clockevents: prevent endless loop lockup
[linux-2.6.git] / kernel / time / tick-oneshot.c
1 /*
2  * linux/kernel/time/tick-oneshot.c
3  *
4  * This file contains functions which manage high resolution tick
5  * related events.
6  *
7  * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
8  * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
9  * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
10  *
11  * This code is licenced under the GPL version 2. For details see
12  * kernel-base/COPYING.
13  */
14 #include <linux/cpu.h>
15 #include <linux/err.h>
16 #include <linux/hrtimer.h>
17 #include <linux/interrupt.h>
18 #include <linux/percpu.h>
19 #include <linux/profile.h>
20 #include <linux/sched.h>
21 #include <linux/tick.h>
22
23 #include "tick-internal.h"
24
25 /**
26  * tick_program_event internal worker function
27  */
28 int tick_dev_program_event(struct clock_event_device *dev, ktime_t expires,
29                            int force)
30 {
31         ktime_t now = ktime_get();
32         int i;
33
34         for (i = 0;;) {
35                 int ret = clockevents_program_event(dev, expires, now);
36
37                 if (!ret || !force)
38                         return ret;
39
40                 /*
41                  * We tried 2 times to program the device with the given
42                  * min_delta_ns. If that's not working then we double it
43                  * and emit a warning.
44                  */
45                 if (++i > 2) {
46                         printk(KERN_WARNING "CE: __tick_program_event of %s is "
47                                "stuck %llx %llx\n", dev->name ? dev->name : "?",
48                                now.tv64, expires.tv64);
49                         printk(KERN_WARNING
50                                "CE: increasing min_delta_ns %ld to %ld nsec\n",
51                                dev->min_delta_ns, dev->min_delta_ns << 1);
52                         WARN_ON(1);
53
54                         /* Double the min. delta and try again */
55                         if (!dev->min_delta_ns)
56                                 dev->min_delta_ns = 5000;
57                         else
58                                 dev->min_delta_ns <<= 1;
59                         i = 0;
60                 }
61
62                 now = ktime_get();
63                 expires = ktime_add_ns(now, dev->min_delta_ns);
64         }
65 }
66
67 /**
68  * tick_program_event
69  */
70 int tick_program_event(ktime_t expires, int force)
71 {
72         struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
73
74         return tick_dev_program_event(dev, expires, force);
75 }
76
77 /**
78  * tick_resume_onshot - resume oneshot mode
79  */
80 void tick_resume_oneshot(void)
81 {
82         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
83         struct clock_event_device *dev = td->evtdev;
84
85         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
86         tick_program_event(ktime_get(), 1);
87 }
88
89 /**
90  * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
91  */
92 void tick_setup_oneshot(struct clock_event_device *newdev,
93                         void (*handler)(struct clock_event_device *),
94                         ktime_t next_event)
95 {
96         newdev->event_handler = handler;
97         clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT);
98         tick_dev_program_event(newdev, next_event, 1);
99 }
100
101 /**
102  * tick_switch_to_oneshot - switch to oneshot mode
103  */
104 int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
105 {
106         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
107         struct clock_event_device *dev = td->evtdev;
108
109         if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
110                     !tick_device_is_functional(dev)) {
111
112                 printk(KERN_INFO "Clockevents: "
113                        "could not switch to one-shot mode:");
114                 if (!dev) {
115                         printk(" no tick device\n");
116                 } else {
117                         if (!tick_device_is_functional(dev))
118                                 printk(" %s is not functional.\n", dev->name);
119                         else
120                                 printk(" %s does not support one-shot mode.\n",
121                                        dev->name);
122                 }
123                 return -EINVAL;
124         }
125
126         td->mode = TICKDEV_MODE_ONESHOT;
127         dev->event_handler = handler;
128         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
129         tick_broadcast_switch_to_oneshot();
130         return 0;
131 }
132
133 #ifdef CONFIG_HIGH_RES_TIMERS
134 /**
135  * tick_init_highres - switch to high resolution mode
136  *
137  * Called with interrupts disabled.
138  */
139 int tick_init_highres(void)
140 {
141         return tick_switch_to_oneshot(hrtimer_interrupt);
142 }
143 #endif