linux-kernel - Re: [2.6.28-rc6] oprofile: "opcontrol --start" output two warnings

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: <20081125110935.GF6703@one.firstfloor.org>
Date:	Tue, 25 Nov 2008 12:09:35 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Robert Richter <robert.richter@....com>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [2.6.28-rc6] oprofile: "opcontrol --start" output two warnings

> if so, I think get_stagger() is a bit strange.
> it depend on caller cpu. then if PREEMPT=Y, it return radom result.

Even without PREEMPT it is random because there is no guarantee the
init code is executing on CPU 0

> 
> I'm not sure about oprofile design.
> but if you are right, I think p4_fill_in_addresses shoudn't use smp_processor_id().

Correct.

> 
> Am I missing any point?

No you're right. Always returning 0 in get_stagger() should be ok
I think, at least it wouldn't make anything worse.

Or perhaps figure out if the per cpu addresses are really needed,
if yes then this would need much more changes. But I hope 
that would not be needed.

But someone should better test it, the P4 perfmon handling is certainly
hairy and I don't claim to understand all its intricate details.

-Andi

-- 
ak@...ux.intel.com
--
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/