From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx139.postini.com [74.125.245.139]) by kanga.kvack.org (Postfix) with SMTP id 59C4E6B0034 for ; Mon, 15 Jul 2013 20:54:22 -0400 (EDT) Message-ID: <51E49982.30402@asianux.com> Date: Tue, 16 Jul 2013 08:53:22 +0800 From: Chen Gang MIME-Version: 1.0 Subject: Re: [PATCH] mm/slub.c: use 'unsigned long' instead of 'int' for variable 'slub_debug' References: <51DF5F43.3080408@asianux.com> <0000013fd3283b9c-b5fe217c-fff3-47fd-be0b-31b00faba1f3-000000@email.amazonses.com> <51E33FFE.3010200@asianux.com> <0000013fe2b1bd10-efcc76b5-f75b-4a45-a278-a318e87b2571-000000@email.amazonses.com> In-Reply-To: <0000013fe2b1bd10-efcc76b5-f75b-4a45-a278-a318e87b2571-000000@email.amazonses.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: Pekka Enberg , mpm@selenic.com, linux-mm@kvack.org On 07/15/2013 10:17 PM, Christoph Lameter wrote: > On Mon, 15 Jul 2013, Chen Gang wrote: > >> > On 07/12/2013 09:53 PM, Christoph Lameter wrote: >>> > > On Fri, 12 Jul 2013, Chen Gang wrote: >>> > > >>>> > >> Since all values which can be assigned to 'slub_debug' are 'unsigned >>>> > >> long', recommend also to define 'slub_debug' as 'unsigned long' to >>>> > >> match the type precisely >>> > > >>> > > The bit definitions in slab.h as well as slub.c all assume that these are >>> > > 32 bit entities. See f.e. the defition of the internal slub flags: >>> > > >>> > > /* Internal SLUB flags */ >>> > > #define __OBJECT_POISON 0x80000000UL /* Poison object */ >>> > > #define __CMPXCHG_DOUBLE 0x40000000UL /* Use cmpxchg_double */ >>> > > >> > >> > As far as I know, 'UL' means "unsigned long", is it correct ? > This is the way hex constants are generally specified. > > The C compiler will treat 'UL' as "unsigned long". If we really use 32-bit as unsigned number, better to use 'U' instead of 'UL' (e.g. 0x80000000U instead of 0x80000000UL). Since it is unsigned 32-bit number, it is better to use 'unsigned int' instead of 'int', which can avoid related warnings if "EXTRA_CFLAGS=-W". Thanks. -- Chen Gang -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org