Print warnings when backwards timestamps are detected.
Bug: 7100774
Change-Id: I752fd1680b32ce33d17d6042d6c82e27d7ba9dd2
diff --git a/libs/utils/SystemClock.cpp b/libs/utils/SystemClock.cpp
index 53e0626..fe4ae91 100644
--- a/libs/utils/SystemClock.cpp
+++ b/libs/utils/SystemClock.cpp
@@ -109,6 +109,43 @@
return nanoseconds_to_milliseconds(elapsedRealtimeNano());
}
+#define METHOD_CLOCK_GETTIME 0
+#define METHOD_IOCTL 1
+#define METHOD_SYSTEMTIME 2
+
+static const char *gettime_method_names[] = {
+ "clock_gettime",
+ "ioctl",
+ "systemTime",
+};
+
+static inline void checkTimeStamps(int64_t timestamp,
+ int64_t volatile *prevTimestampPtr,
+ int volatile *prevMethodPtr,
+ int curMethod)
+{
+ /*
+ * Disable the check for SDK since the prebuilt toolchain doesn't contain
+ * gettid, and int64_t is different on the ARM platform
+ * (ie long vs long long).
+ */
+#ifdef ARCH_ARM
+ int64_t prevTimestamp = *prevTimestampPtr;
+ int prevMethod = *prevMethodPtr;
+
+ if (timestamp < prevTimestamp) {
+ ALOGW("time going backwards: prev %lld(%s) vs now %lld(%s), tid=%d",
+ prevTimestamp, gettime_method_names[prevMethod],
+ timestamp, gettime_method_names[curMethod],
+ gettid());
+ }
+ // NOTE - not atomic and may generate spurious warnings if the 64-bit
+ // write is interrupted or not observed as a whole.
+ *prevTimestampPtr = timestamp;
+ *prevMethodPtr = curMethod;
+#endif
+}
+
/*
* native public static long elapsedRealtimeNano();
*/
@@ -117,8 +154,15 @@
#ifdef HAVE_ANDROID_OS
struct timespec ts;
int result = clock_gettime(CLOCK_BOOTTIME, &ts);
+ int64_t timestamp;
+ static volatile int64_t prevTimestamp;
+ static volatile int prevMethod;
+
if (result == 0) {
- return seconds_to_nanoseconds(ts.tv_sec) + ts.tv_nsec;
+ timestamp = seconds_to_nanoseconds(ts.tv_sec) + ts.tv_nsec;
+ checkTimeStamps(timestamp, &prevTimestamp, &prevMethod,
+ METHOD_CLOCK_GETTIME);
+ return timestamp;
}
// CLOCK_BOOTTIME doesn't exist, fallback to /dev/alarm
@@ -129,18 +173,24 @@
if (android_atomic_cmpxchg(-1, fd, &s_fd)) {
close(fd);
}
- result = ioctl(s_fd,
- ANDROID_ALARM_GET_TIME(ANDROID_ALARM_ELAPSED_REALTIME), &ts);
}
+ result = ioctl(s_fd,
+ ANDROID_ALARM_GET_TIME(ANDROID_ALARM_ELAPSED_REALTIME), &ts);
+
if (result == 0) {
- return seconds_to_nanoseconds(ts.tv_sec) + ts.tv_nsec;
+ timestamp = seconds_to_nanoseconds(ts.tv_sec) + ts.tv_nsec;
+ checkTimeStamps(timestamp, &prevTimestamp, &prevMethod, METHOD_IOCTL);
+ return timestamp;
}
// XXX: there was an error, probably because the driver didn't
// exist ... this should return
// a real error, like an exception!
- return systemTime(SYSTEM_TIME_MONOTONIC);
+ timestamp = systemTime(SYSTEM_TIME_MONOTONIC);
+ checkTimeStamps(timestamp, &prevTimestamp, &prevMethod,
+ METHOD_SYSTEMTIME);
+ return timestamp;
#else
return systemTime(SYSTEM_TIME_MONOTONIC);
#endif