linux-kernel - Re: [PATCH] USB: cdc-acm: fix broken runtime suspend

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Message-ID: <20140415091317.GB24422@localhost>
Date:	Tue, 15 Apr 2014 11:13:17 +0200
From:	Johan Hovold <jhovold@...il.com>
To:	Oliver Neukum <oneukum@...e.de>
Cc:	Johan Hovold <jhovold@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org, Peter Hurley <peter@...leysoftware.com>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Xiao Jin <jin.xiao@...el.com>, david.a.cohen@...ux.intel.com,
	yanmin.zhang@...el.com
Subject: Re: [PATCH] USB: cdc-acm: fix broken runtime suspend

On Tue, Apr 15, 2014 at 10:35:19AM +0200, Oliver Neukum wrote:
> On Mon, 2014-04-14 at 21:58 +0200, Johan Hovold wrote:
> 
> > Fix this by implementing a delayed-write queue using urb anchors and
> > making sure to discard the queue properly at shutdown.
> 
> Looks very good, with one exception: acm_tty_close() must
> synchronously resume the device so that the anchor is emptied
> before ASYNCB is cleared.

That isn't necessary as the device is already about to be resumed and
the initialised flag will not be cleared until chars_in_buffer() returns
0 or closing wait times out.

In the first case, the queue has been emptied as the urbs are submitted
at resume(), and in the second case the queue is discarded at
shutdown().

Johan
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