linux-kernel - Re: [PATCH] futex: Consolidate duplicated timer setup code

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Date:   Wed, 24 Apr 2019 18:09:54 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Darren Hart <dvhart@...radead.org>,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        Davidlohr Bueso <dave@...olabs.net>
Subject: Re: [PATCH] futex: Consolidate duplicated timer setup code

On Wed, Apr 24, 2019 at 11:36:51AM -0400, Waiman Long wrote:
> +static inline struct hrtimer_sleeper *
> +futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout,
> +		  int flags, u64 range_ns)
> +{
> +	if (!time)
> +		return NULL;
> +
> +	hrtimer_init_on_stack(&timeout->timer, (flags & FLAGS_CLOCKRT) ?
> +			      CLOCK_REALTIME : CLOCK_MONOTONIC,
> +			      HRTIMER_MODE_ABS);
> +	hrtimer_init_sleeper(timeout, current);
> +	if (range_ns)
> +		hrtimer_set_expires_range_ns(&timeout->timer, *time, range_ns);
> +	else
> +		hrtimer_set_expires(&timeout->timer, *time);

That can be an unconditinoal:

	hrtimer_set_expires_range_ns(&timeout->timer, *time, range_ns);

See how:

  timer->node.expires = ktime_add_safe(time, ns_to_ktime(delta));

is the same as:

  timer->node.expires = time;

when !delta.

> +
> +	return timeout;
> +}

Anyway, looks good otherwise.