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Fix a livelock in TransactionManager #3156

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merged 1 commit into from
Dec 10, 2019
Merged

Fix a livelock in TransactionManager #3156

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17 changes: 13 additions & 4 deletions exist-core/src/main/java/org/exist/storage/txn/TransactionManager.java
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Original file line number Diff line number Diff line change
Expand Up @@ -240,6 +240,8 @@ public void commit(final Txn txn) throws TransactionException {
return;
}

boolean doneCommit = false;

// CAS loop
try {
while (true) {
Expand Down Expand Up @@ -269,11 +271,18 @@ public void commit(final Txn txn) throws TransactionException {
}

// if we are have active transactions and are not preempted by another thread, commit transaction
if (localState > STATE_IDLE && state.compareAndSet(localState, localState - 1)) {
doCommitTransaction(txn);
if (localState > STATE_IDLE) {
if (!doneCommit) {
doCommitTransaction(txn);
// NOTE: doCommitTransaction above might throw an exception before commit which will throw us out of the loop
doneCommit = txn.getState() == Txn.State.COMMITTED;
}

// done... exit CAS loop!
return;
// try and update our state to reflect that we have committed the transaction, if not then loop...
if (state.compareAndSet(localState, localState - 1)) {
// done... exit CAS loop!
return;
}
}
}
} catch (final InterruptedException e) {
Expand Down