On Thu, 13 Oct 2016 13:38:01 -0700 Babu Moger <babu.moger@xxxxxxxxxx> wrote:
> Currently we do not have a way to enable/disable arch specific
> watchdog handlers if it was implemented by any of the architectures.
>
> This patch introduces new functions arch_watchdog_nmi_enable and
> arch_watchdog_nmi_disable which can be used to enable/disable architecture
> specific NMI watchdog handlers. These functions are defined as weak as
> architectures can override their definitions to enable/disable nmi
> watchdog behaviour.
>
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -676,8 +660,13 @@ static void watchdog_nmi_disable(unsigned int cpu)
> }
>
> #else
> -static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
> -static void watchdog_nmi_disable(unsigned int cpu) { return; }
> +/*
> + * These two functions are mostly architecture specific
> + * defining them as weak here.
> + */
> +int __weak arch_watchdog_nmi_enable(unsigned int cpu) { return 0; }
> +void __weak arch_watchdog_nmi_disable(unsigned int cpu) { return; }
> +
> #endif /* CONFIG_HARDLOCKUP_DETECTOR */
This is a strange way of using __weak.
Take a look at (one of many examples) kernel/module.c:module_alloc().
We simply provide a default implementation and some other compilation
unit can override (actually replace) that at link time. No strange
ifdeffing needed.
And I'm not really understanding the interaction with
CONFIG_HARDLOCKUP_DETECTOR here. I haven't really worked out why the
code is all this way but it seems.... odd?
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