Re: [PATCH] arm64: perf: Disable PMU while processing counter overflows

[Aman Priyadarshi <apeureka@amazon.de>]

On Thu, 2021-06-17 at 08:34 +0100, Marc Zyngier wrote:
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> 
> On Thu, 17 Jun 2021 05:51:03 +0100,
> Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> > 
> > On Wed, Jun 16, 2021 at 09:28:59PM +0200, Aman Priyadarshi wrote:
> > > From: Suzuki K Poulose <suzuki.poulose@arm.com>
> > > 
> > > [ Upstream commit 3cce50dfec4a5b0414c974190940f47dd32c6dee ]
> > > 
> > > The arm64 PMU updates the event counters and reprograms the
> > > counters in the overflow IRQ handler without disabling the
> > > PMU. This could potentially cause skews in for group counters,
> > > where the overflowed counters may potentially loose some event
> > > counts, while they are reprogrammed. To prevent this, disable
> > > the PMU while we process the counter overflows and enable it
> > > right back when we are done.
> > > 
> > > This patch also moves the PMU stop/start routines to avoid a
> > > forward declaration.
> > > 
> > > Suggested-by: Mark Rutland <mark.rutland@arm.com>
> > > Cc: Will Deacon <will.deacon@arm.com>
> > > Acked-by: Mark Rutland <mark.rutland@arm.com>
> > > Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> > > Signed-off-by: Will Deacon <will.deacon@arm.com>
> > > Signed-off-by: Aman Priyadarshi <apeureka@amazon.de>
> > > Cc: stable@vger.kernel.org
> > > ---
> > >  arch/arm64/kernel/perf_event.c | 50 +++++++++++++++++++-------------
> > > --
> > >  1 file changed, 28 insertions(+), 22 deletions(-)
> > 
> > What stable tree(s) do you want this applied to?
> 
> I guess that'd be 4.14 and previous stables if the patch actually
> applies.
> 

Correct. I have tested the patch on 4.14.y, can confirm that it applies
cleanly on 4.9.y as well.

Thanks,
Aman Priyadarshi




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