linux-kernel - Re: One-shot high-resolution POSIX timer periodically late

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] [day] [month] [year] [list]

Message-ID: <45C9A666.7010703@free.fr>
Date:	Wed, 07 Feb 2007 11:13:58 +0100
From:	John <linux.kernel@...e.fr>
To:	linux-kernel@...r.kernel.org
CC:	mingo@...e.hu, tglx@...esys.com, johnstul@...ibm.com,
	akpm@...l.org, linux.kernel@...e.fr
Subject: Re: One-shot high-resolution POSIX timer periodically late

Ingo Molnar wrote:

> John wrote:
> 
>> Ingo Molnar wrote:
>> 
>>> 2.6.18-rt7 is pretty old, do you see the problem in 2.6.20-rc6-rt5 too?
>> 
>> Ingo, Thomas,
>> 
>> I cannot reproduce in 2.6.20-rc6-rt6, but it is not strictly an 
>> apples-to-apples comparison because I get a tsc clocksource in 
>> 2.6.20-rc6-rt6, and an acpi_pm clocksource in 2.6.18.6-rt7.
> 
> That suggests that the TSC was not deemed reliable by the newer kernel, 
> which almost always means it's not realiable. I think the problems you 
> were seeing are consistent with TSC being non-monotonic - so the fix is 
> to not use the TSC - and the newer kernel does this automatically.

Ingo,

Perhaps you've mis-read my message?

*2.6.18.6-rt7* installed an acpi_pm clocksource. When I used a boot 
parameter to force the clocksource to tsc, the high-resolution timer 
infrastructure broke (timers expired several *ms* too late).

On the other hand, *2.6.20-rc6-rt6* and *2.6.20-rt2* both installed a 
tsc clock source, and it works.

Therefore, it is not the newer kernel that ignored the tsc, but the 
older kernel. Thus I don't know what to make of your comment :-)

Regards,

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/