linux-kernel - Re: [PATCH v1] timers: Clear must_forward

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Date:   Wed, 1 Aug 2018 18:04:50 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Gaurav Kohli <gkohli@...eaurora.org>
cc:     john.stultz@...aro.org, sboyd@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] timers: Clear must_forward_clk inside base lock

On Wed, 1 Aug 2018, Gaurav Kohli wrote:
> @@ -1657,6 +1657,17 @@ static inline void __run_timers(struct timer_base *base)
>  
>  	raw_spin_lock_irq(&base->lock);
>  
> +	/*
> +	 * The must_forward_clk flag is cleared unconditionally also for
> +	 * the deferrable base. The deferrable base is not affected by idle
> +	 * tracking and never forwarded, so clearing the flag is a NOOP.
> +	 *
> +	 * The fact that the deferrable base is never forwarded can cause
> +	 * large variations in granularity for deferrable timers, but they
> +	 * can be deferred for long periods due to idle anyway.
> +	 */
> +	base->must_forward_clk = false;
> +
>  	while (time_after_eq(jiffies, base->clk)) {
>  
>  		levels = collect_expired_timers(base, heads);
> @@ -1676,19 +1687,6 @@ static __latent_entropy void run_timer_softirq(struct softirq_action *h)
>  {
>  	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
>  
> -	/*
> -	 * must_forward_clk must be cleared before running timers so that any
> -	 * timer functions that call mod_timer will not try to forward the
> -	 * base. idle trcking / clock forwarding logic is only used with
> -	 * BASE_STD timers.

You lost this part of the comment ....

Thanks,

	tglx