1 // SPDX-License-Identifier: GPL-2.0
3  * This file contains the base functions to manage periodic tick
6  * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
7  * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
8  * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
23 #include "tick-internal.h"
26  * Tick devices
30  * Tick next event: keeps track of the tick time. It's updated by the
31  * CPU which handles the tick and protected by jiffies_lock. There is
32  * no requirement to write hold the jiffies seqcount for it.
45  * 2) Hand off the duty in the NOHZ idle case by setting the value to
57 static int tick_do_timer_boot_cpu __read_mostly = -1;
69  * tick_is_oneshot_available - check for a oneshot capable event device
75 	if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))  in tick_is_oneshot_available()
77 	if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))  in tick_is_oneshot_available()
83  * Periodic tick
91 		/* Keep track of the next tick event */  in tick_periodic()
110 	ktime_t next = dev->next_event;  in tick_handle_periodic()
117 	 * update_process_times() -> run_local_timers() ->  in tick_handle_periodic()
120 	if (dev->event_handler != tick_handle_periodic)  in tick_handle_periodic()
136 		 * Have to be careful here. If we're in oneshot mode,  in tick_handle_periodic()
137 		 * before we call tick_periodic() in a loop, we need  in tick_handle_periodic()
139 		 * Otherwise we could get trapped in an infinite  in tick_handle_periodic()
150  * Setup the device for a periodic tick
160 	if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&  in tick_setup_periodic()
183  * Setup the tick device
195 	if (!td->evtdev) {  in tick_setup_device()
197 		 * If no cpu took the do_timer update, assign it to  in tick_setup_device()
205 			 * The boot CPU may be nohz_full, in which case the  in tick_setup_device()
212 		} else if (tick_do_timer_boot_cpu != -1 && !tick_nohz_full_cpu(cpu)) {  in tick_setup_device()
213 			tick_do_timer_boot_cpu = -1;  in tick_setup_device()
215 			 * The boot CPU will stay in periodic (NOHZ disabled)  in tick_setup_device()
221 			 * check in tick_periodic() but this race is harmless.  in tick_setup_device()
228 		 * Startup in periodic mode first.  in tick_setup_device()
230 		td->mode = TICKDEV_MODE_PERIODIC;  in tick_setup_device()
232 		handler = td->evtdev->event_handler;  in tick_setup_device()
233 		next_event = td->evtdev->next_event;  in tick_setup_device()
234 		td->evtdev->event_handler = clockevents_handle_noop;  in tick_setup_device()
237 	td->evtdev = newdev;  in tick_setup_device()
243 	if (!cpumask_equal(newdev->cpumask, cpumask))  in tick_setup_device()
244 		irq_set_affinity(newdev->irq, cpumask);  in tick_setup_device()
249 	 * This allows us to handle this x86 misfeature in a generic  in tick_setup_device()
256 	if (td->mode == TICKDEV_MODE_PERIODIC)  in tick_setup_device()
267 	clockevents_exchange_device(td->evtdev, newdev);  in tick_install_replacement()
269 	if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)  in tick_install_replacement()
276 	if (!cpumask_test_cpu(cpu, newdev->cpumask))  in tick_check_percpu()
278 	if (cpumask_equal(newdev->cpumask, cpumask_of(cpu)))  in tick_check_percpu()
281 	if (newdev->irq >= 0 && !irq_can_set_affinity(newdev->irq))  in tick_check_percpu()
284 	if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))  in tick_check_percpu()
293 	if (!(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) {  in tick_check_preferred()
294 		if (curdev && (curdev->features & CLOCK_EVT_FEAT_ONESHOT))  in tick_check_preferred()
302 	 * rating than a non-CPU local device  in tick_check_preferred()
305 		newdev->rating > curdev->rating ||  in tick_check_preferred()
306 	       !cpumask_equal(curdev->cpumask, newdev->cpumask);  in tick_check_preferred()
334 	curdev = td->evtdev;  in tick_check_new_device()
339 	if (!try_module_get(newdev->owner))  in tick_check_new_device()
353 	if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)  in tick_check_new_device()
365  * tick_broadcast_oneshot_control - Enter/exit broadcast oneshot mode
369  * Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups.
379 	if (!(td->evtdev->features & CLOCK_EVT_FEAT_C3STOP))  in tick_broadcast_oneshot_control()
390  * Called with interrupts disabled. No locking required. If
409 	struct clock_event_device *dev = td->evtdev;  in tick_shutdown()
411 	td->mode = TICKDEV_MODE_PERIODIC;  in tick_shutdown()
419 		dev->event_handler = clockevents_handle_noop;  in tick_shutdown()
420 		td->evtdev = NULL;  in tick_shutdown()
426  * tick_suspend_local - Suspend the local tick device
430  * No locks required. Nothing can change the per cpu device.
436 	clockevents_shutdown(td->evtdev);  in tick_suspend_local()
440  * tick_resume_local - Resume the local tick device
444  * No locks required. Nothing can change the per cpu device.
451 	clockevents_tick_resume(td->evtdev);  in tick_resume_local()
453 		if (td->mode == TICKDEV_MODE_PERIODIC)  in tick_resume_local()
454 			tick_setup_periodic(td->evtdev, 0);  in tick_resume_local()
468  * tick_suspend - Suspend the tick and the broadcast device
474  * No locks required. Nothing can change the per cpu device.
483  * tick_resume - Resume the tick and the broadcast device
488  * No locks required. Nothing can change the per cpu device.
501  * tick_freeze - Suspend the local tick and (possibly) timekeeping.
504  * suspend timekeeping.  Otherwise suspend the local tick.
528  * tick_unfreeze - Resume the local tick and (possibly) timekeeping.
531  * timekeeping.  Otherwise resume the local tick.
551 	tick_freeze_depth--;  in tick_unfreeze()
558  * tick_init - initialize the tick control