poll never return EBADF?

From: KOSAKI Motohiro
Date: Tue May 26 2009 - 05:09:48 EST


I have one stupid question.

"man poll" describe this error code.

> 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
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

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


> 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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