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    SubjectRe: [PATCH] fix oops in usbserial_cleanup function;
    On Fri, 15 Oct 2010 m00150988@huawei.com wrote:

    > From:ma rui <m00150988@huawei.com>
    > 1. I find this bug on OpenSUSE 11.3 which kernel version is 2.6.34, but the latest kernel version 2.6.36-rc7 aslo have this bug. This patch is based on
    > the kernel of 2.6.36-rc7
    > 2. bug report:
    > a. Install huawei datacard dashboard on OpenSUSE 11.3
    > b. Plug in huawei datacard into OpenSUSE 11.3 which kernel version is 2.6.36-rc7
    > c. After the dashboard has detected the device, I pull out the usb datacard
    > d. Close dashboard,then kernel panic will happen in usbserial_clean function
    >
    > Yes, the datacard exit without close the port.
    >
    > But after the dashboard connect internet with hauwei datacard, then Hibernate/resume, the bug will happen too.
    > Do you have any other good idea to resolve this bug,or please apply my patch,thanks. :)
    >
    >
    > Signed-off-by: ma rui <m00150988@huawei.com>
    >
    >
    > diff -uprN -X linux-2.6.36-rc7_orig/Documentation/dontdiff linux-2.6.36-rc7_orig/drivers/usb/serial/usb-serial.c linux-2.6.36-rc7/drivers/usb/serial/usb-serial.c
    > --- linux-2.6.36-rc7_orig/drivers/usb/serial/usb-serial.c 2010-10-06 16:39:52.000000000 -0400
    > +++ linux-2.6.36-rc7/drivers/usb/serial/usb-serial.c 2010-10-15 01:57:36.000000000 -0400
    > @@ -328,6 +328,16 @@ static void serial_cleanup(struct tty_st
    > /* The console is magical. Do not hang up the console hardware
    > * or there will be tears.
    > */
    > + if (NULL == port)
    > + return;
    > + mutex_lock(&port->serial->disc_mutex);
    > + if (port->serial->disconnected) {
    > + return_serial(port->serial);
    > + mutex_unlock(&port->serial->disc_mutex);
    > + return;
    > + }
    > + mutex_unlock(&port->serial->disc_mutex);
    > +
    > if (port->port.console)
    > return;

    This patch is clearly wrong, since it skips some of the actions that
    should be taken by serial_cleanup even if the port is already
    disconnected.

    Besides, the main point of the patch is to avoid problems when
    port = tty->driver_data turns out to be NULL. But the only place where
    tty->driver_data is set to NULL is further below in this same function!
    So the problems should never arise.

    If they do arise, it indicates there's a bug somewhere else. That
    other bug can't be fixed by changing this function.

    Alan Stern



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