time.c
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/*
* Copyright (C) 2000 - 2007 Jeff Dike (jdike{addtoit,linux.intel}.com)
* Licensed under the GPL
*/
#include <stddef.h>
#include <errno.h>
#include <signal.h>
#include <time.h>
#include <sys/time.h>
#include "kern_util.h"
#include "os.h"
#include "internal.h"
int set_interval(void)
{
int usec = UM_USEC_PER_SEC / UM_HZ;
struct itimerval interval = ((struct itimerval) { { 0, usec },
{ 0, usec } });
if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
return -errno;
return 0;
}
int timer_one_shot(int ticks)
{
unsigned long usec = ticks * UM_USEC_PER_SEC / UM_HZ;
unsigned long sec = usec / UM_USEC_PER_SEC;
struct itimerval interval;
usec %= UM_USEC_PER_SEC;
interval = ((struct itimerval) { { 0, 0 }, { sec, usec } });
if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
return -errno;
return 0;
}
/**
* timeval_to_ns - Convert timeval to nanoseconds
* @ts: pointer to the timeval variable to be converted
*
* Returns the scalar nanosecond representation of the timeval
* parameter.
*
* Ripped from linux/time.h because it's a kernel header, and thus
* unusable from here.
*/
static inline long long timeval_to_ns(const struct timeval *tv)
{
return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
tv->tv_usec * UM_NSEC_PER_USEC;
}
long long disable_timer(void)
{
struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } });
long long remain, max = UM_NSEC_PER_SEC / UM_HZ;
if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0)
printk(UM_KERN_ERR "disable_timer - setitimer failed, "
"errno = %d\n", errno);
remain = timeval_to_ns(&time.it_value);
if (remain > max)
remain = max;
return remain;
}
long long os_nsecs(void)
{
struct timeval tv;
gettimeofday(&tv, NULL);
return timeval_to_ns(&tv);
}
#ifdef UML_CONFIG_NO_HZ
static int after_sleep_interval(struct timespec *ts)
{
return 0;
}
static void deliver_alarm(void)
{
alarm_handler(SIGVTALRM, NULL);
}
static unsigned long long sleep_time(unsigned long long nsecs)
{
return nsecs;
}
#else
unsigned long long last_tick;
unsigned long long skew;
static void deliver_alarm(void)
{
unsigned long long this_tick = os_nsecs();
int one_tick = UM_NSEC_PER_SEC / UM_HZ;
/* Protection against the host's time going backwards */
if ((last_tick != 0) && (this_tick < last_tick))
this_tick = last_tick;
if (last_tick == 0)
last_tick = this_tick - one_tick;
skew += this_tick - last_tick;
while (skew >= one_tick) {
alarm_handler(SIGVTALRM, NULL);
skew -= one_tick;
}
last_tick = this_tick;
}
static unsigned long long sleep_time(unsigned long long nsecs)
{
return nsecs > skew ? nsecs - skew : 0;
}
static inline long long timespec_to_us(const struct timespec *ts)
{
return ((long long) ts->tv_sec * UM_USEC_PER_SEC) +
ts->tv_nsec / UM_NSEC_PER_USEC;
}
static int after_sleep_interval(struct timespec *ts)
{
int usec = UM_USEC_PER_SEC / UM_HZ;
long long start_usecs = timespec_to_us(ts);
struct timeval tv;
struct itimerval interval;
/*
* It seems that rounding can increase the value returned from
* setitimer to larger than the one passed in. Over time,
* this will cause the remaining time to be greater than the
* tick interval. If this happens, then just reduce the first
* tick to the interval value.
*/
if (start_usecs > usec)
start_usecs = usec;
start_usecs -= skew / UM_NSEC_PER_USEC;
if (start_usecs < 0)
start_usecs = 0;
tv = ((struct timeval) { .tv_sec = start_usecs / UM_USEC_PER_SEC,
.tv_usec = start_usecs % UM_USEC_PER_SEC });
interval = ((struct itimerval) { { 0, usec }, tv });
if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
return -errno;
return 0;
}
#endif
void idle_sleep(unsigned long long nsecs)
{
struct timespec ts;
/*
* nsecs can come in as zero, in which case, this starts a
* busy loop. To prevent this, reset nsecs to the tick
* interval if it is zero.
*/
if (nsecs == 0)
nsecs = UM_NSEC_PER_SEC / UM_HZ;
nsecs = sleep_time(nsecs);
ts = ((struct timespec) { .tv_sec = nsecs / UM_NSEC_PER_SEC,
.tv_nsec = nsecs % UM_NSEC_PER_SEC });
if (nanosleep(&ts, &ts) == 0)
deliver_alarm();
after_sleep_interval(&ts);
}