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[JENKINS-68122] Avoid deadlock involving RingBufferLogHandler.LogRecordRef class loading (III) #6449

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Apr 9, 2022
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[JENKINS-68122] Avoid deadlock involving RingBufferLogHandler.LogRecordRef class loading (III) #6449

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12 changes: 12 additions & 0 deletions core/src/main/java/hudson/util/RingBufferLogHandler.java
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Original file line number Diff line number Diff line change
Expand Up @@ -24,9 +24,11 @@

package hudson.util;

import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
import java.lang.ref.SoftReference;
import java.util.AbstractList;
import java.util.List;
import java.util.Objects;
import java.util.logging.Handler;
import java.util.logging.Level;
import java.util.logging.LogRecord;
Expand All @@ -36,6 +38,9 @@
*
* @author Kohsuke Kawaguchi
*/
@SuppressFBWarnings(
value = "RV_RETURN_VALUE_IGNORED_NO_SIDE_EFFECT",
justification = "to guard against potential future compiler optimizations")
public class RingBufferLogHandler extends Handler {

private static final int DEFAULT_RING_BUFFER_SIZE = Integer.getInteger(RingBufferLogHandler.class.getName() + ".defaultSize", 256);
Expand All @@ -46,6 +51,13 @@ private static final class LogRecordRef extends SoftReference<LogRecord> {
}
}

static {
// Preload the LogRecordRef class to avoid an ABBA deadlock between agent class loading and logging.
LogRecord r = new LogRecord(Level.INFO, "<preloading>");
// We call Objects.hash() to guard against potential future compiler optimizations.
Objects.hash(new LogRecordRef(r).get());
}

private int start = 0;
private final LogRecordRef[] records;
private int size;
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