add test

test/core/channelz/channel_trace_test.cc

@@ -21,7 +21,9 @@
 #include <stdlib.h>
 
 #include <string>
+#include <thread>
 
+#include "absl/synchronization/notification.h"
 #include "gtest/gtest.h"
 
 #include <grpc/credentials.h>
@@ -317,6 +319,29 @@ TEST(ChannelTracerTest, TestTotalEviction) {
   ValidateChannelTraceCustom(&tracer, kNumEvents + 1, 0);
 }
 
+// Tests that the code is thread-safe.
+TEST(ChannelTracerTest, ThreadSafety) {
+  ExecCtx exec_ctx;
+  ChannelTrace tracer(kEventListMemoryLimit);
+  absl::Notification done;
+  std::vector<std::unique_ptr<std::thread>> threads;
+  for (size_t i = 0; i < 10; ++i) {
+    threads.push_back(std::make_unique<std::thread>(
+        [&]() {
+          do {
+            AddSimpleTrace(&tracer);
+          } while (!done.HasBeenNotified());
+        }));
+  }
+  for (size_t i = 0; i < 10; ++i) {
+    tracer.RenderJson();
+  }
+  done.Notify();
+  for (const auto& thd : threads) {
+    thd->join();
+  }
+}
+
 }  // namespace testing
 }  // namespace channelz
 }  // namespace grpc_core