Re: [PATCH 18/25] hrtimer: Enable soft and hard hrtimer

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 18/25] hrtimer: Enable soft and hard hrtimer
Date	2017-09-26 15:00 +0200
Message-ID	<utXCV-4V5-1@gated-at.bofh.it> (permalink)
References	<ukwLD-5Ay-3@gated-at.bofh.it> <ukwLE-5Ay-13@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Aug 31, 2017 at 12:23:42PM -0000, Anna-Maria Gleixner wrote:
> --- a/include/linux/hrtimer.h
> +++ b/include/linux/hrtimer.h
> @@ -23,6 +23,17 @@
>  #include <linux/timer.h>
>  #include <linux/timerqueue.h>
>  
> +/*
> + * Clock ids for hrtimers which expire in softirq context. These clock ids
> + * are kernel internal and never exported to user space.
> + */
> +#define HRTIMER_BASE_SOFT_MASK	MAX_CLOCKS
> +
> +#define CLOCK_REALTIME_SOFT	(CLOCK_REALTIME	 | HRTIMER_BASE_SOFT_MASK)
> +#define CLOCK_MONOTONIC_SOFT	(CLOCK_MONOTONIC | HRTIMER_BASE_SOFT_MASK)
> +#define CLOCK_BOOTTIME_SOFT	(CLOCK_BOOTTIME	 | HRTIMER_BASE_SOFT_MASK)
> +#define CLOCK_TAI_SOFT		(CLOCK_TAI	 | HRTIMER_BASE_SOFT_MASK)
> +
>  struct hrtimer_clock_base;
>  struct hrtimer_cpu_base;
>  

> --- a/kernel/time/hrtimer.c
> +++ b/kernel/time/hrtimer.c
> @@ -1173,7 +1161,7 @@ u64 hrtimer_get_next_event(void)
>  
>  static inline int hrtimer_clockid_to_base(clockid_t clock_id)
>  {
> +	if (likely(clock_id < MAX_CLOCKS_HRT)) {
>  		int base = hrtimer_clock_to_base_table[clock_id];
>  
>  		if (likely(base != HRTIMER_MAX_CLOCK_BASES))
> @@ -1193,8 +1181,12 @@ static void __hrtimer_init(struct hrtime
>  
>  	cpu_base = raw_cpu_ptr(&hrtimer_bases);
>  
> +	if (mode != HRTIMER_MODE_ABS) {
> +		if (clock_id == CLOCK_REALTIME)
> +			clock_id = CLOCK_MONOTONIC;
> +		else if (clock_id == CLOCK_REALTIME_SOFT)
> +			clock_id = CLOCK_MONOTONIC_SOFT;
> +	}
>  
>  	base = hrtimer_clockid_to_base(clock_id);
>  	timer->base = &cpu_base->clock_base[base];

So why expose these extra bases at all, why not stick another flag in
MODE? These extra bases is a pure implementation detail imo; you could
equally implement the functionality without (albeit at extra cost).

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Re: [PATCH 18/25] hrtimer: Enable soft and hard hrtimer Peter Zijlstra <peterz@infradead.org> - 2017-09-26 15:00 +0200
  Re: [PATCH 18/25] hrtimer: Enable soft and hard hrtimer Anna-Maria Gleixner <anna-maria@linutronix.de> - 2017-09-27 16:20 +0200
    Re: [PATCH 18/25] hrtimer: Enable soft and hard hrtimer Thomas Gleixner <tglx@linutronix.de> - 2017-09-27 18:00 +0200
      Re: [PATCH 18/25] hrtimer: Enable soft and hard hrtimer Peter Zijlstra <peterz@infradead.org> - 2017-09-27 18:50 +0200

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