diff options
Diffstat (limited to 'kernel/time/tick-common.c')
| -rw-r--r-- | kernel/time/tick-common.c | 277 |
1 files changed, 277 insertions, 0 deletions
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c new file mode 100644 index 0000000..46e4381 --- /dev/null +++ b/kernel/time/tick-common.c @@ -0,0 +1,277 @@ +/* + * 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/irq.h> +#include <linux/percpu.h> +#include <linux/profile.h> +#include <linux/sched.h> +#include <linux/tick.h> + +/* + * Tick devices + */ +static DEFINE_PER_CPU(struct tick_device, tick_cpu_device); +/* + * Tick next event: keeps track of the tick time + */ +static ktime_t tick_next_period; +static ktime_t tick_period; +static int tick_do_timer_cpu = -1; +static DEFINE_SPINLOCK(tick_device_lock); + +/* + * Periodic tick + */ +static void tick_periodic(int cpu) +{ + if (tick_do_timer_cpu == cpu) { + write_seqlock(&xtime_lock); + + /* Keep track of the next tick event */ + tick_next_period = ktime_add(tick_next_period, tick_period); + + do_timer(1); + write_sequnlock(&xtime_lock); + } + + 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(); + + tick_periodic(cpu); + + if (dev->mode != CLOCK_EVT_MODE_ONESHOT) + return; + /* + * Setup the next period for devices, which do not have + * periodic mode: + */ + for (;;) { + ktime_t next = ktime_add(dev->next_event, tick_period); + + if (!clockevents_program_event(dev, next, ktime_get())) + return; + tick_periodic(cpu); + } +} + +/* + * Setup the device for a periodic tick + */ +void tick_setup_periodic(struct clock_event_device *dev) +{ + dev->event_handler = tick_handle_periodic; + + if (dev->features & CLOCK_EVT_FEAT_PERIODIC) { + clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC); + } else { + unsigned long seq; + ktime_t next; + + do { + seq = read_seqbegin(&xtime_lock); + next = tick_next_period; + } while (read_seqretry(&xtime_lock, seq)); + + clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); + + for (;;) { + if (!clockevents_program_event(dev, next, ktime_get())) + 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, + cpumask_t 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 == -1) { + tick_do_timer_cpu = cpu; + 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 = newdev; + + /* + * When the device is not per cpu, pin the interrupt to the + * current cpu: + */ + if (!cpus_equal(newdev->cpumask, cpumask)) + irq_set_affinity(newdev->irq, cpumask); + + if (td->mode == TICKDEV_MODE_PERIODIC) + tick_setup_periodic(newdev, 0); +} + +/* + * Check, if the new registered device should be used. + */ +static int tick_check_new_device(struct clock_event_device *newdev) +{ + struct clock_event_device *curdev; + struct tick_device *td; + int cpu, ret = NOTIFY_OK; + unsigned long flags; + cpumask_t cpumask; + + spin_lock_irqsave(&tick_device_lock, flags); + + cpu = smp_processor_id(); + if (!cpu_isset(cpu, newdev->cpumask)) + goto out; + + td = &per_cpu(tick_cpu_device, cpu); + curdev = td->evtdev; + cpumask = cpumask_of_cpu(cpu); + + /* cpu local device ? */ + if (!cpus_equal(newdev->cpumask, cpumask)) { + + /* + * If the cpu affinity of the device interrupt can not + * be set, ignore it. + */ + if (!irq_can_set_affinity(newdev->irq)) + goto out_bc; + + /* + * If we have a cpu local device already, do not replace it + * by a non cpu local device + */ + if (curdev && cpus_equal(curdev->cpumask, cpumask)) + goto out_bc; + } + + /* + * If we have an active device, then check the rating and the oneshot + * feature. + */ + if (curdev) { + /* + * Check the rating + */ + if (curdev->rating >= newdev->rating) + goto out; + } + + /* + * Replace the eventually existing device by the new + * device. + */ + clockevents_exchange_device(curdev, newdev); + tick_setup_device(td, newdev, cpu, cpumask); + ret = NOTIFY_STOP; + +out: + spin_unlock_irqrestore(&tick_device_lock, flags); + return ret; +} + +/* + * 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. + */ +static void tick_shutdown(unsigned int *cpup) +{ + struct tick_device *td = &per_cpu(tick_cpu_device, *cpup); + struct clock_event_device *dev = td->evtdev; + unsigned long flags; + + spin_lock_irqsave(&tick_device_lock, flags); + td->mode = TICKDEV_MODE_PERIODIC; + if (dev) { + /* + * Prevent that the clock events layer tries to call + * the set mode function! + */ + dev->mode = CLOCK_EVT_MODE_UNUSED; + clockevents_exchange_device(dev, NULL); + td->evtdev = NULL; + } + spin_unlock_irqrestore(&tick_device_lock, flags); +} + +/* + * Notification about clock event devices + */ +static int tick_notify(struct notifier_block *nb, unsigned long reason, + void *dev) +{ + switch (reason) { + + case CLOCK_EVT_NOTIFY_ADD: + return tick_check_new_device(dev); + + case CLOCK_EVT_NOTIFY_CPU_DEAD: + tick_shutdown(dev); + break; + + default: + break; + } + + return NOTIFY_OK; +} + +static struct notifier_block tick_notifier = { + .notifier_call = tick_notify, +}; + +/** + * tick_init - initialize the tick control + * + * Register the notifier with the clockevents framework + */ +void __init tick_init(void) +{ + clockevents_register_notifier(&tick_notifier); +} |
