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

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Date:	Thu, 13 Nov 2014 15:41:43 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Benson Leung <bleung@...omium.org>
cc:	johan@...nel.org, <jkosina@...e.cz>, <linux-usb@...r.kernel.org>,
	<linux-input@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<snanda@...omium.org>
Subject: Re: [PATCH] HID: usbhid: get/put around clearing needs_remote_wakeup

On Thu, 13 Nov 2014, Benson Leung wrote:

> usbhid->intf->needs_remote_wakeup is set when a device is
> opened, and is cleared when a device is closed.
> 
> 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);
> 
> The result is that a device that may otherwise autosuspend will
> fail to enter suspend again after all handles to it are closed.
> 
> In usbhid_open, usb_autopm_get_interface is called
> before setting the needs_remote_wakeup flag, and
> usb_autopm_put_interface is called after hid_start_in.
> 
> However, when the device is closed in usbhid_close, the same
> protection isn't there when clearing needs_remote_wakeup. This will
> add that to usbhid_close as well as usbhid_stop.

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?

Alan Stern

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