Re: [PATCH v4 1/2] usb: gadget: udc: core: Invoke usb_gadget_connect only when started

[Linux regression tracking (Thorsten Leemhuis)]

[CCing Francesco Dolcini; and the regression list too, as it should be
in the loop for regressions:
https://docs.kernel.org/admin-guide/reporting-regressions.html]

On 16.05.23 14:53, Alistair wrote:
> On Fri, 2023-04-07 at 03:07 +0000, Badhri Jagan Sridharan wrote:
>> usb_udc_connect_control does not check to see if the udc has already
>> been started. This causes gadget->ops->pullup to be called through
>> usb_gadget_connect when invoked from usb_udc_vbus_handler even before
>> usb_gadget_udc_start is called. Guard this by checking for udc-
>>> started
>> in usb_udc_connect_control before invoking usb_gadget_connect.
> [...]
>> Cc: stable@xxxxxxxxxxxxxxx
>> Fixes: 628ef0d273a6 ("usb: udc: add usb_udc_vbus_handler")
>> Signed-off-by: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
> 
> This patch causes a kernel hang when trying to boot with the
> usb/chipidea/udc.c driver.
> 
> The call stack below causes the hang:
> 
>  - gadget_bind_driver(struct device *dev)
>     - mutex_lock(&udc->connect_lock);
>     - usb_gadget_udc_start_locked(struct usb_udc *udc)
>         - udc->gadget->ops->udc_start(udc->gadget, udc->driver)
> 
> At which point we are calling ci_udc_start(..), but with the
> connect_lock mutex locked.
> 
> ci_udc_start() then calls usb_udc_vbus_handler() which tries to lock
> the connect_lock while it's already locked. Resulting in a kernel hang.
> 
> Reverting this patch fixes the hang.

Not my area of expertise, but I guess it might be the same error as this
one:

https://lore.kernel.org/all/ZF4BvgsOyoKxdPFF@xxxxxxxxxxxxxxxxxxxxxxxxxxxx/

Francesco sent a revert on Friday, but no reaction from Badhri Jagan
Sridharan or Greg yet afaics.

https://lore.kernel.org/all/20230512131435.205464-1-francesco@xxxxxxxxxx/

Ciao, Thorsten