Merge pull request #1934 from brianrob/dev/brianrob/thread-safe-trace…

…eventsession Protect Initialization of TraceEventSession Provider Lists
microsoft · Oct 19, 2023 · a6c8791 · a6c8791
2 parents d52d78f + e76170f
commit a6c8791
Showing 1 changed file with 37 additions and 20 deletions.
diff --git a/src/TraceEvent/TraceEventSession.cs b/src/TraceEvent/TraceEventSession.cs
@@ -1631,27 +1631,35 @@ internal static SortedDictionary<string, Guid> ProviderNameToGuid
             {
                 if (s_providersByName == null)
                 {
-                    s_providersByName = new SortedDictionary<string, Guid>(StringComparer.OrdinalIgnoreCase);
-                    int buffSize = 0;
-                    var hr = TraceEventNativeMethods.TdhEnumerateProviders(null, ref buffSize);
-                    Debug.Assert(hr == 122);     // ERROR_INSUFFICIENT_BUFFER
-                    var buffer = stackalloc byte[buffSize];
-                    var providersDesc = (TraceEventNativeMethods.PROVIDER_ENUMERATION_INFO*)buffer;
-
-                    hr = TraceEventNativeMethods.TdhEnumerateProviders(providersDesc, ref buffSize);
-                    if ((hr == 0) && (providersDesc != null))
+                    lock (s_lock)
                     {
-                        var providers = (TraceEventNativeMethods.TRACE_PROVIDER_INFO*)&providersDesc[1];
-                        for (int i = 0; i < providersDesc->NumberOfProviders; i++)
+                        if (s_providersByName == null)
                         {
-                            var name = new string((char*)&buffer[providers[i].ProviderNameOffset]);
-                            s_providersByName[name] = providers[i].ProviderGuid;
+                            SortedDictionary<string, Guid> providersByName = new SortedDictionary<string, Guid>(StringComparer.OrdinalIgnoreCase);
+                            int buffSize = 0;
+                            var hr = TraceEventNativeMethods.TdhEnumerateProviders(null, ref buffSize);
+                            Debug.Assert(hr == 122);     // ERROR_INSUFFICIENT_BUFFER
+                            var buffer = stackalloc byte[buffSize];
+                            var providersDesc = (TraceEventNativeMethods.PROVIDER_ENUMERATION_INFO*)buffer;
+
+                            hr = TraceEventNativeMethods.TdhEnumerateProviders(providersDesc, ref buffSize);
+                            if ((hr == 0) && (providersDesc != null))
+                            {
+                                var providers = (TraceEventNativeMethods.TRACE_PROVIDER_INFO*)&providersDesc[1];
+                                for (int i = 0; i < providersDesc->NumberOfProviders; i++)
+                                {
+                                    var name = new string((char*)&buffer[providers[i].ProviderNameOffset]);
+                                    providersByName[name] = providers[i].ProviderGuid;
+                                }
+
+                                s_providersByName = providersByName;
+                            }
+                            else
+                            {
+                                Trace.WriteLine("TdhEnumerateProviders failed HR = " + hr);
+                            }
                         }
                     }
-                    else
-                    {
-                        Trace.WriteLine("TdhEnumerateProviders failed HR = " + hr);
-                    }
                 }
                 return s_providersByName;
             }
@@ -1663,10 +1671,18 @@ internal static Dictionary<Guid, string> ProviderGuidToName
             {
                 if (s_providerNames == null)
                 {
-                    s_providerNames = new Dictionary<Guid, string>(ProviderNameToGuid.Count);
-                    foreach (var keyValue in ProviderNameToGuid)
+                    lock (s_lock)
                     {
-                        s_providerNames[keyValue.Value] = keyValue.Key;
+                        if (s_providerNames == null)
+                        {
+                            Dictionary<Guid, string> providerNames = new Dictionary<Guid, string>(ProviderNameToGuid.Count);
+                            foreach (var keyValue in ProviderNameToGuid)
+                            {
+                                providerNames[keyValue.Value] = keyValue.Key;
+                            }
+
+                            s_providerNames = providerNames;
+                        }
                     }
                 }
                 return s_providerNames;
@@ -1721,6 +1737,7 @@ private int ComputeEventIdsBufferSize(IList<int> eventIds)
             return (eventIds.Count - 1) * 2 + sizeof(TraceEventNativeMethods.EVENT_FILTER_EVENT_ID);
         }
 
+        private static object s_lock = new object();
         private static SortedDictionary<string, Guid> s_providersByName;
         private static Dictionary<Guid, string> s_providerNames;