linux-kernel - Re: [RFC patch 4/7] timekeeping: Add NMI safe accessor to mono/boot/real clocks

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Message-ID: <CA+55aFzFnQ9n=kfLCnq_mmDD3aqb+Uy_BHy9234UxCYTPPqBig@mail.gmail.com>
Date:   Fri, 17 Nov 2017 15:12:33 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Prarit Bhargava <prarit@...hat.com>,
        Mark Salyzyn <salyzyn@...roid.com>,
        Petr Mladek <pmladek@...e.com>, Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Joe Perches <joe@...ches.com>
Subject: Re: [RFC patch 4/7] timekeeping: Add NMI safe accessor to
 mono/boot/real clocks

On Fri, Nov 17, 2017 at 3:00 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
>
> Could you indent this better. It looks like timekeeping_delta_to_ns()
> takes 4 arguments, when it really only takes two.

Actually, even better would be to simply not have that ugly three-line
expression from hell.

Maybe it could even be a helper inline function, somethin glike

   static inline u64 tk_delta_ns(struct tk_read_base *tkr)
   {
        u64 cycle = tk_clock_read(tkr);
        u64 delta= clocksource_delta(cycle, tkr->cycle_last, tkr->mask);
        return timekeeping_delta_to_ns(tkr, cycle);
    }

and that whole thing would just become

        now += tk_delta_ns(tkr);

which looks a whole lot more legible. And shouldn't generate any worse code.

(I might have screwed up something, I wrote that in the email client,
maybe I got something wrong.

And my name choice is probably garbage. But you get the idea.

            Linus