Fix ParkingLot::signal does not modify _pending_signal when there is no waiter (#2916)

Author: chenBright

src/brpc/event_dispatcher.cpp

@@ -51,6 +51,7 @@ static void StopAndJoinGlobalDispatchers() {
     delete g_edisp_read_lantency;
     delete g_edisp_write_lantency;
 }
+
 void InitializeGlobalDispatchers() {
     g_edisp_read_lantency = new bvar::LatencyRecorder("event_dispatcher_read_latency");
     g_edisp_write_lantency = new bvar::LatencyRecorder("event_dispatcher_write_latency");

src/bthread/parking_lot.h

@@ -45,10 +45,10 @@ class BAIDU_CACHELINE_ALIGNMENT ParkingLot {
     // Wake up at most `num_task' workers.
     // Returns #workers woken up.
     int signal(int num_task) {
+        _pending_signal.fetch_add((num_task << 1), butil::memory_order_release);
         if (_waiter_num.load(butil::memory_order_relaxed) == 0) {
             return 0;
         }
-        _pending_signal.fetch_add((num_task << 1), butil::memory_order_release);
         return futex_wake_private(&_pending_signal, num_task);
     }
 

src/butil/file_util_posix.cc

@@ -601,7 +601,7 @@ bool CreateDirectoryAndGetError(const FilePath& full_path,
     if (mkdir(i->value().c_str(), 0755/*others can read the dir*/) == 0)
       continue;
     // Mkdir failed, but it might have failed with EEXIST, or some other error
-    // due to the the directory appearing out of thin air. This can occur if
+    // due to the directory appearing out of thin air. This can occur if
     // two processes are trying to create the same file system tree at the same
     // time. Check to see if it exists and make sure it is a directory.
     int saved_errno = errno;