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Message-ID: <54BF3F69.702@gmail.com>
Date: Wed, 21 Jan 2015 06:55:53 +0100
From: "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To: Andy Lutomirski <luto@...capital.net>, Fam Zheng <famz@...hat.com>
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Subject: Re: [PATCH RFC 0/6] epoll: Introduce new syscall "epoll_mod_wait"
On 01/20/2015 11:40 PM, Andy Lutomirski wrote:
> On Tue, Jan 20, 2015 at 1:57 AM, Fam Zheng <famz@...hat.com> wrote:
>> This adds a new system call, epoll_mod_wait. It's described as below:
[...]
>> There is no guartantee that all the commands are executed in order. Only
>> if all the commands are successfully executed (all the error fields are
>> set to 0), events are polled.
>
> If this doesn't happen, what error is returned?
If I read the code correctly: the error of the first epoll_ctl op that fails.
[...]
>> RETURN VALUE
>>
>> When any error occurs, epoll_mod_wait() returns -1 and errno is set
>> appropriately. All the "error" fields in cmds are unchanged before they
>> are executed, and if any cmds are executed, the "error" fields are set
>> to a return code accordingly. See also epoll_ctl for more details of the
>> return code.
>
> Does this mean that callers should initialize the error fields to an
> impossible value first so they can tell which commands were executed?
Yes. (Ugly!)
[...]
>> ERRORS
>>
>> These errors apply on either the return value of epoll_mod_wait or error
>> status for each command, respectively.
>
> Please clarify which errors are returned overall and which are per-command.
Yes, I think this would be valuable as well.
Thanks,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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