Re: [RFC PATCH 2/6] x86: nsecs to cycles conversion

Don Zickus
2013-08-21T18:27:25Z

On Wed, Aug 21, 2013 at 06:42:17PM +0200, Frederic Weisbecker wrote:
> hw_nmi_get_sample_period() is simply a conversion from a period
> to cycles. Lets generalize the API naming so that it can be used for
> wider purpose than just watchdog perf event settings. Also it makes the
> function name less opaque about what it really does.
>

<snip>

> diff --git a/arch/x86/include/asm/cycles.h b/arch/x86/include/asm/cycles.h
> new file mode 100644
> index 0000000..7dedeb3
> --- /dev/null
> +++ b/arch/x86/include/asm/cycles.h
> @@ -0,0 +1,11 @@
> +#ifndef _ASM_X86_CYCLES_H
> +#define _ASM_X86_CYCLES_H
> +
> +#include <linux/time.h>
> +#include <asm/tsc.h>
> +
> +static inline u64 nsecs_to_cycles(u64 nsecs)
> +{
> + return (u64)((cpu_khz) * nsecs) / NSEC_PER_MSEC;
> +}
> +#endif /* #ifndef _ASM_X86_CYCLES_H */
> diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
> index a698d71..4015906 100644
> --- a/arch/x86/kernel/apic/hw_nmi.c
> +++ b/arch/x86/kernel/apic/hw_nmi.c
> @@ -19,13 +19,6 @@
> #include <linux/module.h>
> #include <linux/delay.h>
>
> -#ifdef CONFIG_HARDLOCKUP_DETECTOR
> -u64 hw_nmi_get_sample_period(int watchdog_thresh)
> -{
> - return (u64)(cpu_khz) * 1000 * watchdog_thresh;
> -}
> -#endif
> -
> #ifdef arch_trigger_all_cpu_backtrace
> /* For reliability, we're prepared to waste bits here. */
> static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index 1241d8c..e04887c 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -26,6 +26,7 @@
> #include <linux/sched/rt.h>
>
> #include <asm/irq_regs.h>
> +#include <asm/cycles.h>
> #include <linux/kvm_para.h>
> #include <linux/perf_event.h>

Do you have to wrap the above with #ifdef CONFIG_HARDLOCKUP_DETECTOR?
Otherwise non-x86 boxes won't compile unless I missed stub
nsecs_to_cycles() somewhere.

Cheers,
Don