Wait on the monotonic clock to guard against changes to the system clock.

runtime/vm/thread_linux.cc

Index: runtime/vm/thread_linux.cc
diff --git a/runtime/vm/thread_linux.cc b/runtime/vm/thread_linux.cc
index ef653c735e384dc908727cced86d14a3a2c4cc3d..98b1c66a2a954ca123b336a9b859f0cbfca9468f 100644
--- a/runtime/vm/thread_linux.cc
+++ b/runtime/vm/thread_linux.cc
@@ -18,18 +18,16 @@ namespace dart {
 
 
 static void ComputeTimeSpec(struct timespec* ts, int64_t millis) {
-  struct timeval time;
-  struct timeval delta;
-  // Convert the millis to a timeval delta.
   int64_t secs = millis / 1000;

[siva, 2011/11/14 18:32:28]

Maybe we should have 3 constants to make this more readable:
static const int kMillisPerSecond = 1000;
static const int kNanosPerMillis = 1000 * 1000;
static const int kNanosPerSecond = kNanosPerMillis * kMiliisPerSecond;

[cshapiro, 2011/11/14 22:24:25]

Good idea.  I have added to globals.h time constants borrowed from Chrome's Time
class.

-  int64_t micros = (millis - (secs * 1000)) * 1000;
-  delta.tv_sec = secs;
-  delta.tv_usec = micros;
-  // Get the current time and add the delta. Convert the result to a timespec.
-  int result = gettimeofday(&time, NULL);
+  int64_t nanos = (millis - (secs * 1000)) * 1000 * 1000;
+  int result = clock_gettime(CLOCK_MONOTONIC, ts);
   ASSERT(result == 0);
-  timeradd(&time, &delta, &time);
-  TIMEVAL_TO_TIMESPEC(&time, ts);
+  ts->tv_sec += secs;
+  ts->tv_nsec += nanos;
+  if (ts->tv_nsec >= (1000 * 1000 * 1000)) {
+    ts->tv_sec += 1;
+    ts->tv_nsec -= (1000 * 1000 * 1000);
+  }
 }
 
 
@@ -162,23 +160,37 @@ void Mutex::Unlock() {
 
 
 Monitor::Monitor() {
-  pthread_mutexattr_t attr;
-  int result = pthread_mutexattr_init(&attr);
-  VALIDATE_PTHREAD_RESULT(result);
+  {

[siva, 2011/11/14 18:32:28]

The scoping feels weird why not just name the variables different:
pthread_mutexattr_t mutex_attr;
pthread_condaddr_t cond_attr;

[cshapiro, 2011/11/14 22:24:25]

Yeah, in fact, I wrote it that way originally.  Reverted.  Done.

+    pthread_mutexattr_t attr;
+    int result = pthread_mutexattr_init(&attr);
+    VALIDATE_PTHREAD_RESULT(result);
 
 #if defined(DEBUG)
-  result = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ERRORCHECK);
-  VALIDATE_PTHREAD_RESULT(result);
+    result = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ERRORCHECK);
+    VALIDATE_PTHREAD_RESULT(result);
 #endif  // defined(DEBUG)
 
-  result = pthread_mutex_init(data_.mutex(), &attr);
-  VALIDATE_PTHREAD_RESULT(result);
+    result = pthread_mutex_init(data_.mutex(), &attr);
+    VALIDATE_PTHREAD_RESULT(result);
 
-  result = pthread_mutexattr_destroy(&attr);
-  VALIDATE_PTHREAD_RESULT(result);
+    result = pthread_mutexattr_destroy(&attr);
+    VALIDATE_PTHREAD_RESULT(result);
+  }
 
-  result = pthread_cond_init(data_.cond(), NULL);
-  VALIDATE_PTHREAD_RESULT(result);
+  {
+    pthread_condattr_t attr;
+    int result = pthread_condattr_init(&attr);
+    VALIDATE_PTHREAD_RESULT(result);
+
+    result = pthread_condattr_setclock(&attr, CLOCK_MONOTONIC);
+    VALIDATE_PTHREAD_RESULT(result);
+
+    result = pthread_cond_init(data_.cond(), &attr);
+    VALIDATE_PTHREAD_RESULT(result);
+
+    result = pthread_condattr_destroy(&attr);
+    VALIDATE_PTHREAD_RESULT(result);
+  }
 }