On Wed, May 17, 2023 at 12:23:39PM +0200, Linux regression tracking (Thorsten Leemhuis) wrote:
[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@vger.kernel.org Fixes: 628ef0d273a6 ("usb: udc: add usb_udc_vbus_handler") Signed-off-by: Badhri Jagan Sridharan badhri@google.com
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@francesco-nb.int.toradex.com/
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@dolcini.it/
Revert patches were applied and are in linux-next. I expect those to land in Linus tree with the next pull request from Greg.
Francesco