From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Peter Chen <peter.chen@nxp.com>
Cc: "balbi@kernel.org" <balbi@kernel.org>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
dl-linux-imx <linux-imx@nxp.com>,
Alan Stern <stern@rowland.harvard.edu>
Subject: Re: [PATCH 1/1] usb: gadget: core: wait gadget device .release finishing at usb_del_gadget_udc
Date: Fri, 31 Jul 2020 16:16:32 +0200 [thread overview]
Message-ID: <20200731141632.GB1717752@kroah.com> (raw)
In-Reply-To: <20200731140553.GA8013@b29397-desktop>
On Fri, Jul 31, 2020 at 02:06:20PM +0000, Peter Chen wrote:
> On 20-07-31 14:25:20, Greg Kroah-Hartman wrote:
> > On Fri, Jul 31, 2020 at 12:11:32PM +0000, Peter Chen wrote:
> >
> > Grab a reference from somewhere else and do not give it up for a long
> > time.
> >
>
> So wait_for_completion_timeout is suitable?
NO!!!
> The similar use case is when
> we open the file at the USB Drive at Windows, and we click "Eject", it
> will say "The device is currently in use", and refuse our "Eject"
> operation.
>
> When we try to remove the gadget, if the gadget is in use, we could
> refuse the remove operation, reasonable?
Nope. Remove it please.
> > > > > -static void usb_udc_nop_release(struct device *dev)
> > > > > +static void usb_gadget_release(struct device *dev)
> > > > > {
> > > > > + struct usb_gadget *gadget;
> > > > > +
> > > > > dev_vdbg(dev, "%s\n", __func__);
> > > > > +
> > > > > + gadget = container_of(dev, struct usb_gadget, dev);
> > > > > + complete(&gadget->done);
> > > > > + memset(dev, 0x0, sizeof(*dev));
> > > >
> > > > No, the memory should be freed here, not memset.
> > > >
> > >
> > > This memory is allocated at UDC driver and is freed by UDC driver too.
> >
> > That's wrong, the release function should be where this is released.
>
> So, the release function should be at individual UDC driver, a common
> release function is improper, right?
Depends on how this all works, but again, the release function needs to
free the memory, otherwise this is broken.
> > And this no-op function is horrid. There used to be documentation in
> > the kernel where I could rant about this, but instead, I'll just say,
> > "why are people trying to work around warnings we put in the core kernel
> > to fix common problems? Do they think we did that just because we
> > wanted to be mean???"
> >
>
> So, like kernel doc for device_initialize said, a proper fix for dwc3
> should be zeroed gadget device memory at its own driver before the
> gadget device register to driver core, right?
It should get a totally different, dynamically allocated structure.
NEVER recycle them.
thanks,
greg k-h
next prev parent reply other threads:[~2020-07-31 14:16 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-31 9:59 [PATCH 1/1] usb: gadget: core: wait gadget device .release finishing at usb_del_gadget_udc Peter Chen
2020-07-31 11:55 ` Greg Kroah-Hartman
2020-07-31 12:11 ` Peter Chen
2020-07-31 12:25 ` Greg Kroah-Hartman
2020-07-31 14:06 ` Peter Chen
2020-07-31 14:12 ` Alan Stern
2020-07-31 23:42 ` Peter Chen
2020-08-01 6:53 ` Peter Chen
2020-08-01 7:04 ` Jun Li
2020-08-01 15:44 ` Alan Stern
2020-07-31 14:16 ` Greg Kroah-Hartman [this message]
2020-09-07 7:48 ` Felipe Balbi
2020-09-07 14:18 ` Alan Stern
2020-09-07 14:26 ` Felipe Balbi
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