udpate thread tutorial.md

Author: forhappy

zh/chapter3-Thread/Introduction-to-Thread.md

@@ -262,11 +262,173 @@ thread& operator=(const thread&) = delete;
  t.join();
  }
 
-- `join`: Join 线程。
+- `join`: Join 线程，调用该函数会阻塞当前线程，直到由 `*this` 所标示的线程执行完毕，join 才返回。
+
+ #include <iostream>
+ #include <thread>
+ #include <chrono>
+ 
+ void foo()
+ {
+ // simulate expensive operation
+ std::this_thread::sleep_for(std::chrono::seconds(1));
+ }
+ 
+ void bar()
+ {
+ // simulate expensive operation
+ std::this_thread::sleep_for(std::chrono::seconds(1));
+ }
+ 
+ int main()
+ {
+ std::cout << "starting first helper...\n";
+ std::thread helper1(foo);
+ 
+ std::cout << "starting second helper...\n";
+ std::thread helper2(bar);
+ 
+ std::cout << "waiting for helpers to finish..." << std::endl;
+ helper1.join();
+ helper2.join();
+ 
+ std::cout << "done!\n";
+ }
+
 - `detach`: Detach 线程。
+将当前线程对象所代表的执行实例与该线程对象分离，使得线程的执行可以单独进行。一旦线程执行完毕，它所分配的资源将会被释放。
+
+调用 detach 函数之后：
+
+- `*this` 不再代表任何的线程执行实例。
+- joinable() == false
+- get_id() == std::thread::id()
+
+另外，如果出错或者 `joinable() == false`，则会抛出 `std::system_error`.
+
+ #include <iostream>
+ #include <chrono>
+ #include <thread>
+  
+ void independentThread() 
+ {
+  std::cout << "Starting concurrent thread.\n";
+  std::this_thread::sleep_for(std::chrono::seconds(2));
+  std::cout << "Exiting concurrent thread.\n";
+ }
+  
+ void threadCaller() 
+ {
+  std::cout << "Starting thread caller.\n";
+  std::thread t(independentThread);
+  t.detach();
+  std::this_thread::sleep_for(std::chrono::seconds(1));
+  std::cout << "Exiting thread caller.\n";
+ }
+  
+ int main() 
+ {
+  threadCaller();
+  std::this_thread::sleep_for(std::chrono::seconds(5));
+ }
+
 - `swap`: Swap 线程 。
-- `native_handle`: 返回 native handle。
-- `hardware_concurrency` [static]: 检测硬件并发特性。
+
+ #include <iostream>
+ #include <thread>
+ #include <chrono>
+ 
+ void foo()
+ {
+ std::this_thread::sleep_for(std::chrono::seconds(1));
+ }
+ 
+ void bar()
+ {
+ std::this_thread::sleep_for(std::chrono::seconds(1));
+ }
+ 
+ int main()
+ {
+ std::thread t1(foo);
+ std::thread t2(bar);
+ 
+ std::cout << "thread 1 id: " << t1.get_id() << std::endl;
+ std::cout << "thread 2 id: " << t2.get_id() << std::endl;
+ 
+ std::swap(t1, t2);
+ 
+ std::cout << "after std::swap(t1, t2):" << std::endl;
+ std::cout << "thread 1 id: " << t1.get_id() << std::endl;
+ std::cout << "thread 2 id: " << t2.get_id() << std::endl;
+ 
+ t1.swap(t2);
+ 
+ std::cout << "after t1.swap(t2):" << std::endl;
+ std::cout << "thread 1 id: " << t1.get_id() << std::endl;
+ std::cout << "thread 2 id: " << t2.get_id() << std::endl;
+ 
+ t1.join();
+ t2.join();
+ }
+
+执行结果如下：
+
+ thread 1 id: 1892
+ thread 2 id: 2584
+ after std::swap(t1, t2):
+ thread 1 id: 2584
+ thread 2 id: 1892
+ after t1.swap(t2):
+ thread 1 id: 1892
+ thread 2 id: 2584
+
+- `native_handle`: 返回 native handle（与操作系统相关）。
+
+ #include <thread>
+ #include <iostream>
+ #include <chrono>
+ #include <cstring>
+ #include <pthread.h>
+ 
+ std::mutex iomutex;
+ void f(int num)
+ {
+ std::this_thread::sleep_for(std::chrono::seconds(1));
+ 
+ sched_param sch;
+ int policy; 
+ pthread_getschedparam(pthread_self(), &policy, &sch);
+ std::lock_guard<std::mutex> lk(iomutex);
+ std::cout << "Thread " << num << " is executing at priority "
+ << sch.sched_priority << '\n';
+ }
+ 
+ int main()
+ {
+ std::thread t1(f, 1), t2(f, 2);
+ 
+ sched_param sch;
+ int policy; 
+ pthread_getschedparam(t1.native_handle(), &policy, &sch);
+ sch.sched_priority = 20;
+ if(pthread_setschedparam(t1.native_handle(), SCHED_FIFO, &sch)) {
+ std::cout << "Failed to setschedparam: " << std::strerror(errno) << '\n';
+ }
+ 
+ t1.join();
+ t2.join();
+ }
+
+- `hardware_concurrency` [static]: 检测硬件并发特性，返回当前实现所支持的线程并发数目，然后返回值仅仅只作为系统提示。
+
+ #include <iostream>
+ #include <thread>
+ 
+ int main() {
+ unsigned int n = std::thread::hardware_concurrency();
+ std::cout << n << " concurrent threads are supported.\n";
+ }
 
 ## `std::this_thread` 命名空间中相关辅助函数介绍 ##