On Thu, Feb 5, 2009 at 2:02 AM, Davide Libenzi <davidel@xxxxxxxxxxxxxxx> wrote:
> On Thu, 5 Feb 2009, Michael Kerrisk wrote:
>
>> > Dunno. Probably try the syscall and see if it returned -EINVAL. Does
>> > that work in this case?
>>
>> As youll have seen by now, Ulrich and I noted that it works.
>>
>> > If so, it would be sensible to mention this in
>> > the description somewhere as the approved probing method and to
>> > maintain it.
>>
>> I'll add something to the man page, as this patch progresses.
>
> I see we already have stuff like this inside the man pages:
>
> O_CLOEXEC (Since Linux 2.6.23)
> Enable the close-on-exec flag for the new file descriptor.
> ...
>
> Maybe a similar note for the new flag?
It took a while, but here's the new text in the eventfd.2 (will be in
man-pages-2.36). Could you please ACK, Davide?
EFD_SEMAPHORE (since Linux 2.6.30)
Provide semaphore-like semantics for reads from
the new file descriptor. See below.
...
* If EFD_SEMAPHORE was not specified and the
eventfd counter has a nonzero value, then a
read(2) returns 8 bytes containing that value,
and the counter's value is reset to zero.
* If EFD_SEMAPHORE was specified and the eventfd
counter has a nonzero value, then a read(2)
returns 8 bytes containing the value 1, and the
counter's value is decremented by 1.
Thanks,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/
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