linux-kernel - Re: [RFC PATCH v2 1/5] futex: Add futex_set

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Date:   Thu, 22 Sep 2016 20:45:06 -0400
From:   Waiman Long <waiman.long@....com>
To:     Thomas Gleixner <tglx@...utronix.de>
CC:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Jonathan Corbet <corbet@....net>,
        <linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        Jason Low <jason.low2@....com>,
        Scott J Norton <scott.norton@....com>,
        Douglas Hatch <doug.hatch@....com>
Subject: Re: [RFC PATCH v2 1/5] futex: Add futex_set_timer() helper function

On 09/22/2016 05:31 PM, Thomas Gleixner wrote:
> On Tue, 20 Sep 2016, Waiman Long wrote:
>
> Please be more careful of your subject lines. First thing I thought was
> that you add a helper which is used in later patches to find out that you
> actualy consolidate duplicated code. Something like:
>
>    futex: Consolidate duplicated timer setup code
>
> would have told me right away what this is about.
>
>> This patch adds a new futex_set_timer() function to consolidate all
> Please do not use: "This patch ...". We already know that this is a patch,
> otherwise it would not be tagged [PATCH n/m] in the subject line.
>
> See Documentation/SubmittingPatches ....
>
>> the sleeping hrtime setup code.
> Let me give you a hint:
>
> 1:  The code has three identical code copies to set up the futex timeout.
>
> 2:  Add a helper function and consolidate the call sites.
>
> #1 tells precisely what the problem is
> #2 tells precisely how it is solved
>
> Can you see the difference?
>
>> +/*
>> + * Helper function to set the sleeping hrtimer.
>> + */
>> +static inline void futex_set_timer(ktime_t *time, struct hrtimer_sleeper **pto,
>> +		struct hrtimer_sleeper *timeout, int flags, u64 range_ns)
> Please use futex_setup_timer() as the function name. I was confused when I
> read the other patch that you wanted to "set" the timer before entering
> into the place which would actually need it.
>
>> +{
>> +	if (!time)
>> +		return;
>> +	*pto = timeout;
> Please don't do that. That's a horrible coding style.
>
> What's wrong with returning NULL or the timeout pointer and assign it to
> "to" at the call site?
>
> Thanks,
>
> 	tglx
>

Thanks for the suggestions. I will fix this patch in the next revision.

Cheers,
Longman