1 /*
2 * Copyright (C) 2008 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17
18 /*
19 * System clock functions.
20 */
21
22 #ifdef HAVE_ANDROID_OS
23 #include <linux/ioctl.h>
24 #include <linux/rtc.h>
25 #include <utils/Atomic.h>
26 #include <linux/android_alarm.h>
27 #endif
28
29 #include <sys/time.h>
30 #include <limits.h>
31 #include <fcntl.h>
32 #include <errno.h>
33 #include <string.h>
34
35 #include <utils/SystemClock.h>
36 #include <utils/Timers.h>
37
38 #define LOG_TAG "SystemClock"
39 #include <utils/Log.h>
40
41 namespace android {
42
43 /*
44 * native public static long uptimeMillis();
45 */
uptimeMillis()46 int64_t uptimeMillis()
47 {
48 int64_t when = systemTime(SYSTEM_TIME_MONOTONIC);
49 return (int64_t) nanoseconds_to_milliseconds(when);
50 }
51
52 /*
53 * native public static long elapsedRealtime();
54 */
elapsedRealtime()55 int64_t elapsedRealtime()
56 {
57 return nanoseconds_to_milliseconds(elapsedRealtimeNano());
58 }
59
60 #define METHOD_CLOCK_GETTIME 0
61 #define METHOD_IOCTL 1
62 #define METHOD_SYSTEMTIME 2
63
64 /*
65 * To debug/verify the timestamps returned by the kernel, change
66 * DEBUG_TIMESTAMP to 1 and call the timestamp routine from a single thread
67 * in the test program. b/10899829
68 */
69 #define DEBUG_TIMESTAMP 0
70
71 #if DEBUG_TIMESTAMP && defined(__arm__)
checkTimeStamps(int64_t timestamp,int64_t volatile * prevTimestampPtr,int volatile * prevMethodPtr,int curMethod)72 static inline void checkTimeStamps(int64_t timestamp,
73 int64_t volatile *prevTimestampPtr,
74 int volatile *prevMethodPtr,
75 int curMethod)
76 {
77 /*
78 * Disable the check for SDK since the prebuilt toolchain doesn't contain
79 * gettid, and int64_t is different on the ARM platform
80 * (ie long vs long long).
81 */
82 int64_t prevTimestamp = *prevTimestampPtr;
83 int prevMethod = *prevMethodPtr;
84
85 if (timestamp < prevTimestamp) {
86 static const char *gettime_method_names[] = {
87 "clock_gettime",
88 "ioctl",
89 "systemTime",
90 };
91
92 ALOGW("time going backwards: prev %lld(%s) vs now %lld(%s), tid=%d",
93 prevTimestamp, gettime_method_names[prevMethod],
94 timestamp, gettime_method_names[curMethod],
95 gettid());
96 }
97 // NOTE - not atomic and may generate spurious warnings if the 64-bit
98 // write is interrupted or not observed as a whole.
99 *prevTimestampPtr = timestamp;
100 *prevMethodPtr = curMethod;
101 }
102 #else
103 #define checkTimeStamps(timestamp, prevTimestampPtr, prevMethodPtr, curMethod)
104 #endif
105
106 /*
107 * native public static long elapsedRealtimeNano();
108 */
elapsedRealtimeNano()109 int64_t elapsedRealtimeNano()
110 {
111 #ifdef HAVE_ANDROID_OS
112 struct timespec ts;
113 int result;
114 int64_t timestamp;
115 #if DEBUG_TIMESTAMP
116 static volatile int64_t prevTimestamp;
117 static volatile int prevMethod;
118 #endif
119
120 static int s_fd = -1;
121
122 if (s_fd == -1) {
123 int fd = open("/dev/alarm", O_RDONLY);
124 if (android_atomic_cmpxchg(-1, fd, &s_fd)) {
125 close(fd);
126 }
127 }
128
129 result = ioctl(s_fd,
130 ANDROID_ALARM_GET_TIME(ANDROID_ALARM_ELAPSED_REALTIME), &ts);
131
132 if (result == 0) {
133 timestamp = seconds_to_nanoseconds(ts.tv_sec) + ts.tv_nsec;
134 checkTimeStamps(timestamp, &prevTimestamp, &prevMethod, METHOD_IOCTL);
135 return timestamp;
136 }
137
138 // /dev/alarm doesn't exist, fallback to CLOCK_BOOTTIME
139 result = clock_gettime(CLOCK_BOOTTIME, &ts);
140 if (result == 0) {
141 timestamp = seconds_to_nanoseconds(ts.tv_sec) + ts.tv_nsec;
142 checkTimeStamps(timestamp, &prevTimestamp, &prevMethod,
143 METHOD_CLOCK_GETTIME);
144 return timestamp;
145 }
146
147 // XXX: there was an error, probably because the driver didn't
148 // exist ... this should return
149 // a real error, like an exception!
150 timestamp = systemTime(SYSTEM_TIME_MONOTONIC);
151 checkTimeStamps(timestamp, &prevTimestamp, &prevMethod,
152 METHOD_SYSTEMTIME);
153 return timestamp;
154 #else
155 return systemTime(SYSTEM_TIME_MONOTONIC);
156 #endif
157 }
158
159 }; // namespace android
160