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Don't allow reentrant transactions.

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The database's transaction lock is reentrant, meaning that a thread that's already holding the lock can acquire it again. This would allow a thread that already has a transaction in progress to start another transaction, which could cause transaction isolation issues and/or lock timeouts on the database's internal locks.

Check that the current thread isn't already holding the lock when starting a transaction.
This commit is contained in:
akwizgran
2016-03-31 11:02:52 +01:00
parent 9fbebe2226
commit 7e3d3625aa
2 changed files with 55 additions and 2 deletions
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7
briar-core/src/org/briarproject/db/DatabaseComponentImpl.java
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@@ -59,7 +59,6 @@ import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.logging.Logger;
@@ -80,7 +79,8 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
private final EventBus eventBus;
private final ShutdownManager shutdown;
private final AtomicBoolean closed = new AtomicBoolean(false);
private final ReadWriteLock lock = new ReentrantReadWriteLock(true);
private final ReentrantReadWriteLock lock =
new ReentrantReadWriteLock(true);
private volatile int shutdownHandle = -1;
@@ -119,6 +119,9 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
}
public Transaction startTransaction(boolean readOnly) throws DbException {
// Don't allow reentrant locking
if (lock.getReadHoldCount() > 0) throw new IllegalStateException();
if (lock.getWriteHoldCount() > 0) throw new IllegalStateException();
if (readOnly) lock.readLock().lock();
else lock.writeLock().lock();
try {