On Wed 2015-04-29 13:33:59, Alan Stern wrote:
> On Wed, 29 Apr 2015, Petr Mladek wrote:
>
> > On Wed 2015-04-29 09:18:50, Chris Bainbridge wrote:
> > > Regression in commit 638139eb95d2d241781330a321e88c8dafe46078
> > > Author: Petr Mladek <pmladek@xxxxxxx>
> > > Date: Fri Sep 19 17:32:24 2014 +0200
> > >
> > > usb: hub: allow to process more usb hub events in parallel
> >
> > Anyway, I would suggest to revert this commit. I wonder where I had my
> > head when I sent it.
> >
> > It seems that the other operations with udev->portnum and
> > bus->devnum_next are not guared by bus->usb_address0_mutex.
> > And it seems that this is not the only operation that need to
> > be serialized.
>
> What other operations are you thinking of? In general, drivers should
> not depend on hub operations being serialized. If they do, it's a bug
> and it should be fixed.
I am sorry for the late reply. I have been sick last two weeks.
I think that my primary concern was about
+ release_devnum()
+ update_devnum()
They are called from
+ usb_disconnect()
+ hub_port_connect()
+ hub_port_finish_reset()
+ hub_set_address()
+ hub_port_init()
They modify udev->devnum but they do not take the
bus->usb_address0_mutex. Therefore I think that my commit
638139eb95d2d2417813 ("usb: hub: allow to process more usb hub events
in parallel") is not sufficient because it protects only
choose_devnum() calls by that bus->usb_address0_mutex.
Sigh, the more I stare into the code the less I am sure about a proper
fix.
Best Regards,
Petr
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
