On Sun, Dec 12, 2010 at 01:00:17PM -0600, Yarin wrote:
> As the documentation explains, when poll() is interrupted by a signal, it
> should return -1/EINTR.
> However, I'm getting a return indicating that all of the polling descriptors
> are ready, but when I check their flags out, none of them are
> ready. (Note that the same code behaves as expected on Linux)
> Here's a snippet of code that I wrote to deal smoothly this behavior:
> (specifically, the last line)
> pollfd wait_fd[2];
> wait_fd[0].fd = sock_fd;
> wait_fd[0].events = POLLOUT;
> wait_fd[1].fd = abort_fd;
> wait_fd[1].events = POLLIN;
> int rfds;
> do
> rfds = poll(wait_fd, 2, NULL);
^^^^
> while((rfds < 0 && errno == EINTR) || (rfds > 0 && !wait_fd[0].revents &&
> !wait_fd[1].revents));
This is not valid - poll takes an int argument here. NULL is interpreted
as 0 (return immediately) on most platforms, which means you're
busy-waiting. And that poll() will usually return 0 ("timeout reached").
This matches your observations, as far as I can tell.
I *think* you meant:
while ((rfds = poll(wait_fd, 2, INFTIM)) == -1 && errno == EINTR);
if (rfds == -1)
err(1, "Poll failed");
Note that poll cannot return 0 here.
Joachim
--
TFMotD: poll (2) - synchronous I/O multiplexing
http://www.joachimschipper.nl/
