On Wed, 30 Aug 2006, David Brownell wrote:
> [ Resend ... Greg, this one should likely merge to 2.6.18, and I don't
> think I saw any other fix for this in your current patchset ]
>
> This fixes a locking problem reported by the new lock debug tools which, while
> very cryptic, gave Alan Stern enough info to finger the problem: a routine
> wrongly enabled IRQs on exit, by using the wrong locking/irq primitives.
>
> This patch switches back to the primitives which save/restore IRQ flags.
>
> Signed-off-by: David Brownell <[EMAIL PROTECTED]>
>
> Index: g26/drivers/usb/core/hcd.c
> ===================================================================
> --- g26.orig/drivers/usb/core/hcd.c 2006-07-03 10:45:18.000000000 -0700
> +++ g26/drivers/usb/core/hcd.c 2006-07-25 14:00:14.000000000 -0700
> @@ -632,31 +632,33 @@ static int rh_urb_enqueue (struct usb_hc
>
> /*-------------------------------------------------------------------------*/
>
> -/* Asynchronous unlinks of root-hub control URBs are legal, but they
> - * don't do anything. Status URB unlinks must be made in process context
> - * with interrupts enabled.
> +/* Root hub control URBs are synchronous, so unlinking would be pointless.
> + * Status URBs may not be unlinked from interrupts (del_timer_sync rule).
> */
> static int usb_rh_urb_dequeue (struct usb_hcd *hcd, struct urb *urb)
> {
> + unsigned long flags;
> +
> if (usb_pipeendpoint(urb->pipe) == 0) { /* Control URB */
> if (in_interrupt())
> return 0; /* nothing to do */
>
> - spin_lock_irq(&urb->lock); /* from usb_kill_urb */
> - ++urb->reject;
> - spin_unlock_irq(&urb->lock);
> + spin_lock_irqsave(&urb->lock, flags);
> + ++urb->reject; /* like usb_kill_urb */
> + spin_unlock_irqrestore(&urb->lock, flags);
>
> wait_event(usb_kill_urb_queue,
> atomic_read(&urb->use_count) == 0);
>
> - spin_lock_irq(&urb->lock);
> + spin_lock_irqsave(&urb->lock, flags);
> --urb->reject;
> - spin_unlock_irq(&urb->lock);
> + spin_unlock_irqrestore(&urb->lock, flags);
>
> } else { /* Status URB */
> if (!hcd->uses_new_polling)
> del_timer_sync (&hcd->rh_timer);
> - local_irq_disable ();
> +
> + local_irq_save (flags);
> spin_lock (&hcd_root_hub_lock);
> if (urb == hcd->status_urb) {
> hcd->status_urb = NULL;
> @@ -666,7 +668,7 @@ static int usb_rh_urb_dequeue (struct us
> spin_unlock (&hcd_root_hub_lock);
> if (urb)
> usb_hcd_giveback_urb (hcd, urb, NULL);
> - local_irq_enable ();
> + local_irq_restore (flags);
> }
>
> return 0;
>
>
Oops, crossed lines. Greg, this patch isn't needed. One that you have
already applied (as754) takes care of the problem.
Alan Stern
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