/* * 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);}