Re: [PATCH v3] hrtimer: avoid retrigger_next_event IPI

From: Thomas Gleixner <tglx@linutronix.de>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Anna-Maria Behnsen <anna-maria@linutronix.de>,
	linux-kernel@vger.kernel.org,
	Frederic Weisbecker <frederic@kernel.org>,
	Peter Xu <peterx@redhat.com>,
	Nitesh Narayan Lal <nitesh@redhat.com>,
	Alex Belits <abelits@marvell.com>
Subject: Re: [PATCH v3] hrtimer: avoid retrigger_next_event IPI
Date: Thu, 15 Apr 2021 20:59:30 +0200	[thread overview]
Message-ID: <87im4nv0fh.ffs@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20210415153935.GA69750@fuller.cnet>

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;
> +}