Vijay,

On Mon, Aug 18, 2008 at 1:08 PM, Michael Kerrisk
<[EMAIL PROTECTED]> wrote:
> Hi Viaj
>
> On Tue, Aug 12, 2008 at 7:57 PM, Vijay Kumar <[EMAIL PROTECTED]> wrote:
>> Hi Subrata,
>> this patch adds eventfd counter overflow test cases.
>>
>> Michael, there is a small bug in the eventfd() man page. The man page
>> says that in the select() syscall, exceptfds is set when the counter
>> overflow occurs. But it is readfds/writefds that is set when the
>> counter overflows. POLLERR event in poll() is not equivalent to
>> setting of exceptfds. POLLPRI event in poll() is equivalent to setting
>> of exceptfds.
>
> ( http://www.kernel.org/doc/man-pages/online/pages/man2/eventfd.2.html )
>
> Thanks for spotting that.  I'm not sure why I wrote the text they way
> I did.  But now that you point it out, I consider the behavior a
> design error.  If I'd correctly described the behavior at the start, I
> would have seen that, and suggested to Davide to change the interface
> so that it uses POLLPRI, not POLLERR, (and thus select() exceptfds) to
> notify the overflow condition.  The problem with the current behavior
> is that using select() it is impossible to distinguish the overflow
> condition from the normal case where the eventfd has some non-zero
> value (and is thus both readable and writable).
>
> For ABI stability reasons, I guess we probably can't fix this now.
> Maybe Davide has some thoughts to offer.

I meant to add that I will fix the man page for release 3.08.

Cheers,

Michael

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