lkml.org 
[lkml]   [2015]   [Jan]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRE: [PATCH net-next 1/7] r8152: adjust rx_bottom
    Date
     David Miller [mailto:davem@davemloft.net] 
    > Sent: Sunday, January 25, 2015 2:44 PM
    [...]
    > What keeps rtl_start_rx() from running in parallel with
    > r8152_submit_rx(), or any other accessor of the RX agg->list?

    Forgive my poor English. I would try to describe them clearly.
    The steps about the rx agg->list would be
    1. carrier on or autoresume occurs.
    2. Call rtl_start_rx().
    3. Rx agg->list flows between device and tp->rx_done.
    4. carrier off or autosuspend occurs.
    5. call rtl_stop_rx().

    The rtl_start_rx() would only be called when the linking
    status is changed from off to on or the auto resume occurs.
    And rtl_start_rx() would reinitialize the tp->rx_done and
    all of the rx agg->list. After step 2, the rx agg->list
    would flow between the usb host controller and the driver.
    If r8152_submit_rx() is success, the driver wouldn't own the
    rx agg->list until it is returned from the usb host controller.
    If r8152_submit_rx() is fail, the driver would still own the
    rx agg->list, and queue it to the tp->rx_done with spin lock
    for next try.

    If the status stays in step 3, only the rx_bottom() would submit
    the rx agg. The rtl_start_rx() wouldn't be called suddenly,
    unless the linking down or auto suspend occur first and linking
    on or auto resume occur again. If linking down or auto suspend
    occur, rtl_stop_rx() would be called (step 5). After this step,
    rx_bottom() wouldn't submit rx, and all rx agg->list would stop
    flowing. That is, the tp->rx_done and all rx agg->list wouldn't
    be changed until the next rtl_start_rx() is called.

    Therefore, the flow for each rx agg->list would be
    a. submittd by rtl_start_rx().
    b. goto step c if success, otherwise goto step d.
    c. completed by usb host controller.
    d. queued to tp->rx_done with spin lock.
    e. dequeue from tp->rx_done with spin lock by rx_botoom().
    f. goto step i if link down, otherwise goto step g.
    g. submitted by rx_botoom().
    h. goto step b.
    i. goto step a if link on.

    And the patch change the step g to g1.
    g1. submitted by rx_botoom() if (!ret), otherwise goto step d.

    Best Regards,
    Hayes
    >
    > You also keep using different terminology from me when
    > discussing what lists do or do not need protection, and that
    > is going to make it difficult for anyone to follow our
    > conversation at all.
    >
    > We're talking specifically about RX agg->list objects and
    > whether access to them need synchronization or not.


    \
     
     \ /
      Last update: 2015-01-26 08:41    [W:3.404 / U:0.364 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site