select call takes more time than the given timeout

May 17, 2013

      Hello,

The Select system call has given the timeout of 100 msec and but its
expired after 115 msecs.

I have no fds to read, and just wanted to use select as the timer to
timeout and so some stuff after the timeout happen.

code:

#include <stdio.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/select.h>

main()
{
         int ret;

         struct timeout tv;

         tv.tv_sec = 0;
         tv.tv_usec = 100000;

        while (1) {
         ret = select(5, 0, 0, 0, &tv);
         if (ret == 0) {
            struct timeval t;
             gettimeofday(&t, 0);

            printf("sec = %d-usec = %d\n", t.tv_sec, t.tv_usec);
         }
        }
}

my kernel is older, 2.6.23.

thanks,

select call takes more time than the given timeout

devendra.aaru