c++ - Cancelling thread that is stuck on epoll_wait -

i'm doing event handling c++ , pthreads. have main thread reads event queue defined, , worker thread fills event queue. queue of course thread safe.

the worker thread have list of file descriptors , create epoll system call events on file descriptors. uses epoll_wait wait events on fd's.

now problem. assuming want terminate application cleanly, how can cancel worker thread properly? epoll_wait not 1 of cancellation points of pthread(7) cannot react on pthread_cancel.

the worker thread main() looks this

while(m_workerrunning) {     epoll_wait(m_epolldescriptor, events, maxevents, -1);     //handle events , insert queue } 

the m_workerrunning set true when thread starts , looks can interrupt thread settings m_workerrunning false main thread. problem epoll_wait theoretically can wait forever.

other solution though is: instead of waiting forever (-1) can wait example x time slots, handle no-events case , if m_workerrunning == false exit loop , terminate worker thread cleanly. main thread sets m_workerrunning false, , sleeps x. i'm not sure performance of such epoll_wait , not sure correct x? 500ms? 1s? 10s?

i'd hear experienced advises!

more relevant information: fd's i'm waiting events on, devices in /dev/input technically i'm doing sort of input subsystem. targeted os linux (latest kernel) on arm architecture.

thanks!

you send thread signal interupt blocking call epoll_wait(). if doing modify code this:

while(m_workerrunning)  {   int result = epoll_wait(m_epolldescriptor, events, maxevents, -1);   if (-1 == result)   {     if (eintr == errno)     {       /* handle shutdown request here. */        break;     }     else     {       /* error handling goes here. */     }   }    /* handle events , insert queue. */ } 

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a way add signal handler:

#include <signal.h>  /* generic signal handler doing nothing */ void signal_handler(int sig) {   sig = sig; /* cheat compiler not give warning unused variable. */ }  /* wrapper set signal handler */ int signal_handler_set(int sig, void (*sa_handler)(int)) {   struct sigaction sa = {0};   sa.sa_handler = sa_handler;   return sigaction(sig, &sa, null); } 

to set handler signal sigusr1 do:

if (-1 == signal_handler_set(sigusr1, signal_handler)) {   perror("signal_handler_set() failed"); } 

to send signal sigusr1 process:

if (-1 == kill(<target process' pid>, sigusr1)) {   perror("kill() failed"); } 

to have process send signal itself:

if (-1 == raise(sigusr1)) {   perror("raise() failed"); }