Hi Will, Mark
 
Sorry for bothering you, this need to be reviewed by ARM Perf maintainer,

could you please help review this pathset or comment about it?




Thanks a lot.

 

Hi Will, Mark

Could you help review arm parts of this patchset, please?

For the question mention in both [1] and [2],

quoted

I'd still like Mark's Ack on this, as the approach you have taken doesn't
really sit with what he was suggesting.

I also don't understand how all the CPUs get initialised with your patch,
since the PMU driver will be initialised after SMP is up and running.

The hardlock detector utilizes the softlockup_start_all() to start all
the cpu on watchdog_allowed_mask, which will do watchdog_nmi_enable()
that registers perf event on each CPUs.
Thus we simply need to retry lockup_detector_init() in a single cpu which
will reconfig and call to softlockup_start_all().

Also, the CONFIG_HARDLOCKUP_DETECTOR_PERF selects SOFTLOCKUP_DETECTOR,
IMO, this shows that hardlockup detector supports from softlockup.

quoted

We should know whether pNMIs are possible once we've completed
setup_arch() (and possibly init_IRQ()), long before SMP, so so I reckon
we should have all the information available once we get to
lockup_detector_init(), even if that requires some preparatory rework.

Hardlockup depends on PMU driver , I think the only way is moving
pmu driver at setup_arch() or any point which is earlier than
lockup_detector_init(), and I guess we have to reorganize the architecture
of arm PMU.

The retry function should benifit all the arch/ not only for arm64.
Any arch who needs to probe its pmu as module can use this without providing
a chance to mess up the setup order. 


Please let me know if you have any concern about this, thank you


[1] https://lore.kernel.org/all/CAFA6WYPPgUvHCpN5=EpJ2Us5h5uVWCbBA59C-YwYQX2ovyVeEw@mail.gmail.com/ (local)
[2] https://lore.kernel.org/linux-arm-kernel/20210419170331.GB31045@willie-the-truck/ (local)

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