linux-kernel - Re: [PATCH v5 13/14] epoll: implement epoll

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Date:   Mon, 24 Jun 2019 18:14:25 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Roman Penyaev <rpenyaev@...e.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 13/14] epoll: implement epoll_create2() syscall

On Mon, Jun 24, 2019 at 4:42 PM Roman Penyaev <rpenyaev@...e.de> wrote:
>
> epoll_create2() is needed to accept EPOLL_USERPOLL flags
> and size, i.e. this patch wires up polling from userspace.

Can you explain in the patch description more what it's needed for?

The man page only states that "Since Linux 2.6.8, the size argument
is ignored", so your description above does not explain why you need
to add the size argument back.

> diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl
> index 1db9bbcfb84e..a1d7b695063d 100644
> --- a/arch/alpha/kernel/syscalls/syscall.tbl
> +++ b/arch/alpha/kernel/syscalls/syscall.tbl
> @@ -474,3 +474,5 @@
>  542    common  fsmount                         sys_fsmount
>  543    common  fspick                          sys_fspick
>  544    common  pidfd_open                      sys_pidfd_open
> +# 546  common  clone3                  sys_clone3
> +547    common  epoll_create2                   sys_epoll_create2
> diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
> index ff45d8807cb8..1497f3c87d54 100644
> --- a/arch/arm/tools/syscall.tbl
> +++ b/arch/arm/tools/syscall.tbl
> @@ -449,3 +449,4 @@
>  433    common  fspick                          sys_fspick
>  434    common  pidfd_open                      sys_pidfd_open
>  436    common  clone3                          sys_clone3
> +437    common  epoll_create2                   sys_epoll_create2

The table changes all look correct and complete, provided we
don't get another patch picking the same number.

          Arnd