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From:   richard clark <richard.xnu.clark@gmail.com>
Date:   Tue, 14 Mar 2023 10:31:42 +0800
Message-ID: <CAJNi4rO6TiZFFKTcW3kGgha2Rc0nTsXRLyeqAyYrN3foLbExSQ@mail.gmail.com>
Subject: Re: Question about select and poll system call
To:     linux-kernel@vger.kernel.org
Cc:     torvalds@linux-foundation.org, linux-arm-kernel@lists.infradead.org
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Adding linux-arm-kernel@lists.infradead.org ... for more possible feedback:=
)

On Tue, Mar 14, 2023 at 10:28=E2=80=AFAM richard clark
<richard.xnu.clark@gmail.com> wrote:
>
> Hi, (Sorry, not find the maintainers for this subsystem, so to the lkml)
>
> There're two questions about these system calls:
> 1. According to https://pubs.opengroup.org/onlinepubs/7908799/xsh/select.=
html:
> ERRORS
> [EINVAL]
>       The nfds argument is less than 0 or greater than FD_SETSIZE.
> But the current implementation in Linux like:
>        if (nfds > FD_SETSIZE)
>                nfds =3D FD_SETSIZE
> What's the rationale behind this?
>
> 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
>
> Thanks,