Correct handling of reaper thread in forking binaries

lib/procs.cpp

@@ -157,6 +157,28 @@ void Util::Procs::exit_handler() {
   FAIL_MSG("Giving up with %d children left.", (int)listcopy.size());
 }
 
+// Joins the reaper thread, if any, before a fork
+void Util::Procs::fork_prepare(){
+  tthread::lock_guard<tthread::mutex> guard(plistMutex);
+  if (handler_set){
+    thread_handler = false;
+    if (reaper_thread){
+      reaper_thread->join();
+      delete reaper_thread;
+      reaper_thread = 0;
+    }
+  }
+}
+
+/// Restarts reaper thread if it was joined
+void Util::Procs::fork_complete(){
+  tthread::lock_guard<tthread::mutex> guard(plistMutex);
+  if (handler_set){
+    thread_handler = true;
+    reaper_thread = new tthread::thread(grim_reaper, 0);
+  }
+}
+
 /// Sets up exit and childsig handlers.
 /// Spawns grim_reaper. exit handler despawns grim_reaper
 /// Called by every Start* function.

lib/procs.h

@@ -26,6 +26,8 @@ namespace Util {
       static bool childRunning(pid_t p);
       static tthread::thread * reaper_thread;
       static bool handler_set; ///< If true, the sigchld handler has been setup.
+      static void fork_prepare();
+      static void fork_complete();
       static void setHandler();
       static std::string getOutputOf(char * const * argv);
       static std::string getOutputOf(std::deque<std::string> & argDeq);

lib/util.cpp

@@ -245,8 +245,10 @@ namespace Util{
     int pipeErr[2];
     if (pipe(pipeErr) >= 0){
       //Start reading log messages from the unnamed pipe
+      Util::Procs::fork_prepare();
       pid_t pid = fork();
       if (pid == 0) { //child
+        Util::Procs::fork_complete();
         close(pipeErr[1]);               // close the unneeded pipe file descriptor
         //Close all sockets in the socketList
         for (std::set<int>::iterator it = Util::Procs::socketList.begin(); it != Util::Procs::socketList.end(); ++it){
@@ -264,6 +266,7 @@ namespace Util{
         Util::logParser(pipeErr[0], true_stderr, isatty(true_stderr));
         exit(0);
       }
+      Util::Procs::fork_complete();
       if (pid == -1){
         FAIL_MSG("Failed to fork child process for log handling!");
       }else{

src/controller/controller.cpp

@@ -475,10 +475,10 @@ int main(int argc, char **argv){
   Controller::conf.activate();
   uint64_t reTimer = 0;
   while (Controller::conf.is_active){
+    Util::Procs::fork_prepare();
     pid_t pid = fork();
     if (pid == 0){
-      Util::Procs::handler_set = false;
-      Util::Procs::reaper_thread = 0;
+      Util::Procs::fork_complete();
       {
         struct sigaction new_action;
         new_action.sa_sigaction = handleUSR1;
@@ -488,6 +488,7 @@ int main(int argc, char **argv){
       }
       return main_loop(argc, argv);
     }
+    Util::Procs::fork_complete();
     if (pid == -1){
       FAIL_MSG("Unable to spawn controller process!");
       return 2;

src/input/input.cpp

@@ -157,8 +157,10 @@ namespace Mist {
     config->activate();
     uint64_t reTimer = 0;
     while (config->is_active){
+      Util::Procs::fork_prepare();
       pid_t pid = fork();
       if (pid == 0){
+        Util::Procs::fork_complete();
         if (playerLock){
           //Re-init streamStatus, previously closed
           char pageName[NAME_BUFFER_SIZE];
@@ -173,6 +175,7 @@ namespace Mist {
         if (!preRun()){return 0;}
         return run();
       }
+      Util::Procs::fork_complete();
       if (pid == -1){
         FAIL_MSG("Unable to spawn input process");
         //We failed. Release the kra... semaphores!