AP_HAL_Linux: Thread: allow to override run method

libraries/AP_HAL_Linux/Thread.cpp

@@ -33,12 +33,22 @@ namespace Linux {
 void *Thread::_run_trampoline(void *arg)
 {
     Thread *thread = static_cast<Thread *>(arg);
-
-    thread->_task();
+    thread->_run();
 
     return nullptr;
 }
 
+bool Thread::_run()
+{
+    if (!_task) {
+        return false;
+    }
+
+    _task();
+
+    return true;
+}
+
 bool Thread::start(const char *name, int policy, int prio)
 {
     if (_started) {

libraries/AP_HAL_Linux/Thread.h

@@ -43,6 +43,13 @@ public:
 protected:
     static void *_run_trampoline(void *arg);
 
+    /*
+     * Run the task assigned in the constructor. May be overriden in case it's
+     * preferred to use Thread as an interface or when user wants to aggregate
+     * some initialization or teardown for the thread.
+     */
+    virtual bool _run();
+
     task_t _task;
     bool _started;
     pthread_t _ctx;