From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: [Bug #11342] Linux 2.6.27-rc3: kernel BUG at mm/vmalloc.c - bisected Date: Tue, 26 Aug 2008 09:51:46 -0700 (PDT) Message-ID: References: <20080826072220.GB31876@elte.hu> <20080826.004607.253712060.davem@davemloft.net> <20080826075355.GA7596@elte.hu> <86802c440808260136t3a33a9c8if53b6f70ab9df9e2@mail.gmail.com> Mime-Version: 1.0 Return-path: In-Reply-To: <86802c440808260136t3a33a9c8if53b6f70ab9df9e2-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> Sender: kernel-testers-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: TEXT/PLAIN; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Yinghai Lu Cc: Ingo Molnar , David Miller , Alan.Brunelle-VXdhtT5mjnY@public.gmane.org, travis-sJ/iWh9BUns@public.gmane.org, tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org, rjw-KKrjLPT3xs0@public.gmane.org, Linux Kernel Mailing List , kernel-testers-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andrew Morton , arjan-VuQAYsv1563Yd54FQh9/CA@public.gmane.org, rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org On Tue, 26 Aug 2008, Yinghai Lu wrote: > > wonder if could use "unsigned long *" directly. I would actually suggest something like this: - we continue to have a magic "cpumask_t". - we do different cases for big and small NR_CPUS: #if NR_CPUS <= BITS_PER_LONG /* * Make it an array - that way passing it as an argument will * always pass it as a pointer! */ typedef unsigned long cpumask_t[1]; static inline void create_cpumask(cpumask_t *p) { *p = 0; } static inline void free_cpumask(cpumask_t *p) { } #else typedef unsigned long *cpumask_t; static inline void create_cpumask(cpumask_t *p) { *p = kcalloc(..); } static inline void free_cpumask(cpumask_t *p) { kfree(*p); } #endif and now after you do this, you can just do something like cpumask_t mycpu; create_cpumask(&mycpu); .. free_cpumask(&mycpu); and in between, you can use 'cpumask' as a pointer, because even when it is an array directly allocated on the stack, the array can always degenerate into a pointer by C type rules! And for the small-NR_CPUS case there is zero overhead. Linus