[patch 34/46] tick-management: core functionality

Thomas Gleixner
2007-01-23T22:08:05Z

[-- Attachment #1: tick-management-core.patch --]
[-- Type: text/plain, Size: 8419 bytes --]

From: Thomas Gleixner <tglx@linutronix.de>
From: Ingo Molnar <mingo@elte.hu>

The tick-management code is the first user of the clockevents layer.
It takes clock event devices from the clock events core and uses them
to provide the periodic tick.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
include/linux/tick.h | 25 ++++
init/main.c | 2
kernel/time/Makefile | 3
kernel/time/tick-common.c | 273 ++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 302 insertions(+), 1 deletion(-)

Index: linux-2.6.20-rc4-mm1-bo/include/linux/tick.h
===================================================================
--- /dev/null
+++ linux-2.6.20-rc4-mm1-bo/include/linux/tick.h
@@ -0,0 +1,25 @@
+/* linux/include/linux/tick.h
+ *
+ * This file contains the structure definitions for tick related functions
+ *
+ */
+#ifndef _LINUX_TICK_H
+#define _LINUX_TICK_H
+
+#include <linux/clockchips.h>
+
+#ifdef CONFIG_GENERIC_CLOCKEVENTS
+
+enum tick_device_mode {
+ TICKDEV_MODE_PERIODIC,
+ TICKDEV_MODE_ONESHOT,
+};
+
+struct tick_device {
+ struct clock_event_device *evtdev;
+ enum tick_device_mode mode;
+};
+
+extern void __init tick_init(void);
+
+#endif
Index: linux-2.6.20-rc4-mm1-bo/init/main.c
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/init/main.c
+++ linux-2.6.20-rc4-mm1-bo/init/main.c
@@ -40,6 +40,7 @@
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/efi.h>
+#include <linux/tick.h>
#include <linux/taskstats_kern.h>
#include <linux/delayacct.h>
#include <linux/unistd.h>
@@ -503,6 +504,7 @@ asmlinkage void __init start_kernel(void
* enable them
*/
lock_kernel();
+ tick_init();
boot_cpu_init();
page_address_init();
printk(KERN_NOTICE);
Index: linux-2.6.20-rc4-mm1-bo/kernel/time/Makefile
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/kernel/time/Makefile
+++ linux-2.6.20-rc4-mm1-bo/kernel/time/Makefile
@@ -1,3 +1,4 @@
obj-y += ntp.o clocksource.o jiffies.o

-obj-$(CONFIG_GENERIC_CLOCKEVENTS) += clockevents.o
+obj-$(CONFIG_GENERIC_CLOCKEVENTS) += clockevents.o
+obj-$(CONFIG_GENERIC_CLOCKEVENTS) += tick-common.o
Index: linux-2.6.20-rc4-mm1-bo/kernel/time/tick-common.c
===================================================================
--- /dev/null
+++ linux-2.6.20-rc4-mm1-bo/kernel/time/tick-common.c
@@ -0,0 +1,273 @@
+/*
+ * 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))
+ 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))
+ 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;
+}
+
+/*
+ * Called with irqs disabled
+ */
+static inline void tick_do_resume(int cpu)
+{
+ struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
+
+ if (td->mode == TICKDEV_MODE_PERIODIC)
+ tick_setup_periodic(td->evtdev, 0);
+}
+
+/*
+ * Resume tick devices
+ */
+static void tick_resume(void)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&tick_device_lock, flags);
+ tick_do_resume(smp_processor_id());
+ 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_RESUME:
+ tick_resume();
+ 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);
+}

--