static void nbd_read(void *opaque)
{
    NBDClient *client = opaque;

    if (client->recv_coroutine) {
        qemu_coroutine_enter(client->recv_coroutine, NULL);
    } else {
        qemu_coroutine_enter(qemu_coroutine_create(nbd_trip), client);
    }
}

static void test_co_queue(void)
{
    Coroutine *c1;
    Coroutine *c2;

    c1 = qemu_coroutine_create(c1_fn);
    c2 = qemu_coroutine_create(c2_fn);

    qemu_coroutine_enter(c1, c2);
    memset(c1, 0xff, sizeof(Coroutine));
    qemu_coroutine_enter(c2, NULL);
}

static void coroutine_fn verify_entered_step_1(void *opaque)
{
    Coroutine *self = qemu_coroutine_self();
    Coroutine *coroutine;

    g_assert(qemu_coroutine_entered(self));

    coroutine = qemu_coroutine_create(verify_entered_step_2, self);
    g_assert(!qemu_coroutine_entered(coroutine));
    qemu_coroutine_enter(coroutine);
    g_assert(!qemu_coroutine_entered(coroutine));
    qemu_coroutine_enter(coroutine);
}

static void test_self(void)
{
    Coroutine *coroutine;

    coroutine = qemu_coroutine_create(verify_self);
    qemu_coroutine_enter(coroutine, coroutine);
}

static int do_co_write_zeroes(int64_t offset, int count, int *total)
{
    Coroutine *co;
    CoWriteZeroes data = {
        .offset = offset,
        .count  = count,
        .total  = total,
        .done   = false,
    };

    co = qemu_coroutine_create(co_write_zeroes_entry);
    qemu_coroutine_enter(co, &data);
    while (!data.done) {
        qemu_aio_wait();
    }
    if (data.ret < 0) {
        return data.ret;
    } else {
        return 1;
    }
}

static int do_write_compressed(char *buf, int64_t offset, int count, int *total)
{
    int ret;

    ret = bdrv_write_compressed(bs, offset >> 9, (uint8_t *)buf, count >> 9);
    if (ret < 0) {
        return ret;
    }
    *total = count;
    return 1;
}

int simple_bus_fdt_init(char *bus_node_path, FDTMachineInfo *fdti, void *unused)
{
    int i;
    int num_children = qemu_devtree_get_num_children(fdti->fdt, bus_node_path,
                                                        1);
    char **children = qemu_devtree_get_children(fdti->fdt, bus_node_path, 1);
    int initialRoutinesPending = fdti->routinesPending;

    DB_PRINT("num child devices: %d\n", num_children);

    for (i = 0; i < num_children; i++) {
        struct FDTInitNodeArgs *init_args = g_malloc0(sizeof(*init_args));
        init_args->node_path = children[i];
        init_args->fdti = fdti;
        fdti->routinesPending++;
        qemu_coroutine_enter(qemu_coroutine_create(fdt_init_node), init_args);
    }

    if (fdti->routinesPending != initialRoutinesPending) {
        bdrv_drain_all();
    }

    g_free(children);
    return 0;
}

static void test_lifecycle(void)
{
    Coroutine *coroutine;
    bool done = false;

    /* Create, enter, and return from coroutine */
    coroutine = qemu_coroutine_create(set_and_exit);
    qemu_coroutine_enter(coroutine, &done);
    g_assert(done); /* expect done to be true (first time) */

    /* Repeat to check that no state affects this test */
    done = false;
    coroutine = qemu_coroutine_create(set_and_exit);
    qemu_coroutine_enter(coroutine, &done);
    g_assert(done); /* expect done to be true (second time) */
}

void block_job_enter(BlockJob *job)
{
    block_job_iostatus_reset(job);
    if (job->co && !job->busy) {
        qemu_coroutine_enter(job->co, NULL);
    }
}

static void mirror_iteration_done(MirrorOp *op, int ret)
{
    MirrorBlockJob *s = op->s;
    struct iovec *iov;
    int64_t chunk_num;
    int i, nb_chunks, sectors_per_chunk;

    trace_mirror_iteration_done(s, op->sector_num, op->nb_sectors, ret);

    s->in_flight--;
    iov = op->qiov.iov;
    for (i = 0; i < op->qiov.niov; i++) {
        MirrorBuffer *buf = (MirrorBuffer *) iov[i].iov_base;
        QSIMPLEQ_INSERT_TAIL(&s->buf_free, buf, next);
        s->buf_free_count++;
    }

    sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
    chunk_num = op->sector_num / sectors_per_chunk;
    nb_chunks = op->nb_sectors / sectors_per_chunk;
    bitmap_clear(s->in_flight_bitmap, chunk_num, nb_chunks);
    if (s->cow_bitmap && ret >= 0) {
        bitmap_set(s->cow_bitmap, chunk_num, nb_chunks);
    }

    g_slice_free(MirrorOp, op);
    qemu_coroutine_enter(s->common.co, NULL);
}

static void iscsi_co_generic_bh_cb(void *opaque)
{
    struct IscsiTask *iTask = opaque;
    iTask->complete = 1;
    qemu_bh_delete(iTask->bh);
    qemu_coroutine_enter(iTask->co, NULL);
}

static void test_nesting(void)
{
    Coroutine *root;
    NestData nd = {
        .n_enter  = 0,
        .n_return = 0,
        .max      = 128,
    };

    root = qemu_coroutine_create(nest);
    qemu_coroutine_enter(root, &nd);

    /* Must enter and return from max nesting level */
    g_assert_cmpint(nd.n_enter, ==, nd.max);
    g_assert_cmpint(nd.n_return, ==, nd.max);
}

/*
 * Check that yield/enter transfer control correctly
 */

static void coroutine_fn yield_5_times(void *opaque)
{
    bool *done = opaque;
    int i;

    for (i = 0; i < 5; i++) {
        qemu_coroutine_yield();
    }
    *done = true;
}

static int do_co_write_zeroes(int64_t offset, int count, int *total)
{
    Coroutine *co;
    CoWriteZeroes data = {
        .offset = offset,
        .count  = count,
        .total  = total,
        .done   = false,
    };

    co = qemu_coroutine_create(co_write_zeroes_entry);
    qemu_coroutine_enter(co, &data);
    while (!data.done) {
        qemu_aio_wait();
    }
    if (data.ret < 0) {
        return data.ret;
    } else {
        return 1;
    }
}

static int do_load_vmstate(char *buf, int64_t offset, int count, int *total)
{
    *total = bdrv_load_vmstate(bs, (uint8_t *)buf, offset, count);
    if (*total < 0) {
        return *total;
    }
    return 1;
}

static void
iscsi_co_generic_cb(struct iscsi_context *iscsi, int status,
                        void *command_data, void *opaque)
{
    struct IscsiTask *iTask = opaque;
    struct scsi_task *task = command_data;

    iTask->complete = 1;
    iTask->status = status;
    iTask->do_retry = 0;
    iTask->task = task;

    if (iTask->retries-- > 0 && status == SCSI_STATUS_CHECK_CONDITION
        && task->sense.key == SCSI_SENSE_UNIT_ATTENTION) {
        iTask->do_retry = 1;
        goto out;
    }

    if (status != SCSI_STATUS_GOOD) {
        error_report("iSCSI: Failure. %s", iscsi_get_error(iscsi));
    }

out:
    if (iTask->co) {
        qemu_coroutine_enter(iTask->co, NULL);
    }
}

static void mirror_start_job(BlockDriverState *bs, BlockDriverState *target,
                             const char *replaces,
                             int64_t speed, int64_t granularity,
                             int64_t buf_size,
                             BlockdevOnError on_source_error,
                             BlockdevOnError on_target_error,
                             BlockDriverCompletionFunc *cb,
                             void *opaque, Error **errp,
                             const BlockJobDriver *driver,
                             bool is_none_mode, BlockDriverState *base)
{
    MirrorBlockJob *s;

    if (granularity == 0) {
        /* Choose the default granularity based on the target file's cluster
         * size, clamped between 4k and 64k.  */
        BlockDriverInfo bdi;
        if (bdrv_get_info(target, &bdi) >= 0 && bdi.cluster_size != 0) {
            granularity = MAX(4096, bdi.cluster_size);
            granularity = MIN(65536, granularity);
        } else {
            granularity = 65536;
        }
    }

    assert ((granularity & (granularity - 1)) == 0);

    if ((on_source_error == BLOCKDEV_ON_ERROR_STOP ||
         on_source_error == BLOCKDEV_ON_ERROR_ENOSPC) &&
        !bdrv_iostatus_is_enabled(bs)) {
        error_set(errp, QERR_INVALID_PARAMETER, "on-source-error");
        return;
    }


    s = block_job_create(driver, bs, speed, cb, opaque, errp);
    if (!s) {
        return;
    }

    s->replaces = g_strdup(replaces);
    s->on_source_error = on_source_error;
    s->on_target_error = on_target_error;
    s->target = target;
    s->is_none_mode = is_none_mode;
    s->base = base;
    s->granularity = granularity;
    s->buf_size = MAX(buf_size, granularity);

    s->dirty_bitmap = bdrv_create_dirty_bitmap(bs, granularity, errp);
    if (!s->dirty_bitmap) {
        return;
    }
    bdrv_set_enable_write_cache(s->target, true);
    bdrv_set_on_error(s->target, on_target_error, on_target_error);
    bdrv_iostatus_enable(s->target);
    s->common.co = qemu_coroutine_create(mirror_run);
    trace_mirror_start(bs, s, s->common.co, opaque);
    qemu_coroutine_enter(s->common.co, s);
}

static void qemu_gluster_complete_aio(void *opaque)
{
    GlusterAIOCB *acb = (GlusterAIOCB *)opaque;

    qemu_bh_delete(acb->bh);
    acb->bh = NULL;
    qemu_coroutine_enter(acb->coroutine, NULL);
}

static void iscsi_retry_timer_expired(void *opaque)
{
    struct IscsiTask *iTask = opaque;
    iTask->complete = 1;
    if (iTask->co) {
        qemu_coroutine_enter(iTask->co, NULL);
    }
}

static void test_entered(void)
{
    Coroutine *coroutine;

    coroutine = qemu_coroutine_create(verify_entered_step_1, NULL);
    g_assert(!qemu_coroutine_entered(coroutine));
    qemu_coroutine_enter(coroutine);
}

static void restart_coroutine(void *opaque)
{
    Coroutine *co = opaque;

    DPRINTF("co=%p", co);

    qemu_coroutine_enter(co, NULL);
}

static gboolean qio_channel_yield_enter(QIOChannel *ioc,
                                        GIOCondition condition,
                                        gpointer opaque)
{
    QIOChannelYieldData *data = opaque;
    qemu_coroutine_enter(data->co);
    return FALSE;
}

void block_job_resume(BlockJob *job)
{
    job->paused = false;
    block_job_iostatus_reset(job);
    if (job->co && !job->busy) {
        qemu_coroutine_enter(job->co, NULL);
    }
}