/*
 * linux/kernel/time/tick-broadcast-hrtimer.c
 * This file emulates a local clock event device
 * via a pseudo clock device.
 */
#include <linux/cpu.h>
#include <linux/err.h>
#include <linux/hrtimer.h>
#include <linux/interrupt.h>
#include <linux/percpu.h>
#include <linux/profile.h>
#include <linux/clockchips.h>
#include <linux/sched.h>
#include <linux/smp.h>
#include <linux/module.h>

#include "tick-internal.h"

static struct hrtimer bctimer;

static int bc_shutdown(struct clock_event_device *evt)
{
	/*
	 * Note, we cannot cancel the timer here as we might
	 * run into the following live lock scenario:
	 *
	 * cpu 0		cpu1
	 * lock(broadcast_lock);
	 *			hrtimer_interrupt()
	 *			bc_handler()
	 *			   tick_handle_oneshot_broadcast();
	 *			    lock(broadcast_lock);
	 * hrtimer_cancel()
	 *  wait_for_callback()
	 */
	hrtimer_try_to_cancel(&bctimer);
	return 0;
}

/*
 * This is called from the guts of the broadcast code when the cpu
 * which is about to enter idle has the earliest broadcast timer event.
 */
static int bc_set_next(ktime_t expires, struct clock_event_device *bc)
{
	int bc_moved;
	/*
	 * We try to cancel the timer first. If the callback is on
	 * flight on some other cpu then we let it handle it. If we
	 * were able to cancel the timer nothing can rearm it as we
	 * own broadcast_lock.
	 *
	 * However we can also be called from the event handler of
	 * ce_broadcast_hrtimer itself when it expires. We cannot
	 * restart the timer because we are in the callback, but we
	 * can set the expiry time and let the callback return
	 * HRTIMER_RESTART.
	 *
	 * Since we are in the idle loop at this point and because
	 * hrtimer_{start/cancel} functions call into tracing,
	 * calls to these functions must be bound within RCU_NONIDLE.
	 */
	RCU_NONIDLE({
			bc_moved = hrtimer_try_to_cancel(&bctimer) >= 0;
			if (bc_moved)
				hrtimer_start(&bctimer, expires,
					      HRTIMER_MODE_ABS_PINNED);});
	if (bc_moved) {
		/* Bind the "device" to the cpu */
		bc->bound_on = smp_processor_id();
	} else if (bc->bound_on == smp_processor_id()) {
		hrtimer_set_expires(&bctimer, expires);
	}
	return 0;
}

static struct clock_event_device ce_broadcast_hrtimer = {
	.name			= "bc_hrtimer",
	.set_state_shutdown	= bc_shutdown,
	.set_next_ktime		= bc_set_next,
	.features		= CLOCK_EVT_FEAT_ONESHOT |
				  CLOCK_EVT_FEAT_KTIME |
				  CLOCK_EVT_FEAT_HRTIMER,
	.rating			= 0,
	.bound_on		= -1,
	.min_delta_ns		= 1,
	.max_delta_ns		= KTIME_MAX,
	.min_delta_ticks	= 1,
	.max_delta_ticks	= ULONG_MAX,
	.mult			= 1,
	.shift			= 0,
	.cpumask		= cpu_all_mask,
};

static enum hrtimer_restart bc_handler(struct hrtimer *t)
{
	ce_broadcast_hrtimer.event_handler(&ce_broadcast_hrtimer);

	if (clockevent_state_oneshot(&ce_broadcast_hrtimer))
		if (ce_broadcast_hrtimer.next_event != KTIME_MAX)
			return HRTIMER_RESTART;

	return HRTIMER_NORESTART;
}

void tick_setup_hrtimer_broadcast(void)
{
	hrtimer_init(&bctimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
	bctimer.function = bc_handler;
	clockevents_register_device(&ce_broadcast_hrtimer);
}
/option><option value='15'>15</option><option value='20'>20</option><option value='25'>25</option><option value='30'>30</option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Jungseung Lee &lt;js07.lee@samsung.com&gt;</td><td class='right'>2016-12-12 16:46:43 -0800</td></tr>
<tr><th>committer</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2016-12-12 18:55:10 -0800</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/?id=39a0e975c37dee93fa1b8ea5f7eacd1c4c8a586e'>39a0e975c37dee93fa1b8ea5f7eacd1c4c8a586e</a> (<a href='/cgit.cgi/linux/net-next.git/patch/?id=39a0e975c37dee93fa1b8ea5f7eacd1c4c8a586e'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?id=39a0e975c37dee93fa1b8ea5f7eacd1c4c8a586e'>34df14285ce89f83a93f6053a897bcd371dc1e15</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/?id=30f74aa0854c2d5a331b507b14fe421ba4980511'>30f74aa0854c2d5a331b507b14fe421ba4980511</a> (<a href='/cgit.cgi/linux/net-next.git/diff/?id=39a0e975c37dee93fa1b8ea5f7eacd1c4c8a586e&amp;id2=30f74aa0854c2d5a331b507b14fe421ba4980511'>diff</a>)</td></tr></table>
<div class='commit-subject'>init: reduce rootwait polling interval time to 5ms</div><div class='commit-msg'>For several devices, the rootwait time is sensitive because it directly
affects booting time.  The polling interval of rootwait is currently
100ms.  To save unnessesary waiting time, reduce the polling interval to
5 ms.

[akpm@linux-foundation.org: remove used-once #define]
Link: http://lkml.kernel.org/r/20161207060743.1728-1-js07.lee@samsung.com
Signed-off-by: Jungseung Lee &lt;js07.lee@samsung.com&gt;
Cc: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
Cc: Christoph Hellwig &lt;hch@lst.de&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=39a0e975c37dee93fa1b8ea5f7eacd1c4c8a586e'>Diffstat</a></div><table summary='diffstat' class='diffstat'>