Am Dienstag, 12. August 2003 17:57 schrieb Alan Stern:
> On Tue, 12 Aug 2003 [EMAIL PROTECTED] wrote:
>
> > Now that I mentioned that inserting usb-storage hangs forever
> > and then causes a SCSI oops, the question arises how the hang
> > is caused. It turns out to be a semaphore deadlock.
> >
> > What happens is that base/bus.c:bus_add_driver() downs
> > down_write(&bus->subsys.rwsem);
> > and then later usb/core/hub.c:usb_reset_device() downs
> > down_read(&gdev->bus->subsys.rwsem);
> >
> > This is the same semaphore, and we have a deadlock.
>
> Is there any reason for that down_read() in hub.c:usb_reset_device()?
> There's already another semaphore in place to protect against having more
> than one device in the address-0 state.
>
> Maybe it's an attempt to protect against the "device-morphed" possibility.
> I'm planning a re-write of that whole area. For now, it would probably be
> okay to remove the down_read() and up_read() in usb_reset_device().
No, it is a guard against probe() which is bound to fail during a reset.
Regards
Oliver
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