public void CanEnterLocksSync()
{
var myLock = new AsyncReaderWriterLockSlim();
myLock.EnterReadLock();
Assert.IsTrue(myLock.TryEnterReadLock(0));
Assert.IsFalse(myLock.TryEnterWriteLock(0));
myLock.ExitReadLock();
myLock.ExitReadLock();
myLock.EnterWriteLock();
Assert.IsFalse(myLock.TryEnterReadLock(0));
Assert.IsFalse(myLock.TryEnterWriteLock(0));
myLock.ExitWriteLock();
}
public void DowngradeLockAllowsReadLock()
{
var myLock = new AsyncReaderWriterLockSlim();
myLock.EnterWriteLock();
Assert.IsFalse(myLock.TryEnterWriteLock(0));
Assert.IsFalse(myLock.TryEnterReadLock(0));
// After downgrading the lock and after the try to get the write lock is canceled,
// it should be possible to enter another read lock.
myLock.DowngradeWriteLockToReadLock();
Assert.IsFalse(myLock.TryEnterWriteLock(0));
Assert.IsTrue(myLock.TryEnterReadLock(0));
myLock.ExitReadLock();
myLock.ExitReadLock();
}
public void ThrowsOperationCanceledException()
{
var myLock = new AsyncReaderWriterLockSlim();
try
{
// Should throw without entering the lock.
myLock.EnterReadLock(new CancellationToken(true));
}
catch (OperationCanceledException)
{
// Check that the read lock actually was not entered.
Assert.IsTrue(myLock.TryEnterWriteLock(0));
throw;
}
}
public void WaitingReaderIsReleasedAfterWaitingWriterCanceled()
{
var myLock = new AsyncReaderWriterLockSlim();
// Thread A enters a read lock.
myLock.EnterReadLock();
// Thread B wants to enter a write lock within 2 seconds. Because Thread A holds
// a read lock, Thread B will not get the write lock.
bool threadBResult = true;
var threadB = new Thread(() =>
{
bool result = myLock.TryEnterWriteLock(600);
Volatile.Write(ref threadBResult, result);
});
threadB.Start();
// Wait a bit before starting the next thread, to ensure Thread B is already
// in the TryEnter...() call.
Thread.Sleep(200);
// Thread C wants to enter a read lock. It should get the lock after
// 2 seconds because Thread B cancels its try to get the write lock after
// that time.
var threadC = new Thread(() =>
{
myLock.EnterReadLock();
});
threadC.Start();
threadB.Join();
threadC.Join();
Assert.IsFalse(Volatile.Read(ref threadBResult));
myLock.EnterReadLock();
}