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Re: [PATCH 6/8] MIPS: call set_cpu_online() on the uping cpu with irq di

To: Yong Zhang <yong.zhang0@gmail.com>
Subject: Re: [PATCH 6/8] MIPS: call set_cpu_online() on the uping cpu with irq disabled
From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Date: Mon, 21 May 2012 16:09:16 +0530
Cc: linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, ralf@linux-mips.org, sshtylyov@mvista.com, david.daney@cavium.com, sshtylyov@mvista.com, "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
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On 05/21/2012 11:30 AM, Yong Zhang wrote:

> From: Yong Zhang <yong.zhang@windriver.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@gmail.com>
> Acked-by: David Daney <david.daney@cavium.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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