[Libguestfs] [PATCH libnbd] lib/poll.c: Retry poll after EINTR

[Nir Soffer]

On Thu, Oct 28, 2021 at 3:59 PM Eric Blake <eblake at redhat.com> wrote:
>
> Sorry for a late reply...
>
> On Sat, Oct 23, 2021 at 11:10:08AM +0100, Richard W.M. Jones wrote:
> > > Fixing this in nbd_unlock_poll() avoids this issue in the entire
> > > library, when we wait for command completion. This seems more useful
> > > that fixing it in all libnbd clients.
> > >
> > > +++ b/lib/poll.c
> > > @@ -57,8 +57,11 @@ nbd_unlocked_poll (struct nbd_handle *h, int timeout)
> > >     * would allow other threads to close file descriptors which we have
> > >     * passed to poll.
> > >     */
> > > -  r = poll (fds, 1, timeout);
> > > -  debug (h, "poll end: r=%d revents=%x", r, fds[0].revents);
> > > +  do {
> > > +    r = poll (fds, 1, timeout);
> > > +    debug (h, "poll end: r=%d revents=%x", r, fds[0].revents);
> > > +  } while (r == -1 && errno == EINTR);
> > > +
> > >    if (r == -1) {
> > >      set_error (errno, "poll");
> > >      return -1;
> >
> > I think this is a perfectly reasonable solution, and better than
> > modifying the language bindings.  I guess Eric should have the final
> > word here, but from my point of view ACK.
>
> As a library, libnbd has no idea if the overall program has installed
> signal handlers that may trigger EINTR, so being robust by retrying
> seems the sanest approach. ACK from me as well.

Thanks, I pushed the change now.