linux-kernel - Re: [PATCH v3] hrtimer: avoid retrigger_next

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Message-ID: <87im4nv0fh.ffs@nanos.tec.linutronix.de>
Date:   Thu, 15 Apr 2021 20:59:30 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Marcelo Tosatti <mtosatti@...hat.com>
Cc:     Anna-Maria Behnsen <anna-maria@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Frederic Weisbecker <frederic@...nel.org>,
        Peter Xu <peterx@...hat.com>,
        Nitesh Narayan Lal <nitesh@...hat.com>,
        Alex Belits <abelits@...vell.com>
Subject: Re: [PATCH v3] hrtimer: avoid retrigger_next_event IPI

On Thu, Apr 15 2021 at 12:39, Marcelo Tosatti wrote:
> +static bool need_reprogram_timer(struct hrtimer_cpu_base *cpu_base)
> +{
> +	unsigned int active = 0;
> +
> +	if (cpu_base->softirq_activated)
> +		return true;
> +
> +	active = cpu_base->active_bases & HRTIMER_ACTIVE_SOFT;
> +	active = active | (cpu_base->active_bases & HRTIMER_ACTIVE_HARD);

It's not entirely clear to me what that 'active' variable business above
is doing and why it's needed at all. But I might be missing something.

> +	return (cpu_base->active_bases & CLOCK_SET_BASES) != 0;
> +}