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    SubjectRe: [PATCH] perf/core: generate overflow signal when samples are dropped (WAS: Re: [REGRESSION] perf/core: PMU interrupts dropped if we entered the kernel in the "skid" region)
    On Tue, Jul 11, 2017 at 2:03 AM, Ingo Molnar <mingo@kernel.org> wrote:
    >
    > * Kyle Huey <me@kylehuey.com> wrote:
    >
    >> On Wed, Jul 5, 2017 at 10:07 PM, Robert O'Callahan <robert@ocallahan.org> wrote:
    >> > On Tue, Jul 4, 2017 at 3:21 AM, Mark Rutland <mark.rutland@arm.com> wrote:
    >> >> Should any of those be moved into the "should be dropped" pile?
    >> >
    >> > Why not be conservative and clear every sample you're not sure about?
    >> >
    >> > We'd appreciate a fix sooner rather than later here, since rr is
    >> > currently broken on every stable Linux kernel and our attempts to
    >> > implement a workaround have failed.
    >> >
    >> > (We have separate "interrupt" and "measure" counters, and I thought we
    >> > might work around this regression by programming the "interrupt"
    >> > counter to count kernel events as well as user events (interrupting
    >> > early is OK), but that caused our (completely separate) "measure"
    >> > counter to report off-by-one results (!), which seems to be a
    >> > different bug present on a range of older kernels.)
    >>
    >> This seems to have stalled out here unfortunately.
    >>
    >> Can we get a consensus (from ingo or peterz?) on Mark's question? Or,
    >> alternatively, can we move the patch at the top of this thread forward
    >> on the stable branches until we do reach an answer to that question?
    >>
    >> We've abandoned hope of working around this problem in rr and are
    >> currently broken for all of our users with an up-to-date kernel, so
    >> the situation for us is rather dire at the moment I'm afraid.
    >
    > Sorry about that - I've queued up a revert for the original commit and will send
    > the fix to Linus later today. I've added a -stable tag as well so it can be
    > forwarded to Greg the moment it hits upstream.

    Great, thank you.

    - Kyle

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