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

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Date:   Mon, 24 Jun 2019 18:25:52 +0200
From:   Roman Penyaev <rpenyaev@...e.de>
To:     Arnd Bergmann <arnd@...db.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 2019-06-24 18:14, Arnd Bergmann wrote:
> 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?

Sure. Will update on next iteration.

> 
> 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.

Good.  I had doubts, because on some archs there is a gap,
(sys_clone3 was missing).  So I left a placeholder, so
can be uncommented when sys_clone3 is implemented.

--
Roman