Re: [PATCH 33/45] cris/smp: Use get/put_online_cpus_atomic() to prevent CPU offline

[Jesper Nilsson <jesper.nilsson@axis.com>]

On Sun, Jun 23, 2013 at 07:15:39PM +0530, Srivatsa S. Bhat wrote:
> Once stop_machine() is gone from the CPU offline path, we won't be able
> to depend on disabling preemption to prevent CPUs from going offline
> from under us.
> 
> Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going
> offline, while invoking from atomic context.
> 
> Cc: Mikael Starvik <starvik@axis.com>

Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>

> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: linux-cris-kernel@axis.com
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
> ---
> 
>  arch/cris/arch-v32/kernel/smp.c |    5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arch/cris/arch-v32/kernel/smp.c b/arch/cris/arch-v32/kernel/smp.c
> index cdd1202..b2d4612 100644
> --- a/arch/cris/arch-v32/kernel/smp.c
> +++ b/arch/cris/arch-v32/kernel/smp.c
> @@ -13,6 +13,7 @@
>  #include <linux/init.h>
>  #include <linux/timex.h>
>  #include <linux/sched.h>
> +#include <linux/cpu.h>
>  #include <linux/kernel.h>
>  #include <linux/cpumask.h>
>  #include <linux/interrupt.h>
> @@ -222,6 +223,7 @@ void flush_tlb_common(struct mm_struct* mm, struct vm_area_struct* vma, unsigned
>  	unsigned long flags;
>  	cpumask_t cpu_mask;
>  
> +	get_online_cpus_atomic();
>  	spin_lock_irqsave(&tlbstate_lock, flags);
>  	cpu_mask = (mm == FLUSH_ALL ? cpu_all_mask : *mm_cpumask(mm));
>  	cpumask_clear_cpu(smp_processor_id(), &cpu_mask);
> @@ -230,6 +232,7 @@ void flush_tlb_common(struct mm_struct* mm, struct vm_area_struct* vma, unsigned
>  	flush_addr = addr;
>  	send_ipi(IPI_FLUSH_TLB, 1, cpu_mask);
>  	spin_unlock_irqrestore(&tlbstate_lock, flags);
> +	put_online_cpus_atomic();
>  }
>  
>  void flush_tlb_all(void)
> @@ -319,10 +322,12 @@ int smp_call_function(void (*func)(void *info), void *info, int wait)
>  	data.info = info;
>  	data.wait = wait;
>  
> +	get_online_cpus_atomic();
>  	spin_lock(&call_lock);
>  	call_data = &data;
>  	ret = send_ipi(IPI_CALL, wait, cpu_mask);
>  	spin_unlock(&call_lock);
> +	put_online_cpus_atomic();
>  
>  	return ret;
>  }
> 
> --
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/^JN - Jesper Nilsson
-- 
               Jesper Nilsson -- jesper.nilsson@axis.com