Re: [V3 PATCH] x86: avoid calling arch_trigger_all_cpu_backtrace()at the same time on SMP

[Ingo Molnar]

Hm, another thing i noticed is that there's two of these:

>  #ifdef ARCH_HAS_NMI_WATCHDOG
> +/* "in progress" flag of arch_trigger_all_cpu_backtrace */
> +static unsigned long backtrace_flag;
> +
>  void arch_trigger_all_cpu_backtrace(void)
>  {
>  	int i;
> +	unsigned long flags;
> +
> +	/*
> +	 * Have to disable irq here, as the
> +	 * arch_trigger_all_cpu_backtrace() could be
> +	 * triggered by "spin_lock()" with irqs on.
> +	 */
> +	local_irq_save(flags);

> +/* "in progress" flag of arch_trigger_all_cpu_backtrace */
> +static unsigned long backtrace_flag;
> +
>  void arch_trigger_all_cpu_backtrace(void)
>  {
>  	int i;
> +	unsigned long flags;
> +
> +	/*
> +	 * Have to disable irq here, as the
> +	 * arch_trigger_all_cpu_backtrace() could be
> +	 * triggered by "spin_lock()" with irqs on.
> +	 */
> +	local_irq_save(flags);
> +
> +	if (test_and_set_bit(0, &backtrace_flag))

A fair amount of code is being duplicated in two places - which is not nice. Lets 
try to create a shared facility instead?

Thanks,

	Ingo
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