[SDK] Fix memory leak in TlsRandomNumberGenerator() constructor (open-telemetry#2661)

Author: hongweipeng

sdk/src/common/random.cc

@@ -5,6 +5,7 @@
 #include "src/common/random.h"
 #include "src/common/platform/fork.h"
 
+#include <atomic>
 #include <cstring>
 #include <random>
 
@@ -26,12 +27,17 @@ class TlsRandomNumberGenerator
   TlsRandomNumberGenerator() noexcept
   {
     Seed();
-    platform::AtFork(nullptr, nullptr, OnFork);
+    if (!flag.test_and_set())
+    {
+      platform::AtFork(nullptr, nullptr, OnFork);
+    }
   }
 
   static FastRandomNumberGenerator &engine() noexcept { return engine_; }
 
 private:
+  static std::atomic_flag flag;
+
   static thread_local FastRandomNumberGenerator engine_;
 
   static void OnFork() noexcept { Seed(); }
@@ -44,6 +50,7 @@ class TlsRandomNumberGenerator
   }
 };
 
+std::atomic_flag TlsRandomNumberGenerator::flag;
 thread_local FastRandomNumberGenerator TlsRandomNumberGenerator::engine_{};
 }  // namespace
 

sdk/test/common/random_test.cc

@@ -4,7 +4,10 @@
 #include "src/common/random.h"
 
 #include <algorithm>
+#include <atomic>
 #include <iterator>
+#include <thread>
+#include <vector>
 
 #include <gtest/gtest.h>
 using opentelemetry::sdk::common::Random;
@@ -34,3 +37,27 @@ TEST(RandomTest, GenerateRandomBuffer)
         std::equal(std::begin(buf1_vector), std::end(buf1_vector), std::begin(buf2_vector)));
   }
 }
+
+void doSomethingOnce(std::atomic_uint *count)
+{
+  static std::atomic_flag flag;
+  if (!flag.test_and_set())
+  {
+    (*count)++;
+  }
+}
+
+TEST(RandomTest, AtomicFlagMultiThreadTest)
+{
+  std::vector<std::thread> threads;
+  std::atomic_uint count(0);
+  for (int i = 0; i < 10; ++i)
+  {
+    threads.push_back(std::thread(doSomethingOnce, &count));
+  }
+  for (auto &t : threads)
+  {
+    t.join();
+  }
+  EXPECT_EQ(1, count.load());
+}