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Message-ID: <20150910195532.GK8114@mtj.duckdns.org>
Date: Thu, 10 Sep 2015 15:55:32 -0400
From: Tejun Heo <tj@...nel.org>
To: Tang Chen <tangchen@...fujitsu.com>
Cc: jiang.liu@...ux.intel.com, mika.j.penttila@...il.com,
mingo@...hat.com, akpm@...ux-foundation.org, rjw@...ysocki.net,
hpa@...or.com, yasu.isimatu@...il.com,
isimatu.yasuaki@...fujitsu.com, kamezawa.hiroyu@...fujitsu.com,
izumi.taku@...fujitsu.com, gongzhaogang@...pur.com,
qiaonuohan@...fujitsu.com, x86@...nel.org,
linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, Gu Zheng <guz.fnst@...fujitsu.com>
Subject: Re: [PATCH v2 5/7] x86, acpi, cpu-hotplug: Introduce
apicid_to_cpuid[] array to store persistent cpuid <-> apicid mapping.
Hello,
So, overall, I think this is the right way to go although I have no
idea whether the acpi part is okay.
> +/*
> + * 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?
> +static int cpuid_to_apicid[] = {
> + [0 ... NR_CPUS - 1] = -1,
> +};
And maybe mention how the two variables are synchronized?
> +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?
Thanks.
--
tejun
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