Merge branch 'fb' into devel
[linux-2.6] / 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 }