linux-kernel - Re: [PATCH 8/9] irq_work: Make self-IPIs optable

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Date:	Fri, 16 Nov 2012 11:09:43 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: Re: [PATCH 8/9] irq_work: Make self-IPIs optable

On Fri, 2012-11-16 at 03:21 +0100, Frederic Weisbecker wrote:
>  
>  /*
>   * Claim the entry so that no one else will poke at it.
> @@ -68,14 +59,18 @@ void __weak arch_irq_work_raise(void)
>   */
>  static void __irq_work_queue(struct irq_work *work)
>  {
> -	bool empty;
> -
>  	preempt_disable();
>  
> -	empty = llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
> -	/* The list was empty, raise self-interrupt to start processing. */
> -	if (empty)
> -		arch_irq_work_raise();
> +	llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
> +
> +	/*
> +	 * If the work is flagged as "lazy", just wait for the next tick
> +	 * to run it. Otherwise, or if the tick is stopped, raise the irq work.

Speaking more Greek? ;-)

How about:

	If the work is not "lazy" or the tick is stopped, raise the irq
	work interrupt (if supported by the arch), otherwise, just wait
	for the next tick.

Other than that, Acked-by: Steven Rostedt <rostedt@...dmis.org>

-- Steve

> +	 */
> +	if (!(work->flags & IRQ_WORK_LAZY) || tick_nohz_tick_stopped()) {
> +		if (!this_cpu_cmpxchg(irq_work_raised, 0, 1))
> +			arch_irq_work_raise();
> +	}
>  


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