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

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Message-ID: <df0884df-5044-893b-65e2-7ed17c078448@redhat.com>
Date:   Wed, 24 Apr 2019 12:32:46 -0400
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
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 4/24/19 12:09 PM, Peter Zijlstra wrote:
> 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.


That is true. I will update it accordingly.

Thanks,
Longman