From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f54.google.com (mail-pa0-f54.google.com [209.85.220.54]) by kanga.kvack.org (Postfix) with ESMTP id 920266B0038 for ; Sat, 26 Sep 2015 05:53:52 -0400 (EDT) Received: by pacex6 with SMTP id ex6so128263972pac.0 for ; Sat, 26 Sep 2015 02:53:52 -0700 (PDT) Received: from heian.cn.fujitsu.com ([59.151.112.132]) by mx.google.com with ESMTP id ut10si11536664pac.203.2015.09.26.02.53.51 for ; Sat, 26 Sep 2015 02:53:51 -0700 (PDT) Message-ID: <56066AC9.6020703@cn.fujitsu.com> Date: Sat, 26 Sep 2015 17:52:09 +0800 From: Tang Chen MIME-Version: 1.0 Subject: Re: [PATCH v2 5/7] x86, acpi, cpu-hotplug: Introduce apicid_to_cpuid[] array to store persistent cpuid <-> apicid mapping. References: <1441859269-25831-1-git-send-email-tangchen@cn.fujitsu.com> <1441859269-25831-6-git-send-email-tangchen@cn.fujitsu.com> <20150910195532.GK8114@mtj.duckdns.org> In-Reply-To: <20150910195532.GK8114@mtj.duckdns.org> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo Cc: jiang.liu@linux.intel.com, mika.j.penttila@gmail.com, mingo@redhat.com, akpm@linux-foundation.org, rjw@rjwysocki.net, hpa@zytor.com, yasu.isimatu@gmail.com, isimatu.yasuaki@jp.fujitsu.com, kamezawa.hiroyu@jp.fujitsu.com, izumi.taku@jp.fujitsu.com, gongzhaogang@inspur.com, qiaonuohan@cn.fujitsu.com, x86@kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, tangchen@cn.fujitsu.com Hi tj, On 09/11/2015 03:55 AM, Tejun Heo wrote: > Hello, > > So, overall, I think this is the right way to go although I have no > idea whether the acpi part is okay. Thank you very much for reviewing. :) > >> +/* >> + * Current allocated max logical CPU ID plus 1. >> + * All allocated CPU ID should be in [0, max_logical_cpuid), >> + * so the maximum of max_logical_cpuid is nr_cpu_ids. >> + * >> + * NOTE: Reserve 0 for BSP. >> + */ >> +static int max_logical_cpuid = 1; > Rename it to nr_logical_cpuids and just mention that it's allocated > contiguously? OK. > >> +static int cpuid_to_apicid[] = { >> + [0 ... NR_CPUS - 1] = -1, >> +}; > And maybe mention how the two variables are synchronized? User should call allocate_logical_cpuid() to get a new logical cpuid. This allocator will ensure the synchronization. Will mention it in the comment. > >> +static int allocate_logical_cpuid(int apicid) >> +{ >> + int i; >> + >> + /* >> + * cpuid <-> apicid mapping is persistent, so when a cpu is up, >> + * check if the kernel has allocated a cpuid for it. >> + */ >> + for (i = 0; i < max_logical_cpuid; i++) { >> + if (cpuid_to_apicid[i] == apicid) >> + return i; >> + } >> + >> + /* Allocate a new cpuid. */ >> + if (max_logical_cpuid >= nr_cpu_ids) { >> + WARN_ONCE(1, "Only %d processors supported." >> + "Processor %d/0x%x and the rest are ignored.\n", >> + nr_cpu_ids - 1, max_logical_cpuid, apicid); >> + return -1; >> + } > So, the original code didn't have this failure mode, why is this > different for the new code? It is not different. Since max_logical_cpuid is new, this is ensure it won't go beyond NR_CPUS. Thanks. > > Thanks. > -- 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