stdin

stdin

diff --git a/foo.cc b/foo.cc
index 3c4f06c..51e8965 100644
--- a/foo.cc
+++ b/foo.cc
@@ -33,11 +33,13 @@ Bank* Bank::global_instance = nullptr;
 // Singleton instance of the bank
 Bank* Bank::instance() {
     // avoid multiple creations of a bank instance
-    global_lock.lock();
     if (global_instance == nullptr) {
-       global_instance = new Bank;
+        global_lock.lock();
+        if (global_instance == nullptr) {
+           global_instance = new Bank;
+        }
+        global_lock.unlock();
     }
-    global_lock.unlock();
     return global_instance;
 }