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      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  */
     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  */
     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(ARCH_ARM)
     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  */
    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