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    Subject[PATCH 30/32] net/9p: replace p9_poll_task with a work
    Date
    Now that cmwq can handle high concurrency, it's more efficient to use
    work than a dedicated kthread. Convert p9_poll_proc() to a work
    function for p9_poll_work and make p9_pollwake() schedule it on each
    poll event. The work is sync flushed on module exit.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    Cc: Eric Van Hensbergen <ericvh@gmail.com>
    Cc: Ron Minnich <rminnich@sandia.gov>
    Cc: Latchesar Ionkov <lucho@ionkov.net>
    Cc: v9fs-developer@lists.sourceforge.net
    ---
    Lightly tested with userland server. Seems to work fine. Please feel
    free to take it into the subsystem tree or simply ack - I'll route it
    through the wq tree.

    Thanks.

    net/9p/trans_fd.c | 32 ++++++++------------------------
    1 files changed, 8 insertions(+), 24 deletions(-)

    diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
    index e9f797d..a30471e 100644
    --- a/net/9p/trans_fd.c
    +++ b/net/9p/trans_fd.c
    @@ -153,9 +153,11 @@ struct p9_conn {
    unsigned long wsched;
    };

    +static void p9_poll_workfn(struct work_struct *work);
    +
    static DEFINE_SPINLOCK(p9_poll_lock);
    static LIST_HEAD(p9_poll_pending_list);
    -static struct task_struct *p9_poll_task;
    +static DECLARE_WORK(p9_poll_work, p9_poll_workfn);

    static void p9_mux_poll_stop(struct p9_conn *m)
    {
    @@ -515,15 +517,14 @@ static int p9_pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
    container_of(wait, struct p9_poll_wait, wait);
    struct p9_conn *m = pwait->conn;
    unsigned long flags;
    - DECLARE_WAITQUEUE(dummy_wait, p9_poll_task);

    spin_lock_irqsave(&p9_poll_lock, flags);
    if (list_empty(&m->poll_pending_link))
    list_add_tail(&m->poll_pending_link, &p9_poll_pending_list);
    spin_unlock_irqrestore(&p9_poll_lock, flags);

    - /* perform the default wake up operation */
    - return default_wake_function(&dummy_wait, mode, sync, key);
    + schedule_work(&p9_poll_work);
    + return 1;
    }

    /**
    @@ -1046,12 +1047,12 @@ static struct p9_trans_module p9_fd_trans = {
    *
    */

    -static int p9_poll_proc(void *a)
    +static void p9_poll_workfn(struct work_struct *work)
    {
    unsigned long flags;

    P9_DPRINTK(P9_DEBUG_TRANS, "start %p\n", current);
    - repeat:
    +
    spin_lock_irqsave(&p9_poll_lock, flags);
    while (!list_empty(&p9_poll_pending_list)) {
    struct p9_conn *conn = list_first_entry(&p9_poll_pending_list,
    @@ -1066,28 +1067,11 @@ static int p9_poll_proc(void *a)
    }
    spin_unlock_irqrestore(&p9_poll_lock, flags);

    - set_current_state(TASK_INTERRUPTIBLE);
    - if (list_empty(&p9_poll_pending_list)) {
    - P9_DPRINTK(P9_DEBUG_TRANS, "sleeping...\n");
    - schedule();
    - }
    - __set_current_state(TASK_RUNNING);
    -
    - if (!kthread_should_stop())
    - goto repeat;
    -
    P9_DPRINTK(P9_DEBUG_TRANS, "finish\n");
    - return 0;
    }

    int p9_trans_fd_init(void)
    {
    - p9_poll_task = kthread_run(p9_poll_proc, NULL, "v9fs-poll");
    - if (IS_ERR(p9_poll_task)) {
    - printk(KERN_WARNING "v9fs: mux: creating poll task failed\n");
    - return PTR_ERR(p9_poll_task);
    - }
    -
    v9fs_register_trans(&p9_tcp_trans);
    v9fs_register_trans(&p9_unix_trans);
    v9fs_register_trans(&p9_fd_trans);
    @@ -1097,7 +1081,7 @@ int p9_trans_fd_init(void)

    void p9_trans_fd_exit(void)
    {
    - kthread_stop(p9_poll_task);
    + flush_work_sync(&p9_poll_work);
    v9fs_unregister_trans(&p9_tcp_trans);
    v9fs_unregister_trans(&p9_unix_trans);
    v9fs_unregister_trans(&p9_fd_trans);
    --
    1.7.1


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