* poll never return EBADF?
@ 2009-05-26 9:09 KOSAKI Motohiro
2009-06-02 4:45 ` Michael Kerrisk
0 siblings, 1 reply; 3+ messages in thread
From: KOSAKI Motohiro @ 2009-05-26 9:09 UTC (permalink / raw)
To: LKML, Michael Kerrisk, linux-man; +Cc: 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?
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: poll never return EBADF?
2009-05-26 9:09 poll never return EBADF? KOSAKI Motohiro
@ 2009-06-02 4:45 ` Michael Kerrisk
2009-06-02 4:49 ` Michael Kerrisk
0 siblings, 1 reply; 3+ messages in thread
From: Michael Kerrisk @ 2009-06-02 4:45 UTC (permalink / raw)
To: KOSAKI Motohiro; +Cc: LKML, linux-man
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
^ permalink raw reply [flat|nested] 3+ messages in thread
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2009-05-26 9:09 poll never return EBADF? KOSAKI Motohiro
2009-06-02 4:45 ` Michael Kerrisk
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