Greg Clayton <gclay...@apple.com> wrote on 16/02/2017 17:17:41:
> this is just the first packet we send after sending the "ack" down > to the remote server. When we send the "ack", we don't need a > response, then we send the "QStartNoAckMode" packet and actually > wait for a response. If we don't get one, then we bail. So this is > just the first packet that is sent that expects a response. I've been doing some more investigation and this seems to be true but it looks like the actual "ack" might be part of the problem. In GDBRemoteCommunicationClient::HandshakeWithServer lldb sends an Ack() packet (a '+') then calls ReadPacket until it doesn't succeed in reading any more packets to make sure everything outstanding has been read. Then it does QueryNoAckModeSupported. What seems to be happening in the passing case is that ReadPacket returns with a result of ErrorReplyTimeout. In the failing case ReadPacket returns ErrorDisconnected. This seems to be happening because in the failing case (without the delay) the underlying "recv" call returns 0 indicating end-of-file and then GDBRemoteCommunication::WaitForPacketNoLock calls Disconnect and returns ErrorDisconnected to HandshakeWithServer. HandshakeWithServer seems to rely on ReadPacket failing to read successfully but with a type of error that means the connection is still valid. In the bad case it's failing with an error that means lldb has disconnected. As yet I don't understand exactly why it reads an empty response in the failing case. I'm not sure if there's something queued or if it's managing to start talking to the remote process before it's finished starting. Moving the sleep(1) just before GDBRemoteCommunicationClient::HandshakeWithServer seems to work (with the sleep inside Disconnect() removed) so I think this is on the right path. I'll continue investigating and see if I can determine why. It might be the problem is on the server side and lldb-server is passing back the connection details before the new process is ready for the client. Howard. Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
_______________________________________________ lldb-dev mailing list lldb-dev@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
