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

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Date:   Wed, 17 May 2023 12:23:39 +0200
From:   "Linux regression tracking (Thorsten Leemhuis)" 
        <regressions@...mhuis.info>
To:     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
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org,
        Linux kernel regressions list <regressions@...ts.linux.dev>,
        Francesco Dolcini <francesco@...cini.it>
Subject: Re: [PATCH v4 1/2] usb: gadget: udc: core: Invoke usb_gadget_connect
 only when started

[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/

Ciao, Thorsten