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From:   Thomas Gleixner <tglx@linutronix.de>
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To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Lorenzo Colitti <lorenzo@google.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        Maciej =?utf-8?Q?=C5=BBenczykowski?= <zenczykowski@gmail.com>,
        Ingo Molnar <mingo@kernel.org>,
        Anna-Maria Behnsen <anna-maria@linutronix.de>,
        lkml <linux-kernel@vger.kernel.org>,
        mikael.beckius@windriver.com,
        Maciej =?utf-8?Q?=C5=BBenczykowski?= <maze@google.com>,
        Will Deacon <will@kernel.org>
Subject: Re: [PATCH] hrtimer: Avoid double reprogramming in __hrtimer_start_range_ns()
In-Reply-To: <YIa0qWdxM7vIsf/4@hirez.programming.kicks-ass.net>
References: <CAHo-OowM2jRNuvyDf-T8rzr6ZgUztXqY7m_JhuFvQ+uB8N3ZrQ@mail.gmail.com> <YHXRWoVIYLL4rYG9@kroah.com> <CAKD1Yr1DnDTELUX2DQtPDtAoDMqCz6dV+TZbBuC1CFm32O8MrA@mail.gmail.com> <87r1jbv6jc.ffs@nanos.tec.linutronix.de> <CAKD1Yr1o=zN5K9PaB3wag5xOS2oY6AzEsV6dmL7pnTysK_GOhA@mail.gmail.com> <87eef5qbrx.ffs@nanos.tec.linutronix.de> <87v989topu.ffs@nanos.tec.linutronix.de> <YIaKnuZDfffmmAdM@hirez.programming.kicks-ass.net> <87sg3dtedf.ffs@nanos.tec.linutronix.de> <YIa0qWdxM7vIsf/4@hirez.programming.kicks-ass.net>
Date:   Mon, 26 Apr 2021 16:27:08 +0200
Message-ID: <87k0opt937.ffs@nanos.tec.linutronix.de>
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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 ...