[PATCH] tick-management: core functionality

With 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>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/tick.h b/include/linux/tick.h
new file mode 100644 (file)
index 0000000..e5c0a4e
--- /dev/null
+++ b/include/linux/tick.h
@@ -0,0 +1,31 @@
+/*  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);
+
+#else
+
+static inline void tick_init(void) { }
+
+#endif
+
+#endif

diff --git a/init/main.c b/init/main.c
index 2421e1544127e155207e593e86e6162dcc5b37c3..953500b02ac4136f4ad30aa0ea6b285019234131 100644 (file)
--- a/init/main.c
+++ b/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>
@@ -515,6 +516,7 @@ asmlinkage void __init start_kernel(void)
  * enable them
  */
        lock_kernel();
+       tick_init();
        boot_cpu_init();
        page_address_init();
        printk(KERN_NOTICE);

diff --git a/kernel/time/Makefile b/kernel/time/Makefile
index 2bf1805914d0ce7183d7d5b10d33eabc60962239..337daef72755efb110688374363c5002a829d1b4 100644 (file)
--- a/kernel/time/Makefile
+++ b/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

diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
new file mode 100644 (file)
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);
+}