[Mono.Debugger.Soft] Fix VirtualMachine detaching (#17020)

* Revert "[Mono.Debugger.Soft] Properly close connections"

This reverts commit 2da77073731dc88cfef40ed5a838e53896eca7d1.

This was previously reverted because it was causing issues and it still does. It is a hack fix. We signal the connection for closing and next we send the dispose command over the network. This is obviously racy.

* [Mono.Debugger.Soft] Make sure receiving thread always closes

When we want to close the connection, setting the close flag is not enough, because a thread can be already stuck in a blocking receive, without getting to check the flag. We fix this by additionaly breaking the connection, by using socket.Shutdown.

Fixes https://github.com/mono/mono/issues/7377

* Bump API snapshot submodule

2 files changed, 12 insertions, 1 deletions

diff --git a/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/Connection.cs b/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/Connection.cs
index 7e895773bc2..3e2cf5f33af 100644
--- a/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/Connection.cs
+++ b/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/Connection.cs
@@ -1318,6 +1318,8 @@ namespace Mono.Debugger.Soft
 		protected abstract int TransportSend (byte[] buf, int buf_offset, int len);
 		protected abstract void TransportSetTimeouts (int send_timeout, int receive_timeout);
 		protected abstract void TransportClose ();
+		// Shutdown breaks all communication, resuming blocking waits
+		protected abstract void TransportShutdown ();
 
 		internal VersionInfo Version;
 		
@@ -1434,6 +1436,7 @@ namespace Mono.Debugger.Soft
 
 		internal void Close () {
 			closed = true;
+			TransportShutdown ();
 		}
 
 		internal bool IsClosed {
@@ -2865,6 +2868,11 @@ namespace Mono.Debugger.Soft
 		{
 			socket.Close ();
 		}
+
+		protected override void TransportShutdown ()
+		{
+			socket.Shutdown (SocketShutdown.Both);
+		}
 	}
 
 	/* This is the interface exposed by the debugger towards the debugger agent */
diff --git a/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/VirtualMachine.cs b/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/VirtualMachine.cs
index 1912626d228..c9026a02682 100644
--- a/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/VirtualMachine.cs
+++ b/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/VirtualMachine.cs
@@ -150,8 +150,11 @@ namespace Mono.Debugger.Soft
 		}
 
 		public void Detach () {
-			conn.Close ();
+			// Notify the application that we are detaching
 			conn.VM_Dispose ();
+			// Close the connection. No further messages can be sent
+			// over the connection after this point.
+			conn.Close ();
 			notify_vm_event (EventType.VMDisconnect, SuspendPolicy.None, 0, 0, null, 0);
 		}