嘗試用c11的條件變數和mutex寫了一個讀寫鎖，c11條件變數

嘗試用c11的條件變數和mutex寫了一個讀寫鎖，c11條件變數

大家多多指正哈~

https://github.com/fishCi/c11/blob/master/rwlock.cpp

#include<thread>#include<mutex>#include<iostream>#include<unistd.h>#include<condition_variable>using namespace std;class rwlock {    private:        mutex _lock;        condition_variable _wcon, _rcon;        unsigned _writer, _reader;        int _active;    public:        void read_lock() {            unique_lock<mutex> lock(_lock);            ++_reader;            while(_active < 0 || _writer > 0)                _rcon.wait(lock);            --_reader;            ++_active;        }        void write_lock() {            unique_lock<mutex> lock(_lock);            ++_writer;            while(_active != 0)                _wcon.wait(lock);            --_writer;            _active = -1;        }        void unlock() {            unique_lock<mutex> lock(_lock);            if(_active > 0) {                --_active;                if(_active == 0) _wcon.notify_one();            }else{                _active = 0;                if(_writer > 0) _wcon.notify_one();                else if(_reader > 0) _rcon.notify_all();            }        }        rwlock():_writer(0),_reader(0),_active(0){        }};void t1(rwlock* rwl) {    while(1) {        cout << "I want to write." << endl;        rwl->write_lock();        cout << "writing..." << endl;        sleep(5);        rwl->unlock();        sleep(5);    }}void t2(rwlock* rwl) {    while(1) {        cout << "t2-I want to read." << endl;        rwl->read_lock();        cout << "t2-reading..." << endl;        sleep(1);        rwl->unlock();    }}void t3(rwlock* rwl) {    while(1) {        cout << "t3-I want to read." << endl;        rwl->read_lock();        cout << "t3-reading..." << endl;        sleep(1);        rwl->unlock();    }}int main(){    rwlock* rwl = new rwlock();    thread th1(t1,rwl);    thread th2(t2,rwl);    thread th3(t3,rwl);    th1.join();    th2.join();    th3.join();    return 0;}

什是讀寫鎖?用java設計一個簡單的讀寫鎖

package com;

import java.util.Date;

public class InterruptTest {

public static void main(String args []){

MyThread test=new MyThread();
test.start();

try{
Thread.sleep(2000);

}catch(InterruptedException e){
e.printStackTrace();
}
test.interrupt();

}
}

class MyThread extends Thread{

public void run(){

while(true){
System.out.println("---"+new Date()+"---");

try{
Thread.sleep(2000);
}catch(InterruptedException e){
e.printStackTrace();
return ;
}

}
}
}
 
條件變數 教

pthread_mutex_lock(&q);
while(work==null)
pthread_cond_wait(&r,&q);
//代碼
pthread_mutex_unlock(&q);

pthread_mutex_lock(&q);
//代碼
pthread_nutex_unlock(&q);
pthread_cond_signal(&r);

大俠已經解釋得差不多了，我只補充一下。

1、線程2 並沒有等待訊號量，所以線程1裡沒必要加上
pthread_cond_signal(&cond2);

2、線程1在 wait signal 時會自動解鎖，所以並不會出現死結的情況