On Wed, Jun 13, 2018 at 10:43:24AM +0200, Peter Zijlstra wrote:

On Tue, Jun 12, 2018 at 05:57:34PM -0700, Ricardo Neri wrote:

quoted

The current default implementation of the hardlockup detector assumes that
it is implemented using perf events.

The sparc and powerpc things are very much not using perf.

Isn't it true that the current hardlockup detector
(under kernel/watchdog_hld.c) is based on perf? As far as I understand,
this hardlockup detector is constructed using perf events for architectures
that don't provide an NMI watchdog. Perhaps I can be more specific and say
that this synthetized detector is based on perf.

On a side note, I saw that powerpc might use a perf-based hardlockup
detector if it has perf events [1].

Please let me know if my understanding is not correct.

Thanks and BR,
Ricardo

[1]. https://elixir.bootlin.com/linux/v4.17/source/arch/powerpc/Kconfig#L218