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[GR-64664] Fix JFR epoch id. #11102

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Merged
merged 1 commit into from
Apr 30, 2025
Merged

[GR-64664] Fix JFR epoch id. #11102

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8 changes: 7 additions & 1 deletion substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jfr/traceid/JfrTraceIdEpoch.java
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,7 @@
import org.graalvm.nativeimage.Platforms;

import com.oracle.svm.core.Uninterruptible;
import com.oracle.svm.core.thread.Target_java_lang_VirtualThread;
import com.oracle.svm.core.thread.VMOperation;

import jdk.graal.compiler.api.replacements.Fold;
Expand All @@ -43,7 +44,12 @@ public class JfrTraceIdEpoch {
private static final long EPOCH_0_BIT = 0b01;
private static final long EPOCH_1_BIT = 0b10;

private long epochId;
/**
* Start the epoch id at 1, so that we can inject fields into JDK classes that store the epoch
* id (see for example {@link Target_java_lang_VirtualThread#jfrEpochId}). This avoids problems
* with uninitialized injected fields that have the value 0 by default.
*/
private long epochId = 1;

@Fold
public static JfrTraceIdEpoch getInstance() {
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11 changes: 2 additions & 9 deletions ...rc/com.oracle.svm.core/src/com/oracle/svm/core/thread/Target_java_lang_VirtualThread.java
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Expand Up @@ -123,8 +123,8 @@ public final class Target_java_lang_VirtualThread {
// Checkstyle: resume

@Inject //
@RecomputeFieldValue(kind = RecomputeFieldValue.Kind.Custom, declClass = ResetToMinusOneTransformer.class) //
public long jfrEpochId = -1;
@RecomputeFieldValue(kind = RecomputeFieldValue.Kind.Reset) //
public long jfrEpochId;

@Alias
private static native ForkJoinPool createDefaultScheduler();
Expand Down Expand Up @@ -602,10 +602,3 @@ static Thread asThread(Object obj) {
private VirtualThreadHelper() {
}
}

final class ResetToMinusOneTransformer implements FieldValueTransformer {
@Override
public Object transform(Object receiver, Object originalValue) {
return -1L;
}
}