From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752245Ab1AXUBH (ORCPT ); Mon, 24 Jan 2011 15:01:07 -0500 Received: from mgw2.diku.dk ([130.225.96.92]:39825 "EHLO mgw2.diku.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751301Ab1AXUBF (ORCPT ); Mon, 24 Jan 2011 15:01:05 -0500 Date: Mon, 24 Jan 2011 21:00:59 +0100 (CET) From: Julia Lawall To: Ryan Mallon Cc: Russell King , kernel-janitors@vger.kernel.org, Nicolas Ferre , Jean-Christophe PLAGNIOL-VILLARD , Andrew Victor , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/4] arch/arm/mach-at91/clock.c: Add missing IS_ERR test In-Reply-To: <4D3DD964.9020107@bluewatersys.com> Message-ID: References: <1295898922-18822-1-git-send-email-julia@diku.dk> <1295898922-18822-3-git-send-email-julia@diku.dk> <4D3DD964.9020107@bluewatersys.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 25 Jan 2011, Ryan Mallon wrote: > On 01/25/2011 08:55 AM, Julia Lawall wrote: > > Function clk_get, defined just below this code, returns ERR_PTR not NULL in > > an error case. > > > > The semantic match that finds this problem is as follows: > > (http://coccinelle.lip6.fr/) > > > > // > > @r@ > > identifier f; > > @@ > > f(...) { ... return ERR_PTR(...); } > > > > @@ > > identifier r.f, fld; > > expression x; > > statement S1,S2; > > @@ > > x = f(...) > > ... when != IS_ERR(x) > > ( > > if (IS_ERR(x) ||...) S1 else S2 > > | > > *x->fld > > ) > > // > > I'm always really impressed by this tool :-). > > > > > Signed-off-by: Julia Lawall > > > > --- > > arch/arm/mach-at91/clock.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/arch/arm/mach-at91/clock.c b/arch/arm/mach-at91/clock.c > > index 9113da6..c9ee6d0 100644 > > --- a/arch/arm/mach-at91/clock.c > > +++ b/arch/arm/mach-at91/clock.c > > @@ -224,7 +224,7 @@ void __init at91_clock_associate(const char *id, struct device *dev, const char > > { > > struct clk *clk = clk_get(NULL, id); > > > > - if (!dev || !clk || !IS_ERR(clk_get(dev, func))) > > + if (!dev || IS_ERR(clk) || !IS_ERR(clk_get(dev, func))) > > return; > > I think we want: > > if (!dev || !clk || IS_ERR(clk) || !IS_ERR(clk_get(dev, func))) > return; > > Since it is valid to return a NULL clk, and we don't want to try and > dereference it if that is the case. Looking at the given defintion of clk_get, I can't see how that could happen: struct clk *clk_get(struct device *dev, const char *id) { struct clk *clk; list_for_each_entry(clk, &clocks, node) { if (strcmp(id, clk->name) == 0) return clk; if (clk->function && (dev == clk->dev) && strcmp(id, clk->function) == 0) return clk; } return ERR_PTR(-ENOENT); } Both paths to the non-ERR_PTR return dereference clk. julia > We could also probably drop the !IS_ERR(clk_get(dev, func)) check, since > as far as I can tell it is just checking to see if the clock is already > associated, but there is no harm in re-assigning the same values, and > the two assignments in at91_clock_associate are going to be much quicker > than the lookup in clk_get. > > ~Ryan > > -- > Bluewater Systems Ltd - ARM Technology Solution Centre > > Ryan Mallon 5 Amuri Park, 404 Barbadoes St > ryan@bluewatersys.com PO Box 13 889, Christchurch 8013 > http://www.bluewatersys.com New Zealand > Phone: +64 3 3779127 Freecall: Australia 1800 148 751 > Fax: +64 3 3779135 USA 1800 261 2934 > -- > To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >