Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753245AbZFFJYS (ORCPT ); Sat, 6 Jun 2009 05:24:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752855AbZFFJYG (ORCPT ); Sat, 6 Jun 2009 05:24:06 -0400 Received: from mx2.redhat.com ([66.187.237.31]:47999 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751858AbZFFJYF (ORCPT ); Sat, 6 Jun 2009 05:24:05 -0400 Message-ID: <4A2A356B.6090102@redhat.com> Date: Sat, 06 Jun 2009 12:22:51 +0300 From: Avi Kivity User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Rusty Russell CC: Yinghai Lu , Ingo Molnar , Andrew Morton , Thomas Gleixner , "H. Peter Anvin" , "linux-kernel@vger.kernel.org" , Linus Torvalds Subject: Re: [PATCH] cpumask: alloc blank cpumask left over References: <4A2835D8.6040903@kernel.org> <200906051428.08299.rusty@rustcorp.com.au> <4A28B3A9.3010505@kernel.org> <200906052311.57762.rusty@rustcorp.com.au> In-Reply-To: <200906052311.57762.rusty@rustcorp.com.au> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1712 Lines: 54 Rusty Russell wrote: > On Fri, 5 Jun 2009 03:26:57 pm Yinghai Lu wrote: > >> Rusty Russell wrote: >> >>> On Fri, 5 Jun 2009 06:31:31 am Yinghai Lu wrote: >>> >>>> avoid suprise when MAXSMP is enabled >>>> >>>> Signed-off-by: Yinghai Lu >>>> >>> I understand the temptation, but two questions arise: >>> 1) Shouldn't we actually audit to see if any of these are currently >>> problems, >>> >> those are defined as static cpumask_var_t, and if MAXSMP is not used, they >> are cleared already >> > > OK, here's what I've got in my tree. Ingo, I think this should go in the > current -rc to avoid nasty bugs. > > BTW, the original alloc_cpumask_var did zero; that was dropped after arguments > over efficiency and fitting with other interfaces, but I clearly had the old > semantics in my head for a while. > > Using __GFP_ZERO is equivalent to using memset() instead of cpumask_clear(). It's better to call cpumask_clear() or provide an API to alloc+clear. Further, what about the non-MAXSMP case: static inline bool alloc_cpumask_var(cpumask_var_t *mask, gfp_t flags) { return true; } We explicity clear on MAXSMP and rely on static initialization for the non-MAXSMP, laying a neat trap for anyone who makes the variable non-static. Let's be less subtle that that. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain. -- 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/