Messages in this thread | | | Date | Tue, 2 Jun 2009 06:45:22 +0200 | Subject | Re: poll never return EBADF? | From | Michael Kerrisk <> |
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Hello Motohiro,
On Tue, May 26, 2009 at 11:09 AM, KOSAKI Motohiro <kosaki.motohiro@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.
> ================ 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().
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 Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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