From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756069Ab2ASAFH (ORCPT ); Wed, 18 Jan 2012 19:05:07 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:40957 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753000Ab2ASAFE (ORCPT ); Wed, 18 Jan 2012 19:05:04 -0500 From: "Rafael J. Wysocki" To: Simon Glass Subject: Re: [PATCH 3/3] serial: 8250: Add a wakeup_capable module param Date: Thu, 19 Jan 2012 01:08:32 +0100 User-Agent: KMail/1.13.6 (Linux/3.2.0+; KDE/4.6.0; x86_64; ; ) Cc: paulmck@linux.vnet.ibm.com, Alan Cox , LKML , "Greg Kroah-Hartman" , linux-serial@vger.kernel.org References: <1326826563-32215-1-git-send-email-sjg@chromium.org> <20120118041720.GA2431@linux.vnet.ibm.com> In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201201190108.32794.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday, January 18, 2012, Simon Glass wrote: > [+cc Rafael J. Wysocki who I think wrote the wakeup.c code] > > Hi Alan, Paul, > > On Tue, Jan 17, 2012 at 8:17 PM, Paul E. McKenney > wrote: > > On Tue, Jan 17, 2012 at 08:10:36PM +0000, Alan Cox wrote: > >> On Tue, 17 Jan 2012 10:56:03 -0800 > >> Simon Glass wrote: > >> > >> > Since serial_core now does not make serial ports wake-up capable by > >> > default, add a parameter to support this feature in the 8250 UART. > >> > This is the only UART where I think this feature is useful. > >> > >> NAK > >> > >> Things should just work for users. Magic parameters is not an > >> improvement. If its a performance problem someone needs to fix the rcu > >> sync overhead or stop using rcu on that path. > > OK fair enough, I agree. Every level I move down the source tree > affects more people though. > > > > > I must say that I lack context here, even after looking at the patch, > > but the synchronize_rcu_expedited() primitives can be used if the latency > > of synchronize_rcu() is too large. > > > > Let me provide a bit of context. The serial_core code seems to be the > only place in the kernel that does this: > > device_init_wakeup(tty_dev, 1); > device_set_wakeup_enable(tty_dev, 0); It shouldn't do that. It should just do device_set_wakeup_capable(tty_dev, true) instead. Thanks, Rafael