Am Donnerstag, 11. Dezember 2003 10:45 schrieb Duncan Sands:
> > > > > __usb_set_configuration - lockless version
> > > > > usb_set_configuration - locked version
> > > >
> > > > Partially done.
> > > > That's what the _physical version of usb_reset_device() is about.
> > >
> > > Unfortunately, usb_physical_reset_device calls usb_set_configuration
> > > which takes dev->serialize.
> >
> > That is bad, but the solution is obvious.
> > All such operations need a _physical version.
> > At first sight this may look less elegant than some lock dropping schemes,
> > but it is a solution that produces obviously correct code paths with
> > respect to locking.
>
> Hi Oliver, I agree, except that there are several layers of locking: dev->serialize
> but also the bus rwsem. So does "physical" mean no subsys.rwsem or no
> dev->serialize or both?
"physical" means no locking at all. It's the caller's responsibility.
> int usb_reset_device(struct usb_device *udev)
> {
> struct device *gdev = &udev->dev;
> int r;
>
> down_read(&gdev->bus->subsys.rwsem);
> r = usb_physical_reset_device(udev);
> up_read(&gdev->bus->subsys.rwsem);
>
> return r;
> }
That's what the core cares about. No probe() while a reset is in
progress. Taking the semaphore ensures that.
Regards
Oliver
-------------------------------------------------------
This SF.net email is sponsored by: IBM Linux Tutorials.
Become an expert in LINUX or just sharpen your skills. Sign up for IBM's
Free Linux Tutorials. Learn everything from the bash shell to sys admin.
Click now! http://ads.osdn.com/?ad_id=1278&alloc_id=3371&op=click
_______________________________________________
[EMAIL PROTECTED]
To unsubscribe, use the last form field at:
https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
