linux-kernel - Re: [PATCH 6/8] MIPS: call set_cpu_online() on the uping cpu with irq disabled

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Message-ID: <4FBA1B54.3@linux.vnet.ibm.com>
Date:	Mon, 21 May 2012 16:09:16 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Yong Zhang <yong.zhang0@...il.com>
CC:	linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org,
	ralf@...ux-mips.org, sshtylyov@...sta.com, david.daney@...ium.com,
	sshtylyov@...sta.com,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Subject: Re: [PATCH 6/8] MIPS: call set_cpu_online() on the uping cpu with
 irq disabled

On 05/21/2012 11:30 AM, Yong Zhang wrote:

> From: Yong Zhang <yong.zhang@...driver.com>
> 
> To prevent a problem as commit 5fbd036b [sched: Cleanup cpu_active madness]
> and commit 2baab4e9 [sched: Fix select_fallback_rq() vs cpu_active/cpu_online]
> try to resolve, move set_cpu_online() to the brought up CPU and with irq
> disabled.
> 
> Signed-off-by: Yong Zhang <yong.zhang0@...il.com>
> Acked-by: David Daney <david.daney@...ium.com>
> ---
>  arch/mips/kernel/smp.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
> index 73a268a..042145f 100644
> --- a/arch/mips/kernel/smp.c
> +++ b/arch/mips/kernel/smp.c
> @@ -122,6 +122,8 @@ asmlinkage __cpuinit void start_secondary(void)
> 
>  	notify_cpu_starting(cpu);
> 
> +	set_cpu_online(cpu, true);
> +


You will also need to use ipi_call_lock/unlock() around this.
See how x86 does it. (MIPS also selects USE_GENERIC_SMP_HELPERS).

Regards,
Srivatsa S. Bhat

>  	set_cpu_sibling_map(cpu);
> 
>  	cpu_set(cpu, cpu_callin_map);
> @@ -249,8 +251,6 @@ int __cpuinit __cpu_up(unsigned int cpu)
>  	while (!cpu_isset(cpu, cpu_callin_map))
>  		udelay(100);
> 
> -	set_cpu_online(cpu, true);
> -
>  	return 0;
>  }
> 

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