linux-kernel - Re: [PATCH v2] ARM: Don't use complete() during __cpu

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Date:	Tue, 10 Feb 2015 14:05:01 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	Mark Rutland <mark.rutland@....com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>
Subject: Re: [PATCH v2] ARM: Don't use complete() during __cpu_die

On 02/10/15 13:49, Stephen Boyd wrote:
>>> diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
>>> index fe0386c751b2..4d213b24db60 100644
>>> --- a/arch/arm/kernel/smp.c
>>> +++ b/arch/arm/kernel/smp.c
>>> @@ -174,18 +174,19 @@ static int platform_cpu_kill(unsigned int cpu)
>>>  	return 1;
>>>  }
>>>  
>>> -static int platform_cpu_disable(unsigned int cpu)
>>> +int platform_can_hotplug_cpu(unsigned int cpu)
>>>  {
>>>  	if (smp_ops.cpu_disable)
>>> -		return smp_ops.cpu_disable(cpu);
>>> +		return smp_ops.cpu_disable(cpu) ? 0 : 1;
>>>  

BTW, we also need this

        /* cpu_die must be specified to support hotplug */
        if (!smp_ops.cpu_die)
                return 0;

otherwise it seems that we can have a situation where cpu_die() does
nothing besides unexpectedly jump to secondary_start_kernel() before
generic cpu hotplug facilities expect it to.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

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