PR44411: Make VMSystem.nanoTime independent of wall time where possible.

2010-11-04  Andrew John Hughes  <ahughes@redhat.com>

	Provide a fallback for systems without POSIX timers.
	* native/jni/java-lang/java_lang_VMSystem.c:
	(currentTimeMillis): New function which provides
	the behaviour for both Java_java_lang_VMSystem_currentTimeMillis
	and the fallback by obtaining the result of gettimeofday.
	(Java_java_lang_VMSystem_nanoTime): Return currentTimeMillis
	multiplied by a 1000 if a monotonic clock is unavailable.
	(Java_java_lang_VMSystem_currentTimeMillis): Split main behaviour
	out into currentTimeMillis and then return its result divided by a
	1000.

2010-07-08  Roland Brand  <roland.brand@ergon.ch>
	Pekka Enberg  <penberg@kernel.org>

	PR classpath/44411
	* native/jni/java-lang/java_lang_VMSystem.c:
	(Java_java_lang_VMSystem_nanoTime): Implement
	using POSIX monotonic clock support and clock_gettime.
	(Java_java_lang_VMSystem_currentTimeMillis):
	Use old nanoTime method (which uses gettimeofday) to
	provide the current time in milliseconds.
	* vm/reference/java/lang/VMSystem.java:
	(currentTimeMillis()): Make native with its own implementation
	rather than using nanoTime, which should be
	independent of wall-clock time.

3 files changed, 75 insertions, 12 deletions

diff --git a/ChangeLog b/ChangeLog
index 37857759c..7af3d32f1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,31 @@
+2010-11-04  Andrew John Hughes  <ahughes@redhat.com>
+
+	Provide a fallback for systems without POSIX timers.
+	* native/jni/java-lang/java_lang_VMSystem.c:
+	(currentTimeMillis): New function which provides
+	the behaviour for both Java_java_lang_VMSystem_currentTimeMillis
+	and the fallback by obtaining the result of gettimeofday.
+	(Java_java_lang_VMSystem_nanoTime): Return currentTimeMillis
+	multiplied by a 1000 if a monotonic clock is unavailable.
+	(Java_java_lang_VMSystem_currentTimeMillis): Split main behaviour
+	out into currentTimeMillis and then return its result divided by a
+	1000.
+
+2010-07-08  Roland Brand  <roland.brand@ergon.ch>
+	Pekka Enberg  <penberg@kernel.org>
+
+	PR classpath/44411
+	* native/jni/java-lang/java_lang_VMSystem.c:
+	(Java_java_lang_VMSystem_nanoTime): Implement
+	using POSIX monotonic clock support and clock_gettime.
+	(Java_java_lang_VMSystem_currentTimeMillis):
+	Use old nanoTime method (which uses gettimeofday) to
+	provide the current time in milliseconds.
+	* vm/reference/java/lang/VMSystem.java:
+	(currentTimeMillis()): Make native with its own implementation
+	rather than using nanoTime, which should be
+	independent of wall-clock time.
+
 2010-05-09  Ivan Maidanski  <ivmai@mail.ru>
 
 	* gnu/java/security/Properties.java: Only
diff --git a/native/jni/java-lang/java_lang_VMSystem.c b/native/jni/java-lang/java_lang_VMSystem.c
index d20322791..a71247d12 100644
--- a/native/jni/java-lang/java_lang_VMSystem.c
+++ b/native/jni/java-lang/java_lang_VMSystem.c
@@ -39,8 +39,12 @@ exception statement from your version. */
 
 #include <jcl.h>
 
+#include <time.h>
 #include <sys/time.h>
 #include <stdlib.h>
+#include <errno.h>
+#include <unistd.h>
+#include <string.h>
 
 /*
  * Class:     java_lang_VMSystem
@@ -111,6 +115,22 @@ Java_java_lang_VMSystem_setErr (JNIEnv * env,
   (*env)->SetStaticObjectField (env, cls, field, obj);
 }
 
+static jlong currentTimeMillis(JNIEnv * env)
+{
+  /* Note: this implementation copied directly from Japhar's, by Chris Toshok. */
+  jlong result;
+  struct timeval tp;
+
+  if (gettimeofday (&tp, NULL) == -1)
+    (*env)->FatalError (env, "gettimeofday call failed.");
+
+  result = (jlong) tp.tv_sec;
+  result *= (jlong)1000000L;
+  result += (jlong)tp.tv_usec;
+
+  return result;
+}
+
 /*
  * Class:     java_lang_VMSystem
  * Method:    nanoTime
@@ -118,22 +138,40 @@ Java_java_lang_VMSystem_setErr (JNIEnv * env,
  */
 JNIEXPORT jlong JNICALL
 Java_java_lang_VMSystem_nanoTime
-  (JNIEnv * env __attribute__ ((__unused__)),
+  (JNIEnv * env,
    jclass thisClass __attribute__ ((__unused__)))
 {
-  /* Note: this implementation copied directly from Japhar's, by Chris Toshok. */
+#ifdef _POSIX_MONOTONIC_CLOCK
   jlong result;
-  struct timeval tp;
+  struct timespec tp;
 
-  if (gettimeofday (&tp, NULL) == -1)
-    (*env)->FatalError (env, "gettimeofday call failed.");
+  if (clock_gettime (CLOCK_MONOTONIC, &tp) == -1) {
+    char error[64];
+    snprintf(error, 64, "clock_gettime call failed: %s.", strerror(errno));
+    (*env)->FatalError (env, error);
+  }
 
   result = (jlong) tp.tv_sec;
-  result *= (jlong)1000000L;
-  result += (jlong)tp.tv_usec;
-  result *= (jlong)1000;
+  result *= (jlong)1000000000L;
+  result += (jlong)tp.tv_nsec;
 
   return result;
+#else
+  return currentTimeMillis(env) * (jlong)1000;
+#endif
+}
+
+/*
+ * Class:     java_lang_VMSystem
+ * Method:    currentTimeMillis
+ * Signature: ()J
+ */
+JNIEXPORT jlong JNICALL
+Java_java_lang_VMSystem_currentTimeMillis
+  (JNIEnv * env,
+   jclass thisClass __attribute__ ((__unused__)))
+{
+  return currentTimeMillis(env) / (jlong)1000L;
 }
 
 JNIEXPORT jstring JNICALL
diff --git a/vm/reference/java/lang/VMSystem.java b/vm/reference/java/lang/VMSystem.java
index a19466328..0b3d69200 100644
--- a/vm/reference/java/lang/VMSystem.java
+++ b/vm/reference/java/lang/VMSystem.java
@@ -129,10 +129,7 @@ final class VMSystem
    * @return the current time
    * @see java.util.Date
    */
-   static long currentTimeMillis()
-   {
-     return nanoTime() / 1000000L;
-   }
+  static native long currentTimeMillis();
 
   /**
    * <p>