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Groups > linux.kernel > #1537966

Re: Perf hotplug lockup in v4.9-rc8

From Mark Rutland <mark.rutland@arm.com>
Newsgroups linux.kernel
Subject Re: Perf hotplug lockup in v4.9-rc8
Date 2016-12-07 19:10 +0100
Message-ID <sLOPg-3wa-9@gated-at.bofh.it> (permalink)
References <sLKVk-LK-25@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Wed, Dec 07, 2016 at 01:52:17PM +0000, Mark Rutland wrote:
> Hi all
> 
> Jeremy noticed a kernel lockup on arm64 when the perf tool was used in
> parallel with hotplug, which I've reproduced on arm64 and x86(-64) with
> v4.9-rc8. In both cases I'm using defconfig; I've tried enabling lockdep
> but it was silent for arm64 and x86.

It looks like we're trying to install a task-bound event into a context
where task_cpu(ctx->task) is dead, and thus the cpu_function_call() in
perf_install_in_context() fails. We retry repeatedly.

On !PREEMPT (as with x86 defconfig), we manage to prevent the hotplug
machinery from making progress, and this turns into a livelock.

On PREEMPT (as with arm64 defconfig), I'm somewhat lost.

Thanks,
Mark.

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Thread

Perf hotplug lockup in v4.9-rc8 Mark Rutland <mark.rutland@arm.com> - 2016-12-07 15:00 +0100
  Re: Perf hotplug lockup in v4.9-rc8 Mark Rutland <mark.rutland@arm.com> - 2016-12-07 15:40 +0100
    Re: Perf hotplug lockup in v4.9-rc8 Mark Rutland <mark.rutland@arm.com> - 2016-12-07 17:50 +0100
  Re: Perf hotplug lockup in v4.9-rc8 Mark Rutland <mark.rutland@arm.com> - 2016-12-07 19:10 +0100
    Re: Perf hotplug lockup in v4.9-rc8 Peter Zijlstra <peterz@infradead.org> - 2016-12-07 19:40 +0100
      Re: Perf hotplug lockup in v4.9-rc8 Mark Rutland <mark.rutland@arm.com> - 2016-12-07 21:00 +0100
      Re: Perf hotplug lockup in v4.9-rc8 Peter Zijlstra <peterz@infradead.org> - 2016-12-09 15:00 +0100

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