linux-kernel - Re: gettimeofday() jumping into the future

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]

Message-ID: <3c1737210708250944u7043c9e1j3be70674a1b55911@mail.gmail.com>
Date:	Sat, 25 Aug 2007 18:44:40 +0200
From:	"Michael Smith" <msmith@...h.org>
To:	"john stultz" <johnstul@...ibm.com>
Cc:	"Peter Zijlstra" <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, "Andy Wingo" <wingo@...endo.com>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Ingo Molnar" <mingo@...e.hu>
Subject: Re: gettimeofday() jumping into the future

>
> Hmm. That does sound like unsycned TSCs. Normally Intel systems don't
> skew unless they are NUMA systems or you're entering low power states.
> We try to catch both of those cases, so I'm not sure how you box is
> slipping through.
>
> Can you run the following test to verify that the TSCs are skewed?

I ran this for the past two days, multiple copies to put some load on
the system (the initial problem with gettimeofday() was easier to
reproduce under load). Nothing.

So, I guess that rules out unsynced TSCs as the cause? Or perhaps it
only happens in other conditions, for some reason. I'm on holidays
right now, but my coworkers should be able to continue investigating
other possible causes.

Thanks for the advice/test program.

Mike
-
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/