linux-kernel - Re: [PATCH] HID: usbhid: get/put around clearing needs_remote

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Message-ID: <Pine.LNX.4.44L0.1411131611001.945-100000@iolanthe.rowland.org>
Date:	Thu, 13 Nov 2014 16:18:47 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Benson Leung <bleung@...omium.org>
cc:	johan@...nel.org, Jiri Kosina <jkosina@...e.cz>,
	<linux-usb@...r.kernel.org>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Sameer Nanda <snanda@...omium.org>
Subject: Re: [PATCH] HID: usbhid: get/put around clearing needs_remote_wakeup

On Thu, 13 Nov 2014, Benson Leung wrote:

> On Thu, Nov 13, 2014 at 12:41 PM, Alan Stern <stern@...land.harvard.edu> wrote:
> > usbhid_stop probably doesn't need it.  And it should be possible to fix
> > usbhid_close more easily just by interchanging the two lines:
> >
> > -                       usb_kill_urb(usbhid->urbin);
> >                         usbhid->intf->needs_remote_wakeup = 0;
> > +                       usb_kill_urb(usbhid->urbin);
> >
> > Have you tried this?
> 
> Yes, I tried that as well, and that does work.
> 
> I used the get/put because that's the way it was done in other
> drivers, for example in synusb_close() in
> drivers/input/mouse/synaptics_usb.c

In the patch description, you wrote:

> When a usbhid device that does not support remote wake
> ( i.e. !device_can_wakeup() ) is closed, we fail out of
> autosuspend_check() because the autosuspend check is called
> before the flag is cleared as a result of usb_kill_urb(usbhid->urbin);

If you interchange the two lines then the flag _will_ be cleared before
usb_kill_urb() and autosuspend_check() can run.  This means your patch
description is bogus.

Alan Stern

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