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572 lines
14 KiB
572 lines
14 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* This file contains the base functions to manage periodic tick |
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* related events. |
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* |
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* Copyright(C) 2005-2006, Thomas Gleixner <[email protected]> |
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* Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar |
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* Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner |
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*/ |
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#include <linux/cpu.h> |
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#include <linux/err.h> |
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#include <linux/hrtimer.h> |
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#include <linux/interrupt.h> |
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#include <linux/nmi.h> |
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#include <linux/percpu.h> |
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#include <linux/profile.h> |
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#include <linux/sched.h> |
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#include <linux/module.h> |
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#include <trace/events/power.h> |
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#include <asm/irq_regs.h> |
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#include "tick-internal.h" |
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/* |
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* Tick devices |
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*/ |
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DEFINE_PER_CPU(struct tick_device, tick_cpu_device); |
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/* |
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* Tick next event: keeps track of the tick time. It's updated by the |
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* CPU which handles the tick and protected by jiffies_lock. There is |
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* no requirement to write hold the jiffies seqcount for it. |
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*/ |
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ktime_t tick_next_period; |
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/* |
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* tick_do_timer_cpu is a timer core internal variable which holds the CPU NR |
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* which is responsible for calling do_timer(), i.e. the timekeeping stuff. This |
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* variable has two functions: |
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* |
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* 1) Prevent a thundering herd issue of a gazillion of CPUs trying to grab the |
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* timekeeping lock all at once. Only the CPU which is assigned to do the |
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* update is handling it. |
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* |
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* 2) Hand off the duty in the NOHZ idle case by setting the value to |
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* TICK_DO_TIMER_NONE, i.e. a non existing CPU. So the next cpu which looks |
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* at it will take over and keep the time keeping alive. The handover |
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* procedure also covers cpu hotplug. |
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*/ |
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int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT; |
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#ifdef CONFIG_NO_HZ_FULL |
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/* |
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* tick_do_timer_boot_cpu indicates the boot CPU temporarily owns |
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* tick_do_timer_cpu and it should be taken over by an eligible secondary |
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* when one comes online. |
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*/ |
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static int tick_do_timer_boot_cpu __read_mostly = -1; |
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#endif |
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/* |
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* Debugging: see timer_list.c |
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*/ |
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struct tick_device *tick_get_device(int cpu) |
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{ |
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return &per_cpu(tick_cpu_device, cpu); |
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} |
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/** |
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* tick_is_oneshot_available - check for a oneshot capable event device |
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*/ |
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int tick_is_oneshot_available(void) |
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{ |
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struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); |
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if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT)) |
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return 0; |
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if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) |
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return 1; |
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return tick_broadcast_oneshot_available(); |
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} |
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/* |
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* Periodic tick |
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*/ |
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static void tick_periodic(int cpu) |
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{ |
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if (tick_do_timer_cpu == cpu) { |
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raw_spin_lock(&jiffies_lock); |
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write_seqcount_begin(&jiffies_seq); |
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/* Keep track of the next tick event */ |
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tick_next_period = ktime_add_ns(tick_next_period, TICK_NSEC); |
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do_timer(1); |
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write_seqcount_end(&jiffies_seq); |
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raw_spin_unlock(&jiffies_lock); |
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update_wall_time(); |
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} |
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update_process_times(user_mode(get_irq_regs())); |
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profile_tick(CPU_PROFILING); |
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} |
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/* |
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* Event handler for periodic ticks |
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*/ |
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void tick_handle_periodic(struct clock_event_device *dev) |
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{ |
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int cpu = smp_processor_id(); |
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ktime_t next = dev->next_event; |
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tick_periodic(cpu); |
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#if defined(CONFIG_HIGH_RES_TIMERS) || defined(CONFIG_NO_HZ_COMMON) |
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/* |
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* The cpu might have transitioned to HIGHRES or NOHZ mode via |
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* update_process_times() -> run_local_timers() -> |
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* hrtimer_run_queues(). |
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*/ |
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if (dev->event_handler != tick_handle_periodic) |
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return; |
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#endif |
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if (!clockevent_state_oneshot(dev)) |
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return; |
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for (;;) { |
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/* |
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* Setup the next period for devices, which do not have |
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* periodic mode: |
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*/ |
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next = ktime_add_ns(next, TICK_NSEC); |
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if (!clockevents_program_event(dev, next, false)) |
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return; |
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/* |
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* Have to be careful here. If we're in oneshot mode, |
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* before we call tick_periodic() in a loop, we need |
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* to be sure we're using a real hardware clocksource. |
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* Otherwise we could get trapped in an infinite |
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* loop, as the tick_periodic() increments jiffies, |
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* which then will increment time, possibly causing |
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* the loop to trigger again and again. |
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*/ |
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if (timekeeping_valid_for_hres()) |
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tick_periodic(cpu); |
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} |
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} |
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/* |
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* Setup the device for a periodic tick |
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*/ |
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void tick_setup_periodic(struct clock_event_device *dev, int broadcast) |
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{ |
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tick_set_periodic_handler(dev, broadcast); |
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/* Broadcast setup ? */ |
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if (!tick_device_is_functional(dev)) |
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return; |
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if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) && |
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!tick_broadcast_oneshot_active()) { |
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clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC); |
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} else { |
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unsigned int seq; |
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ktime_t next; |
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do { |
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seq = read_seqcount_begin(&jiffies_seq); |
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next = tick_next_period; |
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} while (read_seqcount_retry(&jiffies_seq, seq)); |
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clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT); |
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for (;;) { |
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if (!clockevents_program_event(dev, next, false)) |
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return; |
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next = ktime_add_ns(next, TICK_NSEC); |
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} |
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} |
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} |
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#ifdef CONFIG_NO_HZ_FULL |
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static void giveup_do_timer(void *info) |
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{ |
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int cpu = *(unsigned int *)info; |
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WARN_ON(tick_do_timer_cpu != smp_processor_id()); |
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tick_do_timer_cpu = cpu; |
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} |
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static void tick_take_do_timer_from_boot(void) |
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{ |
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int cpu = smp_processor_id(); |
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int from = tick_do_timer_boot_cpu; |
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if (from >= 0 && from != cpu) |
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smp_call_function_single(from, giveup_do_timer, &cpu, 1); |
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} |
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#endif |
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/* |
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* Setup the tick device |
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*/ |
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static void tick_setup_device(struct tick_device *td, |
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struct clock_event_device *newdev, int cpu, |
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const struct cpumask *cpumask) |
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{ |
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void (*handler)(struct clock_event_device *) = NULL; |
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ktime_t next_event = 0; |
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/* |
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* First device setup ? |
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*/ |
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if (!td->evtdev) { |
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/* |
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* If no cpu took the do_timer update, assign it to |
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* this cpu: |
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*/ |
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if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) { |
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tick_do_timer_cpu = cpu; |
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tick_next_period = ktime_get(); |
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#ifdef CONFIG_NO_HZ_FULL |
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/* |
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* The boot CPU may be nohz_full, in which case set |
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* tick_do_timer_boot_cpu so the first housekeeping |
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* secondary that comes up will take do_timer from |
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* us. |
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*/ |
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if (tick_nohz_full_cpu(cpu)) |
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tick_do_timer_boot_cpu = cpu; |
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} else if (tick_do_timer_boot_cpu != -1 && |
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!tick_nohz_full_cpu(cpu)) { |
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tick_take_do_timer_from_boot(); |
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tick_do_timer_boot_cpu = -1; |
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WARN_ON(tick_do_timer_cpu != cpu); |
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#endif |
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} |
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/* |
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* Startup in periodic mode first. |
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*/ |
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td->mode = TICKDEV_MODE_PERIODIC; |
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} else { |
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handler = td->evtdev->event_handler; |
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next_event = td->evtdev->next_event; |
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td->evtdev->event_handler = clockevents_handle_noop; |
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} |
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td->evtdev = newdev; |
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/* |
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* When the device is not per cpu, pin the interrupt to the |
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* current cpu: |
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*/ |
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if (!cpumask_equal(newdev->cpumask, cpumask)) |
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irq_set_affinity(newdev->irq, cpumask); |
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/* |
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* When global broadcasting is active, check if the current |
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* device is registered as a placeholder for broadcast mode. |
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* This allows us to handle this x86 misfeature in a generic |
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* way. This function also returns !=0 when we keep the |
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* current active broadcast state for this CPU. |
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*/ |
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if (tick_device_uses_broadcast(newdev, cpu)) |
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return; |
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if (td->mode == TICKDEV_MODE_PERIODIC) |
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tick_setup_periodic(newdev, 0); |
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else |
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tick_setup_oneshot(newdev, handler, next_event); |
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} |
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void tick_install_replacement(struct clock_event_device *newdev) |
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{ |
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struct tick_device *td = this_cpu_ptr(&tick_cpu_device); |
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int cpu = smp_processor_id(); |
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clockevents_exchange_device(td->evtdev, newdev); |
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tick_setup_device(td, newdev, cpu, cpumask_of(cpu)); |
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if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) |
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tick_oneshot_notify(); |
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} |
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static bool tick_check_percpu(struct clock_event_device *curdev, |
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struct clock_event_device *newdev, int cpu) |
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{ |
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if (!cpumask_test_cpu(cpu, newdev->cpumask)) |
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return false; |
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if (cpumask_equal(newdev->cpumask, cpumask_of(cpu))) |
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return true; |
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/* Check if irq affinity can be set */ |
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if (newdev->irq >= 0 && !irq_can_set_affinity(newdev->irq)) |
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return false; |
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/* Prefer an existing cpu local device */ |
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if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu))) |
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return false; |
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return true; |
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} |
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static bool tick_check_preferred(struct clock_event_device *curdev, |
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struct clock_event_device *newdev) |
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{ |
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/* Prefer oneshot capable device */ |
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if (!(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) { |
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if (curdev && (curdev->features & CLOCK_EVT_FEAT_ONESHOT)) |
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return false; |
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if (tick_oneshot_mode_active()) |
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return false; |
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} |
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/* |
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* Use the higher rated one, but prefer a CPU local device with a lower |
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* rating than a non-CPU local device |
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*/ |
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return !curdev || |
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newdev->rating > curdev->rating || |
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!cpumask_equal(curdev->cpumask, newdev->cpumask); |
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} |
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/* |
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* Check whether the new device is a better fit than curdev. curdev |
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* can be NULL ! |
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*/ |
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bool tick_check_replacement(struct clock_event_device *curdev, |
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struct clock_event_device *newdev) |
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{ |
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if (!tick_check_percpu(curdev, newdev, smp_processor_id())) |
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return false; |
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return tick_check_preferred(curdev, newdev); |
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} |
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/* |
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* Check, if the new registered device should be used. Called with |
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* clockevents_lock held and interrupts disabled. |
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*/ |
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void tick_check_new_device(struct clock_event_device *newdev) |
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{ |
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struct clock_event_device *curdev; |
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struct tick_device *td; |
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int cpu; |
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cpu = smp_processor_id(); |
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td = &per_cpu(tick_cpu_device, cpu); |
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curdev = td->evtdev; |
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if (!tick_check_replacement(curdev, newdev)) |
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goto out_bc; |
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if (!try_module_get(newdev->owner)) |
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return; |
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/* |
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* Replace the eventually existing device by the new |
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* device. If the current device is the broadcast device, do |
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* not give it back to the clockevents layer ! |
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*/ |
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if (tick_is_broadcast_device(curdev)) { |
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clockevents_shutdown(curdev); |
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curdev = NULL; |
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} |
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clockevents_exchange_device(curdev, newdev); |
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tick_setup_device(td, newdev, cpu, cpumask_of(cpu)); |
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if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) |
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tick_oneshot_notify(); |
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return; |
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out_bc: |
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/* |
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* Can the new device be used as a broadcast device ? |
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*/ |
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tick_install_broadcast_device(newdev, cpu); |
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} |
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/** |
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* tick_broadcast_oneshot_control - Enter/exit broadcast oneshot mode |
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* @state: The target state (enter/exit) |
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* |
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* The system enters/leaves a state, where affected devices might stop |
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* Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups. |
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* |
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* Called with interrupts disabled, so clockevents_lock is not |
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* required here because the local clock event device cannot go away |
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* under us. |
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*/ |
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int tick_broadcast_oneshot_control(enum tick_broadcast_state state) |
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{ |
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struct tick_device *td = this_cpu_ptr(&tick_cpu_device); |
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if (!(td->evtdev->features & CLOCK_EVT_FEAT_C3STOP)) |
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return 0; |
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return __tick_broadcast_oneshot_control(state); |
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} |
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EXPORT_SYMBOL_GPL(tick_broadcast_oneshot_control); |
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#ifdef CONFIG_HOTPLUG_CPU |
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/* |
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* Transfer the do_timer job away from a dying cpu. |
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* |
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* Called with interrupts disabled. No locking required. If |
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* tick_do_timer_cpu is owned by this cpu, nothing can change it. |
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*/ |
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void tick_handover_do_timer(void) |
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{ |
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if (tick_do_timer_cpu == smp_processor_id()) |
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tick_do_timer_cpu = cpumask_first(cpu_online_mask); |
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} |
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/* |
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* Shutdown an event device on a given cpu: |
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* |
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* This is called on a life CPU, when a CPU is dead. So we cannot |
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* access the hardware device itself. |
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* We just set the mode and remove it from the lists. |
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*/ |
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void tick_shutdown(unsigned int cpu) |
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{ |
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struct tick_device *td = &per_cpu(tick_cpu_device, cpu); |
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struct clock_event_device *dev = td->evtdev; |
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td->mode = TICKDEV_MODE_PERIODIC; |
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if (dev) { |
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/* |
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* Prevent that the clock events layer tries to call |
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* the set mode function! |
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*/ |
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clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED); |
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clockevents_exchange_device(dev, NULL); |
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dev->event_handler = clockevents_handle_noop; |
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td->evtdev = NULL; |
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} |
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} |
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#endif |
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/** |
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* tick_suspend_local - Suspend the local tick device |
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* |
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* Called from the local cpu for freeze with interrupts disabled. |
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* |
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* No locks required. Nothing can change the per cpu device. |
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*/ |
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void tick_suspend_local(void) |
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{ |
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struct tick_device *td = this_cpu_ptr(&tick_cpu_device); |
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clockevents_shutdown(td->evtdev); |
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} |
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/** |
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* tick_resume_local - Resume the local tick device |
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* |
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* Called from the local CPU for unfreeze or XEN resume magic. |
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* |
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* No locks required. Nothing can change the per cpu device. |
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*/ |
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void tick_resume_local(void) |
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{ |
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struct tick_device *td = this_cpu_ptr(&tick_cpu_device); |
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bool broadcast = tick_resume_check_broadcast(); |
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clockevents_tick_resume(td->evtdev); |
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if (!broadcast) { |
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if (td->mode == TICKDEV_MODE_PERIODIC) |
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tick_setup_periodic(td->evtdev, 0); |
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else |
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tick_resume_oneshot(); |
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} |
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} |
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/** |
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* tick_suspend - Suspend the tick and the broadcast device |
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* |
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* Called from syscore_suspend() via timekeeping_suspend with only one |
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* CPU online and interrupts disabled or from tick_unfreeze() under |
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* tick_freeze_lock. |
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* |
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* No locks required. Nothing can change the per cpu device. |
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*/ |
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void tick_suspend(void) |
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{ |
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tick_suspend_local(); |
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tick_suspend_broadcast(); |
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} |
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/** |
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* tick_resume - Resume the tick and the broadcast device |
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* |
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* Called from syscore_resume() via timekeeping_resume with only one |
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* CPU online and interrupts disabled. |
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* |
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* No locks required. Nothing can change the per cpu device. |
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*/ |
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void tick_resume(void) |
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{ |
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tick_resume_broadcast(); |
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tick_resume_local(); |
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} |
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#ifdef CONFIG_SUSPEND |
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static DEFINE_RAW_SPINLOCK(tick_freeze_lock); |
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static unsigned int tick_freeze_depth; |
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/** |
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* tick_freeze - Suspend the local tick and (possibly) timekeeping. |
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* |
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* Check if this is the last online CPU executing the function and if so, |
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* suspend timekeeping. Otherwise suspend the local tick. |
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* |
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* Call with interrupts disabled. Must be balanced with %tick_unfreeze(). |
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* Interrupts must not be enabled before the subsequent %tick_unfreeze(). |
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*/ |
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void tick_freeze(void) |
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{ |
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raw_spin_lock(&tick_freeze_lock); |
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tick_freeze_depth++; |
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if (tick_freeze_depth == num_online_cpus()) { |
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trace_suspend_resume(TPS("timekeeping_freeze"), |
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smp_processor_id(), true); |
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system_state = SYSTEM_SUSPEND; |
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sched_clock_suspend(); |
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timekeeping_suspend(); |
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} else { |
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tick_suspend_local(); |
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} |
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raw_spin_unlock(&tick_freeze_lock); |
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} |
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/** |
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* tick_unfreeze - Resume the local tick and (possibly) timekeeping. |
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* |
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* Check if this is the first CPU executing the function and if so, resume |
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* timekeeping. Otherwise resume the local tick. |
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* |
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* Call with interrupts disabled. Must be balanced with %tick_freeze(). |
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* Interrupts must not be enabled after the preceding %tick_freeze(). |
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*/ |
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void tick_unfreeze(void) |
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{ |
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raw_spin_lock(&tick_freeze_lock); |
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if (tick_freeze_depth == num_online_cpus()) { |
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timekeeping_resume(); |
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sched_clock_resume(); |
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system_state = SYSTEM_RUNNING; |
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trace_suspend_resume(TPS("timekeeping_freeze"), |
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smp_processor_id(), false); |
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} else { |
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touch_softlockup_watchdog(); |
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tick_resume_local(); |
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} |
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tick_freeze_depth--; |
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raw_spin_unlock(&tick_freeze_lock); |
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} |
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#endif /* CONFIG_SUSPEND */ |
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/** |
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* tick_init - initialize the tick control |
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*/ |
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void __init tick_init(void) |
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{ |
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tick_broadcast_init(); |
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tick_nohz_init(); |
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}
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