Question

我正在研究多线程代码，其中线程必须在特定时间内休眠。我不想浪费CPU周期并且想要/必须使用定时器。这或多或少是我想要达到的目标。

我的单线程代码似乎工作正常。

#include <cstdlib>
#include <iostream>
#include <time.h>
#include <sys/siginfo.h>
#include <signal.h>
#include <unistd.h>

volatile sig_atomic_t print_flag = false;

void handle_alarm(int sig)
{
    print_flag = true;
}

int main(int argc, char *argv[])
{
    //struct sigevent event;


    signal( SIGALRM, handle_alarm ); // Install handler first,

    timer_t timerid;
    struct itimerspec timer;

    timer_create(CLOCK_REALTIME,NULL,&timerid);

    timer.it_value.tv_sec = 1;
    timer.it_value.tv_nsec = 0;
    timer.it_interval.tv_sec = 0;
    timer.it_interval.tv_sec = 0;

    std::cout << "Setting timer" << std::endl;

    timer_settime(timerid,0,&timer,NULL);

    pause();

    std::cout << "Hello\n" << std::endl;

    return EXIT_SUCCESS;
}

但我的多线程卡在执行中。我的主线程在等待线程时陷入困境，而thread1在设置定时器时卡住了。知道为什么thread1没有完成执行吗？

#include <cstdlib>
#include <iostream>
#include <time.h>
#include <sys/siginfo.h>
#include <signal.h>
#include <unistd.h>
#include <pthread.h>


volatile sig_atomic_t print_flag = false;

void handle_alarm(int sig)
{
    print_flag = true;
}
void *mythread(void* time)
{
    signal( SIGALRM, handle_alarm ); // Install handler first,

    timer_t timerid;
    struct itimerspec timer;

    timer_create(CLOCK_REALTIME,NULL,&timerid);

    timer.it_value.tv_sec = *(int*)time;
    timer.it_value.tv_nsec = 0;
    timer.it_interval.tv_sec = 0;
    timer.it_interval.tv_sec = 0;

    std::cout << "Setting timer" << std::endl;

    timer_settime(timerid,0,&timer,NULL);

    pause();

    std::cout << "Hello" << *(int*)time << std::endl;

}

int main(int argc, char *argv[])
{

    pthread_t thread1, thread2;

    std::cout << "Started threads\n" << std::endl;

    int temp1 = 10,temp2 = 5;

    pthread_create(&thread1, NULL, &mythread,(void*) &temp1);
    pthread_create(&thread2, NULL, &mythread,(void*) &temp2);

    std::cout << "Waiting for threads\n" << std::endl;

    pthread_join(thread1,NULL);
    pthread_join(thread2,NULL);

    std::cout << "Done\n" << std::endl;

    return EXIT_SUCCESS;
}

编辑：

我用几种方法做到了，

通过使用nanosleep，它只是克服了一个问题，忙着等待。
使用clock_nanosleep，它类似于nanosleep，除了它使用相对时钟
使用timer_settime（pulse），线程等待给定时间的脉冲，最后输出

Answer 1

我这样做了

struct sigevent         event;
struct itimerspec       itime;
timer_t                 timer_id;
int                     chid, rcvid;
my_message_t            msg;

chid = ChannelCreate(0);

// following code is used to get kick every pulse period time
// which is 20ms
event.sigev_notify = SIGEV_PULSE;
event.sigev_coid = ConnectAttach(ND_LOCAL_NODE, 0,
        chid,
        _NTO_SIDE_CHANNEL, 0);
event.sigev_priority = getprio(0);
event.sigev_code = _PULSE_CODE_MINAVAIL;
timer_create(CLOCK_REALTIME, &event, &timer_id);

// 20 ms to nano seconds
itime.it_value.tv_sec = 0;
itime.it_value.tv_nsec = 20000000;
itime.it_interval.tv_sec = 0;
itime.it_interval.tv_nsec = 20000000;
timer_settime(timer_id, 0, &itime, NULL);

SERVO1DELAY1.tv_sec = 0;
SERVO1DELAY1.tv_nsec = 100000;

while(1)
{
    rcvid = MsgReceive(chid, &msg, sizeof(msg), NULL);
    if (rcvid == 0)
    {
        // make pulse high for appropriate time
        out8( data_handle_A, HIGH );
        InterruptDisable();
        nanospin(&SERVO1DELAY1);
        InterruptEnable();
        out8( data_handle_A, LOW );
    }
}

使用计时器和信号代替睡眠c / c ++

1 个答案: