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

On 8 January 2015 at 12:10, Paolo Bonzini [off-list ref] wrote:

On 08/01/2015 10:16, Fam Zheng wrote:

quoted

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 <redacted>
---
 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/