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: releng/6.1/sys/kern/subr_taskqueue.c 158179 2006-04-30 16:44:43Z cvs2svn $");
   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/taskqueue.h>
   41 #include <sys/unistd.h>
   42 
   43 static MALLOC_DEFINE(M_TASKQUEUE, "taskqueue", "Task Queues");
   44 static void     *taskqueue_giant_ih;
   45 static void     *taskqueue_ih;
   46 static STAILQ_HEAD(taskqueue_list, taskqueue) taskqueue_queues;
   47 static struct mtx taskqueue_queues_mutex;
   48 
   49 struct taskqueue {
   50         STAILQ_ENTRY(taskqueue) tq_link;
   51         STAILQ_HEAD(, task)     tq_queue;
   52         const char              *tq_name;
   53         taskqueue_enqueue_fn    tq_enqueue;
   54         void                    *tq_context;
   55         struct task             *tq_running;
   56         struct mtx              tq_mutex;
   57         struct proc             **tq_pproc;
   58 };
   59 
   60 static void     init_taskqueue_list(void *data);
   61 
   62 static void
   63 init_taskqueue_list(void *data __unused)
   64 {
   65 
   66         mtx_init(&taskqueue_queues_mutex, "taskqueue list", NULL, MTX_DEF);
   67         STAILQ_INIT(&taskqueue_queues);
   68 }
   69 SYSINIT(taskqueue_list, SI_SUB_INTRINSIC, SI_ORDER_ANY, init_taskqueue_list,
   70     NULL);
   71 
   72 struct taskqueue *
   73 taskqueue_create(const char *name, int mflags,
   74                  taskqueue_enqueue_fn enqueue, void *context,
   75                  struct proc **pp)
   76 {
   77         struct taskqueue *queue;
   78 
   79         queue = malloc(sizeof(struct taskqueue), M_TASKQUEUE, mflags | M_ZERO);
   80         if (!queue)
   81                 return 0;
   82 
   83         STAILQ_INIT(&queue->tq_queue);
   84         queue->tq_name = name;
   85         queue->tq_enqueue = enqueue;
   86         queue->tq_context = context;
   87         queue->tq_pproc = pp;
   88         mtx_init(&queue->tq_mutex, "taskqueue", NULL, MTX_DEF);
   89 
   90         mtx_lock(&taskqueue_queues_mutex);
   91         STAILQ_INSERT_TAIL(&taskqueue_queues, queue, tq_link);
   92         mtx_unlock(&taskqueue_queues_mutex);
   93 
   94         return queue;
   95 }
   96 
   97 /*
   98  * Signal a taskqueue thread to terminate.
   99  */
  100 static void
  101 taskqueue_terminate(struct proc **pp, struct taskqueue *tq)
  102 {
  103         struct proc *p;
  104 
  105         p = *pp;
  106         *pp = NULL;
  107         if (p) {
  108                 wakeup_one(tq);
  109                 PROC_LOCK(p);              /* NB: insure we don't miss wakeup */
  110                 mtx_unlock(&tq->tq_mutex); /* let taskqueue thread run */
  111                 msleep(p, &p->p_mtx, PWAIT, "taskqueue_destroy", 0);
  112                 PROC_UNLOCK(p);
  113                 mtx_lock(&tq->tq_mutex);
  114         }
  115 }
  116 
  117 void
  118 taskqueue_free(struct taskqueue *queue)
  119 {
  120 
  121         mtx_lock(&taskqueue_queues_mutex);
  122         STAILQ_REMOVE(&taskqueue_queues, queue, taskqueue, tq_link);
  123         mtx_unlock(&taskqueue_queues_mutex);
  124 
  125         mtx_lock(&queue->tq_mutex);
  126         taskqueue_run(queue);
  127         taskqueue_terminate(queue->tq_pproc, queue);
  128         mtx_destroy(&queue->tq_mutex);
  129         free(queue, M_TASKQUEUE);
  130 }
  131 
  132 /*
  133  * Returns with the taskqueue locked.
  134  */
  135 struct taskqueue *
  136 taskqueue_find(const char *name)
  137 {
  138         struct taskqueue *queue;
  139 
  140         mtx_lock(&taskqueue_queues_mutex);
  141         STAILQ_FOREACH(queue, &taskqueue_queues, tq_link) {
  142                 if (strcmp(queue->tq_name, name) == 0) {
  143                         mtx_lock(&queue->tq_mutex);
  144                         mtx_unlock(&taskqueue_queues_mutex);
  145                         return queue;
  146                 }
  147         }
  148         mtx_unlock(&taskqueue_queues_mutex);
  149         return NULL;
  150 }
  151 
  152 int
  153 taskqueue_enqueue(struct taskqueue *queue, struct task *task)
  154 {
  155         struct task *ins;
  156         struct task *prev;
  157 
  158         mtx_lock(&queue->tq_mutex);
  159 
  160         /*
  161          * Count multiple enqueues.
  162          */
  163         if (task->ta_pending) {
  164                 task->ta_pending++;
  165                 mtx_unlock(&queue->tq_mutex);
  166                 return 0;
  167         }
  168 
  169         /*
  170          * Optimise the case when all tasks have the same priority.
  171          */
  172         prev = STAILQ_LAST(&queue->tq_queue, task, ta_link);
  173         if (!prev || prev->ta_priority >= task->ta_priority) {
  174                 STAILQ_INSERT_TAIL(&queue->tq_queue, task, ta_link);
  175         } else {
  176                 prev = 0;
  177                 for (ins = STAILQ_FIRST(&queue->tq_queue); ins;
  178                      prev = ins, ins = STAILQ_NEXT(ins, ta_link))
  179                         if (ins->ta_priority < task->ta_priority)
  180                                 break;
  181 
  182                 if (prev)
  183                         STAILQ_INSERT_AFTER(&queue->tq_queue, prev, task, ta_link);
  184                 else
  185                         STAILQ_INSERT_HEAD(&queue->tq_queue, task, ta_link);
  186         }
  187 
  188         task->ta_pending = 1;
  189         queue->tq_enqueue(queue->tq_context);
  190 
  191         mtx_unlock(&queue->tq_mutex);
  192 
  193         return 0;
  194 }
  195 
  196 void
  197 taskqueue_run(struct taskqueue *queue)
  198 {
  199         struct task *task;
  200         int owned, pending;
  201 
  202         owned = mtx_owned(&queue->tq_mutex);
  203         if (!owned)
  204                 mtx_lock(&queue->tq_mutex);
  205         while (STAILQ_FIRST(&queue->tq_queue)) {
  206                 /*
  207                  * Carefully remove the first task from the queue and
  208                  * zero its pending count.
  209                  */
  210                 task = STAILQ_FIRST(&queue->tq_queue);
  211                 STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
  212                 pending = task->ta_pending;
  213                 task->ta_pending = 0;
  214                 queue->tq_running = task;
  215                 mtx_unlock(&queue->tq_mutex);
  216 
  217                 task->ta_func(task->ta_context, pending);
  218 
  219                 mtx_lock(&queue->tq_mutex);
  220                 queue->tq_running = NULL;
  221                 wakeup(task);
  222         }
  223 
  224         /*
  225          * For compatibility, unlock on return if the queue was not locked
  226          * on entry, although this opens a race window.
  227          */
  228         if (!owned)
  229                 mtx_unlock(&queue->tq_mutex);
  230 }
  231 
  232 void
  233 taskqueue_drain(struct taskqueue *queue, struct task *task)
  234 {
  235         WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "taskqueue_drain");
  236 
  237         mtx_lock(&queue->tq_mutex);
  238         while (task->ta_pending != 0 || task == queue->tq_running)
  239                 msleep(task, &queue->tq_mutex, PWAIT, "-", 0);
  240         mtx_unlock(&queue->tq_mutex);
  241 }
  242 
  243 static void
  244 taskqueue_swi_enqueue(void *context)
  245 {
  246         swi_sched(taskqueue_ih, 0);
  247 }
  248 
  249 static void
  250 taskqueue_swi_run(void *dummy)
  251 {
  252         taskqueue_run(taskqueue_swi);
  253 }
  254 
  255 static void
  256 taskqueue_swi_giant_enqueue(void *context)
  257 {
  258         swi_sched(taskqueue_giant_ih, 0);
  259 }
  260 
  261 static void
  262 taskqueue_swi_giant_run(void *dummy)
  263 {
  264         taskqueue_run(taskqueue_swi_giant);
  265 }
  266 
  267 void
  268 taskqueue_thread_loop(void *arg)
  269 {
  270         struct taskqueue **tqp, *tq;
  271 
  272         tqp = arg;
  273         tq = *tqp;
  274         mtx_lock(&tq->tq_mutex);
  275         do {
  276                 taskqueue_run(tq);
  277                 msleep(tq, &tq->tq_mutex, PWAIT, "-", 0); 
  278         } while (*tq->tq_pproc != NULL);
  279 
  280         /* rendezvous with thread that asked us to terminate */
  281         wakeup_one(tq);
  282         mtx_unlock(&tq->tq_mutex);
  283         kthread_exit(0);
  284 }
  285 
  286 void
  287 taskqueue_thread_enqueue(void *context)
  288 {
  289         struct taskqueue **tqp, *tq;
  290 
  291         tqp = context;
  292         tq = *tqp;
  293 
  294         mtx_assert(&tq->tq_mutex, MA_OWNED);
  295         wakeup_one(tq);
  296 }
  297 
  298 TASKQUEUE_DEFINE(swi, taskqueue_swi_enqueue, 0,
  299                  swi_add(NULL, "task queue", taskqueue_swi_run, NULL, SWI_TQ,
  300                      INTR_MPSAFE, &taskqueue_ih)); 
  301 
  302 TASKQUEUE_DEFINE(swi_giant, taskqueue_swi_giant_enqueue, 0,
  303                  swi_add(NULL, "Giant task queue", taskqueue_swi_giant_run,
  304                      NULL, SWI_TQ_GIANT, 0, &taskqueue_giant_ih)); 
  305 
  306 TASKQUEUE_DEFINE_THREAD(thread);
  307 
  308 int
  309 taskqueue_enqueue_fast(struct taskqueue *queue, struct task *task)
  310 {
  311         struct task *ins;
  312         struct task *prev;
  313 
  314         mtx_lock_spin(&queue->tq_mutex);
  315 
  316         /*
  317          * Count multiple enqueues.
  318          */
  319         if (task->ta_pending) {
  320                 task->ta_pending++;
  321                 mtx_unlock_spin(&queue->tq_mutex);
  322                 return 0;
  323         }
  324 
  325         /*
  326          * Optimise the case when all tasks have the same priority.
  327          */
  328         prev = STAILQ_LAST(&queue->tq_queue, task, ta_link);
  329         if (!prev || prev->ta_priority >= task->ta_priority) {
  330                 STAILQ_INSERT_TAIL(&queue->tq_queue, task, ta_link);
  331         } else {
  332                 prev = 0;
  333                 for (ins = STAILQ_FIRST(&queue->tq_queue); ins;
  334                      prev = ins, ins = STAILQ_NEXT(ins, ta_link))
  335                         if (ins->ta_priority < task->ta_priority)
  336                                 break;
  337 
  338                 if (prev)
  339                         STAILQ_INSERT_AFTER(&queue->tq_queue, prev, task, ta_link);
  340                 else
  341                         STAILQ_INSERT_HEAD(&queue->tq_queue, task, ta_link);
  342         }
  343 
  344         task->ta_pending = 1;
  345         queue->tq_enqueue(queue->tq_context);
  346 
  347         mtx_unlock_spin(&queue->tq_mutex);
  348 
  349         return 0;
  350 }
  351 
  352 static void
  353 taskqueue_run_fast(struct taskqueue *queue)
  354 {
  355         struct task *task;
  356         int pending;
  357 
  358         mtx_lock_spin(&queue->tq_mutex);
  359         while (STAILQ_FIRST(&queue->tq_queue)) {
  360                 /*
  361                  * Carefully remove the first task from the queue and
  362                  * zero its pending count.
  363                  */
  364                 task = STAILQ_FIRST(&queue->tq_queue);
  365                 STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
  366                 pending = task->ta_pending;
  367                 task->ta_pending = 0;
  368                 mtx_unlock_spin(&queue->tq_mutex);
  369 
  370                 task->ta_func(task->ta_context, pending);
  371 
  372                 mtx_lock_spin(&queue->tq_mutex);
  373         }
  374         mtx_unlock_spin(&queue->tq_mutex);
  375 }
  376 
  377 struct taskqueue *taskqueue_fast;
  378 static void     *taskqueue_fast_ih;
  379 
  380 static void
  381 taskqueue_fast_schedule(void *context)
  382 {
  383         swi_sched(taskqueue_fast_ih, 0);
  384 }
  385 
  386 static void
  387 taskqueue_fast_run(void *dummy)
  388 {
  389         taskqueue_run_fast(taskqueue_fast);
  390 }
  391 
  392 static void
  393 taskqueue_define_fast(void *arg)
  394 {
  395 
  396         taskqueue_fast = malloc(sizeof(struct taskqueue), M_TASKQUEUE,
  397             M_NOWAIT | M_ZERO);
  398         if (!taskqueue_fast) {
  399                 printf("%s: Unable to allocate fast task queue!\n", __func__);
  400                 return;
  401         }
  402 
  403         STAILQ_INIT(&taskqueue_fast->tq_queue);
  404         taskqueue_fast->tq_name = "fast";
  405         taskqueue_fast->tq_enqueue = taskqueue_fast_schedule;
  406         mtx_init(&taskqueue_fast->tq_mutex, "taskqueue_fast", NULL, MTX_SPIN);
  407 
  408         mtx_lock(&taskqueue_queues_mutex);
  409         STAILQ_INSERT_TAIL(&taskqueue_queues, taskqueue_fast, tq_link);
  410         mtx_unlock(&taskqueue_queues_mutex);
  411 
  412         swi_add(NULL, "Fast task queue", taskqueue_fast_run,
  413                 NULL, SWI_TQ_FAST, INTR_MPSAFE, &taskqueue_fast_ih);
  414 }
  415 SYSINIT(taskqueue_fast, SI_SUB_CONFIGURE, SI_ORDER_SECOND,
  416     taskqueue_define_fast, NULL);

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