Re: Question about select and poll system call

[richard clark]

On Wed, Mar 15, 2023 at 4:59 PM David Laight <David.Laight@xxxxxxxxxx> wrote:
>
> > 2. Can we unify the two different system calls? For example, using
> > poll(...) to implement the frontend select call(...), is there
> > something I'm missing for current implementation? The Cons and Pros,
> > etc
>
> The underlying code that implements them is common.
>
> Beware that the glibc select() wrappers have their own limit
> on the highest fd.
> Exceeding that limit (probably 1024) will cause buffer overruns
> in the application (One of the Android apps I uses crashes that way).

Ah, interesting. Seems glibc doesn't make that limit from my testing
code snippet in last email...

>
> select() also doesn't scale well for sparse lists of fds.
> So it really is best to use poll() and never select().
> (Although for very large fd lists epoll() may be a better choice.)
>
>         David
>
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)