linux-kernel - Re: oprofile broken in 2.6.21 SMP (was Re: Remove constructor from buffer

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Message-Id: <20070514201232.ad4768f9.akpm@linux-foundation.org>
Date:	Mon, 14 May 2007 20:12:32 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Benjamin LaHaise <bcrl@...ck.org>
Cc:	Andi Kleen <ak@...e.de>, Christoph Lameter <clameter@....com>,
	linux-kernel@...r.kernel.org,
	Chuck Ebbert <76306.1226@...puserve.com>
Subject: Re: oprofile broken in 2.6.21 SMP (was Re: Remove constructor from
 buffer_head)

On Sun, 13 May 2007 16:38:16 -0400 Benjamin LaHaise <bcrl@...ck.org> wrote:

> On Sat, May 05, 2007 at 11:31:20AM +0200, Andi Kleen wrote:
> > Hmm, after a opcontrol --reset i see the same issue now. Don't know what's 
> > wrong, but it must be something different from the .20 perfctr allocation
> > problem.
> > 
> > It looks like the daemon doesn't get any data from the kernel
> 
> I finally had time to track this down.  The breakage is caused by "[PATCH] 
> x86-64: Let oprofile reserve MSR on all CPUs".  Oprofile is already calling 
> the reserve functions on each CPU in the system when it sets up the MSRs.  
> This results in oprofile getting a reservation failure on CPUs above 0.  The 
> following makes oprofile adapt to the API change for now -- oprofile 
> still needs to be modified to perform the reservations earlier during its 
> initialization, but that's a little bit more involved than the immediate 
> bug fix.  This only affects systems with more than 1 CPU.  This patch has 
> been through limited testing (Athlon 64 X2 and Core 2, but not on the P4) on 
> x86 and x86-64 (Core 2 only).

Unfortunately we've left this a bit too late - your patch is patching code which
isn't there any more in mainline and we also need a 2.6.21.x fix.

So perhaps we could merge your "immediate bugfix" into -stable and implement the
"more involved" fix for 2.6.22.

Andi, any preferences?
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