Hello Motohiro,
On Tue, May 26, 2009 at 11:09 AM, KOSAKI Motohiro
<[email protected]> 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
>> Why don't we remove EBADF description?
>
> Yes, that seems corrrrect for me. I've removed it for the next release (3.22).
And I forgot to say: thanks for the very detailed bug report!
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