/*-
 * Copyright (c) 2000 Doug Rabson
 * Copyright (c) 2014 Jeff Roberson
 * Copyright (c) 2016 Matthew Macy
 * 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>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/cpumask.h>
#include <sys/kernel.h>
#include <sys/libkern.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/proc.h>
#include <sys/sched.h>
#include <sys/gtaskqueue.h>
#include <sys/unistd.h>
#include <machine/stdarg.h>

static MALLOC_DEFINE(M_GTASKQUEUE, "gtaskqueue", "Group Task Queues");
static void     gtaskqueue_thread_enqueue(void *);
static void     gtaskqueue_thread_loop(void *arg);
static int      task_is_running(struct gtaskqueue *queue, struct gtask *gtask);
static void     gtaskqueue_drain_locked(struct gtaskqueue *queue, struct gtask *gtask);

TASKQGROUP_DEFINE(softirq, ncpus, 1);

struct gtaskqueue_busy {
        struct gtask            *tb_running;
        u_int                    tb_seq;
        LIST_ENTRY(gtaskqueue_busy) tb_link;
};

typedef void (*gtaskqueue_enqueue_fn)(void *context);

struct gtaskqueue {
        STAILQ_HEAD(, gtask)    tq_queue;
        LIST_HEAD(, gtaskqueue_busy) tq_active;
        u_int                   tq_seq;
        int                     tq_callouts;
        struct lock             tq_lock;
        gtaskqueue_enqueue_fn   tq_enqueue;
        void                    *tq_context;
        const char              *tq_name;
        struct thread           **tq_threads;
        int                     tq_tcount;
        int                     tq_flags;
#if 0
        taskqueue_callback_fn   tq_callbacks[TASKQUEUE_NUM_CALLBACKS];
        void                    *tq_cb_contexts[TASKQUEUE_NUM_CALLBACKS];
#endif
};

#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 TQ_LOCK(tq)             lockmgr(&(tq)->tq_lock, LK_EXCLUSIVE)
#define TQ_ASSERT_LOCKED(tq)    KKASSERT(lockstatus(&(tq)->tq_lock, NULL) != 0)
#define TQ_UNLOCK(tq)           lockmgr(&(tq)->tq_lock, LK_RELEASE);
#define TQ_ASSERT_UNLOCKED(tq)  KKASSERT(lockstatus(&(tq)->tq_lock, NULL) == 0)

#ifdef INVARIANTS
static void
gtask_dump(struct gtask *gtask)
{
        kprintf("gtask: %p ta_flags=%x ta_priority=%d ta_func=%p "
                "ta_context=%p\n",
                gtask, gtask->ta_flags, gtask->ta_priority,
                gtask->ta_func, gtask->ta_context);
}
#endif

static __inline int
TQ_SLEEP(struct gtaskqueue *tq, void *p, const char *wm)
{
        return (lksleep(p, &tq->tq_lock, 0, wm, 0));
}

static struct gtaskqueue *
_gtaskqueue_create(const char *name, int mflags,
                 taskqueue_enqueue_fn enqueue, void *context,
                 int lkflags, const char *mtxname __unused)
{
        struct gtaskqueue *queue;

        queue = kmalloc(sizeof(struct gtaskqueue),
                        M_GTASKQUEUE, mflags | M_ZERO);
        if (!queue) {
                kprintf("_gtaskqueue_create: kmalloc failed %08x\n", mflags);
                return (NULL);
        }

        STAILQ_INIT(&queue->tq_queue);
        LIST_INIT(&queue->tq_active);
        queue->tq_enqueue = enqueue;
        queue->tq_context = context;
        queue->tq_name = name ? name : "taskqueue";
        queue->tq_flags |= TQ_FLAGS_ACTIVE;
        if (enqueue == gtaskqueue_thread_enqueue)
                queue->tq_flags |= TQ_FLAGS_UNLOCKED_ENQUEUE;
        lockinit(&queue->tq_lock, queue->tq_name, 0, 0);

        return (queue);
}

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

        while (tq->tq_tcount > 0 || tq->tq_callouts > 0) {
                wakeup(tq);
                TQ_SLEEP(tq, pp, "gtq_destroy");
        }
}

static void __unused
gtaskqueue_free(struct gtaskqueue *queue)
{

        TQ_LOCK(queue);
        queue->tq_flags &= ~TQ_FLAGS_ACTIVE;
        gtaskqueue_terminate(queue->tq_threads, queue);
        KASSERT(LIST_EMPTY(&queue->tq_active), ("Tasks still running?"));
        KASSERT(queue->tq_callouts == 0, ("Armed timeout tasks"));
        lockuninit(&queue->tq_lock);
        kfree(queue->tq_threads, M_GTASKQUEUE);
        /*kfree(queue->tq_name, M_GTASKQUEUE);*/
        kfree(queue, M_GTASKQUEUE);
}

/*
 * Wait for all to complete, then prevent it from being enqueued
 */
void
grouptask_block(struct grouptask *grouptask)
{
        struct gtaskqueue *queue = grouptask->gt_taskqueue;
        struct gtask *gtask = &grouptask->gt_task;

#ifdef INVARIANTS
        if (queue == NULL) {
                gtask_dump(gtask);
                panic("queue == NULL");
        }
#endif
        TQ_LOCK(queue);
        gtask->ta_flags |= TASK_NOENQUEUE;
        gtaskqueue_drain_locked(queue, gtask);
        TQ_UNLOCK(queue);
}

void
grouptask_unblock(struct grouptask *grouptask)
{
        struct gtaskqueue *queue = grouptask->gt_taskqueue;
        struct gtask *gtask = &grouptask->gt_task;

#ifdef INVARIANTS
        if (queue == NULL) {
                gtask_dump(gtask);
                panic("queue == NULL");
        }
#endif
        TQ_LOCK(queue);
        gtask->ta_flags &= ~TASK_NOENQUEUE;
        TQ_UNLOCK(queue);
}

int
grouptaskqueue_enqueue(struct gtaskqueue *queue, struct gtask *gtask)
{
#ifdef INVARIANTS
        if (queue == NULL) {
                gtask_dump(gtask);
                panic("queue == NULL");
        }
#endif
        TQ_LOCK(queue);
        if (gtask->ta_flags & TASK_ENQUEUED) {
                TQ_UNLOCK(queue);
                return (0);
        }
        if (gtask->ta_flags & TASK_NOENQUEUE) {
                TQ_UNLOCK(queue);
                return (EAGAIN);
        }
        STAILQ_INSERT_TAIL(&queue->tq_queue, gtask, ta_link);
        gtask->ta_flags |= TASK_ENQUEUED;
        TQ_UNLOCK(queue);
        if ((queue->tq_flags & TQ_FLAGS_BLOCKED) == 0)
                queue->tq_enqueue(queue->tq_context);
        return (0);
}

static void
gtaskqueue_task_nop_fn(void *context)
{
}

/*
 * Block until all currently queued tasks in this taskqueue
 * have begun execution.  Tasks queued during execution of
 * this function are ignored.
 */
static void
gtaskqueue_drain_tq_queue(struct gtaskqueue *queue)
{
        struct gtask t_barrier;

        if (STAILQ_EMPTY(&queue->tq_queue))
                return;

        /*
         * 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.
         */
        GTASK_INIT(&t_barrier, 0, USHRT_MAX, gtaskqueue_task_nop_fn, &t_barrier);
        STAILQ_INSERT_TAIL(&queue->tq_queue, &t_barrier, ta_link);
        t_barrier.ta_flags |= TASK_ENQUEUED;

        /*
         * Once the barrier has executed, all previously queued tasks
         * have completed or are currently executing.
         */
        while (t_barrier.ta_flags & TASK_ENQUEUED)
                TQ_SLEEP(queue, &t_barrier, "gtq_qdrain");
}

/*
 * Block until all currently executing tasks for this taskqueue
 * complete.  Tasks that begin execution during the execution
 * of this function are ignored.
 */
static void
gtaskqueue_drain_tq_active(struct gtaskqueue *queue)
{
        struct gtaskqueue_busy *tb;
        u_int seq;

        if (LIST_EMPTY(&queue->tq_active))
                return;

        /* 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, "gtq_adrain");
                        goto restart;
                }
        }

        /* Release taskqueue_terminate(). */
        queue->tq_callouts--;
        if ((queue->tq_flags & TQ_FLAGS_ACTIVE) == 0)
                wakeup_one(queue->tq_threads);
}

void
gtaskqueue_block(struct gtaskqueue *queue)
{

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

void
gtaskqueue_unblock(struct gtaskqueue *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
gtaskqueue_run_locked(struct gtaskqueue *queue)
{
        struct gtaskqueue_busy tb;
        struct gtask *gtask;
#if 0
        struct epoch_tracker et;
        bool in_net_epoch;
#endif

        KASSERT(queue != NULL, ("tq is NULL"));
        TQ_ASSERT_LOCKED(queue);
        tb.tb_running = NULL;
        LIST_INSERT_HEAD(&queue->tq_active, &tb, tb_link);
#if 0
        in_net_epoch = false;
#endif

        while ((gtask = STAILQ_FIRST(&queue->tq_queue)) != NULL) {
                STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
                gtask->ta_flags &= ~TASK_ENQUEUED;
                tb.tb_running = gtask;
                tb.tb_seq = ++queue->tq_seq;
                TQ_UNLOCK(queue);

                KASSERT(gtask->ta_func != NULL, ("task->ta_func is NULL"));
#if 0
                if (!in_net_epoch && TASK_IS_NET(gtask)) {
                        in_net_epoch = true;
                        NET_EPOCH_ENTER(et);
                } else if (in_net_epoch && !TASK_IS_NET(gtask)) {
                        NET_EPOCH_EXIT(et);
                        in_net_epoch = false;
                }
#endif
                gtask->ta_func(gtask->ta_context);

                TQ_LOCK(queue);
                wakeup(gtask);
        }
#if 0
        if (in_net_epoch)
                NET_EPOCH_EXIT(et);
#endif
        LIST_REMOVE(&tb, tb_link);
}

static int
task_is_running(struct gtaskqueue *queue, struct gtask *gtask)
{
        struct gtaskqueue_busy *tb;

        TQ_ASSERT_LOCKED(queue);
        LIST_FOREACH(tb, &queue->tq_active, tb_link) {
                if (tb->tb_running == gtask)
                        return (1);
        }
        return (0);
}

static int
gtaskqueue_cancel_locked(struct gtaskqueue *queue, struct gtask *gtask)
{

        if (gtask->ta_flags & TASK_ENQUEUED)
                STAILQ_REMOVE(&queue->tq_queue, gtask, gtask, ta_link);
        gtask->ta_flags &= ~TASK_ENQUEUED;
        return (task_is_running(queue, gtask) ? EBUSY : 0);
}

int
gtaskqueue_cancel(struct gtaskqueue *queue, struct gtask *gtask)
{
        int error;

        TQ_LOCK(queue);
        error = gtaskqueue_cancel_locked(queue, gtask);
        TQ_UNLOCK(queue);

        return (error);
}

static void
gtaskqueue_drain_locked(struct gtaskqueue *queue, struct gtask *gtask)
{
        while ((gtask->ta_flags & TASK_ENQUEUED) || task_is_running(queue, gtask))
                TQ_SLEEP(queue, gtask, "gtq_drain");
}

void
gtaskqueue_drain(struct gtaskqueue *queue, struct gtask *gtask)
{
        TQ_LOCK(queue);
        gtaskqueue_drain_locked(queue, gtask);
        TQ_UNLOCK(queue);
}

void
gtaskqueue_drain_all(struct gtaskqueue *queue)
{

        TQ_LOCK(queue);
        gtaskqueue_drain_tq_queue(queue);
        gtaskqueue_drain_tq_active(queue);
        TQ_UNLOCK(queue);
}

static int __printflike(4, 0)
_gtaskqueue_start_threads(struct gtaskqueue **tqp, int count, int pri,
                          const char *name, __va_list ap)
{
        char ktname[MAXCOMLEN + 1];
        struct thread *td;
        struct gtaskqueue *tq;
        int i, error;

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

        kvsnprintf(ktname, sizeof(ktname), name, ap);
        tq = *tqp;

        tq->tq_threads = kmalloc(sizeof(struct thread *) * count,
                                 M_GTASKQUEUE, M_WAITOK | M_ZERO);

        for (i = 0; i < count; i++) {
                int cpu = i % ncpus;
                if (count == 1) {
                        error = lwkt_create(gtaskqueue_thread_loop, tqp,
                                            &tq->tq_threads[i], NULL,
                                            TDF_NOSTART, cpu,
                                            "%s", ktname);
                } else {
                        error = lwkt_create(gtaskqueue_thread_loop, tqp,
                                            &tq->tq_threads[i], NULL,
                                            TDF_NOSTART, cpu,
                                            "%s_%d", ktname, i);
                }
                if (error) {
                        /* should be ok to continue, taskqueue_free will dtrt */
                        kprintf("%s: lwkt_create(%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];
                lwkt_setpri_initial(td, pri);
                lwkt_schedule(td);
        }

        return (0);
}

static int __printflike(4, 5)
gtaskqueue_start_threads(struct gtaskqueue **tqp, int count, int pri,
                         const char *name, ...)
{
        __va_list ap;
        int error;

        __va_start(ap, name);
        error = _gtaskqueue_start_threads(tqp, count, pri, name, ap);
        __va_end(ap);
        return (error);
}

#if 0
static inline void
gtaskqueue_run_callback(struct gtaskqueue *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]);
}
#endif

static void
gtaskqueue_thread_loop(void *arg)
{
        struct gtaskqueue **tqp, *tq;

        tqp = arg;
        tq = *tqp;
#if 0
        gtaskqueue_run_callback(tq, TASKQUEUE_CALLBACK_TYPE_INIT);
#endif
        TQ_LOCK(tq);
        while ((tq->tq_flags & TQ_FLAGS_ACTIVE) != 0) {
                /* XXX ? */
                gtaskqueue_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, "-");
        }
        gtaskqueue_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.
         */
#if 0
        TQ_UNLOCK(tq);
        gtaskqueue_run_callback(tq, TASKQUEUE_CALLBACK_TYPE_SHUTDOWN);
        TQ_LOCK(tq);
#endif

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

static void
gtaskqueue_thread_enqueue(void *context)
{
        struct gtaskqueue **tqp, *tq;

        tqp = context;
        tq = *tqp;
        wakeup_one(tq);
}

/*
 * NOTE: FreeBSD uses MTX_SPIN locks, which doesn't make a whole lot
 *       of sense (over-use of spin-locks in general). In DFly we
 *       want to use blockable locks for almost everything.
 */
static struct gtaskqueue *
gtaskqueue_create_fast(const char *name, int mflags,
                       taskqueue_enqueue_fn enqueue, void *context)
{
        return _gtaskqueue_create(name, mflags, enqueue, context,
                                  0, "fast_taskqueue");
}

struct taskqgroup_cpu {
        LIST_HEAD(, grouptask) tgc_tasks;
        struct gtaskqueue *tgc_taskq;
        int             tgc_cnt;
        int             tgc_cpu;
};

struct taskqgroup {
        struct taskqgroup_cpu tqg_queue[MAXCPU];
        struct lock     tqg_lock;
        const char *    tqg_name;
        int             tqg_cnt;
};

struct taskq_bind_task {
        struct gtask bt_task;
        int     bt_cpuid;
};

static void
taskqgroup_cpu_create(struct taskqgroup *qgroup, int idx, int cpu)
{
        struct taskqgroup_cpu *qcpu;

        qcpu = &qgroup->tqg_queue[idx];
        LIST_INIT(&qcpu->tgc_tasks);
        qcpu->tgc_taskq = gtaskqueue_create_fast(NULL, M_WAITOK,
                                                 gtaskqueue_thread_enqueue,
                                                 &qcpu->tgc_taskq);
        gtaskqueue_start_threads(&qcpu->tgc_taskq, 1, TDPRI_KERN_DAEMON,
                                 "%s_%d", qgroup->tqg_name, idx);
        qcpu->tgc_cpu = cpu;
}

/*
 * Find the taskq with least # of tasks that doesn't currently have any
 * other queues from the uniq identifier.
 */
static int
taskqgroup_find(struct taskqgroup *qgroup, void *uniq)
{
        struct grouptask *n;
        int i, idx, mincnt;
        int strict;

        KKASSERT(lockstatus(&qgroup->tqg_lock, NULL) != 0);
        KASSERT(qgroup->tqg_cnt != 0,
            ("qgroup %s has no queues", qgroup->tqg_name));

        /*
         * Two passes: first scan for a queue with the least tasks that
         * does not already service this uniq id.  If that fails simply find
         * the queue with the least total tasks.
         */
        for (idx = -1, mincnt = INT_MAX, strict = 1; mincnt == INT_MAX;
            strict = 0) {
                for (i = 0; i < qgroup->tqg_cnt; i++) {
                        if (qgroup->tqg_queue[i].tgc_cnt > mincnt)
                                continue;
                        if (strict) {
                                LIST_FOREACH(n, &qgroup->tqg_queue[i].tgc_tasks,
                                    gt_list)
                                        if (n->gt_uniq == uniq)
                                                break;
                                if (n != NULL)
                                        continue;
                        }
                        mincnt = qgroup->tqg_queue[i].tgc_cnt;
                        idx = i;
                }
        }
        if (idx == -1)
                panic("%s: failed to pick a qid.", __func__);

        return (idx);
}

void
taskqgroup_attach(struct taskqgroup *qgroup, struct grouptask *gtask,
    void *uniq, device_t dev, struct resource *irq, const char *name)
{
        int cpu, qid, error;

        KASSERT(qgroup->tqg_cnt > 0,
            ("qgroup %s has no queues", qgroup->tqg_name));

        gtask->gt_uniq = uniq;
        ksnprintf(gtask->gt_name, GROUPTASK_NAMELEN, "%s", name ? name : "grouptask");
        gtask->gt_dev = dev;
        gtask->gt_irq = irq;
        gtask->gt_cpu = -1;
        lockmgr(&qgroup->tqg_lock, LK_EXCLUSIVE);
        qid = taskqgroup_find(qgroup, uniq);
        qgroup->tqg_queue[qid].tgc_cnt++;
        LIST_INSERT_HEAD(&qgroup->tqg_queue[qid].tgc_tasks, gtask, gt_list);
        gtask->gt_taskqueue = qgroup->tqg_queue[qid].tgc_taskq;
        if (dev != NULL && irq != NULL) {
                cpu = qgroup->tqg_queue[qid].tgc_cpu;
                gtask->gt_cpu = cpu;
                lockmgr(&qgroup->tqg_lock, LK_RELEASE);
#if 0
                /*
                 * XXX FreeBSD created a mess by separating out the cpu
                 * binding from bus_setup_intr().  Punt for now.
                 */
                error = bus_bind_intr(dev, irq, cpu);
#endif
                error = 0;

                if (error)
                        kprintf("%s: binding interrupt failed for %s: %d\n",
                            __func__, gtask->gt_name, error);
        } else {
                lockmgr(&qgroup->tqg_lock, LK_RELEASE);
        }
}

int
taskqgroup_attach_cpu(struct taskqgroup *qgroup, struct grouptask *gtask,
    void *uniq, int cpu, device_t dev, struct resource *irq, const char *name)
{
        int i, qid, error;

        gtask->gt_uniq = uniq;
        ksnprintf(gtask->gt_name, GROUPTASK_NAMELEN, "%s", name ? name : "grouptask");
        gtask->gt_dev = dev;
        gtask->gt_irq = irq;
        gtask->gt_cpu = cpu;
        lockmgr(&qgroup->tqg_lock, LK_EXCLUSIVE);
        for (i = 0, qid = -1; i < qgroup->tqg_cnt; i++) {
                if (qgroup->tqg_queue[i].tgc_cpu == cpu) {
                        qid = i;
                        break;
                }
        }
        if (qid == -1) {
                lockmgr(&qgroup->tqg_lock, LK_RELEASE);
                kprintf("%s: qid not found for %s cpu=%d\n",
                        __func__, gtask->gt_name, cpu);
                return (EINVAL);
        }
        qgroup->tqg_queue[qid].tgc_cnt++;
        LIST_INSERT_HEAD(&qgroup->tqg_queue[qid].tgc_tasks, gtask, gt_list);
        gtask->gt_taskqueue = qgroup->tqg_queue[qid].tgc_taskq;
        cpu = qgroup->tqg_queue[qid].tgc_cpu;
        lockmgr(&qgroup->tqg_lock, LK_RELEASE);

        if (dev != NULL && irq != NULL) {
#if 0
                /*
                 * XXX FreeBSD created a mess by separating out the cpu
                 * binding from bus_setup_intr().  Punt for now.
                 */
                error = bus_bind_intr(dev, irq, cpu);
#endif
                error = 0;

                if (error) {
                        kprintf("%s: binding interrupt failed for %s: %d\n",
                            __func__, gtask->gt_name, error);
                }
        }
        return (0);
}

void
taskqgroup_detach(struct taskqgroup *qgroup, struct grouptask *gtask)
{
        int i;

        grouptask_block(gtask);
        lockmgr(&qgroup->tqg_lock, LK_EXCLUSIVE);
        for (i = 0; i < qgroup->tqg_cnt; i++)
                if (qgroup->tqg_queue[i].tgc_taskq == gtask->gt_taskqueue)
                        break;
        if (i == qgroup->tqg_cnt)
                panic("%s: task %s not in group", __func__, gtask->gt_name);
        qgroup->tqg_queue[i].tgc_cnt--;
        LIST_REMOVE(gtask, gt_list);
        lockmgr(&qgroup->tqg_lock, LK_RELEASE);
        gtask->gt_taskqueue = NULL;
        gtask->gt_task.ta_flags &= ~TASK_NOENQUEUE;
}

static void
taskqgroup_binder(void *ctx)
{
        struct taskq_bind_task *gtask;

        gtask = ctx;
        lwkt_migratecpu(gtask->bt_cpuid);
        kfree(gtask, M_DEVBUF);
}

void
taskqgroup_bind(struct taskqgroup *qgroup)
{
        struct taskq_bind_task *gtask;
        int i;

        /*
         * Bind taskqueue threads to specific CPUs, if they have been assigned
         * one.
         */
        if (qgroup->tqg_cnt == 1)
                return;

        for (i = 0; i < qgroup->tqg_cnt; i++) {
                gtask = kmalloc(sizeof(*gtask), M_DEVBUF, M_WAITOK);
                GTASK_INIT(&gtask->bt_task, 0, 0, taskqgroup_binder, gtask);
                gtask->bt_cpuid = qgroup->tqg_queue[i].tgc_cpu;
                grouptaskqueue_enqueue(qgroup->tqg_queue[i].tgc_taskq,
                                       &gtask->bt_task);
        }
}

struct taskqgroup *
taskqgroup_create(const char *name, int cnt, int stride)
{
        struct taskqgroup *qgroup;
        int cpu, i, j;

        qgroup = kmalloc(sizeof(*qgroup), M_GTASKQUEUE, M_WAITOK | M_ZERO);
        lockinit(&qgroup->tqg_lock, "taskqgroup", 0, 0);
        qgroup->tqg_name = name;
        qgroup->tqg_cnt = cnt;

        for (cpu = i = 0; i < cnt; i++) {
                taskqgroup_cpu_create(qgroup, i, cpu);
                for (j = 0; j < stride; j++)
                        cpu = (cpu + 1) % ncpus;
        }
        return (qgroup);
}

void
taskqgroup_destroy(struct taskqgroup *qgroup)
{
}

void
taskqgroup_drain_all(struct taskqgroup *tqg)
{
        struct gtaskqueue *q;

        for (int i = 0; i < ncpus; i++) {
                q = tqg->tqg_queue[i].tgc_taskq;
                if (q == NULL)
                        continue;
                gtaskqueue_drain_all(q);
        }
}