linux-kernel - Re: [patch] x86_64: fix sched

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: <20070525110543.GM8094@one.firstfloor.org>
Date:	Fri, 25 May 2007 13:05:43 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Satyam Sharma <satyam.sharma@...il.com>,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, rusty@...tcorp.com.au
Subject: Re: [patch] x86_64: fix sched_clock()

On Fri, May 25, 2007 at 11:03:15AM +0200, Andi Kleen wrote:
> > This?    I sent it to you earlier this week:
> 
> Sorry haven't processed those yet.
> 
> Ah. The correct fix here is to clear the tsc flag in boot_cpu_data
> when the option is set. Will do that.

Hmm I double checked this now; tsc_disable indeed clears
X86_FEATURE_TSC in identify_cpu and that should be always
called before anything sched_clock related runs on a CPU.

Also the only possibly faulting division is protected
by a cpu_has_tsc which even checks boot_cpu_data. this means
even if the resync frequency code was called for
some reason before the identify_cpu of a AP it should
still work. For the BP this definitely cannot happen.

I also tried it with qemu myself (both one and two cpus) and it worked

Rusty, was this really on a standard kernel? Was it with multiple
CPUs? 

-Andi
-
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/