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Date: Wed, 16 Apr 2025 21:08:17 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: James Clark <james.clark@linaro.org>
Cc: Oliver Sang <oliver.sang@intel.com>, oe-lkp@lists.linux.dev,
	lkp@intel.com, linux-kernel@vger.kernel.org, x86@kernel.org,
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	Mark Rutland <mark.rutland@arm.com>,
	Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: [tip:perf/core] [perf] da916e96e2:
 BUG:KASAN:null-ptr-deref_in_put_event
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In-Reply-To: <20250416084610.GI4031@noisy.programming.kicks-ass.net>

On Wed, Apr 16, 2025 at 10:46:10AM +0200, Peter Zijlstra wrote:
> On Tue, Apr 15, 2025 at 04:52:56PM +0100, James Clark wrote:
> > Unrelated to the pointer deref issue, I'm also seeing perf stat not working
> > due to this commit. And that's both with and without this fixup:
> > 
> >  -> perf stat -- true
> > 
> >  Performance counter stats for 'true':
> > 
> >      <not counted> msec task-clock
> > 
> >      <not counted>      context-switches
> > 
> >      <not counted>      cpu-migrations
> > 
> >      <not counted>      page-faults
> > 
> >      <not counted>      armv8_cortex_a53/instructions/
> > 
> >      <not counted>      armv8_cortex_a57/instructions/
> > 
> >      <not counted>      armv8_cortex_a53/cycles/
> > 
> >      <not counted>      armv8_cortex_a57/cycles/
> > 
> >      <not counted>      armv8_cortex_a53/branches/
> > 
> >      <not counted>      armv8_cortex_a53/branch-misses/
> > 
> >      <not counted>      armv8_cortex_a57/branch-misses/
> > 
> > 
> >        0.074139992 seconds time elapsed
> > 
> >        0.000000000 seconds user
> >        0.054797000 seconds sys
> > 
> > Didn't look into it more other than bisecting it to this commit, but I can
> > dig more unless the issue is obvious. This is on Arm big.LITTLE, although I
> > didn't test it elsewhere so I'm not sure if that's relevant or not.
> 
> I can reproduce on x86 alderlake (first machine I tried), so let me go
> have a quick poke.

Could you please try queue.git/perf/core ? I've fixed this and found
another problem.

I'll post the patches tomorrow, after the robot has had a go.