linux-kernel - Re: [PATCH AUTOSEL 5.1 054/141] usb: gadget: storage: Remove warning message

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Date:   Fri, 19 Jul 2019 05:27:31 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Sasha Levin <sashal@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     EJ Hsu <ejh@...dia.com>, Alan Stern <stern@...land.harvard.edu>,
        "Felipe Balbi" <felipe.balbi@...ux.intel.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH AUTOSEL 5.1 054/141] usb: gadget: storage: Remove warning
 message

Hi Sasha,

Sasha Levin wrote:
> From: EJ Hsu <ejh@...dia.com>
>
> [ Upstream commit e70b3f5da00119e057b7faa557753fee7f786f17 ]
>
> This change is to fix below warning message in following scenario:
> usb_composite_setup_continue: Unexpected call
>
> When system tried to enter suspend, the fsg_disable() will be called to
> disable fsg driver and send a signal to fsg_main_thread. However, at
> this point, the fsg_main_thread has already been frozen and can not
> respond to this signal. So, this signal will be pended until
> fsg_main_thread wakes up.
>
> Once system resumes from suspend, fsg_main_thread will detect a signal
> pended and do some corresponding action (in handle_exception()). Then,
> host will send some setup requests (get descriptor, set configuration...)
> to UDC driver trying to enumerate this device. During the handling of "set
> configuration" request, it will try to sync up with fsg_main_thread by
> sending a signal (which is the same as the signal sent by fsg_disable)
> to it. In a similar manner, once the fsg_main_thread receives this
> signal, it will call handle_exception() to handle the request.
>
> However, if the fsg_main_thread wakes up from suspend a little late and
> "set configuration" request from Host arrives a little earlier,
> fsg_main_thread might come across the request from "set configuration"
> when it handles the signal from fsg_disable(). In this case, it will
> handle this request as well. So, when fsg_main_thread tries to handle
> the signal sent from "set configuration" later, there will nothing left
> to do and warning message "Unexpected call" is printed.
>
> Acked-by: Alan Stern <stern@...land.harvard.edu>
> Signed-off-by: EJ Hsu <ejh@...dia.com>
> Signed-off-by: Felipe Balbi <felipe.balbi@...ux.intel.com>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>  drivers/usb/gadget/function/f_mass_storage.c | 21 ++++++++++++++------
>  drivers/usb/gadget/function/storage_common.h |  1 +
>  2 files changed, 16 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/usb/gadget/function/f_mass_storage.c b/drivers/usb/gadget/function/f_mass_storage.c
> index 043f97ad8f22..982c3e89eb0d 100644
> --- a/drivers/usb/gadget/function/f_mass_storage.c
> +++ b/drivers/usb/gadget/function/f_mass_storage.c
>

This patch may have issue. It was reverted upstream. Please don't queue
to stable.

BR,
Thinh