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
set_interval(void)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
timer_one_shot(int ticks)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 */
timeval_to_ns(const struct timeval * tv)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
disable_timer(void)60 long long disable_timer(void)
61 {
62 struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } });
63 long long 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
os_nsecs(void)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
after_sleep_interval(struct timespec * ts)85 static int after_sleep_interval(struct timespec *ts)
86 {
87 return 0;
88 }
89
deliver_alarm(void)90 static void deliver_alarm(void)
91 {
92 alarm_handler(SIGVTALRM, NULL);
93 }
94
sleep_time(unsigned long long nsecs)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
deliver_alarm(void)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
sleep_time(unsigned long long nsecs)126 static unsigned long long sleep_time(unsigned long long nsecs)
127 {
128 return nsecs > skew ? nsecs - skew : 0;
129 }
130
timespec_to_us(const struct timespec * ts)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
after_sleep_interval(struct timespec * ts)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
idle_sleep(unsigned long long nsecs)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 }
189