cherry pick from svn r35222

Change-Id: Id0ffe967ffba5097536892f75ba7eb2c42a952b9

src/bthread/butex.cpp

@@ -653,7 +653,7 @@ int butex_wait(void* arg, int expected_value, const timespec* abstime) {
         }
     }
 #ifdef SHOW_BTHREAD_BUTEX_WAITER_COUNT_IN_VARS
-    bvar::Adder<int64_t>* num_waiters = *butex_waiter_count();
+    bvar::Adder<int64_t>& num_waiters = butex_waiter_count();
     num_waiters << 1;
 #endif
 

src/bthread/parking_lot.h

@@ -27,8 +27,13 @@ namespace bthread {
 // Park idle workers.
 class BAIDU_CACHELINE_ALIGNMENT ParkingLot {
 public:
-    struct State {
+    class State {
+    public:
+        State(): val(0) {}
         bool stopped() const { return val & 1; }
+    private:
+    friend class ParkingLot;
+        State(int val) : val(val) {}
         int val;
     };
 
@@ -43,8 +48,7 @@ public:
 
     // Get a state for later wait().
     State get_state() {
-        const State st = {_pending_signal.load(base::memory_order_acquire)};
-        return st;
+        return _pending_signal.load(base::memory_order_acquire);
     }
 
     // Wait for tasks.

src/bthread/task_group.cpp

@@ -174,9 +174,6 @@ void TaskGroup::run_main_task() {
     
     TaskGroup* dummy = this;
     bthread_t tid;
-#ifndef BTHREAD_DONT_SAVE_PARKING_STATE
-    _last_pl_state = _pl->get_state();
-#endif
     while (wait_task(&tid)) {
         TaskGroup::sched_to(&dummy, tid);
         DCHECK_EQ(this, dummy);