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    Subject[34-longterm 220/260] staging: usbip: Process event flags without delay
    Date
    From: Max Vozeler <mvz@vozeler.com>

    commit 584c5b7cf06194464240280483ee0376cdddbbae upstream.

    The way the event handler works can cause it to delay
    events until eventual wakeup for another event.

    For example, on device detach (vhci):

    - Write to sysfs detach file
    -> usbip_event_add(VDEV_EVENT_DOWN)
    -> wakeup()

    #define VDEV_EVENT_DOWN (USBIP_EH_SHUTDOWN | USBIP_EH_RESET).

    - Event thread wakes up and passes the event to
    event_handler() to process.

    - It processes and clears the USBIP_EH_SHUTDOWN
    flag then returns.

    - The outer event loop (event_handler_loop()) calls
    wait_event_interruptible().

    The processing of the second flag which is part of
    VDEV_EVENT_DOWN (USBIP_EH_RESET) did not happen yet.
    It is delayed until the next event.

    This means the ->reset callback may not happen for
    a long time (if ever), leaving the usbip port in a
    weird state which prevents its reuse.

    This patch changes the handler to process all flags
    before waiting for another wakeup.

    I have verified this change to fix a problem which
    prevented reattach of a usbip device. It also helps
    for socket errors which missed the RESET as well.

    The delayed event processing also affects the stub
    side of usbip and the error handling there.

    Signed-off-by: Max Vozeler <mvz@vozeler.com>
    Reported-by: Marco Lancione <marco@optikam.com>
    Tested-by: Luc Jalbert <ljalbert@optikam.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
    ---
    drivers/staging/usbip/usbip_event.c | 16 +++-------------
    1 files changed, 3 insertions(+), 13 deletions(-)

    diff --git a/drivers/staging/usbip/usbip_event.c b/drivers/staging/usbip/usbip_event.c
    index a2566f1..af3832b 100644
    --- a/drivers/staging/usbip/usbip_event.c
    +++ b/drivers/staging/usbip/usbip_event.c
    @@ -38,21 +38,13 @@ static int event_handler(struct usbip_device *ud)
    ud->eh_ops.shutdown(ud);

    ud->event &= ~USBIP_EH_SHUTDOWN;
    -
    - break;
    }

    - /* Stop the error handler. */
    - if (ud->event & USBIP_EH_BYE)
    - return -1;
    -
    /* Reset the device. */
    if (ud->event & USBIP_EH_RESET) {
    ud->eh_ops.reset(ud);

    ud->event &= ~USBIP_EH_RESET;
    -
    - break;
    }

    /* Mark the device as unusable. */
    @@ -60,13 +52,11 @@ static int event_handler(struct usbip_device *ud)
    ud->eh_ops.unusable(ud);

    ud->event &= ~USBIP_EH_UNUSABLE;
    -
    - break;
    }

    - /* NOTREACHED */
    - printk(KERN_ERR "%s: unknown event\n", __func__);
    - return -1;
    + /* Stop the error handler. */
    + if (ud->event & USBIP_EH_BYE)
    + return -1;
    }

    return 0;
    --
    1.7.3.3


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