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From: Thomas Gleixner <tglx@linutronix.de>
To: Huacai Chen <chenhc@lemote.com>
Cc: Andy Lutomirski <luto@kernel.org>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	chenhuacai@gmail.com, linux-kernel@vger.kernel.org,
	stable@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
	Paul Burton <paul.burton@mips.com>,
	linux-mips@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 110/110] lib/vdso: Improve do_hres() and update vdso data unconditionally
Date: Mon, 21 Oct 2019 16:52:28 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1910211648200.1904@nanos.tec.linutronix.de> (raw)
In-Reply-To: <1571662320-1280-1-git-send-email-chenhc@lemote.com>

On Mon, 21 Oct 2019, Huacai Chen wrote:
> @@ -50,7 +50,7 @@ static int do_hres(const struct vdso_data *vd, clockid_t clk,
>  		cycles = __arch_get_hw_counter(vd->clock_mode);
>  		ns = vdso_ts->nsec;
>  		last = vd->cycle_last;
> -		if (unlikely((s64)cycles < 0))
> +		if (unlikely(cycles == U64_MAX))
>  			return -1;

That used to create worse code than the weird (s64) type cast which has the
same effect. Did you double check that there is no change?

Thanks,

	tglx

WARNING: multiple messages have this Message-ID (diff)
From: Thomas Gleixner <tglx@linutronix.de>
To: Huacai Chen <chenhc@lemote.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	chenhuacai@gmail.com, linux-kernel@vger.kernel.org,
	stable@vger.kernel.org, linux-mips@vger.kernel.org,
	Paul Burton <paul.burton@mips.com>,
	Andy Lutomirski <luto@kernel.org>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 110/110] lib/vdso: Improve do_hres() and update vdso data unconditionally
Date: Mon, 21 Oct 2019 16:52:28 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1910211648200.1904@nanos.tec.linutronix.de> (raw)
In-Reply-To: <1571662320-1280-1-git-send-email-chenhc@lemote.com>

On Mon, 21 Oct 2019, Huacai Chen wrote:
> @@ -50,7 +50,7 @@ static int do_hres(const struct vdso_data *vd, clockid_t clk,
>  		cycles = __arch_get_hw_counter(vd->clock_mode);
>  		ns = vdso_ts->nsec;
>  		last = vd->cycle_last;
> -		if (unlikely((s64)cycles < 0))
> +		if (unlikely(cycles == U64_MAX))
>  			return -1;

That used to create worse code than the weird (s64) type cast which has the
same effect. Did you double check that there is no change?

Thanks,

	tglx

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  reply	other threads:[~2019-10-21 14:52 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-21 12:52 [PATCH 110/110] lib/vdso: Improve do_hres() and update vdso data unconditionally Huacai Chen
2019-10-21 12:52 ` Huacai Chen
2019-10-21 14:52 ` Thomas Gleixner [this message]
2019-10-21 14:52   ` Thomas Gleixner
2019-10-21 14:58   ` Thomas Gleixner
2019-10-21 14:58     ` Thomas Gleixner
2019-10-22  2:42     ` Huacai Chen
2019-10-22  2:42       ` Huacai Chen
2019-10-23  8:48       ` Thomas Gleixner
2019-10-23  8:48         ` Thomas Gleixner

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