Re: [linux-usb-devel] Re: [OOPS, usbcore, releaseintf] 2.6.0-test10-mm1

From: Alan Stern (stern_at_rowland.harvard.edu)
Date: 12/11/03

  • Next message: Craig Bradney: "Re: Fixes for nforce2 hard lockup, apic, io-apic, udma133 covered" 
    Date:	Thu, 11 Dec 2003 10:19:51 -0500 (EST)
To: Duncan Sands <baldrick@free.fr>

    On Thu, 11 Dec 2003, Duncan Sands wrote:

    > On Wednesday 10 December 2003 19:19, Alan Stern wrote:
    > >
    > > I don't understand the problem. What's wrong with dropping dev->serialize
    > > before calling usb_reset_device() or usb_set_configuration() and then
    > > reacquiring it afterward?
    >
    > The problem is that between dropping the lock and usb_set_configuration (or
    > whatever) picking it up again, the device may be disconnected, so usb_set_configuration
    > needs to handle the case of being called after disconnect (it doesn't seem to
    > check for that right now, but I only had a quick look).

    It should handle that okay (provided you retain a reference to the
    usb_device so that it doesn't get deallocated). Although it wouldn't hurt
    to change one of the tests from

            if (dev->state != USB_STATE_ADDRESS)

    to

            if (dev->state > USB_STATE_ADDRESS)

    > Also, after usbfs picks up
    > the lock again it needs to check for disconnect. None of this is a big deal, but
    > it could all be avoided by a simpler change: provide a usb_physical_set_configuration
    > (or whatever), which is usb_set_configuration without taking dev->serialize.

    I agree that it would ease things to provide entry points for set_config
    and reset_device that require the caller to hold dev->serialize already.
    The issue you and Oliver noted about holding the bus semaphore will go
    away when I finally get around to rewriting usb_reset_device().

    Alan Stern

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