linux-kernel - Re: [PATCH 33/36] AArch64: Generic timers support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 13 Jul 2012 11:30:12 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Catalin Marinas <catalin.marinas@....com>
CC:	Arnd Bergmann <arnd@...db.de>, Marc Zyngier <Marc.Zyngier@....com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Deepak Saxena <dsaxena@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Walleij <linus.ml.walleij@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Will Deacon <Will.Deacon@....com>,
	Mike Turquette <mike.turquette@...aro.org>,
	Marc Zyngier <maz@...terjones.org>
Subject: Re: [PATCH 33/36] AArch64: Generic timers support

On 07/13/2012 09:02 AM, Catalin Marinas wrote:
> On Fri, Jul 13, 2012 at 01:40:03PM +0100, Arnd Bergmann wrote:
>> Hmm, in the quest to eliminate CLOCK_TICK_RATE entirely, could we
>> make a Kconfig symbol that is selected for all architectures that
>> (may) rely on a periodic timer tick and require this to be set?
>>
>> Architectures that always have a working clock source would then just
>> not include the timex.h header and #define ACT_HZ HZ in common code.
>
> Would something like below be enough?

Looks interesting. Although I've not had a chance to follow through in 
more detail to see what that might impact.  But something like this 
seems like a good approach.


> Also, are there any implications if we boot with clocksource=jiffies?

You'd probably see an maximum error of:
	 (tick-device-granularity/2)/(1sec/HZ).

If that ends up larger then 100ppm you'd have a fairly poor clock, 
although NTP can correct for up to 500ppm.

thanks
-john

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/