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CBL-8402 : Fix data race on SerialExecutor.currentThread #495

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Merged
pasin merged 1 commit into from
Jun 8, 2026
Merged

CBL-8402 : Fix data race on SerialExecutor.currentThread #495

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15 changes: 11 additions & 4 deletions common/main/java/com/couchbase/lite/internal/exec/SerialExecutor.java
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;

import com.couchbase.lite.LogDomain;
import com.couchbase.lite.internal.logging.Log;
Expand Down Expand Up @@ -55,7 +56,9 @@ class SerialExecutor implements ExecutionService.CloseableExecutor {
@Nullable
private CountDownLatch stopLatch;

private long currentThread = -1;
// Id of the pool thread currently running a task for this executor
@NonNull
private final AtomicLong currentThread = new AtomicLong(-1);

SerialExecutor(@NonNull ThreadPoolExecutor executor) {
Preconditions.assertNotNull(executor, "executor");
Expand Down Expand Up @@ -120,7 +123,7 @@ public boolean stop(long timeout, @NonNull TimeUnit unit) {

@Override
public boolean isInsideExecutor() {
return Thread.currentThread().getId() == currentThread;
return Thread.currentThread().getId() == currentThread.get();
}

@NonNull
Expand Down Expand Up @@ -164,9 +167,13 @@ private void executeTask(@Nullable InstrumentedTask prevTask) {
if (nextTask == null) { return; }

try { executor.execute(() -> {
currentThread = Thread.currentThread().getId();
final long tid = Thread.currentThread().getId();
currentThread.set(tid);
try { nextTask.run(); }
finally { currentThread = -1; }
finally {
// Clear only if unchanged: the next task may already have claimed it.
currentThread.compareAndSet(tid, -1);
}
}); }
catch (RuntimeException e) {
Log.w(LogDomain.DATABASE, "Catastrophic executor failure (Serial Executor)!", e);
Expand Down
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