Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753836AbbK3NLv (ORCPT ); Mon, 30 Nov 2015 08:11:51 -0500 Received: from www.linutronix.de ([62.245.132.108]:51563 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752231AbbK3NLu (ORCPT ); Mon, 30 Nov 2015 08:11:50 -0500 Date: Mon, 30 Nov 2015 14:11:03 +0100 (CET) From: Thomas Gleixner To: Qais Yousef cc: linux-kernel@vger.kernel.org, jason@lakedaemon.net, marc.zyngier@arm.com, jiang.liu@linux.intel.com, ralf@linux-mips.org, linux-mips@linux-mips.org Subject: Re: [PATCH v2 04/19] genirq: Add new struct ipi_mask and helper functions In-Reply-To: <565C3771.7040202@imgtec.com> Message-ID: References: <1448453217-3874-1-git-send-email-qais.yousef@imgtec.com> <1448453217-3874-5-git-send-email-qais.yousef@imgtec.com> <565C3771.7040202@imgtec.com> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1491 Lines: 38 On Mon, 30 Nov 2015, Qais Yousef wrote: > On 11/30/2015 11:20 AM, Thomas Gleixner wrote: > > On Wed, 25 Nov 2015, Qais Yousef wrote: > > > cpumask is limited to NR_CPUS. Introduce ipi_mask which allows us to > > > address > > > cpu range that is higher than NR_CPUS which is required for drivers to > > > send > > > IPIs for coprocessor that are outside Linux CPU range. > > I have second thoughts on this. > > > > cpumask is indeed limited to NR_CPUS or in case of CPUMASK_ON_STACK > > limited to nr_cpu_ids. > > > > But, that's not an issue for that coprocessor case. Let's assume you > > have 16 Linux CPUs and 4 coprocessors. So you set the number of > > possible cpus (NR_CPUS) to 20. That makes the cpumask sizeof 20. > > > > The boot-process sets the number of available cpus to 16. So the > > Linux side will never try to access anything beyond cpu15. > > > > But you can spare that extra mask magic and simply use cpumask. Sorry > > that I did not think about that earlier. > > > > > Yes it would be much better to reuse it but wouldn't the runtime checks > against nr_cpu_ids create problems especially when CPUMASK_ON_STACK is > defined? nr_cpu_ids == find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1; Thanks, tglx -- 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/