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learnmoreonce
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ch5
1 parent 726b7cf commit 7515d9b

13 files changed

Lines changed: 89 additions & 42 deletions

‎Cpp-Concurrency-in-Action/CMakeLists.txt‎

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@@ -2,11 +2,18 @@ cmake_minimum_required(VERSION 3.6)
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project(Cpp_Concurrency_in_Action)
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SET (CMAKE_C_COMPILER "/usr/bin/clang")
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SET(CMAKE_CXX_COMPILER "clang++")
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#set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14 -lpthread ")
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set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14 -lpthread -stdlib=libc++ -lc++abi ")
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#set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -stdlib=libc++ -std=c++14 -lc++abi -lboost_thread -lboost_system ")
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set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} --std=c++1z -lpthread -stdlib=libc++ -lc++abi ")
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#set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14 -lpthread ")
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add_subdirectory(ch1)
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add_subdirectory(ch2)
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add_subdirectory(ch3)
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add_subdirectory(ch4)
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add_subdirectory(ch4)
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add_subdirectory(ch5)

‎Cpp-Concurrency-in-Action/ch5/CMakeLists.txt‎

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add_executable(listing_5.0.3_atomic_default listing_5.0.3_atomic_default.cpp)
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add_executable(listing_5.0.4_atomic_flag_test_and_set listing_5.0.4_atomic_flag_test_and_set.cpp)
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add_executable(listing_5.1.1 listing_5.1.1.cpp)
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add_executable(listing_5.1.2 listing_5.1.2.cpp)
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add_executable(listing_5.1.3 listing_5.1.3.cpp)

‎Cpp-Concurrency-in-Action/ch5/listing_5.0.0std_atomic.cpp‎

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#include <atomic>
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/*
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原子类型对象的主要特点就是从不同线程访问不会导致数据竞争(data race)。
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因此从不同线程访问某个原子对象是良性 (well-defined) 行为,

‎Cpp-Concurrency-in-Action/ch5/listing_5.0.1integal_整数特化.cpp‎

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@@ -1,12 +1,9 @@
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//
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// Created by shen on 16-11-6.
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//
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/*
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* 另外，C++11 标准库 std::atomic 提供了针对整形(integral)和指针类型的特化实现，分别定义如下：
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/*
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另外，C++11 标准库 std::atomic 提供了针对整形(integral)和指针类型的特化实现，分别定义如下：
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针对整形(integal)的特化，其中 integal 代表了如下类型
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char, signed char, unsigned char, short, unsigned short, int, unsigned int,
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long, unsigned long, long long, unsigned long long, char16_t, char32_t, wchar_t：
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char, signed char, unsigned char, short, unsigned short, int, unsigned int,
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long, unsigned long, long long, unsigned long long, char16_t, char32_t, wchar_t：
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*/
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template <> struct atomic<integral> {
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bool is_lock_free() const volatile;

‎Cpp-Concurrency-in-Action/ch5/listing_5.0.2_atomic指针特化.cpp‎

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@@ -1,6 +1,4 @@
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//
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// Created by shen on 16-11-6.
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//
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template <class T> struct atomic<T*> {
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bool is_lock_free() const volatile;
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bool is_lock_free() const;

‎Cpp-Concurrency-in-Action/ch5/listing_5.0.3_atomic_default.cpp‎

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@@ -1,8 +1,4 @@
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//
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// Created by shen on 16-11-6.
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//
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include <iostream> // std::cout
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#include <iostream> // std::cout
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#include <atomic> // std::atomic, std::atomic_flag, ATOMIC_FLAG_INIT
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#include <thread> // std::thread, std::this_thread::yield
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#include <vector> // std::vector
@@ -13,9 +9,9 @@ std::atomic_flag winner = ATOMIC_FLAG_INIT;
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void do_count1m(int id)
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{
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while (!ready) { std::this_thread::yield(); } // 等待 ready 变为 true.
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while (!ready) { std::this_thread::yield(); } //礼让线程,等待ready变为true.
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for (volatile int i=0; i<1000000; ++i) {} // 计数
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for (volatile int i=0; i<100000000; ++i) {} // 计数
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if (!winner.test_and_set()) {
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std::cout << "thread #" << id << " won!\n";
@@ -26,7 +22,7 @@ int main ()
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{
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std::vector<std::thread> threads;
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std::cout << "spawning 10 threads that count to 1 million...\n";
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for (int i=1; i<=10; ++i) threads.push_back(std::thread(count1m,i));
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for (int i=1; i<=10; ++i) threads.push_back(std::thread(do_count1m,i));
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ready = true;
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for (auto& th : threads) th.join();

‎Cpp-Concurrency-in-Action/ch5/listing_5.0.4_atomic_flag_test_and_set.cpp‎

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// atomic_flag as a spinning lock
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#include <iostream> // std::cout
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#include <atomic> // std::atomic_flag
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#include <thread> // std::thread
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#include <vector> // std::vector
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#include <sstream> // std::stringstream
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/*
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bool test_and_set (memory_order sync = memory_order_seq_cst) noexcept;
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Sets the atomic_flag and returns whether it was already set immediately before the call.
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The entire operation is atomic (an atomic read-modify-write operation):
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the value is not affected by other threads between the instant its value
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is read (to be returned) and the moment it is modified by this function.
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true if the flag was set before the call.
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false otherwise.
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*/
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std::atomic_flag lock_stream = ATOMIC_FLAG_INIT;
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std::stringstream stream;
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void append_number(int x) {
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while (lock_stream.test_and_set()) {}
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stream << "thread #" << x << '\n';
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lock_stream.clear();
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}
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int main ()
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{
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std::vector<std::thread> threads;
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for (int i=1; i<=10; ++i) threads.push_back(std::thread(append_number,i));
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for (auto& th : threads) th.join();
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std::cout << stream.str();
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return 0;
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}

‎Cpp-Concurrency-in-Action/ch5/listing_5.1.1.cpp‎

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@@ -1,6 +1,3 @@
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//
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// Created by shen on 16-11-6.
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//
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#include <iostream> // std::cout
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#include <atomic> // std::atomic, std::atomic_flag, ATOMIC_FLAG_INIT
@@ -22,15 +19,21 @@ void count1m(int id)
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// 如果某个线程率先执行完上面的计数过程，则输出自己的 ID.
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// 此后其他线程执行 test_and_set 是 if 语句判断为 false，
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// 因此不会输出自身 ID.
25-
if (!winner.test_and_set()) {
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if (!winner.test_and_set()) {//之前未被设置，返回true。
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std::cout << "thread #" << id << " won!\n";
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}
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};
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/*
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test_and_set() 函数检查 std::atomic_flag 标志，如果 std::atomic_flag 之前没有被设置过，
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则设置 std::atomic_flag 的标志，并返回先前该 std::atomic_flag 对象是否被设置过，如果之前
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std::atomic_flag 对象已被设置，则返回 true，否则返回 false。
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test_and_set() 函数检查 std::atomic_flag 标志
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(一):
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1),如果 std::atomic_flag 之前没有被设置过，
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2),则设置 std::atomic_flag 的标志，并返回先前该 std::atomic_flag 对象是否被设置过.
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(二):
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1),如果之前std::atomic_flag 对象已被设置，则返回 true
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2),否则返回 false。
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test-and-set 操作是原子的（因此 test-and-set 是原子 read-modify-write （RMW）操作）
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*/
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‎Cpp-Concurrency-in-Action/ch5/listing_5.1.2.cpp‎

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//
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// Created by shen on 16-11-6.
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//
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#include <iostream> // std::cout
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#include <atomic> // std::atomic_flag

‎Cpp-Concurrency-in-Action/ch5/listing_5.1.3.cpp‎

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//
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// Created by shen on 16-11-6.
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//
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#include <thread>
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#include <vector>
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}
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}
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/*http://www.cnblogs.com/haippy/p/3252056.html
30+
/*
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在上面的程序中，std::atomic_flag 对象 lock 的上锁操作可以理解为 lock.test_and_set(std::memory_order_acquire);
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(此处指定了 Memory Order，更多有关 Memory Order 的概念，我会在后续的文章中介绍)，
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(此处指定了 Memory Order，更多有关 Memory Order 的概念 )
3633
解锁操作相当与 lock.clear(std::memory_order_release)。
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在上锁的时候，如果 lock.test_and_set 返回 false，则表示上锁成功（此时 while 不会进入自旋状态），
3835
因为此前 lock 的标志位为 false(即没有线程对 lock 进行上锁操作)，但调用 test_and_set 后 lock 的标志位为 true，

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