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    Subject[patch 13/47] USB: fix interrupt disabling for HCDs with shared interrupt handlers
    2.6.25-stable review patch.  If anyone has any objections, please let us
    know.

    ------------------
    From: Stefan Becker <Stefan.Becker@nokia.com>

    commit de85422b94ddb23c021126815ea49414047c13dc upstream

    As has been discussed several times on LKML, IRQF_SHARED | IRQF_DISABLED
    doesn't work reliably, i.e. a shared interrupt handler CAN'T be certain to
    be called with interrupts disabled. Most USB HCD handlers use IRQF_DISABLED
    and therefore havoc can break out if they share their interrupt with a
    handler that doesn't use it.

    On my test machine the yenta_socket interrupt handler (no IRQF_DISABLED)
    was registered before ehci_hcd and one uhci_hcd instance. Therefore all
    usb_hcd_irq() invocations for ehci_hcd and for one uhci_hcd instance
    happened with interrupts enabled. That led to random lockups as USB core
    HCD functions that acquire the same spinlock could be called twice
    from interrupt handlers.

    This patch updates usb_hcd_irq() to always disable/restore interrupts.
    usb_add_hcd() will silently remove any IRQF_DISABLED requested from HCD code.

    Signed-off-by: Stefan Becker <stefan.becker@nokia.com>
    Acked-by: David Brownell <david-b@pacbell.net>
    Acked-by: Alan Stern <stern@rowland.harvard.edu>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    drivers/usb/core/hcd.c | 42 ++++++++++++++++++++++++++++++------------
    1 file changed, 30 insertions(+), 12 deletions(-)

    --- a/drivers/usb/core/hcd.c
    +++ b/drivers/usb/core/hcd.c
    @@ -1685,19 +1685,30 @@ EXPORT_SYMBOL_GPL(usb_bus_start_enum);
    irqreturn_t usb_hcd_irq (int irq, void *__hcd)
    {
    struct usb_hcd *hcd = __hcd;
    - int start = hcd->state;
    + unsigned long flags;
    + irqreturn_t rc;

    - if (unlikely(start == HC_STATE_HALT ||
    - !test_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags)))
    - return IRQ_NONE;
    - if (hcd->driver->irq (hcd) == IRQ_NONE)
    - return IRQ_NONE;
    -
    - set_bit(HCD_FLAG_SAW_IRQ, &hcd->flags);
    -
    - if (unlikely(hcd->state == HC_STATE_HALT))
    - usb_hc_died (hcd);
    - return IRQ_HANDLED;
    + /* IRQF_DISABLED doesn't work correctly with shared IRQs
    + * when the first handler doesn't use it. So let's just
    + * assume it's never used.
    + */
    + local_irq_save(flags);
    +
    + if (unlikely(hcd->state == HC_STATE_HALT ||
    + !test_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags))) {
    + rc = IRQ_NONE;
    + } else if (hcd->driver->irq(hcd) == IRQ_NONE) {
    + rc = IRQ_NONE;
    + } else {
    + set_bit(HCD_FLAG_SAW_IRQ, &hcd->flags);
    +
    + if (unlikely(hcd->state == HC_STATE_HALT))
    + usb_hc_died(hcd);
    + rc = IRQ_HANDLED;
    + }
    +
    + local_irq_restore(flags);
    + return rc;
    }

    /*-------------------------------------------------------------------------*/
    @@ -1861,6 +1872,13 @@ int usb_add_hcd(struct usb_hcd *hcd,

    /* enable irqs just before we start the controller */
    if (hcd->driver->irq) {
    +
    + /* IRQF_DISABLED doesn't work as advertised when used together
    + * with IRQF_SHARED. As usb_hcd_irq() will always disable
    + * interrupts we can remove it here.
    + */
    + irqflags &= ~IRQF_DISABLED;
    +
    snprintf(hcd->irq_descr, sizeof(hcd->irq_descr), "%s:usb%d",
    hcd->driver->description, hcd->self.busnum);
    if ((retval = request_irq(irqnum, &usb_hcd_irq, irqflags,
    --


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