Re: [PATCH] usb: hub: Fix usb enumeration issue due to address0 race

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Nov 16, 2021 at 12:16:30AM +0200, Mathias Nyman wrote:
> xHC hardware can only have one slot in default state with address 0
> waiting for a unique address at a time, otherwise "undefined behavior
> may occur" according to xhci spec 5.4.3.4
> 
> The address0_mutex exists to prevent this across both xhci roothubs.
> 
> If hub_port_init() fails, it may unlock the mutex and exit with a xhci
> slot in default state. If the other xhci roothub calls hub_port_init()
> at this point we end up with two slots in default state.
> 
> Make sure the address0_mutex protects the slot default state across
> hub_port_init() retries, until slot is addressed or disabled.
> 
> Note, one known minor case is not fixed by this patch.
> If device needs to be reset during resume, but fails all hub_port_init()
> retries in usb_reset_and_verify_device(), then it's possible the slot is
> still left in default state when address0_mutex is unlocked.
> 
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>

What commit id does this "fix"?

thanks,

greg k-h