Messages in this thread | | | Subject | Re: Repost: Bug with select? | From | Philippe Troin <> | Date | 25 Jul 2003 17:35:17 -0700 |
| |
Eli Barzilay <eli@barzilay.org> writes:
> [This is a second post, since I didn't get any replies the first time. > It looks more like a bug now, which sounds strange for something that > common...] > > When I run the following program, and block the terminal's output > (C-s), the `select' doesn't seem to have any effect, resulting in a > 100% cpu usage (this is on a RH8, with 2.4.18). I wouldn't be > surprised if I'm doing something stupid, but it does seem to work fine > on Solaris. > > Is there anything wrong with this, or is this some bug? > > ====================================================================== > #include <unistd.h> > #include <fcntl.h> > int main() { > int flags, fd, len; fd_set writefds; > fd = 1; > flags = fcntl(fd, F_GETFL, 0); > fcntl(fd, F_SETFL, flags | O_NONBLOCK); > while (1) { > FD_ZERO(&writefds); > FD_SET(fd, &writefds); > len = select(fd + 1, NULL, &writefds, NULL, NULL); > if (!FD_ISSET(fd,&writefds)) exit(0); > len = write(fd, "hi\n", 3); > } > fcntl(fd, F_SETFL, flags); > } > ======================================================================
Looks like a bug to me. Strace says:
select(2, NULL, [1], NULL, NULL) = 1 (out [1]) write(1, "hi\n", 3) = -1 EAGAIN (Resource temporarily unavailable)
forever.
Then select() should not return fd 1 as writable, at least not reapeatedly.
Phil. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |