Messages in this thread | | | Date | Wed, 7 Dec 2016 17:53:47 +0000 | From | Mark Rutland <> | Subject | Re: Perf hotplug lockup in v4.9-rc8 |
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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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