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关于pthread_mutex多个线程忙等待问题?

0
悬赏园豆:100 [待解决问题]

文档说如果对一个已加锁的mutex再次加锁pthread_mutex_lock会形成一个等待队列。可是这个示例有点奇怪,我知道线程没有放弃cpu,可是为什么后面输出的hello不到数量?

ifndef THREAD_POOL_H

define THREAD_POOL_H

include <pthread.h>

include <errno.h>

include <iostream>

include <unistd.h>

include <queue>

class sample
{
public:
void process();
};

template <typename T>
class threadPool
{
public:
threadPool();
void append(T &s);
static void worker(void s);

private:
std::queue<T *> tasks;
pthread_t threads[5];
bool run = true;
pthread_mutex_t t;
};

// template <typename T>
// void threadPool<T>::append(T& s)
// {
// pthread_t t;
// pthread_create(&t,nullptr,worker,&s);
// pthread_detach(t);
// }
template <typename T>
threadPool<T>::threadPool() : tasks()
{
pthread_mutex_init(&t,nullptr);
for(int i=0;i<5;++i)
{
pthread_create(&threads[i],nullptr,worker,this);
pthread_detach(threads[i]);
}
}

template <typename T>
void threadPool<T>::append(T &s)
{
pthread_mutex_lock(&t);
tasks.push(&s);
printf("%d append.\n",pthread_self());
pthread_mutex_unlock(&t);
}

template <typename T>
void threadPool<T>::worker(void s)
{
auto pool=static_cast<threadPool<T>*>(s);
while (pool->run)
{
pthread_mutex_lock(&(pool->t));
if (pool->tasks.empty())
{
pthread_mutex_unlock(&(pool->t));
printf("%d get the lock but continue.\n",pthread_self());
continue;
}
auto work = pool->tasks.front();
pool->tasks.pop();
printf("%d get the lock and print\n",pthread_self());
pthread_mutex_unlock(&(pool->t));
work->process();
}
return nullptr;
}

endif //!THREAD_POOL_H

include "thread_pool.h"

void sample::process()
{
std::cout<<"hello world.\n"<<std::endl;
}

include "thread_pool.h"

include <iostream>

int main(int argc, char **argv)
{
threadPool<sample> pool;
sample d[100];
for(int i=0;i<100;++i)
{
pool.append(d[i]);
}
return 0;
}
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hello world.
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1285158720 append.
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1234736896 get the lock and print
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头晕了一下午,麻烦大佬出来解救众生。

manch1n的主页 manch1n | 初学一级 | 园豆:84
提问于:2019-05-12 01:02
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所有回答(1)
0

main函数已经退出了,其他打印都看不到了
main末尾加个 getchar() 或者同步等待下

2012 | 园豆:18932 (专家六级) | 2019-05-13 09:00
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