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Date:   Mon, 1 Oct 2018 20:15:28 +0200 (CEST)
From:   Thomas Gleixner <tglx@linutronix.de>
To:     Mark Salyzyn <salyzyn@android.com>
cc:     linux-kernel@vger.kernel.org, James Morse <james.morse@arm.com>,
        Russell King <linux@armlinux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Dmitry Safonov <dsafonov@virtuozzo.com>,
        John Stultz <john.stultz@linaro.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Laura Abbott <labbott@redhat.com>,
        Kees Cook <keescook@chromium.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Andy Gross <andy.gross@linaro.org>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        Andrew Pinski <apinski@cavium.com>,
        linux-arm-kernel@lists.infradead.org,
        Jeremy Linton <Jeremy.Linton@arm.com>,
        android-kernel@android.com, Jinbum Park <jinb.park7@gmail.com>,
        Ingo Molnar <mingo@kernel.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: RESEND [PATCH v6 11/12] lib: vdso: Add support for
 CLOCK_BOOTTIME
In-Reply-To: <20181001175845.168430-12-salyzyn@android.com>
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References: <20181001175845.168430-1-salyzyn@android.com> <20181001175845.168430-12-salyzyn@android.com>
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On Mon, 1 Oct 2018, Mark Salyzyn wrote:
>  
> +static notrace int do_boottime(const struct vdso_data *vd, struct timespec *ts)
> +{
> +	u32 seq, mult, shift;
> +	u64 nsec, cycle_last;
> +	vdso_wtm_clock_nsec_t wtm_nsec;
> +
> +	/* open coding timespec_add_ns to save a ts->tv_nsec = 0 */
> +	ts->tv_sec = sec + __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);
> +	ts->tv_nsec = nsec;
> +
> +	return 0;
> +}
> +

Instead of adding yet another copy of the same code you might want to look
at the rework I did for the x86 vdso in order to support CLOCK_TAI w/o
running into the issue of the clock switch case being compiled into a jump
table and then the compile asking for retpoline.

  http://lkml.kernel.org/r/20180917124533.329334911@linutronix.de

Thanks,

	tglx