linux-kernel - Re: [PATCH v2 11/22] arm64: Populate cpuinfo after notify_cpu

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Date:	Fri, 9 Oct 2015 16:01:24 +0100
From:	"Suzuki K. Poulose" <Suzuki.Poulose@....com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	linux-arm-kernel@...ts.infradead.org, mark.rutland@....com,
	Vladimir.Murzin@....com, steve.capper@...aro.org,
	ard.biesheuvel@...aro.org, marc.zyngier@....com,
	will.deacon@....com, linux-kernel@...r.kernel.org,
	edward.nevill@...aro.org, aph@...hat.com, james.morse@....com,
	andre.przywara@....com, dave.martin@....com
Subject: Re: [PATCH v2 11/22] arm64: Populate cpuinfo after
 notify_cpu_starting

On 08/10/15 11:46, Suzuki K. Poulose wrote:
> On 08/10/15 11:15, Catalin Marinas wrote:
>> On Mon, Oct 05, 2015 at 06:02:00PM +0100, Suzuki K. Poulose wrote:
>>> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
>>> index cb3e0d8..6987de4 100644
>>> --- a/arch/arm64/kernel/smp.c
>>> +++ b/arch/arm64/kernel/smp.c
>>> @@ -163,14 +163,14 @@ asmlinkage void secondary_start_kernel(void)
>>>           cpu_ops[cpu]->cpu_postboot();
>>>
>>>       /*
>>> -     * Log the CPU info before it is marked online and might get read.
>>> +     * Enable GIC and timers.
>>>        */
>>> -    cpuinfo_store_cpu();
>>> +    notify_cpu_starting(cpu);
>>>
>>>       /*
>>> -     * Enable GIC and timers.
>>> +     * Log the CPU info before it is marked online and might get read.
>>>        */
>>> -    notify_cpu_starting(cpu);
>>> +    cpuinfo_store_cpu();
>>>
>>>       smp_store_cpu_info(cpu);
>>
>> You can move the cpuinfo_store_cpu() call directly to
>> smp_store_cpu_info().
>>
>
> That looks better, Thanks.

On a second look, smp_store_cpu_info() is also called from
smp_prepare_cpus() by the Boot CPU to update its topology
information, just after init_cpu_topology(). So moving the
cpuinfo_store_cpu() could be called for the boot CPU (which
we don't want, as it takes a different route to storing the
info).

One thing we could do is:

- Move init_cpu_topology() to setup_processor()
- Have the boot CPU update the topology from setup_processor()
   there, without going via the smp_store_cpu_info()
- Remove the smp_store_cpu_info() from smp_prepare_cpus().

Should we do that ? Or retain the code as above ?

Suzuki

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