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    SubjectRe: [PATCH] usb-serial regression fix
    On Mon, Mar 12, 2007 at 09:55:14PM -0400, Mark Lord wrote:
    > Jim Radford wrote:
    > >On Mon, Mar 12, 2007 at 05:18:19PM -0700, Greg KH wrote:
    > >>On Mon, Mar 12, 2007 at 03:59:22PM -0700, Jim Radford wrote:
    > >>>On Mon, Mar 12, 2007 at 03:42:35PM -0700, Jim Radford wrote:
    > >>>>On Mon, Mar 12, 2007 at 01:33:31PM -0700, Greg KH wrote:
    > >>>>>On Mon, Mar 12, 2007 at 04:22:22PM -0400, Mark Lord wrote:
    > >>>>>>Oliver Neukum wrote:
    > >>>>>>>>Mark Lord wrote:
    > >>>>>>>>>Okay, from that part (above), the problem is obvious:
    > >>>>>>>>>in that the "MCT U232 converter now disconnected"
    > >>>>>>>>>appears, and then we continue to try and call the
    > >>>>>>>>>driver's method.. Oops!

    > >>>>>>>IMHO shutdown() is using serial->port[] and bombs.
    > >>>>>>>Could you reverse the order here?

    > >>>Do not NULL serial->port[i] since it is used in ->shutdown().
    > >>>This wasn't an issue until the order or ->shutdown() and
    > >>>device_unregister was corrected.

    > >>> for (i = 0; i < serial->num_ports; ++i)
    > >>> if (serial->port[i]->dev.parent != NULL) {
    > >>> device_unregister(&serial->port[i]->dev);
    > >>>- serial->port[i] = NULL;
    > >>> }

    > >>But shouldn't you null it out somewhere? It will be an "empty"
    > >>pointer at some point in time...

    > >Not as far as I can see. The serial structure that ->port[i] is in
    > >gets kfree()ed soon after, in the same function, and nothing in
    > >between, other than ->shutdown(), uses ->port[]. I assume it was
    > >someone being overly cautious.

    > So where does the memory get freed -- the structure pointed at
    > by the serial->port[i] thingie ? It's not a leak, is it?

    It gets free'd through device_unregister

    for (i = 0; i < num_ports; ++i) {
    ...
    port->dev.release = &port_release;
    ...
    retval = device_register(&port->dev);

    which means that until all the drivers get converted to use
    ->port_probe() and ->port_remove() (which gets called by
    device_unregister) and stop using the ->port[] array in ->shutdown()
    we need to have ->shutdown() called before device_unregister.

    > > > > Look at changeset d9a7ecacac5f8274d2afce09aadcf37bdb42b93a in Linus's
    > > > > tree from Jim Radford:

    > > > > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=d9a7ecacac5f8274d2afce09aadcf37bdb42b93a

    So, this patch should be reverted for now.

    -Jim
    -
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