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 "kern_util.h"
  13 #include "os.h"
  14 #include "process.h"
  15 #include "user.h"
  16
  17 int set_interval(void)
  18 {
  19         int usec = UM_USEC_PER_SEC / UM_HZ;
  20         struct itimerval interval = ((struct itimerval) { { 0, usec },
  21                                                           { 0, usec } });
  22
  23         if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
  24                 return -errno;
  25
  26         return 0;
  27 }
  28
  29 int timer_one_shot(int ticks)
  30 {
  31         unsigned long usec = ticks * UM_USEC_PER_SEC / UM_HZ;
  32         unsigned long sec = usec / UM_USEC_PER_SEC;
  33         struct itimerval interval;
  34
  35         usec %= UM_USEC_PER_SEC;
  36         interval = ((struct itimerval) { { 0, 0 }, { sec, usec } });
  37
  38         if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
  39                 return -errno;
  40
  41         return 0;
  42 }
  43
  44 /**
  45  * timeval_to_ns - Convert timeval to nanoseconds
  46  * @ts:         pointer to the timeval variable to be converted
  47  *
  48  * Returns the scalar nanosecond representation of the timeval
  49  * parameter.
  50  *
  51  * Ripped from linux/time.h because it's a kernel header, and thus
  52  * unusable from here.
  53  */
  54 static inline long long timeval_to_ns(const struct timeval *tv)
  55 {
  56         return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
  57                 tv->tv_usec * UM_NSEC_PER_USEC;
  58 }
  59
  60 long long disable_timer(void)
  61 {
  62         struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } });
  63         int remain, max = UM_NSEC_PER_SEC / UM_HZ;
  64
  65         if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0)
  66                 printk(UM_KERN_ERR "disable_timer - setitimer failed, "
  67                        "errno = %d\n", errno);
  68
  69         remain = timeval_to_ns(&time.it_value);
  70         if (remain > max)
  71                 remain = max;
  72
  73         return remain;
  74 }
  75
  76 long long os_nsecs(void)
  77 {
  78         struct timeval tv;
  79
  80         gettimeofday(&tv, NULL);
  81         return timeval_to_ns(&tv);
  82 }
  83
  84 #ifdef UML_CONFIG_NO_HZ
  85 static int after_sleep_interval(struct timespec *ts)
  86 {
  87         return 0;
  88 }
  89
  90 static void deliver_alarm(void)
  91 {
  92         alarm_handler(SIGVTALRM, NULL);
  93 }
  94
  95 static unsigned long long sleep_time(unsigned long long nsecs)
  96 {
  97         return nsecs;
  98 }
  99
 100 #else
 101 unsigned long long last_tick;
 102 unsigned long long skew;
 103
 104 static void deliver_alarm(void)
 105 {
 106         unsigned long long this_tick = os_nsecs();
 107         int one_tick = UM_NSEC_PER_SEC / UM_HZ;
 108
 109         /* Protection against the host's time going backwards */
 110         if ((last_tick != 0) && (this_tick < last_tick))
 111                 this_tick = last_tick;
 112
 113         if (last_tick == 0)
 114                 last_tick = this_tick - one_tick;
 115
 116         skew += this_tick - last_tick;
 117
 118         while (skew >= one_tick) {
 119                 alarm_handler(SIGVTALRM, NULL);
 120                 skew -= one_tick;
 121         }
 122
 123         last_tick = this_tick;
 124 }
 125
 126 static unsigned long long sleep_time(unsigned long long nsecs)
 127 {
 128         return nsecs > skew ? nsecs - skew : 0;
 129 }
 130
 131 static inline long long timespec_to_us(const struct timespec *ts)
 132 {
 133         return ((long long) ts->tv_sec * UM_USEC_PER_SEC) +
 134                 ts->tv_nsec / UM_NSEC_PER_USEC;
 135 }
 136
 137 static int after_sleep_interval(struct timespec *ts)
 138 {
 139         int usec = UM_USEC_PER_SEC / UM_HZ;
 140         long long start_usecs = timespec_to_us(ts);
 141         struct timeval tv;
 142         struct itimerval interval;
 143
 144         /*
 145          * It seems that rounding can increase the value returned from
 146          * setitimer to larger than the one passed in.  Over time,
 147          * this will cause the remaining time to be greater than the
 148          * tick interval.  If this happens, then just reduce the first
 149          * tick to the interval value.
 150          */
 151         if (start_usecs > usec)
 152                 start_usecs = usec;
 153
 154         start_usecs -= skew / UM_NSEC_PER_USEC;
 155         if (start_usecs < 0)
 156                 start_usecs = 0;
 157
 158         tv = ((struct timeval) { .tv_sec  = start_usecs / UM_USEC_PER_SEC,
 159                                  .tv_usec = start_usecs % UM_USEC_PER_SEC });
 160         interval = ((struct itimerval) { { 0, usec }, tv });
 161
 162         if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
 163                 return -errno;
 164
 165         return 0;
 166 }
 167 #endif
 168
 169 void idle_sleep(unsigned long long nsecs)
 170 {
 171         struct timespec ts;
 172
 173         /*
 174          * nsecs can come in as zero, in which case, this starts a
 175          * busy loop.  To prevent this, reset nsecs to the tick
 176          * interval if it is zero.
 177          */
 178         if (nsecs == 0)
 179                 nsecs = UM_NSEC_PER_SEC / UM_HZ;
 180
 181         nsecs = sleep_time(nsecs);
 182         ts = ((struct timespec) { .tv_sec       = nsecs / UM_NSEC_PER_SEC,
 183                                   .tv_nsec      = nsecs % UM_NSEC_PER_SEC });
 184
 185         if (nanosleep(&ts, &ts) == 0)
 186                 deliver_alarm();
 187         after_sleep_interval(&ts);
 188 }