linux-kernel - Re: [PATCH] usb: gadget: f_mass_storage: cahnge wait_event to wait_event

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Date:   Thu, 21 Jan 2021 12:22:40 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Oh Eomji <eomji.oh@...sung.com>
Cc:     balbi@...nel.org, "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Bart Van Assche <bvanassche@....org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: gadget: f_mass_storage: cahnge wait_event to
 wait_event_timeout

On Thu, Jan 21, 2021 at 03:56:45PM +0900, Oh Eomji wrote:
> Changed to return a timeout error if there is no response for a certain
> period of time in order to solve the problem of waiting for a event
> complete while executing unbind.
> 
> Signed-off-by: Oh Eomji <eomji.oh@...sung.com>
> ---
>  drivers/usb/gadget/function/f_mass_storage.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/gadget/function/f_mass_storage.c b/drivers/usb/gadget/function/f_mass_storage.c
> index 950c943..b474840 100644
> --- a/drivers/usb/gadget/function/f_mass_storage.c
> +++ b/drivers/usb/gadget/function/f_mass_storage.c
> @@ -3000,7 +3000,7 @@ static void fsg_unbind(struct usb_configuration *c, struct usb_function *f)
>  	if (fsg->common->fsg == fsg) {
>  		__raise_exception(fsg->common, FSG_STATE_CONFIG_CHANGE, NULL);
>  		/* FIXME: make interruptible or killable somehow? */
> -		wait_event(common->fsg_wait, common->fsg != fsg);
> +		wait_event_timeout(common->fsg_wait, common->fsg != fsg, HZ / 4);

That's a random choice of a timeout value.

Please document this really really really well as to why you picked this
number, and what it means.

Also, is the commet above this line still correct now?

thanks,

greg k-h