// SPDX-License-Identifier: GPL-2.0 /* * This file contains the base functions to manage periodic tick * related events. * * Copyright(C) 2005-2006, Thomas Gleixner <[email protected]> * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner */ #include <linux/compiler.h> #include <linux/cpu.h> #include <linux/err.h> #include <linux/hrtimer.h> #include <linux/interrupt.h> #include <linux/nmi.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. It's updated by the * CPU which handles the tick and protected by jiffies_lock. There is * no requirement to write hold the jiffies seqcount for it. */ ktime_t tick_next_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 = …; #ifdef CONFIG_NO_HZ_FULL /* * tick_do_timer_boot_cpu indicates the boot CPU temporarily owns * tick_do_timer_cpu and it should be taken over by an eligible secondary * when one comes online. */ static int tick_do_timer_boot_cpu __read_mostly = -1; #endif /* * Debugging: see timer_list.c */ struct tick_device *tick_get_device(int cpu) { … } /** * tick_is_oneshot_available - check for a oneshot capable event device */ int tick_is_oneshot_available(void) { … } /* * Periodic tick */ static void tick_periodic(int cpu) { … } /* * Event handler for periodic ticks */ void tick_handle_periodic(struct clock_event_device *dev) { … } /* * Setup the device for a periodic tick */ void tick_setup_periodic(struct clock_event_device *dev, int broadcast) { … } /* * Setup the tick device */ static void tick_setup_device(struct tick_device *td, struct clock_event_device *newdev, int cpu, const struct cpumask *cpumask) { … } void tick_install_replacement(struct clock_event_device *newdev) { … } static bool tick_check_percpu(struct clock_event_device *curdev, struct clock_event_device *newdev, int cpu) { … } static bool tick_check_preferred(struct clock_event_device *curdev, struct clock_event_device *newdev) { … } /* * 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) { … } /* * 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) { … } /** * 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) { … } EXPORT_SYMBOL_GPL(…); #ifdef CONFIG_HOTPLUG_CPU void tick_assert_timekeeping_handover(void) { … } /* * Stop the tick and transfer the timekeeping job away from a dying cpu. */ int tick_cpu_dying(unsigned int dying_cpu) { … } /* * 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) { … } #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) { … } /** * 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) { … } /** * 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_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) { … } #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) { … } /** * 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) { … } #endif /* CONFIG_SUSPEND */ /** * tick_init - initialize the tick control */ void __init tick_init(void) { … }
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