subr_taskqueue.c

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/*-
 * Copyright (c) 2000 Doug Rabson
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$BSDSUniX$");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/interrupt.h>
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/sched.h>
#include <sys/taskqueue.h>
#include <sys/unistd.h>
#include <machine/stdarg.h>

static MALLOC_DEFINE(M_TASKQUEUE, "taskqueue", "Task Queues");
static void     *taskqueue_giant_ih;
static void     *taskqueue_ih;

struct taskqueue_busy {
        struct task     *tb_running;
        TAILQ_ENTRY(taskqueue_busy) tb_link;
};

struct taskqueue {
        STAILQ_HEAD(, task)     tq_queue;
        taskqueue_enqueue_fn    tq_enqueue;
        void                    *tq_context;
        TAILQ_HEAD(, taskqueue_busy) tq_active;
        struct mtx              tq_mutex;
        struct thread           **tq_threads;
        int                     tq_tcount;
        int                     tq_spin;
        int                     tq_flags;
        int                     tq_callouts;
};

#define TQ_FLAGS_ACTIVE         (1 << 0)
#define TQ_FLAGS_BLOCKED        (1 << 1)
#define TQ_FLAGS_PENDING        (1 << 2)

#define DT_CALLOUT_ARMED        (1 << 0)

#define TQ_LOCK(tq)                                                     \
        do {                                                            \
                if ((tq)->tq_spin)                                      \
                        mtx_lock_spin(&(tq)->tq_mutex);                 \
                else                                                    \
                        mtx_lock(&(tq)->tq_mutex);                      \
        } while (0)

#define TQ_UNLOCK(tq)                                                   \
        do {                                                            \
                if ((tq)->tq_spin)                                      \
                        mtx_unlock_spin(&(tq)->tq_mutex);               \
                else                                                    \
                        mtx_unlock(&(tq)->tq_mutex);                    \
        } while (0)

void
_timeout_task_init(struct taskqueue *queue, struct timeout_task *timeout_task,
    int priority, task_fn_t func, void *context)
{

        TASK_INIT(&timeout_task->t, priority, func, context);
        callout_init_mtx(&timeout_task->c, &queue->tq_mutex, 0);
        timeout_task->q = queue;
        timeout_task->f = 0;
}

static __inline int
TQ_SLEEP(struct taskqueue *tq, void *p, struct mtx *m, int pri, const char *wm,
    int t)
{
        if (tq->tq_spin)
                return (msleep_spin(p, m, wm, t));
        return (msleep(p, m, pri, wm, t));
}

static struct taskqueue *
_taskqueue_create(const char *name __unused, int mflags,
                 taskqueue_enqueue_fn enqueue, void *context,
                 int mtxflags, const char *mtxname)
{
        struct taskqueue *queue;

        queue = malloc(sizeof(struct taskqueue), M_TASKQUEUE, mflags | M_ZERO);
        if (!queue)
                return NULL;

        STAILQ_INIT(&queue->tq_queue);
        TAILQ_INIT(&queue->tq_active);
        queue->tq_enqueue = enqueue;
        queue->tq_context = context;
        queue->tq_spin = (mtxflags & MTX_SPIN) != 0;
        queue->tq_flags |= TQ_FLAGS_ACTIVE;
        mtx_init(&queue->tq_mutex, mtxname, NULL, mtxflags);

        return queue;
}

struct taskqueue *
taskqueue_create(const char *name, int mflags,
                 taskqueue_enqueue_fn enqueue, void *context)
{
        return _taskqueue_create(name, mflags, enqueue, context,
                        MTX_DEF, "taskqueue");
}

/*
 * Signal a taskqueue thread to terminate.
 */
static void
taskqueue_terminate(struct thread **pp, struct taskqueue *tq)
{

        while (tq->tq_tcount > 0 || tq->tq_callouts > 0) {
                wakeup(tq);
                TQ_SLEEP(tq, pp, &tq->tq_mutex, PWAIT, "taskqueue_destroy", 0);
        }
}

void
taskqueue_free(struct taskqueue *queue)
{

        TQ_LOCK(queue);
        queue->tq_flags &= ~TQ_FLAGS_ACTIVE;
        taskqueue_terminate(queue->tq_threads, queue);
        KASSERT(TAILQ_EMPTY(&queue->tq_active), ("Tasks still running?"));
        KASSERT(queue->tq_callouts == 0, ("Armed timeout tasks"));
        mtx_destroy(&queue->tq_mutex);
        free(queue->tq_threads, M_TASKQUEUE);
        free(queue, M_TASKQUEUE);
}

static int
taskqueue_enqueue_locked(struct taskqueue *queue, struct task *task)
{
        struct task *ins;
        struct task *prev;

        /*
         * Count multiple enqueues.
         */
        if (task->ta_pending) {
                if (task->ta_pending < USHRT_MAX)
                        task->ta_pending++;
                return (0);
        }

        /*
         * Optimise the case when all tasks have the same priority.
         */
        prev = STAILQ_LAST(&queue->tq_queue, task, ta_link);
        if (!prev || prev->ta_priority >= task->ta_priority) {
                STAILQ_INSERT_TAIL(&queue->tq_queue, task, ta_link);
        } else {
                prev = NULL;
                for (ins = STAILQ_FIRST(&queue->tq_queue); ins;
                     prev = ins, ins = STAILQ_NEXT(ins, ta_link))
                        if (ins->ta_priority < task->ta_priority)
                                break;

                if (prev)
                        STAILQ_INSERT_AFTER(&queue->tq_queue, prev, task, ta_link);
                else
                        STAILQ_INSERT_HEAD(&queue->tq_queue, task, ta_link);
        }

        task->ta_pending = 1;
        if ((queue->tq_flags & TQ_FLAGS_BLOCKED) == 0)
                queue->tq_enqueue(queue->tq_context);
        else
                queue->tq_flags |= TQ_FLAGS_PENDING;

        return (0);
}
int
taskqueue_enqueue(struct taskqueue *queue, struct task *task)
{
        int res;

        TQ_LOCK(queue);
        res = taskqueue_enqueue_locked(queue, task);
        TQ_UNLOCK(queue);

        return (res);
}

static void
taskqueue_timeout_func(void *arg)
{
        struct taskqueue *queue;
        struct timeout_task *timeout_task;

        timeout_task = arg;
        queue = timeout_task->q;
        KASSERT((timeout_task->f & DT_CALLOUT_ARMED) != 0, ("Stray timeout"));
        timeout_task->f &= ~DT_CALLOUT_ARMED;
        queue->tq_callouts--;
        taskqueue_enqueue_locked(timeout_task->q, &timeout_task->t);
}

int
taskqueue_enqueue_timeout(struct taskqueue *queue,
    struct timeout_task *timeout_task, int ticks)
{
        int res;

        TQ_LOCK(queue);
        KASSERT(timeout_task->q == NULL || timeout_task->q == queue,
            ("Migrated queue"));
        KASSERT(!queue->tq_spin, ("Timeout for spin-queue"));
        timeout_task->q = queue;
        res = timeout_task->t.ta_pending;
        if (ticks == 0) {
                taskqueue_enqueue_locked(queue, &timeout_task->t);
        } else {
                if ((timeout_task->f & DT_CALLOUT_ARMED) != 0) {
                        res++;
                } else {
                        queue->tq_callouts++;
                        timeout_task->f |= DT_CALLOUT_ARMED;
                        if (ticks < 0)
                                ticks = -ticks; /* Ignore overflow. */
                }
                if (ticks > 0) {
                        callout_reset(&timeout_task->c, ticks,
                            taskqueue_timeout_func, timeout_task);
                }
        }
        TQ_UNLOCK(queue);
        return (res);
}

static void
taskqueue_drain_running(struct taskqueue *queue)
{

        while (!TAILQ_EMPTY(&queue->tq_active))
                TQ_SLEEP(queue, &queue->tq_active, &queue->tq_mutex,
                    PWAIT, "-", 0);
}

void
taskqueue_block(struct taskqueue *queue)
{

        TQ_LOCK(queue);
        queue->tq_flags |= TQ_FLAGS_BLOCKED;
        TQ_UNLOCK(queue);
}

void
taskqueue_unblock(struct taskqueue *queue)
{

        TQ_LOCK(queue);
        queue->tq_flags &= ~TQ_FLAGS_BLOCKED;
        if (queue->tq_flags & TQ_FLAGS_PENDING) {
                queue->tq_flags &= ~TQ_FLAGS_PENDING;
                queue->tq_enqueue(queue->tq_context);
        }
        TQ_UNLOCK(queue);
}

static void
taskqueue_run_locked(struct taskqueue *queue)
{
        struct taskqueue_busy tb;
        struct task *task;
        int pending;

        mtx_assert(&queue->tq_mutex, MA_OWNED);
        tb.tb_running = NULL;
        TAILQ_INSERT_TAIL(&queue->tq_active, &tb, tb_link);

        while (STAILQ_FIRST(&queue->tq_queue)) {
                /*
                 * Carefully remove the first task from the queue and
                 * zero its pending count.
                 */
                task = STAILQ_FIRST(&queue->tq_queue);
                STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
                pending = task->ta_pending;
                task->ta_pending = 0;
                tb.tb_running = task;
                TQ_UNLOCK(queue);

                task->ta_func(task->ta_context, pending);

                TQ_LOCK(queue);
                tb.tb_running = NULL;
                wakeup(task);
        }
        TAILQ_REMOVE(&queue->tq_active, &tb, tb_link);
        if (TAILQ_EMPTY(&queue->tq_active))
                wakeup(&queue->tq_active);
}

void
taskqueue_run(struct taskqueue *queue)
{

        TQ_LOCK(queue);
        taskqueue_run_locked(queue);
        TQ_UNLOCK(queue);
}

static int
task_is_running(struct taskqueue *queue, struct task *task)
{
        struct taskqueue_busy *tb;

        mtx_assert(&queue->tq_mutex, MA_OWNED);
        TAILQ_FOREACH(tb, &queue->tq_active, tb_link) {
                if (tb->tb_running == task)
                        return (1);
        }
        return (0);
}

static int
taskqueue_cancel_locked(struct taskqueue *queue, struct task *task,
    u_int *pendp)
{

        if (task->ta_pending > 0)
                STAILQ_REMOVE(&queue->tq_queue, task, task, ta_link);
        if (pendp != NULL)
                *pendp = task->ta_pending;
        task->ta_pending = 0;
        return (task_is_running(queue, task) ? EBUSY : 0);
}

int
taskqueue_cancel(struct taskqueue *queue, struct task *task, u_int *pendp)
{
        int error;

        TQ_LOCK(queue);
        error = taskqueue_cancel_locked(queue, task, pendp);
        TQ_UNLOCK(queue);

        return (error);
}

int
taskqueue_cancel_timeout(struct taskqueue *queue,
    struct timeout_task *timeout_task, u_int *pendp)
{
        u_int pending, pending1;
        int error;

        TQ_LOCK(queue);
        pending = !!callout_stop(&timeout_task->c);
        error = taskqueue_cancel_locked(queue, &timeout_task->t, &pending1);
        if ((timeout_task->f & DT_CALLOUT_ARMED) != 0) {
                timeout_task->f &= ~DT_CALLOUT_ARMED;
                queue->tq_callouts--;
        }
        TQ_UNLOCK(queue);

        if (pendp != NULL)
                *pendp = pending + pending1;
        return (error);
}

void
taskqueue_drain(struct taskqueue *queue, struct task *task)
{

        if (!queue->tq_spin)
                WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, __func__);

        TQ_LOCK(queue);
        while (task->ta_pending != 0 || task_is_running(queue, task))
                TQ_SLEEP(queue, task, &queue->tq_mutex, PWAIT, "-", 0);
        TQ_UNLOCK(queue);
}

void
taskqueue_drain_all(struct taskqueue *queue)
{
        struct task *task;

        if (!queue->tq_spin)
                WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, __func__);

        TQ_LOCK(queue);
        task = STAILQ_LAST(&queue->tq_queue, task, ta_link);
        if (task != NULL)
                while (task->ta_pending != 0)
                        TQ_SLEEP(queue, task, &queue->tq_mutex, PWAIT, "-", 0);
        taskqueue_drain_running(queue);
        KASSERT(STAILQ_EMPTY(&queue->tq_queue),
            ("taskqueue queue is not empty after draining"));
        TQ_UNLOCK(queue);
}

void
taskqueue_drain_timeout(struct taskqueue *queue,
    struct timeout_task *timeout_task)
{

        callout_drain(&timeout_task->c);
        taskqueue_drain(queue, &timeout_task->t);
}

static void
taskqueue_swi_enqueue(void *context)
{
        swi_sched(taskqueue_ih, 0);
}

static void
taskqueue_swi_run(void *dummy)
{
        taskqueue_run(taskqueue_swi);
}

static void
taskqueue_swi_giant_enqueue(void *context)
{
        swi_sched(taskqueue_giant_ih, 0);
}

static void
taskqueue_swi_giant_run(void *dummy)
{
        taskqueue_run(taskqueue_swi_giant);
}

int
taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
                        const char *name, ...)
{
        va_list ap;
        struct thread *td;
        struct taskqueue *tq;
        int i, error;
        char ktname[MAXCOMLEN + 1];

        if (count <= 0)
                return (EINVAL);

        tq = *tqp;

        va_start(ap, name);
        vsnprintf(ktname, sizeof(ktname), name, ap);
        va_end(ap);

        tq->tq_threads = malloc(sizeof(struct thread *) * count, M_TASKQUEUE,
            M_NOWAIT | M_ZERO);
        if (tq->tq_threads == NULL) {
                printf("%s: no memory for %s threads\n", __func__, ktname);
                return (ENOMEM);
        }

        for (i = 0; i < count; i++) {
                if (count == 1)
                        error = kthread_add(taskqueue_thread_loop, tqp, NULL,
                            &tq->tq_threads[i], RFSTOPPED, 0, "%s", ktname);
                else
                        error = kthread_add(taskqueue_thread_loop, tqp, NULL,
                            &tq->tq_threads[i], RFSTOPPED, 0,
                            "%s_%d", ktname, i);
                if (error) {
                        /* should be ok to continue, taskqueue_free will dtrt */
                        printf("%s: kthread_add(%s): error %d", __func__,
                            ktname, error);
                        tq->tq_threads[i] = NULL;               /* paranoid */
                } else
                        tq->tq_tcount++;
        }
        for (i = 0; i < count; i++) {
                if (tq->tq_threads[i] == NULL)
                        continue;
                td = tq->tq_threads[i];
                thread_lock(td);
                sched_prio(td, pri);
                sched_add(td, SRQ_BORING);
                thread_unlock(td);
        }

        return (0);
}

void
taskqueue_thread_loop(void *arg)
{
        struct taskqueue **tqp, *tq;

        tqp = arg;
        tq = *tqp;
        TQ_LOCK(tq);
        while ((tq->tq_flags & TQ_FLAGS_ACTIVE) != 0) {
                taskqueue_run_locked(tq);
                /*
                 * Because taskqueue_run() can drop tq_mutex, we need to
                 * check if the TQ_FLAGS_ACTIVE flag wasn't removed in the
                 * meantime, which means we missed a wakeup.
                 */
                if ((tq->tq_flags & TQ_FLAGS_ACTIVE) == 0)
                        break;
                TQ_SLEEP(tq, tq, &tq->tq_mutex, 0, "-", 0);
        }
        taskqueue_run_locked(tq);

        /* rendezvous with thread that asked us to terminate */
        tq->tq_tcount--;
        wakeup_one(tq->tq_threads);
        TQ_UNLOCK(tq);
        kthread_exit();
}

void
taskqueue_thread_enqueue(void *context)
{
        struct taskqueue **tqp, *tq;

        tqp = context;
        tq = *tqp;

        mtx_assert(&tq->tq_mutex, MA_OWNED);
        wakeup_one(tq);
}

TASKQUEUE_DEFINE(swi, taskqueue_swi_enqueue, NULL,
                 swi_add(NULL, "task queue", taskqueue_swi_run, NULL, SWI_TQ,
                     INTR_MPSAFE, &taskqueue_ih)); 

TASKQUEUE_DEFINE(swi_giant, taskqueue_swi_giant_enqueue, NULL,
                 swi_add(NULL, "Giant taskq", taskqueue_swi_giant_run,
                     NULL, SWI_TQ_GIANT, 0, &taskqueue_giant_ih)); 

TASKQUEUE_DEFINE_THREAD(thread);

struct taskqueue *
taskqueue_create_fast(const char *name, int mflags,
                 taskqueue_enqueue_fn enqueue, void *context)
{
        return _taskqueue_create(name, mflags, enqueue, context,
                        MTX_SPIN, "fast_taskqueue");
}

/* NB: for backwards compatibility */
int
taskqueue_enqueue_fast(struct taskqueue *queue, struct task *task)
{
        return taskqueue_enqueue(queue, task);
}

static void     *taskqueue_fast_ih;

static void
taskqueue_fast_enqueue(void *context)
{
        swi_sched(taskqueue_fast_ih, 0);
}

static void
taskqueue_fast_run(void *dummy)
{
        taskqueue_run(taskqueue_fast);
}

TASKQUEUE_FAST_DEFINE(fast, taskqueue_fast_enqueue, NULL,
        swi_add(NULL, "fast taskq", taskqueue_fast_run, NULL,
        SWI_TQ_FAST, INTR_MPSAFE, &taskqueue_fast_ih));

int
taskqueue_member(struct taskqueue *queue, struct thread *td)
{
        int i, j, ret = 0;

        for (i = 0, j = 0; ; i++) {
                if (queue->tq_threads[i] == NULL)
                        continue;
                if (queue->tq_threads[i] == td) {
                        ret = 1;
                        break;
                }
                if (++j >= queue->tq_tcount)
                        break;
        }
        return (ret);
}