On 5/27/10, Erik Faye-Lund <kusmabite@xxxxxxxxxxxxxx> wrote:
> On Thu, May 27, 2010 at 1:00 PM, Erik Faye-Lund
> <kusmabite@xxxxxxxxxxxxxx> wrote:
> > On Thu, May 27, 2010 at 12:10 PM, Jonathan Nieder <jrnieder@xxxxxxxxx> wrote:
> >> Implement the subset of poll() semantics needed by git in terms of
> >> select(), for use by the Interix port. Inspired by commit 6ed807f
> >> (Windows: A rudimentary poll() emulation, 2007-12-01).
> >>
> >
> > A possible problem with this approach is that the maximum number of
> > file descriptors poll can handle limited by RLIMIT_NOFILE, whereas the
> > maximum number of file descriptors select can handle is limited by
> > FD_SETSIZE.
> >
> > I don't think this is a big problem in reality, though - both values
> > seem to be pretty high in most implementations. And IIRC git-daemon is
> > the only one who needs more than 2, and it doesn't even check
> > RLIMIT_NOFILE.
> >
>
>
> To be clear: I think this strategy is the best option (at least for
> non-Windows, where select() might be our only option).
>
> But perhaps you should include a check along the lines of this:
>
> if (nfds > FD_SETSIZE)
> return errno = EINVAL, error("poll: nfds must be below %d", FD_SETSIZE);
>
> Just so we can know when the code fails :)
Well, per your own FD_SET example, the FD_SETSIZE on windows
means different thing than FD_SETSIZE on old-style bitmap-based
select() implementation.
On Unix, it's max fd number + 1, on windows it's max count.
Thus on windows the nfds can safely be larger than FD_SETSIZE,
assuming the actual count is smaller.
RLIMIT_NOFILE - I don't see why it is relevant here, as you
get error on open() when you cross the limit. So how can you
pass more than that meny fds to select()/poll()?
--
marko
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