From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753553AbbJBS3U (ORCPT ); Fri, 2 Oct 2015 14:29:20 -0400 Received: from mail-pa0-f43.google.com ([209.85.220.43]:34512 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752040AbbJBS3R (ORCPT ); Fri, 2 Oct 2015 14:29:17 -0400 Date: Fri, 2 Oct 2015 11:29:14 -0700 From: Dmitry Torokhov To: Pali =?iso-8859-1?Q?Roh=E1r?= Cc: Geliang Tang , Hans de Goede , Masaki Ota , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] Input: alps: drop unlikely before IS_ERR_OR_NULL Message-ID: <20151002182914.GR8437@dtor-ws> References: <03d18502ed7ed417f136c091f417d2d88c147ec6.1443667610.git.geliangtang@163.com> <081982d1188978b6020952afb4c2dcf3bc42fa1f.1443667610.git.geliangtang@163.com> <20151001073019.GE1829@pali> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20151001073019.GE1829@pali> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 01, 2015 at 09:30:19AM +0200, Pali Rohár wrote: > On Thursday 01 October 2015 10:55:30 Geliang Tang wrote: > > IS_ERR_OR_NULL already contain an unlikely compiler flag. Drop it. > > > > Signed-off-by: Geliang Tang > > --- > > drivers/input/mouse/alps.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/input/mouse/alps.c b/drivers/input/mouse/alps.c > > index 4d24686..b4f146a 100644 > > --- a/drivers/input/mouse/alps.c > > +++ b/drivers/input/mouse/alps.c > > @@ -1367,7 +1367,7 @@ static void alps_report_bare_ps2_packet(struct psmouse *psmouse, > > /* On V2 devices the DualPoint Stick reports bare packets */ > > dev = priv->dev2; > > dev2 = psmouse->dev; > > - } else if (unlikely(IS_ERR_OR_NULL(priv->dev3))) { > > + } else if (IS_ERR_OR_NULL(priv->dev3)) { > > /* Register dev3 mouse if we received PS/2 packet first time */ > > if (!IS_ERR(priv->dev3)) > > psmouse_queue_work(psmouse, &priv->dev3_register_work, > > Hm... I do not like this change. If I read code > > if (unlikely(IS_ERR_OR_NULL(priv->dev3))) > > then I know that it is really unlikely that condition will be truth and > so this is some case of error/exception or something that normally does > not happen too much. > > But if I read code > > if (IS_ERR_OR_NULL(priv->dev3)) > > I know nothing about chance that this condition will be truth. Explicit > unlikely in previous example give me more information. Yes, given that this is in packet processing path I prefer having explicit unlikely there. Thanks. -- Dmitry