97 lines
3.0 KiB
C
97 lines
3.0 KiB
C
#ifndef __LINUX_TIMER_WRAPPER_H
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#define __LINUX_TIMER_WRAPPER_H 1
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#include_next <linux/timer.h>
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#include <asm/param.h>
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#include <linux/smp.h>
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extern unsigned long volatile jiffies;
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static inline void setup_timer(struct timer_list * timer,
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void (*function)(unsigned long),
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unsigned long data)
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{
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timer->function = function;
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timer->data = data;
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init_timer(timer);
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}
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/**
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* __round_jiffies - function to round jiffies to a full second
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* @j: the time in (absolute) jiffies that should be rounded
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* @cpu: the processor number on which the timeout will happen
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*
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* __round_jiffies() rounds an absolute time in the future (in jiffies)
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* up or down to (approximately) full seconds. This is useful for timers
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* for which the exact time they fire does not matter too much, as long as
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* they fire approximately every X seconds.
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*
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* By rounding these timers to whole seconds, all such timers will fire
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* at the same time, rather than at various times spread out. The goal
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* of this is to have the CPU wake up less, which saves power.
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*
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* The exact rounding is skewed for each processor to avoid all
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* processors firing at the exact same time, which could lead
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* to lock contention or spurious cache line bouncing.
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*
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* The return value is the rounded version of the @j parameter.
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*/
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static inline unsigned long __round_jiffies(unsigned long j, int cpu)
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{
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int rem;
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unsigned long original = j;
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/*
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* We don't want all cpus firing their timers at once hitting the
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* same lock or cachelines, so we skew each extra cpu with an extra
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* 3 jiffies. This 3 jiffies came originally from the mm/ code which
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* already did this.
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* The skew is done by adding 3*cpunr, then round, then subtract this
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* extra offset again.
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*/
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j += cpu * 3;
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rem = j % HZ;
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/*
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* If the target jiffie is just after a whole second (which can happen
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* due to delays of the timer irq, long irq off times etc etc) then
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* we should round down to the whole second, not up. Use 1/4th second
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* as cutoff for this rounding as an extreme upper bound for this.
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*/
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if (rem < HZ/4) /* round down */
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j = j - rem;
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else /* round up */
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j = j - rem + HZ;
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/* now that we have rounded, subtract the extra skew again */
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j -= cpu * 3;
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if (j <= jiffies) /* rounding ate our timeout entirely; */
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return original;
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return j;
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}
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/**
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* round_jiffies - function to round jiffies to a full second
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* @j: the time in (absolute) jiffies that should be rounded
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*
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* round_jiffies() rounds an absolute time in the future (in jiffies)
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* up or down to (approximately) full seconds. This is useful for timers
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* for which the exact time they fire does not matter too much, as long as
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* they fire approximately every X seconds.
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*
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* By rounding these timers to whole seconds, all such timers will fire
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* at the same time, rather than at various times spread out. The goal
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* of this is to have the CPU wake up less, which saves power.
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*
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* The return value is the rounded version of the @j parameter.
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*/
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static inline unsigned long round_jiffies(unsigned long j)
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{
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return __round_jiffies(j, 0); // FIXME
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}
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#endif
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