On 5/27/10, Erik Faye-Lund <kusmabite@xxxxxxxxxxxxxx> wrote:
> On Thu, May 27, 2010 at 4:11 PM, Marko Kreen <markokr@xxxxxxxxx> wrote:
> > On 5/27/10, Erik Faye-Lund <kusmabite@xxxxxxxxxxxxxx> wrote:
> >> On Thu, May 27, 2010 at 3:58 PM, Marko Kreen <markokr@xxxxxxxxx> wrote:
> >> > On 5/27/10, Erik Faye-Lund <kusmabite@xxxxxxxxxxxxxx> wrote:
> >> >> On Thu, May 27, 2010 at 3:29 PM, Marko Kreen <markokr@xxxxxxxxx> wrote:
> >> >> > 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.
> >> >> >
> >> >>
> >> >>
> >> >> Are you sure this applies for all Unix, not just some given Unix-y system?
> >> >
> >> > Not sure. Just pointing out that the above check is not
> >> > universal enough.
> >> >
> >>
> >>
> >> Isn't it? How could one possibly pass more than max fd number + 1 file
> >> descriptors, since they start at 0? I guess one could specify a given
> >> fd more than once, but that'd be kind of redundant... and also very
> >> unlikely in our case ;)
> >
> > Pass one fd with value 70 it. Check returns error, although
> > everything would work.
> >
>
>
> No, not with the check I posted. I checked nfds, not the value of the
> fds themselves. nfds is clearly the size of the fds array -- if it
> wasn't, it'd be impossible for the poll-implementation to know how big
> the array is!
Ah, ok. I though this is the nfds for select(). In this case it can
still fail, as nfds=1 for poll() can still go over FD_SETSIZE for
select() if the fd value is big enough. On non-windows, that is.
Dunno if this matters for git-daemon..
--
marko
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