linux-kernel - Re: [PATCH 2/5] metag: smp: enable irqs after set_cpu

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Message-ID: <51D26BE7.3050702@linux.vnet.ibm.com>
Date:	Tue, 02 Jul 2013 11:27:59 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	James Hogan <james.hogan@...tec.com>
CC:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Kirill Tkhai <tkhai@...dex.ru>
Subject: Re: [PATCH 2/5] metag: smp: enable irqs after set_cpu_online

On 07/01/2013 09:34 PM, James Hogan wrote:
> In secondary_start_kernel() interrupts should be enabled with
> local_irq_enable() after the cpu is marked as online with
> set_cpu_online(). Otherwise it's possible for a timer interrupt to
> trigger a softirq, which if the cpu is marked as offline may have it's
> affinity altered.
> 
> Reported-by: Kirill Tkhai <tkhai@...dex.ru>
> Signed-off-by: James Hogan <james.hogan@...tec.com>
> Cc: Kirill Tkhai <tkhai@...dex.ru>
> Cc: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> ---

Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>

Regards,
Srivatsa S. Bhat

>  arch/metag/kernel/smp.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/metag/kernel/smp.c b/arch/metag/kernel/smp.c
> index b813515..09979f2 100644
> --- a/arch/metag/kernel/smp.c
> +++ b/arch/metag/kernel/smp.c
> @@ -379,12 +379,7 @@ asmlinkage void secondary_start_kernel(void)
> 
>  	setup_priv();
> 
> -	/*
> -	 * Enable local interrupts.
> -	 */
> -	tbi_startup_interrupt(TBID_SIGNUM_TRT);
>  	notify_cpu_starting(cpu);
> -	local_irq_enable();
> 
>  	pr_info("CPU%u (thread %u): Booted secondary processor\n",
>  		cpu, cpu_2_hwthread_id[cpu]);
> @@ -398,6 +393,12 @@ asmlinkage void secondary_start_kernel(void)
>  	set_cpu_online(cpu, true);
> 
>  	/*
> +	 * Enable local interrupts.
> +	 */
> +	tbi_startup_interrupt(TBID_SIGNUM_TRT);
> +	local_irq_enable();
> +
> +	/*
>  	 * OK, it's off to the idle thread for us
>  	 */
>  	cpu_startup_entry(CPUHP_ONLINE);
> 

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