From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id 059DA6B003D for ; Tue, 28 Apr 2009 23:02:47 -0400 (EDT) Date: Tue, 28 Apr 2009 19:55:27 -0700 From: Andrew Morton Subject: Re: [PATCH 5/5] proc: export more page flags in /proc/kpageflags Message-Id: <20090428195527.4638f58c.akpm@linux-foundation.org> In-Reply-To: <20090429023842.GA10266@localhost> References: <20090428010907.912554629@intel.com> <20090428014920.769723618@intel.com> <20090428143244.4e424d36.akpm@linux-foundation.org> <20090429023842.GA10266@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Wu Fengguang Cc: "linux-kernel@vger.kernel.org" , "kosaki.motohiro@jp.fujitsu.com" , "andi@firstfloor.org" , "mpm@selenic.com" , "adobriyan@gmail.com" , "linux-mm@kvack.org" , Stephen Rothwell , Chandra Seetharaman , Nathan Lynch , Olof Johansson , Helge Deller List-ID: On Wed, 29 Apr 2009 10:38:42 +0800 Wu Fengguang wrote: > > > +#define kpf_copy_bit(uflags, kflags, visible, ubit, kbit) \ > > > + do { \ > > > + if (visible || genuine_linus()) \ > > > + uflags |= ((kflags >> kbit) & 1) << ubit; \ > > > + } while (0); > > > > Did this have to be implemented as a macro? > > > > It's bad, because it might or might not reference its argument, so if > > someone passes it an expression-with-side-effects, the end result is > > unpredictable. A C function is almost always preferable if possible. > > Just tried inline function, the code size is increased slightly: > > text data bss dec hex filename > macro 1804 128 0 1932 78c fs/proc/page.o > inline 1828 128 0 1956 7a4 fs/proc/page.o > hm, I wonder why. Maybe it fixed a bug ;) The code is effectively doing if (expr1) something(); if (expr1) something_else(); if (expr1) something_else2(); etc. Obviously we _hope_ that the compiler turns that into if (expr1) { something(); something_else(); something_else2(); } for us, but it would be good to check... -- 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