linux-kernel - Re: [PATCH v4 1/2] usb: gadget: udc: core: Invoke usb_gadget

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Date:   Wed, 17 May 2023 12:56:59 +0200
From:   "Linux regression tracking (Thorsten Leemhuis)" 
        <regressions@...mhuis.info>
To:     Francesco Dolcini <francesco@...cini.it>,
        Linux regressions mailing list <regressions@...ts.linux.dev>
Cc:     Alistair <alistair@...stair23.me>,
        Badhri Jagan Sridharan <badhri@...gle.com>,
        gregkh@...uxfoundation.org, stern@...land.harvard.edu,
        colin.i.king@...il.com, xuetao09@...wei.com,
        quic_eserrao@...cinc.com, water.zhangjiantao@...wei.com,
        peter.chen@...escale.com, balbi@...com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v4 1/2] usb: gadget: udc: core: Invoke usb_gadget_connect
 only when started

On 17.05.23 12:35, Francesco Dolcini wrote:
> 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@...r.kernel.org
>>>> Fixes: 628ef0d273a6 ("usb: udc: add usb_udc_vbus_handler")
>>>> Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.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.

Ha, sorry, I missed that, as I only looked at lore. Should have looked
in my own regression tracking, there it's marked as "fix incoming", as
regzbot noticed the fix in next...

Ciao, Thorsten