Re: [profile] amortize atomic hit count increments

[Andrew Morton]

William Lee Irwin III <wli@xxxxxxxxxxxxxx> wrote:
>

A few comments which describe the design would be nice...

> +#ifdef CONFIG_SMP
>  +static void __profile_flip_buffers(void *unused)
>  +{
>  +	int cpu = get_cpu();
>  +	unsigned long flags;
>  +
>  +	local_irq_save(flags);
>  +	per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
>  +	local_irq_restore(flags);
>  +	put_cpu();
>  +}

hm.  Does an IPI handler need to disable local IRQs?

>  +static void profile_flip_buffers(void)
>  +{
>  +	static DECLARE_MUTEX(profile_flip_mutex);
>  +	int i, j, cpu;
>  +
>  +	down(&profile_flip_mutex);
>  +	j = per_cpu(cpu_profile_flip, smp_processor_id());

Is this preempt-safe?

>  +	on_each_cpu(__profile_flip_buffers, NULL, 0, 1);
>  +	for_each_online_cpu(cpu) {
>  +		struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];


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