linux-kernel - Re: [PATCH 17/25] hrtimer: Implementation of softirq hrtimer handling

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Date:   Thu, 28 Sep 2017 09:59:50 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     Anna-Maria Gleixner <anna-maria@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Christoph Hellwig <hch@....org>, keescook@...omium.org,
        John Stultz <john.stultz@...aro.org>
Subject: Re: [PATCH 17/25] hrtimer: Implementation of softirq hrtimer
 handling

On Wed, 27 Sep 2017, Peter Zijlstra wrote:
> On Thu, Aug 31, 2017 at 12:23:42PM -0000, Anna-Maria Gleixner wrote:
>  static void __run_hrtimer(struct hrtimer_cpu_base *cpu_base,
>  			  struct hrtimer_clock_base *base,
>  			  struct hrtimer *timer, ktime_t *now,
> -			  bool hardirq)
> +			  unsigned long flags)
>  {
>  	enum hrtimer_restart (*fn)(struct hrtimer *);
>  	int restart;
> @@ -1298,19 +1323,13 @@ static void __run_hrtimer(struct hrtimer
>  	 * protected against migration to a different CPU even if the lock
>  	 * is dropped.
>  	 */
> -	if (hardirq)
> -		raw_spin_unlock(&cpu_base->lock);
> -	else
> -		raw_spin_unlock_irq(&cpu_base->lock);
> +	raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
>  
>  	trace_hrtimer_expire_entry(timer, now);
>  	restart = fn(timer);
>  	trace_hrtimer_expire_exit(timer);
>  
> -	if (hardirq)
> -		raw_spin_lock(&cpu_base->lock);
> -	else
> -		raw_spin_lock_irq(&cpu_base->lock);
> +	raw_spin_lock_irqsave(&cpu_base->lock, flags);

No point in irqsave() here. _irq() is sufficient as we leave the function
right after that.

Thanks,

	tglx