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Potential Deadlock #91

anirudhsanthiar opened this Issue Feb 9, 2016 · 3 comments


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anirudhsanthiar commented Feb 9, 2016

The Connect method in TcpTransport.cs could deadlock. The method is:

 public void Connect(Connection connection, Address address, bool noVerification)
    this.connection = connection;
    var factory = new ConnectionFactory();
    if (noVerification)
        factory.SSL.RemoteCertificateValidationCallback = noneCertValidator;

    this.ConnectAsync(address, factory).GetAwaiter().GetResult();

A GUI client (such as a Windows Forms app) or an MVC client will deadlock if it calls the method as follows:

const string Endpoint = "amqp://guest:guest@localhost:5765";           
Address address = new Address(Endpoint);
var connection = new Connection(address);

(The constructor for the Connection object eventually calls the Connect method above.)

Note that the connect method blocks on a Task object because of the call to GetResult:
this.ConnectAsync(address, factory).GetAwaiter().GetResult();
Blocking on Task objects (Via Task.Wait() or Task.Result or Task.GetAwaiter().GetResult())
is dangerous and could result in deadlocks.
(See, for example


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xinchen10 commented Feb 9, 2016

@anirudhsanthiar you are right. There are also other methods (e.g. SenderLink.Send, ReceiverLink.Recieve) that are blocking on an underlying task. If they are called from a UI thread, the same issue will happen. In such cases, the async methods should be called. For example,

    Connection connection = await Connection.Factory.CreateAsync(address);
    await connection.CloseAsync();

I think we could either improve the documentation to make it obvious or remove the blocking APIs on certain platforms.


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anirudhsanthiar commented Feb 10, 2016

Yes, that would be great. Another option is to configure the await statements in ampqnetlite to not capture context via ConfigureAwait(false) [see, for example, the section under "avoiding context" in 1]


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xinchen10 commented May 4, 2016

The documentation for connection constructors has been updated. The code is also updated to not capture context.

@xinchen10 xinchen10 closed this May 4, 2016

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