Fixed PeriodicTaskExecutor fork handler (#1209) (#1213)

Author: intuibase

agent/native/libcommon/code/PeriodicTaskExecutor.h

@@ -11,7 +11,6 @@
 
 namespace elasticapm::php {
 
-
 class PeriodicTaskExecutor : public ForkableInterface {
 private:
     auto getThreadWorkerFunction() {
@@ -30,7 +29,6 @@ class PeriodicTaskExecutor : public ForkableInterface {
 
     ~PeriodicTaskExecutor() {
         shutdown();
-
         if (thread_.joinable()) {
             thread_.join();
         }
@@ -62,12 +60,17 @@ class PeriodicTaskExecutor : public ForkableInterface {
 
     void prefork() final {
         shutdown();
-        thread_.join();
+        if (thread_.joinable()) {
+            thread_.join();
+        }
     }
 
     void postfork([[maybe_unused]] bool child) final {
         working_ = true;
+
+        mutex_.lock();
         thread_ = std::thread(getThreadWorkerFunction());
+        mutex_.unlock();
         pauseCondition_.notify_all();
     }
 
@@ -107,8 +110,8 @@ class PeriodicTaskExecutor : public ForkableInterface {
     std::chrono::milliseconds sleepInterval_ = std::chrono::milliseconds(20);
     std::vector<task_t> periodicTasks_;
     worker_init_t workerInit_;
-    std::thread thread_;
     std::mutex mutex_;
+    std::thread thread_;
     std::condition_variable pauseCondition_;
     bool working_ = true;
     bool resumed_ = false;

agent/native/libcommon/test/PeriodicTaskExecutorTest.cpp

@@ -47,7 +47,13 @@ TEST(PeriodicTaskExecutorTest, resumeAfterFork) {
 
     periodicTaskExecutor_.setInterval(20ms);
 
-    pthread_atfork(fh_prepare, fh_parent, fh_child);
+
+    static bool pthread_atfork_called = false;
+
+    if (!pthread_atfork_called) {
+        pthread_atfork(fh_prepare, fh_parent, fh_child);
+        pthread_atfork_called = true;
+    }
 
     periodicTaskExecutor_.resumePeriodicTasks();
     std::this_thread::sleep_for(100ms);
@@ -60,7 +66,7 @@ TEST(PeriodicTaskExecutorTest, resumeAfterFork) {
 
     ASSERT_GE(counter.load(), 13); // should be 15 in ideal world
     if (pid == 0) {
-        exit(0);
+        exit(testing::Test::HasFailure());
     }
 }