Re: [PATCH] compat: Add another rudimentary poll() emulation
On Thu, May 27, 2010 at 3:29 PM, Marko Kreen <markokr@gmail.com> wrote:
Show 37 quoted lines
> On 5/27/10, Erik Faye-Lund <kusmabite@googlemail.com> wrote:
>> On Thu, May 27, 2010 at 1:00 PM, Erik Faye-Lund
>> <kusmabite@googlemail.com> wrote:
>> > On Thu, May 27, 2010 at 12:10 PM, Jonathan Nieder <jrnieder@gmail.com> 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?
> 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()?
>
Good point, this was my bad.
--
Erik "kusma" Faye-Lund
Erik Faye-Lund <kusmabite@googlemail.com>