Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756199AbaFQLFG (ORCPT ); Tue, 17 Jun 2014 07:05:06 -0400 Received: from mx0.aculab.com ([213.249.233.131]:47839 "HELO mx0.aculab.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753173AbaFQLFB (ORCPT ); Tue, 17 Jun 2014 07:05:01 -0400 From: David Laight To: "'Peter Hurley'" , Arnd Bergmann , "linuxppc-dev@lists.ozlabs.org" CC: Greg Kroah-Hartman , Karsten Keil , "linux-kernel@vger.kernel.org" , "linux-serial@vger.kernel.org" , One Thousand Gnomes Subject: RE: [PATCH tty-next 14/22] tty: Remove tty_wait_until_sent_from_close() Thread-Topic: [PATCH tty-next 14/22] tty: Remove tty_wait_until_sent_from_close() Thread-Index: AQHPihrgwgSnyL5/CECAg051obYgppt1Ircg Date: Tue, 17 Jun 2014 11:03:50 +0000 Message-ID: <063D6719AE5E284EB5DD2968C1650D6D1725DAF6@AcuExch.aculab.com> References: <1402924639-5164-1-git-send-email-peter@hurleysoftware.com> <1402924639-5164-15-git-send-email-peter@hurleysoftware.com> <4575870.N9RCpZ4UMg@wuerfel> <53A01F02.7000202@hurleysoftware.com> In-Reply-To: <53A01F02.7000202@hurleysoftware.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.202.99.200] Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id s5HB5Nix006369 From: Peter Hurley ... > > I don't understand the second half of the changelog, it doesn't seem > > to fit here: there deadlock that we are trying to avoid here happens > > when the *same* tty needs the lock to complete the function that > > sends the pending data. I don't think we do still do that any more, > > but it doesn't seem related to the tty lock being system-wide or not. > > The tty lock is not used in the i/o path; it's purpose is to > mutually exclude state changes in open(), close() and hangup(). > > The commit that added this [1] comments that _other_ ttys may wait > for this tty to complete, and comments in the code note that this > function should be removed when the system-wide tty mutex was removed > (which happened with the commit noted in the changelog). What happens if another process tries to do a non-blocking open while you are sleeping in close waiting for output to drain? Hopefully this returns before that data has drained. David ????{.n?+???????+%?????ݶ??w??{.n?+????{??G?????{ay?ʇڙ?,j??f???h?????????z_??(?階?ݢj"???m??????G????????????&???~???iO???z??v?^?m???? ????????I?