Re: [PATCH] netfilter: use per-cpu recursive lock (v11)

[Ingo Molnar]

* Stephen Hemminger <shemminger@xxxxxxxxxx> wrote:

> +void xt_info_wrunlock_bh(void)
> +	__releases(xt_info_lock)
> +{
> +	unsigned int i;
> +
> +	for_each_possible_cpu(i) {
> +#if NR_CPUS > (PREEMPT_MASK - 1)
> +		/*
> +		 * Spin_unlock calls preempt_enable, but since we had
> +		 * to adjust the count in xt_info_wrlock_bh, do it again
> +		 */
> +		preempt_disable();
> +#endif
> +		write_unlock(&per_cpu(xt_info_locks, i));
> +	}
> +	local_bh_enable();
> +}

In the global/local lock scheme i proposed this would become:

	global_write_unlock(void)
	{
		write_unlock(&global_lock);
	}

As we dont hold the local locks during the write-locked critical 
section. No loop needed over CPUs, no preempt nesting complications, 
no lockdep complications, etc.

	Ingo
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