HttpServerConnection#DataAvailableHandler(): be aware of being called multiple times concurrently

[Al2Klimov]

refs #6816

[Al2Klimov]

This seems not to make #6815 obsolete in my test setup, but we could let the customer test it.

[dnsmichi]

A similar problem might exist in the JsonRcpConnection class.

[Al2Klimov]

No, JsonRpcConnection#m_DataHandlerMutex is locked only once, in JsonRpcConnection#DataAvailableHandler().

[dnsmichi]

This can be called recursively from within Disconnect() -> TlsStream::Close() -> SignalDataAvailable(). The solution was a while ago to use a recursive mutex for HTTP handles.

[Al2Klimov]

What about Disconnect() is just setting a flag and the data handler is called only in the socket thread?

[dnsmichi]

We'll discuss this offline and focus on this fix.