linux-kernel - Re: 2.6.19-rc5: known regressions (v3)

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Message-ID: <2c0942db0612160320o5f830855y3c607585d5f855f1@mail.gmail.com>
Date:	Sat, 16 Dec 2006 03:20:26 -0800
From:	"Ray Lee" <madrabbit@...il.com>
To:	"Andrew Morton" <akpm@...l.org>
Cc:	"Andi Kleen" <ak@...e.de>, "Eric Dumazet" <dada1@...mosbay.com>,
	"Adrian Bunk" <bunk@...sta.de>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"Stephen Hemminger" <shemminger@...l.org>, gregkh@...e.de,
	"Ingo Molnar" <mingo@...hat.com>,
	"Len Brown" <len.brown@...el.com>, phil.el@...adoo.fr,
	oprofile-list@...ts.sourceforge.net
Subject: Re: 2.6.19-rc5: known regressions (v3)

On 11/22/06, Andrew Morton <akpm@...l.org> wrote:
> On Wed, 22 Nov 2006 11:36:14 +0100
> Andi Kleen <ak@...e.de> wrote:
>
> > On Wednesday 22 November 2006 11:28, Eric Dumazet wrote:
> > > On Wednesday 15 November 2006 11:35, Eric Dumazet wrote:
> > > > On Wednesday 15 November 2006 11:21, Adrian Bunk wrote:
> > > > > Subject    : x86_64: oprofile doesn't work
> > > > > References : http://lkml.org/lkml/2006/10/27/3
> > > > > Submitter  : Prakash Punnoor <prakash@...noor.de>
> > > > > Status     : unknown
> > > >
> > >
> > > I hit the same problem on i386 architecture too, if CONFIG_ACPI is not set.
> >
> > oprofile is still broken because it cannot deal with the lack of perfctr 0.
>
> The kernel is still broken because we changed the interface.

I just got bit by this on 2.6.20-latest (well, of two days ago anyway)
while trying to debug another transient 'kacpid sucks all available
cpu time'. But that's okay, I'm sure it will happen again in a week or
two.

In the meantime, who won this pis^H^H^H discussion?

Mikael Pettersson wrote:
> Andrew Morton writes:
> > Surely the appropriate behaviour is to allow oprofile to steal the NMI and
> > to then put the NMI back to doing the watchdog thing after oprofile has
> > finished with it.
>
> Which is _exactly_ what pre-2.6.19-rc1 kernels did. I implemented
> the in-kernel API allowing real performance counter drivers like
> oprofile (and perfctr) to claim the HW from the NMI watchdog,
> do their work, and then release it which resumed the watchdog.
>
> Note that oprofile (and perfctr) didn't do anything behind the
> NMI watchdog's back. They went via the API. Nothing dodgy going on.

Well, that seems clear.
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