poll never return EBADF?

[KOSAKI Motohiro]

Hi

I have one stupid question.

"man poll" describe this error code.

>ERRORS
> EBADF An invalid file descriptor was given in one of the sets.

but current kernel implementation ignore invalid file descriptor,
not return EBADF.

================ cut code ========================================
static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
{
unsigned int mask;
int fd;

mask = 0;
fd = pollfd->fd;
if (fd >= 0) { //// here
int fput_needed;
struct file * file;

file = fget_light(fd, &fput_needed);
mask = POLLNVAL;
if (file != NULL) { //// and here
mask = DEFAULT_POLLMASK;
if (file->f_op && file->f_op->poll)
mask = file->f_op->poll(file, pwait);
/* Mask out unneeded events. */
mask &= pollfd->events | POLLERR | POLLHUP;
fput_light(file, fput_needed);
}
}
================ end code ========================================

In the other hand, SUSv3 talk about

> POLLNVAL
> The specified fd value is invalid. This flag is only valid in the
> revents member; it shall ignored in the events member.

and

> If the value of fd is less than 0, events shall be ignored, and revents
> shall be set to 0 in that entry on return from poll().

but, no desribe EBADF.
(see http://www.opengroup.org/onlinepubs/009695399/functions/poll.html)

So, I think the implementation is correct.

Why don't we remove EBADF description?

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[Michael Kerrisk]

Hello Motohiro,

On Tue, May 26, 2009 at 11:09 AM, KOSAKI Motohiro
<kosaki....@jp.fujitsu.com> wrote:
> Hi
>
> I have one stupid question.

It doesn't look stupid to me...

> "man poll" describe this error code.
>
>>ERRORS
>> � � � EBADF �An invalid file descriptor was given in one of the sets.

This text seems to have been added in man-pages-1.39 (around 2000),
but with no explanation or note on authorship. I suspect someone was
confused.

> but current kernel implementation ignore invalid file descriptor,
> not return EBADF.

Which is what I understand it should do.

Exactly.

> but, no desribe EBADF.
> (see http://www.opengroup.org/onlinepubs/009695399/functions/poll.html)
>
> So, I think the implementation is correct.

Agreed.

> Why don't we remove EBADF description?

Yes, that seems corrrrect for me. I've removed it for the next release (3.22).

Cheers,

Michael

--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git
man-pages online: http://www.kernel.org/doc/man-pages/online_pages.html
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