std::shared_lock<Mutex>::lock
来自 cppreference.cn
< cpp | thread | shared lock
| void lock(); |
(since C++14) | |
以共享模式锁定关联的互斥量。 有效地调用 mutex()->lock_shared()。
目录 |
[编辑] 参数
(无)
[编辑] 返回值
(无)
[编辑] 异常
- mutex()->lock_shared() 抛出的任何异常。
- 如果没有关联的互斥量，则抛出 std::system_error，错误代码为 std::errc::operation_not_permitted。
- 如果关联的互斥量已经被此
shared_lock锁定（即 owns_lock 返回 true），则抛出 std::system_error，错误代码为 std::errc::resource_deadlock_would_occur。
[编辑] 示例
| 本节尚不完整 原因：展示 shared_lock::lock 的有意义用法 |
运行此代码
#include <iostream> #include <mutex> #include <shared_mutex> #include <string> #include <thread> std::string file = "Original content."; // Simulates a file std::mutex output_mutex; // mutex that protects output operations. std::shared_mutex file_mutex; // reader/writer mutex void read_content(int id) { std::string content; { std::shared_lock lock(file_mutex, std::defer_lock); // Do not lock it first. lock.lock(); // Lock it here. content = file; } std::lock_guard lock(output_mutex); std::cout << "Contents read by reader #" << id << ": " << content << '\n'; } void write_content() { { std::lock_guard file_lock(file_mutex); file = "New content"; } std::lock_guard output_lock(output_mutex); std::cout << "New content saved.\n"; } int main() { std::cout << "Two readers reading from file.\n" << "A writer competes with them.\n"; std::thread reader1{read_content, 1}; std::thread reader2{read_content, 2}; std::thread writer{write_content}; reader1.join(); reader2.join(); writer.join(); std::cout << "The first few operations to file are done.\n"; reader1 = std::thread{read_content, 3}; reader1.join(); }
可能的输出
Two readers reading from file. A writer competes with them. Contents read by reader #1: Original content. Contents read by reader #2: Original content. New content saved. The first few operations to file are done. Contents read by reader #3: New content
[编辑] 参见
| 尝试锁定关联的互斥量 (公共成员函数) | |
| 解锁关联的互斥量 (公共成员函数) |
