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    SubjectRe: [PATCH] mtd_blkdevs: Convert to use the kthread API
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    Date
    On Sun, 2007-04-22 at 13:24 +0100, Christoph Hellwig wrote:
    > This is the full conversion I sent to Dave in April 2006, but never
    > got any feedback to:

    Sorry about that; I need prodding sometimes. I'll provide some now...

    Can you show me why the thread won't now miss a wakeup if it goes to
    sleep just as a new request is added to its queue?

    Having already applied Eric's patch, this is the delta to yours...

    diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
    index 1aa018a..d065dba 100644
    --- a/drivers/mtd/mtd_blkdevs.c
    +++ b/drivers/mtd/mtd_blkdevs.c
    @@ -29,9 +29,7 @@ extern struct mutex mtd_table_mutex;
    extern struct mtd_info *mtd_table[];

    struct mtd_blkcore_priv {
    - struct completion thread_dead;
    - int exiting;
    - wait_queue_head_t thread_wq;
    + struct task_struct *thread;
    struct request_queue *rq;
    spinlock_t queue_lock;
    };
    @@ -85,26 +83,18 @@ static int mtd_blktrans_thread(void *arg)
    current->flags |= PF_MEMALLOC | PF_NOFREEZE;

    spin_lock_irq(rq->queue_lock);
    -
    - while (!tr->blkcore_priv->exiting) {
    + while (!kthread_should_stop()) {
    struct request *req;
    struct mtd_blktrans_dev *dev;
    int res = 0;
    - DECLARE_WAITQUEUE(wait, current);

    req = elv_next_request(rq);

    if (!req) {
    - add_wait_queue(&tr->blkcore_priv->thread_wq, &wait);
    - set_current_state(TASK_INTERRUPTIBLE);
    -
    spin_unlock_irq(rq->queue_lock);
    -
    + set_current_state(TASK_INTERRUPTIBLE);
    schedule();
    - remove_wait_queue(&tr->blkcore_priv->thread_wq, &wait);
    -
    spin_lock_irq(rq->queue_lock);
    -
    continue;
    }

    @@ -123,13 +113,13 @@ static int mtd_blktrans_thread(void *arg)
    }
    spin_unlock_irq(rq->queue_lock);

    - complete_and_exit(&tr->blkcore_priv->thread_dead, 0);
    + return 0;
    }

    static void mtd_blktrans_request(struct request_queue *rq)
    {
    struct mtd_blktrans_ops *tr = rq->queuedata;
    - wake_up(&tr->blkcore_priv->thread_wq);
    + wake_up_process(tr->blkcore_priv->thread);
    }


    @@ -355,7 +345,6 @@ static struct mtd_notifier blktrans_notifier = {

    int register_mtd_blktrans(struct mtd_blktrans_ops *tr)
    {
    - struct task_struct *task;
    int ret, i;

    /* Register the notifier if/when the first device type is
    @@ -379,8 +368,6 @@ int register_mtd_blktrans(struct mtd_blktrans_ops *tr)
    return ret;
    }
    spin_lock_init(&tr->blkcore_priv->queue_lock);
    - init_completion(&tr->blkcore_priv->thread_dead);
    - init_waitqueue_head(&tr->blkcore_priv->thread_wq);

    tr->blkcore_priv->rq = blk_init_queue(mtd_blktrans_request, &tr->blkcore_priv->queue_lock);
    if (!tr->blkcore_priv->rq) {
    @@ -394,13 +381,14 @@ int register_mtd_blktrans(struct mtd_blktrans_ops *tr)
    blk_queue_hardsect_size(tr->blkcore_priv->rq, tr->blksize);
    tr->blkshift = ffs(tr->blksize) - 1;

    - task = kthread_run(mtd_blktrans_thread, tr, "%sd", tr->name);
    - if (IS_ERR(task)) {
    + tr->blkcore_priv->thread = kthread_run(mtd_blktrans_thread, tr,
    + "%sd", tr->name);
    + if (IS_ERR(tr->blkcore_priv->thread)) {
    blk_cleanup_queue(tr->blkcore_priv->rq);
    unregister_blkdev(tr->major, tr->name);
    kfree(tr->blkcore_priv);
    mutex_unlock(&mtd_table_mutex);
    - return PTR_ERR(task);
    + return PTR_ERR(tr->blkcore_priv->thread);
    }

    INIT_LIST_HEAD(&tr->devs);
    @@ -423,9 +411,7 @@ int deregister_mtd_blktrans(struct mtd_blktrans_ops *tr)
    mutex_lock(&mtd_table_mutex);

    /* Clean up the kernel thread */
    - tr->blkcore_priv->exiting = 1;
    - wake_up(&tr->blkcore_priv->thread_wq);
    - wait_for_completion(&tr->blkcore_priv->thread_dead);
    + kthread_stop(tr->blkcore_priv->thread);

    /* Remove it from the list of active majors */
    list_del(&tr->list);

    --
    dwmw2

    -
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