linux-kernel - Re: [GIT PULL] oprofile fixes for v2.6.37

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Date:	Wed, 29 Dec 2010 17:37:43 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Robert Richter <robert.richter@....com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"oprofile-list@...ts.sourceforge.net" 
	<oprofile-list@...ts.sourceforge.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Frédéric Weisbecker <fweisbec@...il.com>
Subject: Re: [GIT PULL] oprofile fixes for v2.6.37


* Robert Richter <robert.richter@....com> wrote:

> Ingo,
> 
> please pull oprofile fixes for v2.6.37 (tip/perf/urgent):
> 
>  git://git.kernel.org/pub/scm/linux/kernel/git/rric/oprofile.git urgent
> 
> (uploaded but not yet sync'ed until now)
> 
> Thanks,
> 
> -Robert
> 
> 
> The following changes since commit e1e359273576ee8fe27021356b064c772ed29af3:
> 
>   ring_buffer: Off-by-one and duplicate events in ring_buffer_read_page (2010-12-23 12:09:30 -0500)
> 
> are available in the git repository at:
>   git://git.kernel.org/pub/scm/linux/kernel/git/rric/oprofile.git urgent
> 
> Andrew Morton (1):
>       arch/x86/oprofile/op_model_amd.c: perform initialisation on a single CPU
> 
>  arch/x86/oprofile/op_model_amd.c |    6 ++++++
>  1 files changed, 6 insertions(+), 0 deletions(-)

Hm, i'm not sure this fix is correct:

 static int op_amd_init(struct oprofile_operations *ops)
 {
+       /*
+        * init_ibs() preforms implictly cpu-local operations, so pin this
+        * thread to its current CPU
+        */
+       preempt_disable();
        init_ibs();
+       preempt_enable();

If init_ibs() is indeed CPU local, then it needs to be called on all CPUs.
Does that happen and if not why not? AFAICS it's only called on one CPU.

Thanks,

	Ingo
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