如何在 C 中使用 SIGEV_THREAD、sigevent 进行 linux-timer(s) 过期处理？

Question

问题：我有定时器运行，定时器到期后需要调用某些函数。输出：Hndlr() 函数中存在段错误

根据 sigevent 的手册页，它说，

SIGEV_THREAD - Notify the process by invoking sigev_notify_function "as if" it were the start function of a new thread. (Among the implement‐ tation possibilities here are that each timer notification could result in the creation of a new thread, or that a single thread is created to receive all notifications.)

The function (sigev_notify_function) is invoked with sigev_value as its sole argument

我确实提到了这个：UNIX/Linux signal handling: SIGEV_THREAD 它说，

sigev_value contains supplementary data that is passed to the function

所以，我写了以下内容，

typedef struct Info
{
enum Status
{
    Start = 1,
    Expire = 2
} TimerStatus;

int data;
timer_t timerId;
} Info_t;

void Hndlr(union sigval *sv)
   { 
       //Upon expiry I want to set this value of t1.TimerStatus Expire:
       //t1.TimerStatus = Expire;
       //So I have done this:
       sv->sival_int = Expire;
   }

   int TimerInit(Info_t *Type)
   {
       struct sigevent sev;
       sev.sigev_notify = SIGEV_THREAD;
       sev.sigev_value.sival_ptr = Type->timerId;
       sev.sigev_value.sival_int = Type->TimerStatus;
       sev.sigev_notify_function = &Hndlr;
       sev.sigev_notify_attributes = 0;

       timer_create(CLOCK_REALTIME, &sev, &(Type->timerId));
 }

 //other code

int main(int argc, char const *argv[])
{
Info_t t1;
t1.TimerStatus = Start;

TimerInit(&t1);
//start timer
//other code
while (1)
{

    if (t1.TimerStatus == Expire)
    {
        //do something, invoke a function
    }
}

return 0;

}

Warning: assignment to ‘void (*)(__sigval_t)’ {aka ‘void (*)(union sigval)’} from 
incompatible pointer type ‘void (*)(union sigval *)’ [-Wincompatible-pointer-types]
     sev.sigev_notify_function = &Hndlr;

因为我在 Hndlr 中使用 union sigval *sv，所以我收到了这个警告。

Q) 如何将枚举类型作为 pass-by-ptr 传递给 Hndlr 并更改它，即 t1.TimerStatus = Expire

PS：涉及timer_set()等的全部代码我没有包括在内，而且还涉及定时器的多个实例。那么，我怎样才能实现这个功能 (Q)？

Answer 1

代码中的一些错误：

定时器到期函数的函数原型错误 Hndlr。
设置 union sigval 的所有成员，而必须设置一个成员。
在另一个线程中修改和读取的变量必须是原子的。

一个工作示例（编译器选项 -std=c11 -pthread -W{all,extra}、链接器选项 -std=c11 -pthread -lrt）：

#include <stdatomic.h>
#include <stdlib.h>
#include <signal.h>
#include <time.h>

enum Status {
    Start = 1,
    Expire = 2
};

typedef struct {
    atomic_int status;
    int data;
    timer_t timerId;
} Info_t;

static void Hndlr(union sigval sigev_value) {
    Info_t* info = sigev_value.sival_ptr;
    atomic_store(&info->status, Expire);
}

void TimerInit(Info_t* info, unsigned seconds) {
    int r;
    struct sigevent sev;
    struct itimerspec its;

    sev.sigev_notify = SIGEV_THREAD;
    sev.sigev_value.sival_ptr = info;
    sev.sigev_notify_function = &Hndlr;
    sev.sigev_notify_attributes = 0;
    r = timer_create(CLOCK_REALTIME, &sev, &info->timerId);
    if(r)
        abort();

    its.it_interval.tv_sec = 0;
    its.it_interval.tv_nsec = 0;
    its.it_value.tv_sec = seconds;
    its.it_value.tv_nsec = 0;
    r = timer_settime(info->timerId, 0, &its, NULL);
    if(r)
        abort();
}

int main() {
    Info_t t1;
    t1.status = Start;
    TimerInit(&t1, 3);
    while(atomic_load(&t1.status) != Expire)
        ;

    return 0;
}

在这个特定的用法中，当计时器回调函数只是存储到一个变量中时，不需要使用另一个线程 SIGEV_THREAD，SIGEV_SIGNAL 也可以工作（设置代码更改是必需的），只要可以用信号句柄 EINTR.

中断的阻塞函数

如何在 C 中使用 SIGEV_THREAD、sigevent 进行 linux-timer(s) 过期处理？

How to use SIGEV_THREAD, sigevent for linux-timer(s) expiration handling in C?

c

linux

multithreading

posix

timer