Revert "Trigger dumps asynchronously (#2533)" (#2541)

This reverts commit 3454261.

Author: nohwnd

src/Microsoft.TestPlatform.Extensions.BlameDataCollector/NetClientHangDumper.cs

@@ -4,12 +4,9 @@
 namespace Microsoft.TestPlatform.Extensions.BlameDataCollector
 {
     using System;
-    using System.Collections.Generic;
     using System.Diagnostics;
     using System.IO;
     using System.Linq;
-    using System.Threading;
-    using System.Threading.Tasks;
     using Microsoft.Diagnostics.NETCore.Client;
     using Microsoft.VisualStudio.TestPlatform.ObjectModel;
     using Microsoft.VisualStudio.TestPlatform.Utilities;
@@ -43,45 +40,35 @@ public void Dump(int processId, string outputDirectory, DumpTypeOption type)
 
             var bottomUpTree = processTree.OrderByDescending(t => t.Level).Select(t => t.Process);
 
-            // Do not suspend processes with NetClient dumper it stops the diagnostic thread running in
-            // them and hang dump request will get stuck forever, because the process is not co-operating.
-            // Instead we start one task per dump asynchronously, and hope that the parent process will start dumping
-            // before the child process is done dumping. This way if the parent is waiting for the children to exit,
-            // we will be dumping it before it observes the child exiting and we get a more accurate results. If we did not
-            // do this, then parent that is awaiting child might exit before we get to dumping it.
-            var tasks = new List<Task>();
-            var timeout = new CancellationTokenSource();
-            timeout.CancelAfter(TimeSpan.FromMinutes(5));
             foreach (var p in bottomUpTree)
             {
-                tasks.Add(Task.Run(
-                    () =>
-                    {
-                    try
-                    {
-                        var outputFile = Path.Combine(outputDirectory, $"{p.ProcessName}_{p.Id}_{DateTime.Now:yyyyMMddTHHmmss}_hangdump.dmp");
-                        EqtTrace.Verbose($"NetClientHangDumper.CollectDump: Selected dump type {type}. Dumping {process.Id} - {process.ProcessName} in {outputFile}. ");
-
-                        var client = new DiagnosticsClient(p.Id);
-
-                        // Connecting the dump generation logging to verbose output to avoid changing the interfaces again -> EqtTrace.IsVerboseEnabled
-                        // before we test this on some big repo.
-                        client.WriteDump(type == DumpTypeOption.Full ? DumpType.Full : DumpType.Normal, outputFile, logDumpGeneration: false);
-                    }
-                    catch (Exception ex)
-                    {
-                        EqtTrace.Error($"NetClientHangDumper.Dump: Error dumping process {p.Id} - {p.ProcessName}: {ex}.");
-                    }
-                }, timeout.Token));
+                try
+                {
+                   p.Suspend();
+                }
+                catch (Exception ex)
+                {
+                    EqtTrace.Error($"NetClientHangDumper.Dump: Error suspending process {p.Id} - {p.ProcessName}: {ex}.");
+                }
             }
 
-            try
-            {
-                Task.WhenAll(tasks).GetAwaiter().GetResult();
-            }
-            catch (TaskCanceledException)
+            foreach (var p in bottomUpTree)
             {
-                EqtTrace.Error($"NetClientHangDumper.Dump: Hang dump timed out.");
+                try
+                {
+                    var outputFile = Path.Combine(outputDirectory, $"{p.ProcessName}_{p.Id}_{DateTime.Now:yyyyMMddTHHmmss}_hangdump.dmp");
+                    EqtTrace.Verbose($"NetClientHangDumper.CollectDump: Selected dump type {type}. Dumping {process.Id} - {process.ProcessName} in {outputFile}. ");
+
+                    var client = new DiagnosticsClient(p.Id);
+
+                    // Connecting the dump generation logging to verbose output to avoid changing the interfaces again -> EqtTrace.IsVerboseEnabled
+                    // before we test this on some big repo.
+                    client.WriteDump(type == DumpTypeOption.Full ? DumpType.Full : DumpType.Normal, outputFile, logDumpGeneration: false);
+                }
+                catch (Exception ex)
+                {
+                    EqtTrace.Error($"NetClientHangDumper.Dump: Error dumping process {p.Id} - {p.ProcessName}: {ex}.");
+                }
             }
 
             foreach (var p in bottomUpTree)
@@ -96,6 +83,6 @@ public void Dump(int processId, string outputDirectory, DumpTypeOption type)
                     EqtTrace.Error($"NetClientHangDumper.Dump: Error killing process {p.Id} - {p.ProcessName}: {ex}.");
                 }
             }
-            }
+        }
     }
 }