2 * Copyright (C) 2000 - 2007 Jeff Dike (jdike{addtoit,linux.intel}.com)
3 * Licensed under the GPL
11 #include "kern_constants.h"
12 #include "kern_util.h"
17 int set_interval(void)
19 int usec = UM_USEC_PER_SEC / UM_HZ;
20 struct itimerval interval = ((struct itimerval) { { 0, usec },
23 if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
29 int timer_one_shot(int ticks)
31 unsigned long usec = ticks * UM_USEC_PER_SEC / UM_HZ;
32 unsigned long sec = usec / UM_USEC_PER_SEC;
33 struct itimerval interval;
35 usec %= UM_USEC_PER_SEC;
36 interval = ((struct itimerval) { { 0, 0 }, { sec, usec } });
38 if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
45 * timeval_to_ns - Convert timeval to nanoseconds
46 * @ts: pointer to the timeval variable to be converted
48 * Returns the scalar nanosecond representation of the timeval
51 * Ripped from linux/time.h because it's a kernel header, and thus
54 static inline long long timeval_to_ns(const struct timeval *tv)
56 return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
57 tv->tv_usec * UM_NSEC_PER_USEC;
60 long long disable_timer(void)
62 struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } });
63 int remain, max = UM_NSEC_PER_SEC / UM_HZ;
65 if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0)
66 printk(UM_KERN_ERR "disable_timer - setitimer failed, "
67 "errno = %d\n", errno);
69 remain = timeval_to_ns(&time.it_value);
76 long long os_nsecs(void)
80 gettimeofday(&tv, NULL);
81 return timeval_to_ns(&tv);
84 #ifdef UML_CONFIG_NO_HZ
85 static int after_sleep_interval(struct timespec *ts)
90 static void deliver_alarm(void)
92 alarm_handler(SIGVTALRM, NULL);
95 static unsigned long long sleep_time(unsigned long long nsecs)
101 unsigned long long last_tick;
102 unsigned long long skew;
104 static void deliver_alarm(void)
106 unsigned long long this_tick = os_nsecs();
107 int one_tick = UM_NSEC_PER_SEC / UM_HZ;
110 last_tick = this_tick - one_tick;
112 skew += this_tick - last_tick;
114 while (skew >= one_tick) {
115 alarm_handler(SIGVTALRM, NULL);
119 last_tick = this_tick;
122 static unsigned long long sleep_time(unsigned long long nsecs)
124 return nsecs > skew ? nsecs - skew : 0;
127 static inline long long timespec_to_us(const struct timespec *ts)
129 return ((long long) ts->tv_sec * UM_USEC_PER_SEC) +
130 ts->tv_nsec / UM_NSEC_PER_USEC;
133 static int after_sleep_interval(struct timespec *ts)
135 int usec = UM_USEC_PER_SEC / UM_HZ;
136 long long start_usecs = timespec_to_us(ts);
138 struct itimerval interval;
141 * It seems that rounding can increase the value returned from
142 * setitimer to larger than the one passed in. Over time,
143 * this will cause the remaining time to be greater than the
144 * tick interval. If this happens, then just reduce the first
145 * tick to the interval value.
147 if (start_usecs > usec)
150 start_usecs -= skew / UM_NSEC_PER_USEC;
151 tv = ((struct timeval) { .tv_sec = start_usecs / UM_USEC_PER_SEC,
152 .tv_usec = start_usecs % UM_USEC_PER_SEC });
153 interval = ((struct itimerval) { { 0, usec }, tv });
155 if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
162 void idle_sleep(unsigned long long nsecs)
167 * nsecs can come in as zero, in which case, this starts a
168 * busy loop. To prevent this, reset nsecs to the tick
169 * interval if it is zero.
172 nsecs = UM_NSEC_PER_SEC / UM_HZ;
174 nsecs = sleep_time(nsecs);
175 ts = ((struct timespec) { .tv_sec = nsecs / UM_NSEC_PER_SEC,
176 .tv_nsec = nsecs % UM_NSEC_PER_SEC });
178 if (nanosleep(&ts, &ts) == 0)
180 after_sleep_interval(&ts);