see #2: revision of parallelism and concurrency

code/7/7.2.critical.section.a.cpp

@@ -0,0 +1,32 @@
+//
+// 7.2.critical.section.a.cpp
+// chapter 7 parallelism and concurrency
+// modern c++ tutorial
+//
+// created by changkun at changkun.de
+// https://github.com/changkun/modern-cpp-tutorial
+//
+
+#include <iostream>
+#include <thread>
+
+int v = 1;
+
+void critical_section(int change_v) {
+    static std::mutex mtx;
+    std::lock_guard<std::mutex> lock(mtx);
+
+    // do contention operations
+    v = change_v;
+
+    // mtx will be destructed when exit this region
+}
+
+int main() {
+    std::thread t1(critical_section, 2), t2(critical_section, 3);
+    t1.join();
+    t2.join();
+
+    std::cout << v << std::endl;
+    return 0;
+}