Am Freitag 29 August 2008 01:00:35 schrieb greg@kroah.com:

quoted text
> From: Takahiro Hirofuchi 

> +			dum->port_status[rhport] |=

quoted text
> +					(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.
> +static void vhci_tx_urb(struct urb *urb)

quoted text
> +{

> +	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
> +static int vhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb,

quoted text
> +			    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
> +	if (ret)

quoted text
> +		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.
> +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.
> +		spin_lock_irqsave(&the_controller->lock, flags);

quoted text
> +	}

> +

> +	spin_unlock_irqrestore(&the_controller->lock, flags);

> +

> +	dbg_vhci_hc("leave\n");

> +	return 0;

> +}

	Regards

		Oliver

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