Messages in this thread | | | From | Oliver Neukum <> | Subject | Re: [PATCH] USB: fix deadlock in HCD code | Date | Wed, 21 May 2008 15:32:59 +0200 |
| |
Am Mittwoch 21 Mai 2008 15:27:50 schrieb Jiri Kosina: > On Wed, 21 May 2008, Oliver Neukum wrote: > > > > hcd_urb_list_lock is used for synchronization between IRQ and non-IRQ > > > contexts, so the non-IRQ context has to disable IRQs in order to prevent > > > deadlocking with IRQ context. > > Which non-irq context is that? > > One example -- assume usb_submit_urb() called from non-IRQ context. Then > > usb_hcd_submit_urb() -> rh_urb_enqueue() -> rh_queue_status() -> > usb_hcd_link_urb_to_ep(). >
This turns out not to be the case. Interrupts are disabled.
static int rh_queue_status (struct usb_hcd *hcd, struct urb *urb) { int retval; unsigned long flags; int len = 1 + (urb->dev->maxchild / 8);
spin_lock_irqsave (&hcd_root_hub_lock, flags); if (hcd->status_urb || urb->transfer_buffer_length < len) { dev_dbg (hcd->self.controller, "not queuing rh status urb\n"); retval = -EINVAL; goto done; }
retval = usb_hcd_link_urb_to_ep(hcd, urb);
I'll investigate.
Regards Oliver
| |