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    SubjectRe: WARNING: at drivers/usb/host/ehci-hcd.c:287
    On Mon, 3 Mar 2008, Christian Kujau wrote:

    > On Mon, 3 Mar 2008, Christian Kujau wrote:
    > > after upgrading to 2.6.25-rc3, kern.log shows:
    > >
    > > [ 1535.884848] ------------[ cut here ]------------
    > > [ 1535.884855] WARNING: at drivers/usb/host/ehci-hcd.c:287
    > Hm, after ~24h of uptime, this message appeared 25 times already.
    > The WLAN USB device was used the whole time, the usb-storage module
    > was hardly used over the day:
    > # grep usb /proc/interrupts
    > 10: 10693403 XT-PIC-XT ohci_hcd:usb3, eth0
    > 11: 10270770 XT-PIC-XT sym53c8xx, ehci_hcd:usb1
    > 12: 91 XT-PIC-XT ohci_hcd:usb2
    > I even tried to trigger the system freeze[0] by using usb-storage
    > and reading a lot from it, but no freeze, and the message could
    > not be triggered either - they pop up every now and then, but too often,
    > IMHO.
    > Can anybody shed some light on this?

    Dave, it seems to me that this must be an example of a race between the
    iaa watchdog timer expiring and end_unlink_async() running. It's not
    good enough for end_unlink_async() to call iaa_watchdog_done(), because
    on an SMP system the timer may already have fired and the watchdog
    routine may be spinning on ehci->lock.

    It's even worse, because end_unlink_async() can call
    start_unlink_async(). If that happens, the watchdog routine will think
    the timer has expired when in fact it has just been restarted.

    How about replacing the


    line in ehci_iaa_watchdog() with

    if (unlikely(!ehci->reclaim ||
    !HC_IS_RUNNING(ehci_to_hcd(ehci)->state) ||
    goto done;

    where "done:" is added just before the spin_unlock_irqrestore?

    Alan Stern

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