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Commit a08ca5d1 authored by Stephen Boyd's avatar Stephen Boyd Committed by John Stultz
Browse files

sched_clock: Use an hrtimer instead of timer 



In the next patch we're going to increase the number of bits that
the generic sched_clock can handle to be greater than 32. With
more than 32 bits the wraparound time can be larger than what can
fit into the units that msecs_to_jiffies takes (unsigned int).
Luckily, the wraparound is initially calculated in nanoseconds
which we can easily use with hrtimers, so switch to using an
hrtimer.

Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: default avatarStephen Boyd <sboyd@codeaurora.org>
[jstultz: Fixup hrtimer intitialization order issue]
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
parent 85c3d2dd

kernel/time/sched_clock.c

+21 −17
Original line number Original line Diff line number Diff line
@@ -8,15 +8,17 @@ 
#include <linux/clocksource.h>

#include <linux/clocksource.h>

#include <linux/init.h>

#include <linux/init.h>

#include <linux/jiffies.h>

#include <linux/jiffies.h>

#include <linux/ktime.h>

#include <linux/kernel.h>

#include <linux/kernel.h>

#include <linux/moduleparam.h>

#include <linux/moduleparam.h>

#include <linux/sched.h>

#include <linux/sched.h>

#include <linux/syscore_ops.h>

#include <linux/syscore_ops.h>

#include <linux/timer.h>

#include <linux/hrtimer.h>

#include <linux/sched_clock.h>

#include <linux/sched_clock.h>

#include <linux/seqlock.h>

#include <linux/seqlock.h>





struct clock_data {

struct clock_data {

	ktime_t wrap_kt;

	u64 epoch_ns;

	u64 epoch_ns;

	u32 epoch_cyc;

	u32 epoch_cyc;

	seqcount_t seq;

	seqcount_t seq;
@@ -26,8 +28,7 @@ struct clock_data { 
	bool suspended;

	bool suspended;

};

};





static void sched_clock_poll(unsigned long wrap_ticks);

static struct hrtimer sched_clock_timer;

static DEFINE_TIMER(sched_clock_timer, sched_clock_poll, 0, 0);

static int irqtime = -1;

static int irqtime = -1;





core_param(irqtime, irqtime, int, 0400);

core_param(irqtime, irqtime, int, 0400);
@@ -93,15 +94,16 @@ static void notrace update_sched_clock(void) 
	raw_local_irq_restore(flags);

	raw_local_irq_restore(flags);

}

}





static void sched_clock_poll(unsigned long wrap_ticks)

static enum hrtimer_restart sched_clock_poll(struct hrtimer *hrt)

{

{

	mod_timer(&sched_clock_timer, round_jiffies(jiffies + wrap_ticks));

	update_sched_clock();

	update_sched_clock();

	hrtimer_forward_now(hrt, cd.wrap_kt);

	return HRTIMER_RESTART;

}

}





void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate)

void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate)

{

{

	unsigned long r, w;

	unsigned long r;

	u64 res, wrap;

	u64 res, wrap;

	char r_unit;

	char r_unit;
@@ -129,19 +131,13 @@ void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate) 




	/* calculate how many ns until we wrap */

	/* calculate how many ns until we wrap */

	wrap = cyc_to_ns((1ULL << bits) - 1, cd.mult, cd.shift);

	wrap = cyc_to_ns((1ULL << bits) - 1, cd.mult, cd.shift);

	do_div(wrap, NSEC_PER_MSEC);

	cd.wrap_kt = ns_to_ktime(wrap - (wrap >> 3));

	w = wrap;





	/* calculate the ns resolution of this counter */

	/* calculate the ns resolution of this counter */

	res = cyc_to_ns(1ULL, cd.mult, cd.shift);

	res = cyc_to_ns(1ULL, cd.mult, cd.shift);

	pr_info("sched_clock: %u bits at %lu%cHz, resolution %lluns, wraps every %lums\n",

	pr_info("sched_clock: %u bits at %lu%cHz, resolution %lluns, wraps every %lluns\n",

		bits, r, r_unit, res, w);

		bits, r, r_unit, res, wrap);





	/*

	 * Start the timer to keep sched_clock() properly updated and

	 * sets the initial epoch.

	 */

	sched_clock_timer.data = msecs_to_jiffies(w - (w / 10));

	update_sched_clock();

	update_sched_clock();





	/*

	/*
@@ -172,12 +168,20 @@ void __init sched_clock_postinit(void) 
	if (read_sched_clock == jiffy_sched_clock_read)

	if (read_sched_clock == jiffy_sched_clock_read)

		setup_sched_clock(jiffy_sched_clock_read, 32, HZ);

		setup_sched_clock(jiffy_sched_clock_read, 32, HZ);





	sched_clock_poll(sched_clock_timer.data);

	update_sched_clock();



	/*

	 * Start the timer to keep sched_clock() properly updated and

	 * sets the initial epoch.

	 */

	hrtimer_init(&sched_clock_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);

	sched_clock_timer.function = sched_clock_poll;

	hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL);

}

}





static int sched_clock_suspend(void)

static int sched_clock_suspend(void)

{

{

	sched_clock_poll(sched_clock_timer.data);

	sched_clock_poll(&sched_clock_timer);

	cd.suspended = true;

	cd.suspended = true;

	return 0;

	return 0;

}

}