原理
std::atomic_flag的方法test_and_set()是原子的昧绣。flag為false時， test_and_set()將flag置為true并返回false; flag為true時谤草， test_and_set()將返回true帘撰。
代碼實(shí)現(xiàn)
#include <pthread.h>
#include <atomic>
#include <iostream>
using namespace std;
int total = 0;
class spinLock {
private:
atomic_flag flag;
public:
spinLock(){};
void lock() {
while (flag.test_and_set()) ;
}
void unlock() {
flag.clear();
}
};
void *taskFunc(void* arg)
{
auto spin = (spinLock *)arg;
while (total < 10) {
spin->lock();
cout << "number:" << total << "; thread:" << pthread_self() << endl;
total++;
spin->unlock();
}
return NULL;
}
int main()
{
pthread_t pthid1, pthid2;
spinLock spin;
pthread_create(&pthid1, NULL, taskFunc, (void *)&spin);
pthread_create(&pthid2, NULL, taskFunc, (void *)&spin);
pthread_join(pthid1, NULL);
pthread_join(pthid2, NULL);
return 0;
}
測試結(jié)果
> g++ -o testspinlock testspinlock.cpp
> ./testspinlock
number:0; thread:0x70000afba000
number:1; thread:0x70000b03d000
number:2; thread:0x70000b03d000
number:3; thread:0x70000b03d000
number:4; thread:0x70000b03d000
number:5; thread:0x70000b03d000
number:6; thread:0x70000b03d000
number:7; thread:0x70000afba000
number:8; thread:0x70000afba000
number:9; thread:0x70000afba000
number:10; thread:0x70000b03d000
