add more lock tutorial.

Author: forhappy

zh/chapter4-Mutex/4.2 Mutex-tutorial.md

@@ -138,3 +138,72 @@
 ### `std::recursive_timed_mutex` 介绍 ###
 
 和 `std:recursive_mutex` 与 `std::mutex` 的关系一样，`std::recursive_timed_mutex` 的特性也可以从 `std::timed_mutex` 推导出来，感兴趣的同鞋可以自行查阅。;-)
+
+### std::lock_guard 介绍 ###
+
+与 Mutex RAII 相关，方便线程对互斥量上锁。例子（[参考](http://www.cplusplus.com/reference/mutex/lock_guard/)）:
+
+    #include <iostream>       // std::cout
+    #include <thread>         // std::thread
+    #include <mutex>          // std::mutex, std::lock_guard
+    #include <stdexcept>      // std::logic_error
+
+    std::mutex mtx;
+
+    void print_even (int x) {
+        if (x%2==0) std::cout << x << " is even\n";
+        else throw (std::logic_error("not even"));
+    }
+
+    void print_thread_id (int id) {
+        try {
+            // using a local lock_guard to lock mtx guarantees unlocking on destruction / exception:
+            std::lock_guard<std::mutex> lck (mtx);
+            print_even(id);
+        }
+        catch (std::logic_error&) {
+            std::cout << "[exception caught]\n";
+        }
+    }
+
+    int main ()
+    {
+        std::thread threads[10];
+        // spawn 10 threads:
+        for (int i=0; i<10; ++i)
+            threads[i] = std::thread(print_thread_id,i+1);
+
+        for (auto& th : threads) th.join();
+
+        return 0;
+    }
+
+### `std::unique_lock` 介绍 ###
+
+与 Mutex RAII 相关，方便线程对互斥量上锁，但提供了更好的上锁和解锁控制。例子（[参考](http://www.cplusplus.com/reference/mutex/unique_lock/)）：
+
+    #include <iostream>       // std::cout
+    #include <thread>         // std::thread
+    #include <mutex>          // std::mutex, std::unique_lock
+
+    std::mutex mtx;           // mutex for critical section
+
+    void print_block (int n, char c) {
+        // critical section (exclusive access to std::cout signaled by lifetime of lck):
+        std::unique_lock<std::mutex> lck (mtx);
+        for (int i=0; i<n; ++i) {
+            std::cout << c;
+        }
+        std::cout << '\n';
+    }
+
+    int main ()
+    {
+        std::thread th1 (print_block,50,'*');
+        std::thread th2 (print_block,50,'$');
+
+        th1.join();
+        th2.join();
+
+        return 0;
+    }