From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756940Ab2ARERc (ORCPT ); Tue, 17 Jan 2012 23:17:32 -0500 Received: from e32.co.us.ibm.com ([32.97.110.150]:37530 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756855Ab2ARERa (ORCPT ); Tue, 17 Jan 2012 23:17:30 -0500 Date: Tue, 17 Jan 2012 20:17:21 -0800 From: "Paul E. McKenney" To: Alan Cox Cc: Simon Glass , LKML , Greg Kroah-Hartman , linux-serial@vger.kernel.org Subject: Re: [PATCH 3/3] serial: 8250: Add a wakeup_capable module param Message-ID: <20120118041720.GA2431@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1326826563-32215-1-git-send-email-sjg@chromium.org> <1326826563-32215-3-git-send-email-sjg@chromium.org> <20120117201036.6d99f98f@pyramind.ukuu.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120117201036.6d99f98f@pyramind.ukuu.org.uk> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12011804-3270-0000-0000-0000034A8A92 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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. Thanx, Paul