linux-kernel - Re: [PATCH 0/3] arm64: perf: Add support for Perf NMI interrupts

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Date:   Mon, 18 May 2020 15:19:46 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Sumit Garg <sumit.garg@...aro.org>
Cc:     Alexandru Elisei <alexandru.elisei@....com>,
        Lecopzer Chen <lecopzer@...il.com>,
        julien.thierry.kdev@...il.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jian-Lin Chen <lecopzer.chen@...iatek.com>,
        alexander.shishkin@...ux.intel.com,
        Catalin Marinas <catalin.marinas@....com>, jolsa@...hat.com,
        acme@...nel.org, Peter Zijlstra <peterz@...radead.org>,
        mingo@...hat.com, linux-mediatek@...ts.infradead.org,
        matthias.bgg@...il.com, namhyung@...nel.org,
        Will Deacon <will@...nel.org>, yj.chiang@...iatek.com,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 0/3] arm64: perf: Add support for Perf NMI interrupts

On Mon, May 18, 2020 at 07:39:23PM +0530, Sumit Garg wrote:
> On Mon, 18 May 2020 at 16:47, Alexandru Elisei <alexandru.elisei@....com> wrote:
> > On 5/18/20 11:45 AM, Mark Rutland wrote:
> > > On Mon, May 18, 2020 at 02:26:00PM +0800, Lecopzer Chen wrote:
> > >> HI Sumit,
> > >>
> > >> Thanks for your information.
> > >>
> > >> I've already implemented IPI (same as you did [1], little difference
> > >> in detail), hardlockup detector and perf in last year(2019) for
> > >> debuggability.
> > >> And now we tend to upstream to reduce kernel maintaining effort.
> > >> I'm glad if someone in ARM can do this work :)
> > >>
> > >> Hi Julien,
> > >>
> > >> Does any Arm maintainers can proceed this action?
> > > Alexandru (Cc'd) has been rebasing and reworking Julien's patches, which
> > > is my preferred approach.
> > >
> > > I understand that's not quite ready for posting since he's investigating
> > > some of the nastier subtleties (e.g. mutual exclusion with the NMI), but
> > > maybe we can put the work-in-progress patches somewhere in the mean
> > > time.
> > >
> > > Alexandru, do you have an idea of what needs to be done, and/or when you
> > > expect you could post that?
> >
> > I'm currently working on rebasing the patches on top of 5.7-rc5, when I have
> > something usable I'll post a link (should be a couple of days). After that I will
> > address the review comments, and I plan to do a thorough testing because I'm not
> > 100% confident that some of the assumptions around the locks that were removed are
> > correct. My guess is this will take a few weeks.
> >
> 
> Thanks Mark, Alex for the status updates on perf NMI feature.
> 
> Alex,
> 
> As the hard-lockup detection patch [1] has a dependency on perf NMI
> patch-set, I will rebase and test hard-lockup detector when you have
> got a working tree. But due to the dependency, I think patch [1]
> should be accepted along with perf NMI patch-set. So would you be open
> to include this patch as part of your series?
> 
> [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2020-May/732227.html

While it depends on the perf NMI bits, I don't think it makes sense to
tie that into the series given it's trying to achieve something very
different.

I think that should be reposted separately once the perf NMI bits are in
shape.

Thanks,
Mark.