linux-kernel - Re: [patch 13/19] GTOD: Mark TSC unusable for highres timers

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:	Sat, 11 Nov 2006 12:14:37 +0100
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andi Kleen <ak@...e.de>
Cc:	Andrew Morton <akpm@...l.org>, Ingo Molnar <mingo@...e.hu>,
	john stultz <johnstul@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>, Len Brown <lenb@...nel.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Roman Zippel <zippel@...ux-m68k.org>
Subject: Re: [patch 13/19] GTOD: Mark TSC unusable for highres timers

On Fri, 2006-11-10 at 10:29 +0100, Andi Kleen wrote:
> > But that's different.
> > 
> > We're limping along in a semi-OK fashion with the TSC.  But now Thomas is
> > proposing that we effectively kill it off for all x86 because of hrtimers.
> 
> I'm totally against that.

I'm working on that. The general disable is indeed overkill. All I need
to prevent is to switch over to highres/dyntick in case that there is no
fallback (e.g. pm_timer) available. Else I end up in a circular
dependency as the emulated tick depends on the monotonic clock.
 
> > And afaict the reason for that is that we're using jiffies to determine if
> > the TSC has gone bad, and that test is getting false positives.
> 
> The i386 clocksource had always trouble with that. e.g.  I have a box
> where the TSC works perfectly fine on a 64bit kernel, but since the new i386
> clocksource code is in it always insists on disabling it shortly after boot.
> My guess is that some of the checks in there are just broken and need
> to be fixed.

It's the unconditional mark_unstable call in ACPI C2 state. /me looks.

	tglx


-
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/