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

[Marc Zyngier <maz@kernel.org>]

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.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.