)
  157 {
  158 
  159         mtx_lock(&taskqueue_queues_mutex);
  160         STAILQ_REMOVE(&taskqueue_queues, queue, taskqueue, tq_link);
  161         mtx_unlock(&taskqueue_queues_mutex);
  162 
  163         TQ_LOCK(queue);
  164         queue->tq_flags &= ~TQ_FLAGS_ACTIVE;
  165         taskqueue_run(queue);
  166         taskqueue_terminate(queue->tq_pproc, queue);
  167         mtx_destroy(&queue->tq_mutex);
  168         free(queue->tq_pproc, M_TASKQUEUE);
  169         free(queue, M_TASKQUEUE);
  170 }
  171 
  172 /*
  173  * Returns with the taskqueue locked.
  174  */
  175 struct taskqueue *
  176 taskqueue_find(const char *name)
  177 {
  178         struct taskqueue *queue;
  179 
  180         mtx_lock(&taskqueue_queues_mutex);
  181         STAILQ_FOREACH(queue, &taskqueue_queues, tq_link) {
  182                 if (strcmp(queue->tq_name, name) == 0) {
  183                         TQ_LOCK(queue);
  184                         mtx_unlock(&taskqueue_queues_mutex);
  185                         return queue;
  186                 }
  187         }
  188         mtx_unlock(&taskqueue_queues_mutex);
  189         return NULL;
  190 }
  191 
  192 int
  193 taskqueue_enqueue(struct taskqueue *queue, struct task *task)
  194 {
  195         struct task *ins;
  196         struct task *prev;
  197 
  198         TQ_LOCK(queue);
  199 
  200         /*
  201          * Count multiple enqueues.
  202          */
  203         if (task->ta_pending) {
  204                 task->ta_pending++;
  205                 TQ_UNLOCK(queue);
  206                 return 0;
  207         }
  208 
  209         /*
  210          * Optimise the case when all tasks have the same priority.
  211          */
  212         prev = STAILQ_LAST(&queue->tq_queue, task, ta_link);
  213         if (!prev || prev->ta_priority >= task->ta_priority) {
  214                 STAILQ_INSERT_TAIL(&queue->tq_queue, task, ta_link);
  215         } else {
  216                 prev = 0;
  217                 for (ins = STAILQ_FIRST(&queue->tq_queue); ins;
  218                      prev = ins, ins = STAILQ_NEXT(ins, ta_link))
  219                         if (ins->ta_priority < task->ta_priority)
  220                                 break;
  221 
  222                 if (prev)
  223                         STAILQ_INSERT_AFTER(&queue->tq_queue, prev, task, ta_link);
  224                 else
  225                         STAILQ_INSERT_HEAD(&queue->tq_queue, task, ta_link);
  226         }
  227 
  228         task->ta_pending = 1;
  229         queue->tq_enqueue(queue->tq_context);
  230 
  231         TQ_UNLOCK(queue);
  232 
  233         return 0;
  234 }
  235 
  236 void
  237 taskqueue_run(struct taskqueue *queue)
  238 {
  239         struct task *task;
  240         int owned, pending;
  241 
  242         owned = mtx_owned(&queue->tq_mutex);
  243         if (!owned)
  244                 TQ_LOCK(queue);
  245         while (STAILQ_FIRST(&queue->tq_queue)) {
  246                 /*
  247                  * Carefully remove the first task from the queue and
  248                  * zero its pending count.
  249                  */
  250                 task = STAILQ_FIRST(&queue->tq_queue);
  251                 STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
  252                 pending = task->ta_pending;
  253                 task->ta_pending = 0;
  254                 queue->tq_running = task;
  255                 TQ_UNLOCK(queue);
  256 
  257                 task->ta_func(task->ta_context, pending);
  258 
  259                 TQ_LOCK(queue);
  260                 queue->tq_running = NULL;
  261                 wakeup(task);
  262         }
  263 
  264         /*
  265          * For compatibility, unlock on return if the queue was not locked
  266          * on entry, although this opens a race window.
  267          */
  268         if (!owned)
  269                 TQ_UNLOCK(queue);
  270 }
  271 
  272 void
  273 taskqueue_drain(struct taskqueue *queue, struct task *task)
  274 {
  275         if (queue->tq_spin) {           /* XXX */
  276                 mtx_lock_spin(&queue->tq_mutex);
  277                 while (task->ta_pending != 0 || task == queue->tq_running)
  278                         msleep_spin(task, &queue->tq_mutex, "-", 0);
  279                 mtx_unlock_spin(&queue->tq_mutex);
  280         } else {
  281                 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, __func__);
  282 
  283                 mtx_lock(&queue->tq_mutex);
  284                 while (task->ta_pending != 0 || task == queue->tq_running)
  285                         msleep(task, &queue->tq_mutex, PWAIT, "-", 0);
  286                 mtx_unlock(&queue->tq_mutex);
  287         }
  288 }
  289 
  290 static void
  291 taskqueue_swi_enqueue(void *context)
  292 {
  293         swi_sched(taskqueue_ih, 0);
  294 }
  295 
  296 static void
  297 taskqueue_swi_run(void *dummy)
  298 {
  299         taskqueue_run(taskqueue_swi);
  300 }
  301 
  302 static void
  303 taskqueue_swi_giant_enqueue(void *context)
  304 {
  305         swi_sched(taskqueue_giant_ih, 0);
  306 }
  307 
  308 static void
  309 taskqueue_swi_giant_run(void *dummy)
  310 {
  311         taskqueue_run(taskqueue_swi_giant);
  312 }
  313 
  314 int
  315 taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
  316                         const char *name, ...)
  317 {
  318         va_list ap;
  319         struct taskqueue *tq;
  320         struct thread *td;
  321         char ktname[MAXCOMLEN];
  322         int i, error;
  323 
  324         if (count <= 0)
  325                 return (EINVAL);
  326         tq = *tqp;
  327 
  328         va_start(ap, name);
  329         vsnprintf(ktname, MAXCOMLEN, name, ap);
  330         va_end(ap);
  331 
  332         tq->tq_pproc = malloc(sizeof(struct proc *) * count, M_TASKQUEUE,
  333             M_NOWAIT | M_ZERO);
  334         if (tq->tq_pproc == NULL) {
  335                 printf("%s: no memory for %s threads\n", __func__, ktname);
  336                 return (ENOMEM);
  337         }
  338 
  339         for (i = 0; i < count; i++) {
  340                 if (count == 1)
  341                         error = kthread_create(taskqueue_thread_loop, tqp,
  342                             &tq->tq_pproc[i], RFSTOPPED, 0, ktname);
  343                 else
  344                         error = kthread_create(taskqueue_thread_loop, tqp,
  345                             &tq->tq_pproc[i], RFSTOPPED, 0, "%s_%d", ktname, i);
  346                 if (error) {
  347                         /* should be ok to continue, taskqueue_free will dtrt */
  348                         printf("%s: kthread_create(%s): error %d",
  349                                 __func__, ktname, error);
  350                         tq->tq_pproc[i] = NULL;         /* paranoid */
  351                 } else
  352                         tq->tq_pcount++;
  353         }
  354         mtx_lock_spin(&sched_lock);
  355         for (i = 0; i < count; i++) {
  356                 if (tq->tq_pproc[i] == NULL)
  357                         continue;
  358                 td = FIRST_THREAD_IN_PROC(tq->tq_pproc[i]);
  359                 sched_prio(td, pri);
  360                 setrunqueue(td, SRQ_BORING);
  361         }
  362         mtx_unlock_spin(&sched_lock);
  363 
  364         return (0);
  365 }
  366 
  367 void
  368 taskqueue_thread_loop(void *arg)
  369 {
  370         struct taskqueue **tqp, *tq;
  371 
  372         tqp = arg;
  373         tq = *tqp;
  374         TQ_LOCK(tq);
  375         do {
  376                 taskqueue_run(tq);
  377                 TQ_SLEEP(tq, tq, &tq->tq_mutex, 0, "-", 0);
  378         } while ((tq->tq_flags & TQ_FLAGS_ACTIVE) != 0);
  379 
  380         /* rendezvous with thread that asked us to terminate */
  381         tq->tq_pcount--;
  382         wakeup_one(tq->tq_pproc);
  383         TQ_UNLOCK(tq);
  384         kthread_exit(0);
  385 }
  386 
  387 void
  388 taskqueue_thread_enqueue(void *context)
  389 {
  390         struct taskqueue **tqp, *tq;
  391 
  392         tqp = context;
  393         tq = *tqp;
  394 
  395         mtx_assert(&tq->tq_mutex, MA_OWNED);
  396         wakeup_one(tq);
  397 }
  398 
  399 TASKQUEUE_DEFINE(swi, taskqueue_swi_enqueue, 0,
  400                  swi_add(NULL, "task queue", taskqueue_swi_run, NULL, SWI_TQ,
  401                      INTR_MPSAFE, &taskqueue_ih)); 
  402 
  403 TASKQUEUE_DEFINE(swi_giant, taskqueue_swi_giant_enqueue, 0,
  404                  swi_add(NULL, "Giant taskq", taskqueue_swi_giant_run,
  405                      NULL, SWI_TQ_GIANT, 0, &taskqueue_giant_ih)); 
  406 
  407 TASKQUEUE_DEFINE_THREAD(thread);
  408 
  409 struct taskqueue *
  410 taskqueue_create_fast(const char *name, int mflags,
  411                  taskqueue_enqueue_fn enqueue, void *context)
  412 {
  413         return _taskqueue_create(name, mflags, enqueue, context,
  414                         MTX_SPIN, "fast_taskqueue");
  415 }
  416 
  417 /* NB: for backwards compatibility */
  418 int
  419 taskqueue_enqueue_fast(struct taskqueue *queue, struct task *task)
  420 {
  421         return taskqueue_enqueue(queue, task);
  422 }
  423 
  424 static void     *taskqueue_fast_ih;
  425 
  426 static void
  427 taskqueue_fast_enqueue(void *context)
  428 {
  429         swi_sched(taskqueue_fast_ih, 0);
  430 }
  431 
  432 static void
  433 taskqueue_fast_run(void *dummy)
  434 {
  435         taskqueue_run(taskqueue_fast);
  436 }
  437 
  438 TASKQUEUE_FAST_DEFINE(fast, taskqueue_fast_enqueue, 0,
  439         swi_add(NULL, "Fast task queue", taskqueue_fast_run, NULL,
  440         SWI_TQ_FAST, INTR_MPSAFE, &taskqueue_fast_ih));

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