SystemClock: use clock_gettime() on devices without /dev/alarm
On devices with an up-to-date kernel, the back-in-time bug affecting
clock_gettime() has been fixed and it can safely be used as an
alternative to the ANDROID_ALARM_GET_TIME ioctl. To ensure consistent
behavior on existing devices, make clock_gettime() a fallback for when
the alarm driver isn't available.
Change-Id: I384af5e7ec9e73e0bad4b6b0f987a8ea4583cba6
Signed-off-by: Greg Hackmann <ghackmann@google.com>
diff --git a/libutils/SystemClock.cpp b/libutils/SystemClock.cpp
index ac8da88..413250f 100644
--- a/libutils/SystemClock.cpp
+++ b/libutils/SystemClock.cpp
@@ -119,22 +119,6 @@
static volatile int prevMethod;
#endif
-#if 0
- /*
- * b/7100774
- * clock_gettime appears to have clock skews and can sometimes return
- * backwards values. Disable its use until we find out what's wrong.
- */
- result = clock_gettime(CLOCK_BOOTTIME, &ts);
- if (result == 0) {
- timestamp = seconds_to_nanoseconds(ts.tv_sec) + ts.tv_nsec;
- checkTimeStamps(timestamp, &prevTimestamp, &prevMethod,
- METHOD_CLOCK_GETTIME);
- return timestamp;
- }
-#endif
-
- // CLOCK_BOOTTIME doesn't exist, fallback to /dev/alarm
static int s_fd = -1;
if (s_fd == -1) {
@@ -153,6 +137,15 @@
return timestamp;
}
+ // /dev/alarm doesn't exist, fallback to CLOCK_BOOTTIME
+ result = clock_gettime(CLOCK_BOOTTIME, &ts);
+ if (result == 0) {
+ timestamp = seconds_to_nanoseconds(ts.tv_sec) + ts.tv_nsec;
+ checkTimeStamps(timestamp, &prevTimestamp, &prevMethod,
+ METHOD_CLOCK_GETTIME);
+ return timestamp;
+ }
+
// XXX: there was an error, probably because the driver didn't
// exist ... this should return
// a real error, like an exception!