subr_taskqueue.c

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/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * 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("$FreeBSD$");
 
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/cpuset.h>
#include <sys/interrupt.h>
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/libkern.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/epoch.h>
#include <sys/sched.h>
#include <sys/smp.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;
static void      taskqueue_fast_enqueue(void *);
static void      taskqueue_swi_enqueue(void *);
static void      taskqueue_swi_giant_enqueue(void *);
 
struct taskqueue_busy {
        struct task             *tb_running;
        u_int                    tb_seq;
        LIST_ENTRY(taskqueue_busy) tb_link;
};
 
struct taskqueue {
        STAILQ_HEAD(, task)     tq_queue;
        LIST_HEAD(, taskqueue_busy) tq_active;
        struct task             *tq_hint;
        u_int                   tq_seq;
        int                     tq_callouts;
        struct mtx_padalign     tq_mutex;
        taskqueue_enqueue_fn    tq_enqueue;
        void                    *tq_context;
        char                    *tq_name;
        struct thread           **tq_threads;
        int                     tq_tcount;
        int                     tq_spin;
        int                     tq_flags;
        taskqueue_callback_fn   tq_callbacks[TASKQUEUE_NUM_CALLBACKS];
        void                    *tq_cb_contexts[TASKQUEUE_NUM_CALLBACKS];
};
 
#define TQ_FLAGS_ACTIVE         (1 << 0)
#define TQ_FLAGS_BLOCKED        (1 << 1)
#define TQ_FLAGS_UNLOCKED_ENQUEUE       (1 << 2)
 
#define DT_CALLOUT_ARMED        (1 << 0)
#define DT_DRAIN_IN_PROGRESS    (1 << 1)
 
#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_ASSERT_LOCKED(tq)    mtx_assert(&(tq)->tq_mutex, MA_OWNED)
 
#define TQ_UNLOCK(tq)                                                   \
        do {                                                            \
                if ((tq)->tq_spin)                                      \
                        mtx_unlock_spin(&(tq)->tq_mutex);               \
                else                                                    \
                        mtx_unlock(&(tq)->tq_mutex);                    \
        } while (0)
#define TQ_ASSERT_UNLOCKED(tq)  mtx_assert(&(tq)->tq_mutex, MA_NOTOWNED)
 
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,
            CALLOUT_RETURNUNLOCKED);
        timeout_task->q = queue;
        timeout_task->f = 0;
}
 
static __inline int
TQ_SLEEP(struct taskqueue *tq, void *p, const char *wm)
{
        if (tq->tq_spin)
                return (msleep_spin(p, (struct mtx *)&tq->tq_mutex, wm, 0));
        return (msleep(p, &tq->tq_mutex, 0, wm, 0));
}
 
static struct taskqueue *
_taskqueue_create(const char *name, int mflags,
                 taskqueue_enqueue_fn enqueue, void *context,
                 int mtxflags, const char *mtxname __unused)
{
        struct taskqueue *queue;
        char *tq_name;
 
        tq_name = malloc(TASKQUEUE_NAMELEN, M_TASKQUEUE, mflags | M_ZERO);
        if (tq_name == NULL)
                return (NULL);
 
        queue = malloc(sizeof(struct taskqueue), M_TASKQUEUE, mflags | M_ZERO);
        if (queue == NULL) {
                free(tq_name, M_TASKQUEUE);
                return (NULL);
        }
 
        snprintf(tq_name, TASKQUEUE_NAMELEN, "%s", (name) ? name : "taskqueue");
 
        STAILQ_INIT(&queue->tq_queue);
        LIST_INIT(&queue->tq_active);
        queue->tq_enqueue = enqueue;
        queue->tq_context = context;
        queue->tq_name = tq_name;
        queue->tq_spin = (mtxflags & MTX_SPIN) != 0;
        queue->tq_flags |= TQ_FLAGS_ACTIVE;
        if (enqueue == taskqueue_fast_enqueue ||
            enqueue == taskqueue_swi_enqueue ||
            enqueue == taskqueue_swi_giant_enqueue ||
            enqueue == taskqueue_thread_enqueue)
                queue->tq_flags |= TQ_FLAGS_UNLOCKED_ENQUEUE;
        mtx_init(&queue->tq_mutex, tq_name, 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, name);
}
 
void
taskqueue_set_callback(struct taskqueue *queue,
    enum taskqueue_callback_type cb_type, taskqueue_callback_fn callback,
    void *context)
{
 
        KASSERT(((cb_type >= TASKQUEUE_CALLBACK_TYPE_MIN) &&
            (cb_type <= TASKQUEUE_CALLBACK_TYPE_MAX)),
            ("Callback type %d not valid, must be %d-%d", cb_type,
            TASKQUEUE_CALLBACK_TYPE_MIN, TASKQUEUE_CALLBACK_TYPE_MAX));
        KASSERT((queue->tq_callbacks[cb_type] == NULL),
            ("Re-initialization of taskqueue callback?"));
 
        queue->tq_callbacks[cb_type] = callback;
        queue->tq_cb_contexts[cb_type] = context;
}
 
/*
 * 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_destroy");
        }
}
 
void
taskqueue_free(struct taskqueue *queue)
{
 
        TQ_LOCK(queue);
        queue->tq_flags &= ~TQ_FLAGS_ACTIVE;
        taskqueue_terminate(queue->tq_threads, queue);
        KASSERT(LIST_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->tq_name, M_TASKQUEUE);
        free(queue, M_TASKQUEUE);
}
 
static int
taskqueue_enqueue_locked(struct taskqueue *queue, struct task *task)
{
        struct task *ins;
        struct task *prev;
 
        KASSERT(task->ta_func != NULL, ("enqueueing task with NULL func"));
        /*
         * Count multiple enqueues.
         */
        if (task->ta_pending) {
                if (task->ta_pending < USHRT_MAX)
                        task->ta_pending++;
                TQ_UNLOCK(queue);
                return (0);
        }
 
        /*
         * Optimise cases when all tasks use small set of priorities.
         * In case of only one priority we always insert at the end.
         * In case of two tq_hint typically gives the insertion point.
         * In case of more then two tq_hint should halve the search.
         */
        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 = queue->tq_hint;
                if (prev && prev->ta_priority >= task->ta_priority) {
                        ins = STAILQ_NEXT(prev, ta_link);
                } else {
                        prev = NULL;
                        ins = STAILQ_FIRST(&queue->tq_queue);
                }
                for (; 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);
                        queue->tq_hint = task;
                } else
                        STAILQ_INSERT_HEAD(&queue->tq_queue, task, ta_link);
        }
 
        task->ta_pending = 1;
        if ((queue->tq_flags & TQ_FLAGS_UNLOCKED_ENQUEUE) != 0)
                TQ_UNLOCK(queue);
        if ((queue->tq_flags & TQ_FLAGS_BLOCKED) == 0)
                queue->tq_enqueue(queue->tq_context);
        if ((queue->tq_flags & TQ_FLAGS_UNLOCKED_ENQUEUE) == 0)
                TQ_UNLOCK(queue);
 
        /* Return with lock released. */
        return (0);
}
 
int
taskqueue_enqueue(struct taskqueue *queue, struct task *task)
{
        int res;
 
        TQ_LOCK(queue);
        res = taskqueue_enqueue_locked(queue, task);
        /* The lock is released inside. */
 
        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);
        /* The lock is released inside. */
}
 
int
taskqueue_enqueue_timeout_sbt(struct taskqueue *queue,
    struct timeout_task *timeout_task, sbintime_t sbt, sbintime_t pr, int flags)
{
        int res;
 
        TQ_LOCK(queue);
        KASSERT(timeout_task->q == NULL || timeout_task->q == queue,
            ("Migrated queue"));
        timeout_task->q = queue;
        res = timeout_task->t.ta_pending;
        if (timeout_task->f & DT_DRAIN_IN_PROGRESS) {
                /* Do nothing */
                TQ_UNLOCK(queue);
                res = -1;
        } else if (sbt == 0) {
                taskqueue_enqueue_locked(queue, &timeout_task->t);
                /* The lock is released inside. */
        } else {
                if ((timeout_task->f & DT_CALLOUT_ARMED) != 0) {
                        res++;
                } else {
                        queue->tq_callouts++;
                        timeout_task->f |= DT_CALLOUT_ARMED;
                        if (sbt < 0)
                                sbt = -sbt; /* Ignore overflow. */
                }
                if (sbt > 0) {
                        if (queue->tq_spin)
                                flags |= C_DIRECT_EXEC;
                        callout_reset_sbt(&timeout_task->c, sbt, pr,
                            taskqueue_timeout_func, timeout_task, flags);
                }
                TQ_UNLOCK(queue);
        }
        return (res);
}
 
int
taskqueue_enqueue_timeout(struct taskqueue *queue,
    struct timeout_task *ttask, int ticks)
{
 
        return (taskqueue_enqueue_timeout_sbt(queue, ttask, ticks * tick_sbt,
            0, C_HARDCLOCK));
}
 
static void
taskqueue_task_nop_fn(void *context, int pending)
{
}
 
/*
 * Block until all currently queued tasks in this taskqueue
 * have begun execution.  Tasks queued during execution of
 * this function are ignored.
 */
static int
taskqueue_drain_tq_queue(struct taskqueue *queue)
{
        struct task t_barrier;
 
        if (STAILQ_EMPTY(&queue->tq_queue))
                return (0);
 
        /*
         * Enqueue our barrier after all current tasks, but with
         * the highest priority so that newly queued tasks cannot
         * pass it.  Because of the high priority, we can not use
         * taskqueue_enqueue_locked directly (which drops the lock
         * anyway) so just insert it at tail while we have the
         * queue lock.
         */
        TASK_INIT(&t_barrier, UCHAR_MAX, taskqueue_task_nop_fn, &t_barrier);
        STAILQ_INSERT_TAIL(&queue->tq_queue, &t_barrier, ta_link);
        queue->tq_hint = &t_barrier;
        t_barrier.ta_pending = 1;
 
        /*
         * Once the barrier has executed, all previously queued tasks
         * have completed or are currently executing.
         */
        while (t_barrier.ta_pending != 0)
                TQ_SLEEP(queue, &t_barrier, "tq_qdrain");
        return (1);
}
 
/*
 * Block until all currently executing tasks for this taskqueue
 * complete.  Tasks that begin execution during the execution
 * of this function are ignored.
 */
static int
taskqueue_drain_tq_active(struct taskqueue *queue)
{
        struct taskqueue_busy *tb;
        u_int seq;
 
        if (LIST_EMPTY(&queue->tq_active))
                return (0);
 
        /* Block taskq_terminate().*/
        queue->tq_callouts++;
 
        /* Wait for any active task with sequence from the past. */
        seq = queue->tq_seq;
restart:
        LIST_FOREACH(tb, &queue->tq_active, tb_link) {
                if ((int)(tb->tb_seq - seq) <= 0) {
                        TQ_SLEEP(queue, tb->tb_running, "tq_adrain");
                        goto restart;
                }
        }
 
        /* Release taskqueue_terminate(). */
        queue->tq_callouts--;
        if ((queue->tq_flags & TQ_FLAGS_ACTIVE) == 0)
                wakeup_one(queue->tq_threads);
        return (1);
}
 
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 (!STAILQ_EMPTY(&queue->tq_queue))
                queue->tq_enqueue(queue->tq_context);
        TQ_UNLOCK(queue);
}
 
static void
taskqueue_run_locked(struct taskqueue *queue)
{
        struct epoch_tracker et;
        struct taskqueue_busy tb;
        struct task *task;
        bool in_net_epoch;
        int pending;
 
        KASSERT(queue != NULL, ("tq is NULL"));
        TQ_ASSERT_LOCKED(queue);
        tb.tb_running = NULL;
        LIST_INSERT_HEAD(&queue->tq_active, &tb, tb_link);
        in_net_epoch = false;
 
        while ((task = STAILQ_FIRST(&queue->tq_queue)) != NULL) {
                STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
                if (queue->tq_hint == task)
                        queue->tq_hint = NULL;
                pending = task->ta_pending;
                task->ta_pending = 0;
                tb.tb_running = task;
                tb.tb_seq = ++queue->tq_seq;
                TQ_UNLOCK(queue);
 
                KASSERT(task->ta_func != NULL, ("task->ta_func is NULL"));
                if (!in_net_epoch && TASK_IS_NET(task)) {
                        in_net_epoch = true;
                        NET_EPOCH_ENTER(et);
                } else if (in_net_epoch && !TASK_IS_NET(task)) {
                        NET_EPOCH_EXIT(et);
                        in_net_epoch = false;
                }
                task->ta_func(task->ta_context, pending);
 
                TQ_LOCK(queue);
                wakeup(task);
        }
        if (in_net_epoch)
                NET_EPOCH_EXIT(et);
        LIST_REMOVE(&tb, tb_link);
}
 
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;
 
        TQ_ASSERT_LOCKED(queue);
        LIST_FOREACH(tb, &queue->tq_active, tb_link) {
                if (tb->tb_running == task)
                        return (1);
        }
        return (0);
}
 
/*
 * Only use this function in single threaded contexts. It returns
 * non-zero if the given task is either pending or running. Else the
 * task is idle and can be queued again or freed.
 */
int
taskqueue_poll_is_busy(struct taskqueue *queue, struct task *task)
{
        int retval;
 
        TQ_LOCK(queue);
        retval = task->ta_pending > 0 || task_is_running(queue, task);
        TQ_UNLOCK(queue);
 
        return (retval);
}
 
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 (queue->tq_hint == task)
                        queue->tq_hint = NULL;
        }
        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) > 0);
        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, "tq_drain");
        TQ_UNLOCK(queue);
}
 
void
taskqueue_drain_all(struct taskqueue *queue)
{
 
        if (!queue->tq_spin)
                WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, __func__);
 
        TQ_LOCK(queue);
        (void)taskqueue_drain_tq_queue(queue);
        (void)taskqueue_drain_tq_active(queue);
        TQ_UNLOCK(queue);
}
 
void
taskqueue_drain_timeout(struct taskqueue *queue,
    struct timeout_task *timeout_task)
{
 
        /*
         * Set flag to prevent timer from re-starting during drain:
         */
        TQ_LOCK(queue);
        KASSERT((timeout_task->f & DT_DRAIN_IN_PROGRESS) == 0,
            ("Drain already in progress"));
        timeout_task->f |= DT_DRAIN_IN_PROGRESS;
        TQ_UNLOCK(queue);
 
        callout_drain(&timeout_task->c);
        taskqueue_drain(queue, &timeout_task->t);
 
        /*
         * Clear flag to allow timer to re-start:
         */
        TQ_LOCK(queue);
        timeout_task->f &= ~DT_DRAIN_IN_PROGRESS;
        TQ_UNLOCK(queue);
}
 
void
taskqueue_quiesce(struct taskqueue *queue)
{
        int ret;
 
        TQ_LOCK(queue);
        do {
                ret = taskqueue_drain_tq_queue(queue);
                if (ret == 0)
                        ret = taskqueue_drain_tq_active(queue);
        } while (ret != 0);
        TQ_UNLOCK(queue);
}
 
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);
}
 
static int
_taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
    cpuset_t *mask, struct proc *p, const char *name, va_list ap)
{
        char ktname[MAXCOMLEN + 1];
        struct thread *td;
        struct taskqueue *tq;
        int i, error;
 
        if (count <= 0)
                return (EINVAL);
 
        vsnprintf(ktname, sizeof(ktname), name, ap);
        tq = *tqp;
 
        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, p,
                            &tq->tq_threads[i], RFSTOPPED, 0, "%s", ktname);
                else
                        error = kthread_add(taskqueue_thread_loop, tqp, p,
                            &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++;
        }
        if (tq->tq_tcount == 0) {
                free(tq->tq_threads, M_TASKQUEUE);
                tq->tq_threads = NULL;
                return (ENOMEM);
        }
        for (i = 0; i < count; i++) {
                if (tq->tq_threads[i] == NULL)
                        continue;
                td = tq->tq_threads[i];
                if (mask) {
                        error = cpuset_setthread(td->td_tid, mask);
                        /*
                         * Failing to pin is rarely an actual fatal error;
                         * it'll just affect performance.
                         */
                        if (error)
                                printf("%s: curthread=%llu: can't pin; "
                                    "error=%d\n",
                                    __func__,
                                    (unsigned long long) td->td_tid,
                                    error);
                }
                thread_lock(td);
                sched_prio(td, pri);
                sched_add(td, SRQ_BORING);
        }
 
        return (0);
}
 
int
taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
    const char *name, ...)
{
        va_list ap;
        int error;
 
        va_start(ap, name);
        error = _taskqueue_start_threads(tqp, count, pri, NULL, NULL, name, ap);
        va_end(ap);
        return (error);
}
 
int
taskqueue_start_threads_in_proc(struct taskqueue **tqp, int count, int pri,
    struct proc *proc, const char *name, ...)
{
        va_list ap;
        int error;
 
        va_start(ap, name);
        error = _taskqueue_start_threads(tqp, count, pri, NULL, proc, name, ap);
        va_end(ap);
        return (error);
}
 
int
taskqueue_start_threads_cpuset(struct taskqueue **tqp, int count, int pri,
    cpuset_t *mask, const char *name, ...)
{
        va_list ap;
        int error;
 
        va_start(ap, name);
        error = _taskqueue_start_threads(tqp, count, pri, mask, NULL, name, ap);
        va_end(ap);
        return (error);
}
 
static inline void
taskqueue_run_callback(struct taskqueue *tq,
    enum taskqueue_callback_type cb_type)
{
        taskqueue_callback_fn tq_callback;
 
        TQ_ASSERT_UNLOCKED(tq);
        tq_callback = tq->tq_callbacks[cb_type];
        if (tq_callback != NULL)
                tq_callback(tq->tq_cb_contexts[cb_type]);
}
 
void
taskqueue_thread_loop(void *arg)
{
        struct taskqueue **tqp, *tq;
 
        tqp = arg;
        tq = *tqp;
        taskqueue_run_callback(tq, TASKQUEUE_CALLBACK_TYPE_INIT);
        TQ_LOCK(tq);
        while ((tq->tq_flags & TQ_FLAGS_ACTIVE) != 0) {
                /* XXX ? */
                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, "-");
        }
        taskqueue_run_locked(tq);
        /*
         * This thread is on its way out, so just drop the lock temporarily
         * in order to call the shutdown callback.  This allows the callback
         * to look at the taskqueue, even just before it dies.
         */
        TQ_UNLOCK(tq);
        taskqueue_run_callback(tq, TASKQUEUE_CALLBACK_TYPE_SHUTDOWN);
        TQ_LOCK(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;
        wakeup_any(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");
}
 
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);
}