thread_pool: fix concurrent access of state variable

the thread workers need access to their current state to exit properly
when they are set to state STOP. However, since the state is kept in
a std::vector for all workers, it seems more appropiate to add a per-thread
running variable rather then mutexing the entire vector.

lib/include/srsran/common/thread_pool.h

@@ -23,6 +23,7 @@
 #include "srsran/adt/circular_buffer.h"
 #include "srsran/adt/move_callback.h"
 #include "srsran/srslog/srslog.h"
+#include <atomic>
 #include <condition_variable>
 #include <functional>
 #include <memory>
@@ -45,6 +46,7 @@ public:
     worker();
     ~worker() = default;
     void     setup(uint32_t id, thread_pool* parent, uint32_t prio = 0, uint32_t mask = 255);
+    void     stop();
     uint32_t get_id();
     void     release();
 
@@ -54,6 +56,7 @@ public:
   private:
     uint32_t     my_id     = 0;
     thread_pool* my_parent = nullptr;
+    std::atomic<bool> running   = {true};
 
     void run_thread();
     void wait_to_start();

lib/src/common/thread_pool.cc

@@ -42,15 +42,20 @@ void thread_pool::worker::setup(uint32_t id, thread_pool* parent, uint32_t prio,
 void thread_pool::worker::run_thread()
 {
   set_name(std::string("WORKER") + std::to_string(my_id));
-  while (my_parent->status[my_id] != STOP) {
+  while (running.load(std::memory_order_relaxed)) {
     wait_to_start();
-    if (my_parent->status[my_id] != STOP) {
+    if (running.load(std::memory_order_relaxed)) {
       work_imp();
       finished();
     }
   }
 }
 
+void thread_pool::worker::stop()
+{
+  running = false;
+}
+
 uint32_t thread_pool::worker::get_id()
 {
   return my_id;
@@ -92,6 +97,7 @@ void thread_pool::stop()
     for (uint32_t i = 0; i < nof_workers; i++) {
       if (workers[i]) {
         debug_thread("stop(): stopping %d\n", i);
+        workers[i]->stop();
         status[i] = STOP;
         cvar_worker[i].notify_all();
         cvar_queue.notify_all();