epoll_wait fails due to EINTR, how to remedy this?

c linux system-calls epoll interrupted-exception
RajSanpui picture RajSanpui · Jul 29, 2011 · Viewed 9.5k times · Source

My epoll_wait fails due to EINTR. My gdb trace shows this:

enter code here
221     in ../nptl/sysdeps/pthread/createthread.c
(gdb) 
224     in ../nptl/sysdeps/pthread/createthread.c
(gdb) 
 [New Thread 0x40988490 (LWP 3589)]

227     in ../nptl/sysdeps/pthread/createthread.c
(gdb) 
epoll_wait error in start timer: Measurement will befor entire duration of execution
epoll_wait: Interrupted system call
[Thread 0x40988490 (LWP 3589) exited]

This string "epoll_wait error in start timer: Measurement will befor entire duration of execution" is printed by me in stderr.

I am not able to make out, how to remedy this EINTR so that epoll_wait can work. Any idea how this EINTR is generated by GDB trace?

Answer

Codo picture Codo · Jul 29, 2011

Certain signal handler will interrupt epoll_wait(), select() and similar system calls on any Unix or Linux. This is by design so you can interrupt these system calls.

You cannot directly remedy it. The typical solution is to explicitly check the errno for EINTR and to execute epoll_wait() again:

int nr;
do {
    nr = epoll_wait(epfd, events, maxevents, timeout);
} while (nr < 0 && errno == EINTR);

Also see: gdb error: Unable to execute epoll_wait: (4) Interrupted system call

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