arch/um/os-Linux/time.c

   1 /*
   2  * Copyright (C) 2000 - 2007 Jeff Dike (jdike{addtoit,linux.intel}.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include <stddef.h>
   7 #include <errno.h>
   8 #include <signal.h>
   9 #include <time.h>
  10 #include <sys/time.h>
  11 #include "kern_constants.h"
  12 #include "os.h"
  13 #include "user.h"
  14
  15 int set_interval(void)
  16 {
  17         int usec = UM_USEC_PER_SEC / UM_HZ;
  18         struct itimerval interval = ((struct itimerval) { { 0, usec },
  19                                                           { 0, usec } });
  20
  21         if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
  22                 return -errno;
  23
  24         return 0;
  25 }
  26
  27 int timer_one_shot(int ticks)
  28 {
  29         unsigned long usec = ticks * UM_USEC_PER_SEC / UM_HZ;
  30         unsigned long sec = usec / UM_USEC_PER_SEC;
  31         struct itimerval interval;
  32
  33         usec %= UM_USEC_PER_SEC;
  34         interval = ((struct itimerval) { { 0, 0 }, { sec, usec } });
  35
  36         if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
  37                 return -errno;
  38
  39         return 0;
  40 }
  41
  42 /**
  43  * timeval_to_ns - Convert timeval to nanoseconds
  44  * @ts:         pointer to the timeval variable to be converted
  45  *
  46  * Returns the scalar nanosecond representation of the timeval
  47  * parameter.
  48  *
  49  * Ripped from linux/time.h because it's a kernel header, and thus
  50  * unusable from here.
  51  */
  52 static inline long long timeval_to_ns(const struct timeval *tv)
  53 {
  54         return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
  55                 tv->tv_usec * UM_NSEC_PER_USEC;
  56 }
  57
  58 long long disable_timer(void)
  59 {
  60         struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } });
  61
  62         if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0)
  63                 printk(UM_KERN_ERR "disable_timer - setitimer failed, "
  64                        "errno = %d\n", errno);
  65
  66         return timeval_to_ns(&time.it_value);
  67 }
  68
  69 long long os_nsecs(void)
  70 {
  71         struct timeval tv;
  72
  73         gettimeofday(&tv, NULL);
  74         return timeval_to_ns(&tv);
  75 }
  76
  77 #ifdef UML_CONFIG_NO_HZ
  78 static int after_sleep_interval(struct timespec *ts)
  79 {
  80         return 0;
  81 }
  82 #else
  83 static inline long long timespec_to_us(const struct timespec *ts)
  84 {
  85         return ((long long) ts->tv_sec * UM_USEC_PER_SEC) +
  86                 ts->tv_nsec / UM_NSEC_PER_USEC;
  87 }
  88
  89 static int after_sleep_interval(struct timespec *ts)
  90 {
  91         int usec = UM_USEC_PER_SEC / UM_HZ;
  92         long long start_usecs = timespec_to_us(ts);
  93         struct timeval tv;
  94         struct itimerval interval;
  95
  96         /*
  97          * It seems that rounding can increase the value returned from
  98          * setitimer to larger than the one passed in.  Over time,
  99          * this will cause the remaining time to be greater than the
 100          * tick interval.  If this happens, then just reduce the first
 101          * tick to the interval value.
 102          */
 103         if (start_usecs > usec)
 104                 start_usecs = usec;
 105         tv = ((struct timeval) { .tv_sec  = start_usecs / UM_USEC_PER_SEC,
 106                                  .tv_usec = start_usecs % UM_USEC_PER_SEC });
 107         interval = ((struct itimerval) { { 0, usec }, tv });
 108
 109         if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
 110                 return -errno;
 111
 112         return 0;
 113 }
 114 #endif
 115
 116 extern void alarm_handler(int sig, struct sigcontext *sc);
 117
 118 void idle_sleep(unsigned long long nsecs)
 119 {
 120         struct timespec ts;
 121
 122         /*
 123          * nsecs can come in as zero, in which case, this starts a
 124          * busy loop.  To prevent this, reset nsecs to the tick
 125          * interval if it is zero.
 126          */
 127         if (nsecs == 0)
 128                 nsecs = UM_NSEC_PER_SEC / UM_HZ;
 129         ts = ((struct timespec) { .tv_sec       = nsecs / UM_NSEC_PER_SEC,
 130                                   .tv_nsec      = nsecs % UM_NSEC_PER_SEC });
 131
 132         if (nanosleep(&ts, &ts) == 0)
 133                 alarm_handler(SIGVTALRM, NULL);
 134         after_sleep_interval(&ts);
 135 }