| /* |
| * linux/kernel/time/tick-common.c |
| * |
| * This file contains the base functions to manage periodic tick |
| * related events. |
| * |
| * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> |
| * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar |
| * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner |
| * |
| * This code is licenced under the GPL version 2. For details see |
| * kernel-base/COPYING. |
| */ |
| #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/sched.h> |
| #include <linux/module.h> |
| #include <trace/events/power.h> |
| |
| #include <asm/irq_regs.h> |
| |
| #include "tick-internal.h" |
| |
| /* |
| * Tick devices |
| */ |
| DEFINE_PER_CPU(struct tick_device, tick_cpu_device); |
| /* |
| * Tick next event: keeps track of the tick time |
| */ |
| ktime_t tick_next_period; |
| ktime_t tick_period; |
| |
| /* |
| * tick_do_timer_cpu is a timer core internal variable which holds the CPU NR |
| * which is responsible for calling do_timer(), i.e. the timekeeping stuff. This |
| * variable has two functions: |
| * |
| * 1) Prevent a thundering herd issue of a gazillion of CPUs trying to grab the |
| * timekeeping lock all at once. Only the CPU which is assigned to do the |
| * update is handling it. |
| * |
| * 2) Hand off the duty in the NOHZ idle case by setting the value to |
| * TICK_DO_TIMER_NONE, i.e. a non existing CPU. So the next cpu which looks |
| * at it will take over and keep the time keeping alive. The handover |
| * procedure also covers cpu hotplug. |
| */ |
| int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT; |
| |
| /* |
| * Debugging: see timer_list.c |
| */ |
| struct tick_device *tick_get_device(int cpu) |
| { |
| return &per_cpu(tick_cpu_device, cpu); |
| } |
| |
| /** |
| * tick_is_oneshot_available - check for a oneshot capable event device |
| */ |
| int tick_is_oneshot_available(void) |
| { |
| struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); |
| |
| if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT)) |
| return 0; |
| if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) |
| return 1; |
| return tick_broadcast_oneshot_available(); |
| } |
| |
| /* |
| * Periodic tick |
| */ |
| static void tick_periodic(int cpu) |
| { |
| if (tick_do_timer_cpu == cpu) { |
| write_seqlock(&jiffies_lock); |
| |
| /* Keep track of the next tick event */ |
| tick_next_period = ktime_add(tick_next_period, tick_period); |
| |
| do_timer(1); |
| write_sequnlock(&jiffies_lock); |
| update_wall_time(); |
| } |
| |
| update_process_times(user_mode(get_irq_regs())); |
| profile_tick(CPU_PROFILING); |
| } |
| |
| /* |
| * Event handler for periodic ticks |
| */ |
| void tick_handle_periodic(struct clock_event_device *dev) |
| { |
| int cpu = smp_processor_id(); |
| ktime_t next = dev->next_event; |
| |
| tick_periodic(cpu); |
| |
| #if defined(CONFIG_HIGH_RES_TIMERS) || defined(CONFIG_NO_HZ_COMMON) |
| /* |
| * The cpu might have transitioned to HIGHRES or NOHZ mode via |
| * update_process_times() -> run_local_timers() -> |
| * hrtimer_run_queues(). |
| */ |
| if (dev->event_handler != tick_handle_periodic) |
| return; |
| #endif |
| |
| if (!clockevent_state_oneshot(dev)) |
| return; |
| for (;;) { |
| /* |
| * Setup the next period for devices, which do not have |
| * periodic mode: |
| */ |
| next = ktime_add(next, tick_period); |
| |
| if (!clockevents_program_event(dev, next, false)) |
| return; |
| /* |
| * Have to be careful here. If we're in oneshot mode, |
| * before we call tick_periodic() in a loop, we need |
| * to be sure we're using a real hardware clocksource. |
| * Otherwise we could get trapped in an infinite |
| * loop, as the tick_periodic() increments jiffies, |
| * which then will increment time, possibly causing |
| * the loop to trigger again and again. |
| */ |
| if (timekeeping_valid_for_hres()) |
| tick_periodic(cpu); |
| } |
| } |
| |
| /* |
| * Setup the device for a periodic tick |
| */ |
| void tick_setup_periodic(struct clock_event_device *dev, int broadcast) |
| { |
| tick_set_periodic_handler(dev, broadcast); |
| |
| /* Broadcast setup ? */ |
| if (!tick_device_is_functional(dev)) |
| return; |
| |
| if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) && |
| !tick_broadcast_oneshot_active()) { |
| clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC); |
| } else { |
| unsigned long seq; |
| ktime_t next; |
| |
| do { |
| seq = read_seqbegin(&jiffies_lock); |
| next = tick_next_period; |
| } while (read_seqretry(&jiffies_lock, seq)); |
| |
| clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT); |
| |
| for (;;) { |
| if (!clockevents_program_event(dev, next, false)) |
| return; |
| next = ktime_add(next, tick_period); |
| } |
| } |
| } |
| |
| /* |
| * Setup the tick device |
| */ |
| static void tick_setup_device(struct tick_device *td, |
| struct clock_event_device *newdev, int cpu, |
| const struct cpumask *cpumask) |
| { |
| ktime_t next_event; |
| void (*handler)(struct clock_event_device *) = NULL; |
| |
| /* |
| * First device setup ? |
| */ |
| if (!td->evtdev) { |
| /* |
| * If no cpu took the do_timer update, assign it to |
| * this cpu: |
| */ |
| if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) { |
| if (!tick_nohz_full_cpu(cpu)) |
| tick_do_timer_cpu = cpu; |
| else |
| tick_do_timer_cpu = TICK_DO_TIMER_NONE; |
| tick_next_period = ktime_get(); |
| tick_period = ktime_set(0, NSEC_PER_SEC / HZ); |
| } |
| |
| /* |
| * Startup in periodic mode first. |
| */ |
| td->mode = TICKDEV_MODE_PERIODIC; |
| } else { |
| handler = td->evtdev->event_handler; |
| next_event = td->evtdev->next_event; |
| td->evtdev->event_handler = clockevents_handle_noop; |
| } |
| |
| td->evtdev = newdev; |
| |
| /* |
| * When the device is not per cpu, pin the interrupt to the |
| * current cpu: |
| */ |
| if (!cpumask_equal(newdev->cpumask, cpumask)) |
| irq_set_affinity(newdev->irq, cpumask); |
| |
| /* |
| * When global broadcasting is active, check if the current |
| * device is registered as a placeholder for broadcast mode. |
| * This allows us to handle this x86 misfeature in a generic |
| * way. This function also returns !=0 when we keep the |
| * current active broadcast state for this CPU. |
| */ |
| if (tick_device_uses_broadcast(newdev, cpu)) |
| return; |
| |
| if (td->mode == TICKDEV_MODE_PERIODIC) |
| tick_setup_periodic(newdev, 0); |
| else |
| tick_setup_oneshot(newdev, handler, next_event); |
| } |
| |
| void tick_install_replacement(struct clock_event_device *newdev) |
| { |
| struct tick_device *td = this_cpu_ptr(&tick_cpu_device); |
| int cpu = smp_processor_id(); |
| |
| clockevents_exchange_device(td->evtdev, newdev); |
| tick_setup_device(td, newdev, cpu, cpumask_of(cpu)); |
| if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) |
| tick_oneshot_notify(); |
| } |
| |
| static bool tick_check_percpu(struct clock_event_device *curdev, |
| struct clock_event_device *newdev, int cpu) |
| { |
| if (!cpumask_test_cpu(cpu, newdev->cpumask)) |
| return false; |
| if (cpumask_equal(newdev->cpumask, cpumask_of(cpu))) |
| return true; |
| /* Check if irq affinity can be set */ |
| if (newdev->irq >= 0 && !irq_can_set_affinity(newdev->irq)) |
| return false; |
| /* Prefer an existing cpu local device */ |
| if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu))) |
| return false; |
| return true; |
| } |
| |
| static bool tick_check_preferred(struct clock_event_device *curdev, |
| struct clock_event_device *newdev) |
| { |
| /* Prefer oneshot capable device */ |
| if (!(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) { |
| if (curdev && (curdev->features & CLOCK_EVT_FEAT_ONESHOT)) |
| return false; |
| if (tick_oneshot_mode_active()) |
| return false; |
| } |
| |
| /* |
| * Use the higher rated one, but prefer a CPU local device with a lower |
| * rating than a non-CPU local device |
| */ |
| return !curdev || |
| newdev->rating > curdev->rating || |
| !cpumask_equal(curdev->cpumask, newdev->cpumask); |
| } |
| |
| /* |
| * Check whether the new device is a better fit than curdev. curdev |
| * can be NULL ! |
| */ |
| bool tick_check_replacement(struct clock_event_device *curdev, |
| struct clock_event_device *newdev) |
| { |
| if (!tick_check_percpu(curdev, newdev, smp_processor_id())) |
| return false; |
| |
| return tick_check_preferred(curdev, newdev); |
| } |
| |
| /* |
| * Check, if the new registered device should be used. Called with |
| * clockevents_lock held and interrupts disabled. |
| */ |
| void tick_check_new_device(struct clock_event_device *newdev) |
| { |
| struct clock_event_device *curdev; |
| struct tick_device *td; |
| int cpu; |
| |
| cpu = smp_processor_id(); |
| if (!cpumask_test_cpu(cpu, newdev->cpumask)) |
| goto out_bc; |
| |
| td = &per_cpu(tick_cpu_device, cpu); |
| curdev = td->evtdev; |
| |
| /* cpu local device ? */ |
| if (!tick_check_percpu(curdev, newdev, cpu)) |
| goto out_bc; |
| |
| /* Preference decision */ |
| if (!tick_check_preferred(curdev, newdev)) |
| goto out_bc; |
| |
| if (!try_module_get(newdev->owner)) |
| return; |
| |
| /* |
| * Replace the eventually existing device by the new |
| * device. If the current device is the broadcast device, do |
| * not give it back to the clockevents layer ! |
| */ |
| if (tick_is_broadcast_device(curdev)) { |
| clockevents_shutdown(curdev); |
| curdev = NULL; |
| } |
| clockevents_exchange_device(curdev, newdev); |
| tick_setup_device(td, newdev, cpu, cpumask_of(cpu)); |
| if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) |
| tick_oneshot_notify(); |
| return; |
| |
| out_bc: |
| /* |
| * Can the new device be used as a broadcast device ? |
| */ |
| tick_install_broadcast_device(newdev); |
| } |
| |
| /** |
| * tick_broadcast_oneshot_control - Enter/exit broadcast oneshot mode |
| * @state: The target state (enter/exit) |
| * |
| * The system enters/leaves a state, where affected devices might stop |
| * Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups. |
| * |
| * Called with interrupts disabled, so clockevents_lock is not |
| * required here because the local clock event device cannot go away |
| * under us. |
| */ |
| int tick_broadcast_oneshot_control(enum tick_broadcast_state state) |
| { |
| struct tick_device *td = this_cpu_ptr(&tick_cpu_device); |
| |
| if (!(td->evtdev->features & CLOCK_EVT_FEAT_C3STOP)) |
| return 0; |
| |
| return __tick_broadcast_oneshot_control(state); |
| } |
| |
| #ifdef CONFIG_HOTPLUG_CPU |
| /* |
| * Transfer the do_timer job away from a dying cpu. |
| * |
| * Called with interrupts disabled. Not locking required. If |
| * tick_do_timer_cpu is owned by this cpu, nothing can change it. |
| */ |
| void tick_handover_do_timer(void) |
| { |
| if (tick_do_timer_cpu == smp_processor_id()) { |
| int cpu = cpumask_first(cpu_online_mask); |
| |
| tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu : |
| TICK_DO_TIMER_NONE; |
| } |
| } |
| |
| /* |
| * Shutdown an event device on a given cpu: |
| * |
| * This is called on a life CPU, when a CPU is dead. So we cannot |
| * access the hardware device itself. |
| * We just set the mode and remove it from the lists. |
| */ |
| void tick_shutdown(unsigned int cpu) |
| { |
| struct tick_device *td = &per_cpu(tick_cpu_device, cpu); |
| struct clock_event_device *dev = td->evtdev; |
| |
| td->mode = TICKDEV_MODE_PERIODIC; |
| if (dev) { |
| /* |
| * Prevent that the clock events layer tries to call |
| * the set mode function! |
| */ |
| clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED); |
| dev->mode = CLOCK_EVT_MODE_UNUSED; |
| clockevents_exchange_device(dev, NULL); |
| dev->event_handler = clockevents_handle_noop; |
| td->evtdev = NULL; |
| } |
| } |
| #endif |
| |
| /** |
| * tick_suspend_local - Suspend the local tick device |
| * |
| * Called from the local cpu for freeze with interrupts disabled. |
| * |
| * No locks required. Nothing can change the per cpu device. |
| */ |
| void tick_suspend_local(void) |
| { |
| struct tick_device *td = this_cpu_ptr(&tick_cpu_device); |
| |
| clockevents_shutdown(td->evtdev); |
| } |
| |
| /** |
| * tick_resume_local - Resume the local tick device |
| * |
| * Called from the local CPU for unfreeze or XEN resume magic. |
| * |
| * No locks required. Nothing can change the per cpu device. |
| */ |
| void tick_resume_local(void) |
| { |
| struct tick_device *td = this_cpu_ptr(&tick_cpu_device); |
| bool broadcast = tick_resume_check_broadcast(); |
| |
| clockevents_tick_resume(td->evtdev); |
| if (!broadcast) { |
| if (td->mode == TICKDEV_MODE_PERIODIC) |
| tick_setup_periodic(td->evtdev, 0); |
| else |
| tick_resume_oneshot(); |
| } |
| } |
| |
| /** |
| * tick_suspend - Suspend the tick and the broadcast device |
| * |
| * Called from syscore_suspend() via timekeeping_suspend with only one |
| * CPU online and interrupts disabled or from tick_unfreeze() under |
| * tick_freeze_lock. |
| * |
| * No locks required. Nothing can change the per cpu device. |
| */ |
| void tick_suspend(void) |
| { |
| tick_suspend_local(); |
| tick_suspend_broadcast(); |
| } |
| |
| /** |
| * tick_resume - Resume the tick and the broadcast device |
| * |
| * Called from syscore_resume() via timekeeping_resume with only one |
| * CPU online and interrupts disabled. |
| * |
| * No locks required. Nothing can change the per cpu device. |
| */ |
| void tick_resume(void) |
| { |
| tick_resume_broadcast(); |
| tick_resume_local(); |
| } |
| |
| #ifdef CONFIG_SUSPEND |
| static DEFINE_RAW_SPINLOCK(tick_freeze_lock); |
| static unsigned int tick_freeze_depth; |
| |
| /** |
| * tick_freeze - Suspend the local tick and (possibly) timekeeping. |
| * |
| * Check if this is the last online CPU executing the function and if so, |
| * suspend timekeeping. Otherwise suspend the local tick. |
| * |
| * Call with interrupts disabled. Must be balanced with %tick_unfreeze(). |
| * Interrupts must not be enabled before the subsequent %tick_unfreeze(). |
| */ |
| void tick_freeze(void) |
| { |
| raw_spin_lock(&tick_freeze_lock); |
| |
| tick_freeze_depth++; |
| if (tick_freeze_depth == num_online_cpus()) { |
| trace_suspend_resume(TPS("timekeeping_freeze"), |
| smp_processor_id(), true); |
| timekeeping_suspend(); |
| } else { |
| tick_suspend_local(); |
| } |
| |
| raw_spin_unlock(&tick_freeze_lock); |
| } |
| |
| /** |
| * tick_unfreeze - Resume the local tick and (possibly) timekeeping. |
| * |
| * Check if this is the first CPU executing the function and if so, resume |
| * timekeeping. Otherwise resume the local tick. |
| * |
| * Call with interrupts disabled. Must be balanced with %tick_freeze(). |
| * Interrupts must not be enabled after the preceding %tick_freeze(). |
| */ |
| void tick_unfreeze(void) |
| { |
| raw_spin_lock(&tick_freeze_lock); |
| |
| if (tick_freeze_depth == num_online_cpus()) { |
| timekeeping_resume(); |
| trace_suspend_resume(TPS("timekeeping_freeze"), |
| smp_processor_id(), false); |
| } else { |
| tick_resume_local(); |
| } |
| |
| tick_freeze_depth--; |
| |
| raw_spin_unlock(&tick_freeze_lock); |
| } |
| #endif /* CONFIG_SUSPEND */ |
| |
| /** |
| * tick_init - initialize the tick control |
| */ |
| void __init tick_init(void) |
| { |
| tick_broadcast_init(); |
| tick_nohz_init(); |
| } |