[2020- 02][debugger] Implementing step through multithreaded code. (#19343)

* [debugger] Implementing step through multithreaded code.
Backport #19103

* Bump API snapshot submodule

Co-authored-by: monojenkins <jo.shields+jenkins@xamarin.com>

4 files changed, 87 insertions, 1 deletions

diff --git a/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/EventRequest.cs b/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/EventRequest.cs
index 69f35f4c0ac..4c9a536838b 100644
--- a/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/EventRequest.cs
+++ b/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/EventRequest.cs
@@ -34,6 +34,11 @@ namespace Mono.Debugger.Soft
 			}
 		}
 
+		public int GetId()
+		{
+			return id;
+		}
+
 		public EventType EventType {
 			get {
 				return etype;
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 c9026a02682..12274864d4c 100644
--- a/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/VirtualMachine.cs
+++ b/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/VirtualMachine.cs
@@ -657,7 +657,9 @@ namespace Mono.Debugger.Soft
 
 		internal EventRequest GetRequest (int id) {
 			lock (requests_lock) {
-				return requests [id];
+				EventRequest obj;
+				requests.TryGetValue (id, out obj);
+				return obj;
 			}
 		}
 
diff --git a/mcs/class/Mono.Debugger.Soft/Test/dtest-app.cs b/mcs/class/Mono.Debugger.Soft/Test/dtest-app.cs
index 1bbb04d4709..e6b79fdd406 100644
--- a/mcs/class/Mono.Debugger.Soft/Test/dtest-app.cs
+++ b/mcs/class/Mono.Debugger.Soft/Test/dtest-app.cs
@@ -613,6 +613,10 @@ public class Tests : TestsBase, ITest2
 			pointers2 ();
 			return 0;
 		}
+		if (args.Length >0 && args [0] == "ss_multi_thread") {
+			ss_multi_thread ();
+			return 0;
+		}
 		return 3;
 	}
 
@@ -862,6 +866,24 @@ public class Tests : TestsBase, ITest2
 	}
 
 	[MethodImplAttribute (MethodImplOptions.NoInlining)]
+	public static void ss_multi_thread () {
+		for (int i = 0; i < 5; i++)
+		{
+			var t = new Thread(mt_ss);
+			t.Name = "Thread_" + i;
+			t.Start();
+		}
+	}
+
+	[MethodImplAttribute (MethodImplOptions.NoInlining)]
+	static void mt_ss()
+	{
+		int a = 12;
+		int b = 13;
+		int c = 13;
+	}
+
+	[MethodImplAttribute (MethodImplOptions.NoInlining)]
 	public static void test_new_exception_filter () {
 		test_new_exception_filter1();
 		test_new_exception_filter2();
diff --git a/mcs/class/Mono.Debugger.Soft/Test/dtest.cs b/mcs/class/Mono.Debugger.Soft/Test/dtest.cs
index 473ce2f355e..d6ca7dc3255 100644
--- a/mcs/class/Mono.Debugger.Soft/Test/dtest.cs
+++ b/mcs/class/Mono.Debugger.Soft/Test/dtest.cs
@@ -65,6 +65,9 @@ public class DebuggerTests
 	Event GetNextEvent () {
 		var es = vm.GetNextEventSet ();
 		Assert.AreEqual (1, es.Events.Length);
+		if (step_req != null && es [0] != null && es [0].Request != null && es [0].Request is StepEventRequest && ((StepEventRequest)es [0].Request).GetId() != step_req.GetId()) {
+			step_req = ((StepEventRequest)es [0].Request);
+		}
 		return es [0];
 	}
 
@@ -5227,6 +5230,60 @@ public class DebuggerTests
 		if (failMessage != null)
 			Assert.Fail (failMessage);
 	}
+	  
+	[Test]
+	public void InvokeSingleStepMultiThread () {
+		vm.Detach ();
+		Start (dtest_app_path, "ss_multi_thread");
+		MethodMirror m = entry_point.DeclaringType.GetMethod ("mt_ss");
+		int firstLineFound = m.Locations [0].LineNumber + 1;
+		int line_first_counter = 5;
+		int line_second_counter = 5;
+		int line_third_counter = 3;
+		Event e = run_until ("ss_multi_thread");
+		EventRequest req = create_step (e);
+		req.Disable ();
+		ReusableBreakpoint breakpoint = new ReusableBreakpoint (this, "mt_ss");
+		breakpoint.Continue ();
+		e = breakpoint.lastEvent;
+		req = create_step (e);
+		while (line_first_counter > 0 || line_second_counter > 0 || line_third_counter > 0) {
+			var thread = e.Thread;
+			var l = thread.GetFrames ()[0].Location;
+			var frame = thread.GetFrames()[0];
+
+      if (l.LineNumber == firstLineFound)
+				line_first_counter--;
+			if (l.LineNumber == firstLineFound + 1)
+				line_second_counter--;
+			if (l.LineNumber == firstLineFound + 2)
+				line_third_counter--;				
+
+			if (req.GetId() != breakpoint.req.GetId()) 
+				req.Disable ();
+			
+			req = create_step (e);
+			((StepEventRequest)req).Size = StepSize.Line;
+			try {
+				if ((e.Thread.GetFrames ()[0].Location.LineNumber == firstLineFound + 1 && (e.Thread.Name.Equals("Thread_0") || e.Thread.Name.Equals("Thread_1"))) || l.LineNumber == firstLineFound + 2) {
+					vm.Resume ();
+					e = GetNextEvent ();
+				}
+				else
+					e = step_over_or_breakpoint ();
+				req =  e.Request;		
+			}
+			catch (Exception z){
+				//expected vmdeath
+				break;
+			}
+		}
+		Assert.AreEqual(0, line_first_counter);
+		Assert.AreEqual(0, line_second_counter);
+		Assert.AreEqual(0, line_third_counter);
+		vm = null;
+	}
+	
 #endif
 } // class DebuggerTests
 } // namespace