UNIX/Linux 信号处理：SIGEV_THREAD
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UNIX/Linux signal handling: SIGEV_THREAD
提问by kingsmasher1
I have put a simple signal handler in my code. I have initialised the sigevent structure, with a handler function to catch the signal.
我在我的代码中放置了一个简单的信号处理程序。我已经初始化了 sigevent 结构，使用处理函数来捕获信号。
Can someone please pin-point as to why the code is not working? Ideally if there is a signal, my handler should be called. But it is not.
有人可以指出为什么代码不起作用吗？理想情况下，如果有信号，则应调用我的处理程序。但事实并非如此。
Please help me, Thanks Kingsmasher1
请帮助我，谢谢 Kingsmasher1
enter code here
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <signal.h>
#include <time.h>
void my_handler(int sival_int, void* sival_ptr)
{
printf("my_handler caught\n");
signal(sig,my_handler);
}
int main()
{
struct sigevent sevp;
sevp.sigev_notify=SIGEV_THREAD;
sevp.sigev_signo=SIGRTMIN;
sevp.sigev_value.sival_ptr=NULL;
sevp.sigev_notify_function=(void*)my_handler;
kill(0,SIGRTMIN); // This should invoke the signal and call the function
}
采纳答案by caf
struct sigeventis not about specifying how the process will handle a signal - struct sigactionand sigaction()are how you do that. Instead, struct sigeventis used to specify how your process will be informed of some asychronous event - like the completion of asychronous IO, or a timer expiring.
struct sigevent是不是指定进程将如何处理的信号-struct sigaction和sigaction()你是如何做到这一点。相反，struct sigevent用于指定如何将某些异步事件通知您的进程 - 例如异步 IO 的完成或计时器到期。
The sigev_notifyfield specifies how the event should be notified:
该sigev_notify字段指定应如何通知事件：
SIGEV_NONE- no notification at all. The remainder of the fields are ignored.SIGEV_SIGNAL- a signal is sent to the process. Thesigev_signofield specifies the signal, thesigev_valuefield contains supplementary data that is passed to the signal handling function, and the remainder of the fields are ignored.SIGEV_THREAD- a function is called in a new thread. Thesigev_notify_functionfield specifies the function that is called,sigev_valuecontains supplementary data that is passed to the function, andsigev_notify_attributesspecifies thread attributes to use for the thread creation. The remainder of the fields are ignored.
SIGEV_NONE- 根本没有通知。其余字段将被忽略。SIGEV_SIGNAL- 向进程发送信号。该sigev_signo字段指定信号，该sigev_value字段包含传递给信号处理函数的补充数据，其余字段将被忽略。SIGEV_THREAD- 在新线程中调用函数。该sigev_notify_function字段指定被调用的函数，sigev_value包含传递给函数的补充数据，并sigev_notify_attributes指定用于创建线程的线程属性。其余字段将被忽略。
Note in particular that if you set SIGEV_THREAD, the sigev_signofield is ignored - the struct sigeventis about specifying eithera thread or a signal as a notification method, not about specifying a thread as the way that a signal should be handled.
请特别注意，如果你设置SIGEV_THREAD，该sigev_signo字段被忽略-struct sigevent是关于指定任何一个线程或信号的通知方法，不是指定一个线程中的信号应该处理方式。
The struct sigeventmust also be passed to a function - like timer_create()- that sets up the asychronous event that will be notified. Simply creating a struct sigeventobject does not do anything special.
该struct sigevent还必须传递给函数-像timer_create()- ，设置了将被通知台异步事件。简单地创建一个struct sigevent对象并没有做任何特别的事情。
If you wish to use a dedicated thread to handle a signal, create the thread up front and have it loop around, blocking on sigwaitinfo(). Use sigprocmask()to block the signal in every other thread.
如果您希望使用专用线程来处理信号，请预先创建线程并使其循环，阻塞在sigwaitinfo(). 用于sigprocmask()在每个其他线程中阻止信号。
回答by Hymanson
I think you are mixing up your signal handling idioms here, you create a sigeventstructure and then do nothing with it and then use signal()within the signal handler. The following code shows a very simple signal handling routine based on your code; note that I have changed the definition of my_handler. If you need more sophisticated handling then sigaction()is probably the system call you need to look into.
我认为你在这里混淆了你的信号处理习惯用法，你创建了一个sigevent结构，然后什么都不做，然后signal()在信号处理程序中使用。以下代码显示了基于您的代码的非常简单的信号处理例程；请注意，我已经更改了my_handler. 如果您需要更复杂的处理，那么sigaction()可能是您需要研究的系统调用。
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <signal.h>
#include <time.h>
void my_handler(int sig)
{
printf("my_handler caught\n");
signal(sig,my_handler);
}
int main()
{
signal(SIGRTMIN,my_handler);
kill(0,SIGRTMIN); // This should invoke the signal and call the function
while(1) ; // Infinite loop in case the program ends before the signal gets caught!
}
This works under cygwinon my windows box (no access to a linux box at the minute).
这适用cygwin于我的 windows 机器（目前无法访问 linux 机器）。
回答by Suganthan Sundaram
I hope this works.
我希望这有效。
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <signal.h>
#include <time.h>
void
my_handler (int sig)
{
printf ("my_handler caught\n");
signal (sig, my_handler);
}
int
main ()
{
int signo;
struct sigevent sevp;
sigset_t set;
if (sigemptyset (&set) == -1)
perror ("sigemptyset");
if (sigaddset (&set, SIGRTMIN) == -1)
perror ("sigaddset");
if (sigprocmask (SIG_BLOCK, &set, NULL) == -1)
perror ("sigprocmask");
sevp.sigev_notify = SIGEV_THREAD;
sevp.sigev_signo = SIGRTMIN;
sevp.sigev_value.sival_ptr = NULL;
kill (0, SIGRTMIN);
if (sigwait (&set, &signo) == 0)
my_handler (signo);
else
perror ("sigwait");
}
