linux-kernel - Re: [PATCH] hrtimer: Avoid double reprogramming in __hrtimer_start_range

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Message-ID: <87k0opt937.ffs@nanos.tec.linutronix.de>
Date:   Mon, 26 Apr 2021 16:27:08 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Lorenzo Colitti <lorenzo@...gle.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Maciej Żenczykowski <zenczykowski@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Anna-Maria Behnsen <anna-maria@...utronix.de>,
        lkml <linux-kernel@...r.kernel.org>,
        mikael.beckius@...driver.com,
        Maciej Żenczykowski <maze@...gle.com>,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH] hrtimer: Avoid double reprogramming in __hrtimer_start_range_ns()

On Mon, Apr 26 2021 at 14:40, Peter Zijlstra wrote:

> On Mon, Apr 26, 2021 at 02:33:00PM +0200, Thomas Gleixner wrote:
>
>> >> +	force_local = base->cpu_base == this_cpu_ptr(&hrtimer_bases);
>> >> +	force_local &= base->cpu_base->next_timer == timer;
>> >
>> > Using bitwise ops on a bool is cute and all, but isn't that more
>> > readable when written like:
>> >
>> > 	force_local = base->cpu_base == this_cpu_ptr(&hrtimer_bases) &&
>> > 		      base->cpu_base->next_timer == timer;
>> >
>> 
>> Which results in an extra conditional branch.
>
> Srlsy, compiler not smart enough?

gcc 8.3 is definitely not ...