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_util.h"
  12 #include "os.h"
  13 #include "internal.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         long long remain, max = UM_NSEC_PER_SEC / UM_HZ;
  62
  63         if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0)
  64                 printk(UM_KERN_ERR "disable_timer - setitimer failed, "
  65                        "errno = %d\n", errno);
  66
  67         remain = timeval_to_ns(&time.it_value);
  68         if (remain > max)
  69                 remain = max;
  70
  71         return remain;
  72 }
  73
  74 long long os_nsecs(void)
  75 {
  76         struct timeval tv;
  77
  78         gettimeofday(&tv, NULL);
  79         return timeval_to_ns(&tv);
  80 }
  81
  82 #ifdef UML_CONFIG_NO_HZ
  83 static int after_sleep_interval(struct timespec *ts)
  84 {
  85         return 0;
  86 }
  87
  88 static void deliver_alarm(void)
  89 {
  90         alarm_handler(SIGVTALRM, NULL);
  91 }
  92
  93 static unsigned long long sleep_time(unsigned long long nsecs)
  94 {
  95         return nsecs;
  96 }
  97
  98 #else
  99 unsigned long long last_tick;
 100 unsigned long long skew;
 101
 102 static void deliver_alarm(void)
 103 {
 104         unsigned long long this_tick = os_nsecs();
 105         int one_tick = UM_NSEC_PER_SEC / UM_HZ;
 106
 107         /* Protection against the host's time going backwards */
 108         if ((last_tick != 0) && (this_tick < last_tick))
 109                 this_tick = last_tick;
 110
 111         if (last_tick == 0)
 112                 last_tick = this_tick - one_tick;
 113
 114         skew += this_tick - last_tick;
 115
 116         while (skew >= one_tick) {
 117                 alarm_handler(SIGVTALRM, NULL);
 118                 skew -= one_tick;
 119         }
 120
 121         last_tick = this_tick;
 122 }
 123
 124 static unsigned long long sleep_time(unsigned long long nsecs)
 125 {
 126         return nsecs > skew ? nsecs - skew : 0;
 127 }
 128
 129 static inline long long timespec_to_us(const struct timespec *ts)
 130 {
 131         return ((long long) ts->tv_sec * UM_USEC_PER_SEC) +
 132                 ts->tv_nsec / UM_NSEC_PER_USEC;
 133 }
 134
 135 static int after_sleep_interval(struct timespec *ts)
 136 {
 137         int usec = UM_USEC_PER_SEC / UM_HZ;
 138         long long start_usecs = timespec_to_us(ts);
 139         struct timeval tv;
 140         struct itimerval interval;
 141
 142         /*
 143          * It seems that rounding can increase the value returned from
 144          * setitimer to larger than the one passed in.  Over time,
 145          * this will cause the remaining time to be greater than the
 146          * tick interval.  If this happens, then just reduce the first
 147          * tick to the interval value.
 148          */
 149         if (start_usecs > usec)
 150                 start_usecs = usec;
 151
 152         start_usecs -= skew / UM_NSEC_PER_USEC;
 153         if (start_usecs < 0)
 154                 start_usecs = 0;
 155
 156         tv = ((struct timeval) { .tv_sec  = start_usecs / UM_USEC_PER_SEC,
 157                                  .tv_usec = start_usecs % UM_USEC_PER_SEC });
 158         interval = ((struct itimerval) { { 0, usec }, tv });
 159
 160         if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
 161                 return -errno;
 162
 163         return 0;
 164 }
 165 #endif
 166
 167 void idle_sleep(unsigned long long nsecs)
 168 {
 169         struct timespec ts;
 170
 171         /*
 172          * nsecs can come in as zero, in which case, this starts a
 173          * busy loop.  To prevent this, reset nsecs to the tick
 174          * interval if it is zero.
 175          */
 176         if (nsecs == 0)
 177                 nsecs = UM_NSEC_PER_SEC / UM_HZ;
 178
 179         nsecs = sleep_time(nsecs);
 180         ts = ((struct timespec) { .tv_sec       = nsecs / UM_NSEC_PER_SEC,
 181                                   .tv_nsec      = nsecs % UM_NSEC_PER_SEC });
 182
 183         if (nanosleep(&ts, &ts) == 0)
 184                 deliver_alarm();
 185         after_sleep_interval(&ts);
 186 }