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_COMMON 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, 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, 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 } 187