Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753464AbaFXMLZ (ORCPT ); Tue, 24 Jun 2014 08:11:25 -0400 Received: from mail3-relais-sop.national.inria.fr ([192.134.164.104]:39494 "EHLO mail3-relais-sop.national.inria.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752484AbaFXMLY (ORCPT ); Tue, 24 Jun 2014 08:11:24 -0400 X-IronPort-AV: E=Sophos;i="5.01,537,1400018400"; d="scan'208";a="68649310" Date: Tue, 24 Jun 2014 14:11:22 +0200 (CEST) From: Julia Lawall X-X-Sender: jll@hadrien To: Joe Perches cc: Julian Calaby , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 00/22] Add and use pci_zalloc_consistent In-Reply-To: <1403594158.29061.10.camel@joe-AO725> Message-ID: References: <20140623172512.GA1390@garbanzo.do-not-panic.com> <1403550809.15811.13.camel@joe-AO725> <1403567322.20657.14.camel@joe-AO725> <1403594158.29061.10.camel@joe-AO725> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) 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, 24 Jun 2014, Joe Perches wrote: > On Tue, 2014-06-24 at 07:24 +0200, Julia Lawall wrote > > On Mon, 23 Jun 2014, Joe Perches wrote: > > > > > $ cat ./scripts/coccinelle/api/alloc/pci_zalloc_consistent.cocci > > > > > /// > > > > > /// Use pci_zalloc_consistent rather than > > > > > /// pci_alloc_consistent followed by memset with 0 > > > > > /// > > > > > /// This considers some simple cases that are common and easy to validate > > > > > /// Note in particular that there are no ...s in the rule, so all of the > > > > > /// matched code has to be contiguous > > > > > /// > > > > > /// Blatantly cribbed from: scripts/coccinelle/api/alloc/kzalloc-simple.cocci > > > > > > > > > > @@ > > > > > type T, T2; > > > > > expression x; > > > > > expression E1,E2,E3; > > > > > statement S; > > > > > @@ > > > > > > > > > > - x = (T)pci_alloc_consistent(E1,E2,E3); > > > > > + x = pci_zalloc_consistent(E1,E2,E3); > > > > > if ((x==NULL) || ...) S > > > > > - memset((T2)x,0,E2); > > > > > > > > I don't know much about SmPL, but wouldn't having that if statement > > > > there reduce your matches? > > > > > > No, not really. > > > > > > Almost none of the pci_alloc_consistent calls > > > do not have a test for failure immediately after > > > them. > > > Do not or do? > > Sorry, English double negative. > > As far as I know, almost every instance of pci_alloc_consistent > is followed by an if. > > Exceptions exist in: > > drivers/isdn/hardware/eicon/divasmain.c > drivers/staging/slicoss/slicoss.c > drivers/tty/synclink_gt.c > > There might be others, but I didn't look too hard. > > > The advantage of the if is that you are sure that nothing strange happens > > to x between alloc and memset. But a problem can be that sometimes people > > allocate two things, and then do error checking for both of them. Then > > you rule would not match. Or the set the return variable to an error code > > before doing the check rather than in the if branch. > > > > You could put the following between the malloc and the memset in stead of > > the if. > > > > ... when != ( f(...,x,...) | <+...x...+> = E3 ) > > when != ( while(...) S | for(...;...;...) S ) > > > > This has given reasonable results for kmalloc and memset. > > Thanks for that. > > It might be nice to add that to the kzalloc example > in scripts/coccinelle I will do that. Thanks. julia -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/