Re: [RESEND PATCH 2/3] epoll: Add implementation for epoll_pwait1

[Michael Kerrisk (man-pages)]

On 8 January 2015 at 12:10, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
>
> On 08/01/2015 10:16, Fam Zheng wrote:
>> Unlike ppoll(2), which accepts a timespec argument "timeout_ts" to
>> specify the timeout, epoll_wait(2) and epoll_pwait(2) expect a
>> microsecond timeout in int type.
>>
>> This is an obstacle for applications in switching from ppoll to epoll,
>> if they want nanosecond resolution in their event loops.
>>
>> Therefore, adding this variation of epoll wait interface, giving user an
>> option with *both* advantages, is a reasonable move: there could be
>> constantly scalable performance polling many fds, while having a
>> nanosecond timeout precision (assuming it has properly set up timer
>> slack with prctl(2)).
>>
>> Signed-off-by: Fam Zheng <famz@xxxxxxxxxx>
>> ---
>>  fs/eventpoll.c           | 24 ++++++++++++++++++++++++
>>  include/linux/syscalls.h |  4 ++++
>>  kernel/sys_ni.c          |  3 +++
>>  3 files changed, 31 insertions(+)
>
> As mentioned by Miklos in the non-resent version, please add a flags
> argument.  Invalid flags should return -EINVAL.
>
> In fact, we could already use the flags argument to specify an absolute
> timeout, which is a nice thing to have for QEMU too.

Nice! It looks like we found this iteration of "failure to include a
flags argument is a mistake" already!

Cheers,

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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