Re: [PATCH 3/5] kernel/watchdog: adapt the watchdog_hld interface for async model

[Petr Mladek]

On Wed 2021-09-15 11:51:01, Pingfan Liu wrote:
> When lockup_detector_init()->watchdog_nmi_probe(), PMU may be not ready
> yet. E.g. on arm64, PMU is not ready until
> device_initcall(armv8_pmu_driver_init).  And it is deeply integrated
> with the driver model and cpuhp. Hence it is hard to push this
> initialization before smp_init().
> 
> But it is easy to take an opposite approach by enabling watchdog_hld to
> get the capability of PMU async.

This is another cryptic description. I have probably got it after
looking at the 5th patch (was not Cc :-(

> The async model is achieved by introducing an extra parameter notifier
> of watchdog_nmi_probe().

I would say that the code is horrible and looks too complex.

What about simply calling watchdog_nmi_probe() and
lockup_detector_setup() once again when watchdog_nmi_probe()
failed in lockup_detector_init()?

Or do not call lockup_detector_init() at all in
kernel_init_freeable() when PMU is not ready yet.

Best Regards,
Petr