linux-kernel - Re: [PATCH 1/2] usb: gadget: r8a66597: Fix two possible sleep-in-atomic-context bugs in init

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Message-ID: <87efh0o6f9.fsf@belgarion.home>
Date:   Thu, 21 Jun 2018 11:06:02 +0200
From:   Robert Jarzmik <robert.jarzmik@...e.fr>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     balbi@...nel.org, gregkh@...uxfoundation.org,
        nicolas.ferre@...rochip.com, keescook@...omium.org,
        allen.lkml@...il.com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] usb: gadget: r8a66597: Fix two possible sleep-in-atomic-context bugs in init_controller()

Jia-Ju Bai <baijiaju1990@...il.com> writes:

> The driver may sleep with holding a spinlock.
> The function call paths (from bottom to top) in Linux-4.16.7 are:
>
> [FUNC] msleep
> drivers/usb/gadget/udc/r8a66597-udc.c, 839: 
> 		msleep in init_controller
> drivers/usb/gadget/udc/r8a66597-udc.c, 96: 
> 		init_controller in r8a66597_usb_disconnect
> drivers/usb/gadget/udc/r8a66597-udc.c, 93: 
> 		spin_lock in r8a66597_usb_disconnect

That should not happen...

If think the issue you have is that your usb_connect() and usb_disconnect() are
called from interrupt context. I think the proper fix, as what is done in most
udc phys, is to schedule a workqueue, see drivers/usb/phy/phy-gpio-vbus-usb.c,
gpio_vbus_data.vbus.

Cheers.

--
Robert