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 #define TQ_FLAGS_BLOCKED        (1 << 1)
   67 #define TQ_FLAGS_PENDING        (1 << 2)
   68 
   69 static __inline void
   70 TQ_LOCK(struct taskqueue *tq)
   71 {
   72         if (tq->tq_spin)
   73                 mtx_lock_spin(&tq->tq_mutex);
   74         else
   75                 mtx_lock(&tq->tq_mutex);
   76 }
   77 
   78 static __inline void
   79 TQ_UNLOCK(struct taskqueue *tq)
   80 {
   81         if (tq->tq_spin)
   82                 mtx_unlock_spin(&tq->tq_mutex);
   83         else
   84                 mtx_unlock(&tq->tq_mutex);
   85 }
   86 
   87 static void     init_taskqueue_list(void *data);
   88 
   89 static __inline int
   90 TQ_SLEEP(struct taskqueue *tq, void *p, struct mtx *m, int pri, const char *wm,
   91     int t)
   92 {
   93         if (tq->tq_spin)
   94                 return (msleep_spin(p, m, wm, t));
   95         return (msleep(p, m, pri, wm, t));
   96 }
   97 
   98 static void
   99 init_taskqueue_list(void *data __unused)
  100 {
  101 
  102         mtx_init(&taskqueue_queues_mutex, "taskqueue list", NULL, MTX_DEF);
  103         STAILQ_INIT(&taskqueue_queues);
  104 }
  105 SYSINIT(taskqueue_list, SI_SUB_INTRINSIC, SI_ORDER_ANY, init_taskqueue_list,
  106     NULL);
  107 
  108 static struct taskqueue *
  109 _taskqueue_create(const char *name, int mflags,
  110                  taskqueue_enqueue_fn enqueue, void *context,
  111                  int mtxflags, const char *mtxname)
  112 {
  113         struct taskqueue *queue;
  114 
  115         queue = malloc(sizeof(struct taskqueue), M_TASKQUEUE, mflags | M_ZERO);
  116         if (!queue)
  117                 return 0;
  118 
  119         STAILQ_INIT(&queue->tq_queue);
  120         queue->tq_name = name;
  121         queue->tq_enqueue = enqueue;
  122         queue->tq_context = context;
  123         queue->tq_spin = (mtxflags & MTX_SPIN) != 0;
  124         queue->tq_flags |= TQ_FLAGS_ACTIVE;
  125         mtx_init(&queue->tq_mutex, mtxname, NULL, mtxflags);
  126 
  127         mtx_lock(&taskqueue_queues_mutex);
  128         STAILQ_INSERT_TAIL(&taskqueue_queues, queue, tq_link);
  129         mtx_unlock(&taskqueue_queues_mutex);
  130 
  131         return queue;
  132 }
  133 
  134 struct taskqueue *
  135 taskqueue_create(const char *name, int mflags,
  136                  taskqueue_enqueue_fn enqueue, void *context)
  137 {
  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         if ((queue->tq_flags & TQ_FLAGS_BLOCKED) == 0)
  230                 queue->tq_enqueue(queue->tq_context);
  231         else
  232                 queue->tq_flags |= TQ_FLAGS_PENDING;
  233 
  234         TQ_UNLOCK(queue);
  235 
  236         return 0;
  237 }
  238 
  239 void
  240 taskqueue_block(struct taskqueue *queue)
  241 {
  242 
  243         TQ_LOCK(queue);
  244         queue->tq_flags |= TQ_FLAGS_BLOCKED;
  245         TQ_UNLOCK(queue);
  246 }
  247 
  248 void
  249 taskqueue_unblock(struct taskqueue *queue)
  250 {
  251 
  252         TQ_LOCK(queue);
  253         queue->tq_flags &= ~TQ_FLAGS_BLOCKED;
  254         if (queue->tq_flags & TQ_FLAGS_PENDING) {
  255                 queue->tq_flags &= ~TQ_FLAGS_PENDING;
  256                 queue->tq_enqueue(queue->tq_context);
  257         }
  258         TQ_UNLOCK(queue);
  259 }
  260 
  261 void
  262 taskqueue_run(struct taskqueue *queue)
  263 {
  264         struct task *task;
  265         int owned, pending;
  266 
  267         owned = mtx_owned(&queue->tq_mutex);
  268         if (!owned)
  269                 TQ_LOCK(queue);
  270         while (STAILQ_FIRST(&queue->tq_queue)) {
  271                 /*
  272                  * Carefully remove the first task from the queue and
  273                  * zero its pending count.
  274                  */
  275                 task = STAILQ_FIRST(&queue->tq_queue);
  276                 STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
  277                 pending = task->ta_pending;
  278                 task->ta_pending = 0;
  279                 queue->tq_running = task;
  280                 TQ_UNLOCK(queue);
  281 
  282                 task->ta_func(task->ta_context, pending);
  283 
  284                 TQ_LOCK(queue);
  285                 queue->tq_running = NULL;
  286                 wakeup(task);
  287         }
  288 
  289         /*
  290          * For compatibility, unlock on return if the queue was not locked
  291          * on entry, although this opens a race window.
  292          */
  293         if (!owned)
  294                 TQ_UNLOCK(queue);
  295 }
  296 
  297 void
  298 taskqueue_drain(struct taskqueue *queue, struct task *task)
  299 {
  300         if (queue->tq_spin) {           /* XXX */
  301                 mtx_lock_spin(&queue->tq_mutex);
  302                 while (task->ta_pending != 0 || task == queue->tq_running)
  303                         msleep_spin(task, &queue->tq_mutex, "-", 0);
  304                 mtx_unlock_spin(&queue->tq_mutex);
  305         } else {
  306                 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, __func__);
  307 
  308                 mtx_lock(&queue->tq_mutex);
  309                 while (task->ta_pending != 0 || task == queue->tq_running)
  310                         msleep(task, &queue->tq_mutex, PWAIT, "-", 0);
  311                 mtx_unlock(&queue->tq_mutex);
  312         }
  313 }
  314 
  315 static void
  316 taskqueue_swi_enqueue(void *context)
  317 {
  318         swi_sched(taskqueue_ih, 0);
  319 }
  320 
  321 static void
  322 taskqueue_swi_run(void *dummy)
  323 {
  324         taskqueue_run(taskqueue_swi);
  325 }
  326 
  327 static void
  328 taskqueue_swi_giant_enqueue(void *context)
  329 {
  330         swi_sched(taskqueue_giant_ih, 0);
  331 }
  332 
  333 static void
  334 taskqueue_swi_giant_run(void *dummy)
  335 {
  336         taskqueue_run(taskqueue_swi_giant);
  337 }
  338 
  339 int
  340 taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
  341                         const char *name, ...)
  342 {
  343         va_list ap;
  344         struct taskqueue *tq;
  345         struct thread *td;
  346         char ktname[MAXCOMLEN];
  347         int i, error;
  348 
  349         if (count <= 0)
  350                 return (EINVAL);
  351         tq = *tqp;
  352 
  353         va_start(ap, name);
  354         vsnprintf(ktname, MAXCOMLEN, name, ap);
  355         va_end(ap);
  356 
  357         tq->tq_pproc = malloc(sizeof(struct proc *) * count, M_TASKQUEUE,
  358             M_NOWAIT | M_ZERO);
  359         if (tq->tq_pproc == NULL) {
  360                 printf("%s: no memory for %s threads\n", __func__, ktname);
  361                 return (ENOMEM);
  362         }
  363 
  364         for (i = 0; i < count; i++) {
  365                 if (count == 1)
  366                         error = kthread_create(taskqueue_thread_loop, tqp,
  367                             &tq->tq_pproc[i], RFSTOPPED, 0, ktname);
  368                 else
  369                         error = kthread_create(taskqueue_thread_loop, tqp,
  370                             &tq->tq_pproc[i], RFSTOPPED, 0, "%s_%d", ktname, i);
  371                 if (error) {
  372                         /* should be ok to continue, taskqueue_free will dtrt */
  373                         printf("%s: kthread_create(%s): error %d",
  374                                 __func__, ktname, error);
  375                         tq->tq_pproc[i] = NULL;         /* paranoid */
  376                 } else
  377                         tq->tq_pcount++;
  378         }
  379         for (i = 0; i < count; i++) {
  380                 if (tq->tq_pproc[i] == NULL)
  381                         continue;
  382                 td = FIRST_THREAD_IN_PROC(tq->tq_pproc[i]);
  383                 thread_lock(td);
  384                 sched_prio(td, pri);
  385                 sched_add(td, SRQ_BORING);
  386                 thread_unlock(td);
  387         }
  388 
  389         return (0);
  390 }
  391 
  392 void
  393 taskqueue_thread_loop(void *arg)
  394 {
  395         struct taskqueue **tqp, *tq;
  396 
  397         tqp = arg;
  398         tq = *tqp;
  399         TQ_LOCK(tq);
  400         while ((tq->tq_flags & TQ_FLAGS_ACTIVE) != 0) {
  401                 taskqueue_run(tq);
  402                 TQ_SLEEP(tq, tq, &tq->tq_mutex, 0, "-", 0);
  403         }
  404 
  405         /* rendezvous with thread that asked us to terminate */
  406         tq->tq_pcount--;
  407         wakeup_one(tq->tq_pproc);
  408         TQ_UNLOCK(tq);
  409         kthread_exit(0);
  410 }
  411 
  412 void
  413 taskqueue_thread_enqueue(void *context)
  414 {
  415         struct taskqueue **tqp, *tq;
  416 
  417         tqp = context;
  418         tq = *tqp;
  419 
  420         mtx_assert(&tq->tq_mutex, MA_OWNED);
  421         wakeup_one(tq);
  422 }
  423 
  424 TASKQUEUE_DEFINE(swi, taskqueue_swi_enqueue, 0,
  425                  swi_add(NULL, "task queue", taskqueue_swi_run, NULL, SWI_TQ,
  426                      INTR_MPSAFE, &taskqueue_ih)); 
  427 
  428 TASKQUEUE_DEFINE(swi_giant, taskqueue_swi_giant_enqueue, 0,
  429                  swi_add(NULL, "Giant taskq", taskqueue_swi_giant_run,
  430                      NULL, SWI_TQ_GIANT, 0, &taskqueue_giant_ih)); 
  431 
  432 TASKQUEUE_DEFINE_THREAD(thread);
  433 
  434 struct taskqueue *
  435 taskqueue_create_fast(const char *name, int mflags,
  436                  taskqueue_enqueue_fn enqueue, void *context)
  437 {
  438         return _taskqueue_create(name, mflags, enqueue, context,
  439                         MTX_SPIN, "fast_taskqueue");
  440 }
  441 
  442 /* NB: for backwards compatibility */
  443 int
  444 taskqueue_enqueue_fast(struct taskqueue *queue, struct task *task)
  445 {
  446         return taskqueue_enqueue(queue, task);
  447 }
  448 
  449 static void     *taskqueue_fast_ih;
  450 
  451 static void
  452 taskqueue_fast_enqueue(void *context)
  453 {
  454         swi_sched(taskqueue_fast_ih, 0);
  455 }
  456 
  457 static void
  458 taskqueue_fast_run(void *dummy)
  459 {
  460         taskqueue_run(taskqueue_fast);
  461 }
  462 
  463 TASKQUEUE_FAST_DEFINE(fast, taskqueue_fast_enqueue, 0,
  464         swi_add(NULL, "Fast task queue", taskqueue_fast_run, NULL,
  465         SWI_TQ_FAST, INTR_MPSAFE, &taskqueue_fast_ih));

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