Am Freitag 29 August 2008 01:00:35 schrieb greg@kroah.com:
quoted text
> From: Takahiro Hirofuchi <hirofuchi@users.sourceforge.net>

quoted text
> +			dum->port_status[rhport] |=
> +					(1 << USB_PORT_FEAT_C_SUSPEND);
> +			dum->port_status[rhport] &=
> +					~(1 << USB_PORT_FEAT_SUSPEND);
> +			dum->resuming = 0;
> +			dum->re_timeout = 0;
> +			/* if (dum->driver && dum->driver->resume) {
> +			 *	spin_unlock (&dum->lock);

I realise it is commented out, but still.

The resume method may sleep. It is documented as such. Thus it can
reenable interrupts. Therefore you can deadlock if you don't use irqrestore.


quoted text
> +static void vhci_tx_urb(struct urb *urb)
> +{
> +	struct vhci_device *vdev = get_vdev(urb->dev);
> +	struct vhci_priv *priv;
> +	unsigned long flag;
> +
> +	if (!vdev) {
> +		err("could not get virtual device");
> +		/* BUG(); */
> +		return;
> +	}
> +
> +	spin_lock_irqsave(&vdev->priv_lock, flag);
> +
> +	priv = kzalloc(sizeof(struct vhci_priv), GFP_ATOMIC);

There's no reason to hold the lock longer than necessary by
allocating memory in the lock section.

[..]
quoted text
> +	wake_up(&vdev->waitq_tx);
> +	spin_unlock_irqrestore(&vdev->priv_lock, flag);

again

quoted text
> +static int vhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb,
> +			    gfp_t mem_flags)
> +{

This is called in the context of usb_submit_urb()

[..]
quoted text
> +	ret = usb_hcd_link_urb_to_ep(hcd, urb);

This can fail for any urb due to urb->reject

quoted text
> +	if (ret)
> +		goto no_need_unlink;

The branch would be taken

[..]
quoted text
> +no_need_unlink:
> +	spin_unlock_irqrestore(&the_controller->lock, flags);
> +
> +	usb_hcd_giveback_urb(vhci_to_hcd(the_controller), urb, urb->status);

This calls urb->complete. If the completion handler takes a spinlock
which is held when usb_submit_urb() was called, you deadlock.

quoted text
> +static int vhci_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)

[..]
quoted text
> +		spin_unlock_irqrestore(&the_controller->lock, flags);
> +		usb_hcd_giveback_urb(vhci_to_hcd(the_controller), urb,
> +								urb->status);

This must be called with interrupts disabled.

quoted text
> +		spin_lock_irqsave(&the_controller->lock, flags);
> +	}
> +
> +	spin_unlock_irqrestore(&the_controller->lock, flags);
> +
> +	dbg_vhci_hc("leave\n");
> +	return 0;
> +}

	Regards
		Oliver
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