tags 339037 fixed-upstream
thanks
Hello Avery,
> If you read the LEASES section of fcntl(2), it explains that open() with
> O_NONBLOCK could cause open to return EWOULDBLOCK. This is not explained
> anywhere on the open() page; open() has many possible return codes, none
> of which are EWOULDBLOCK. (There is a comment about opening fifos in
> nonblocking mode, but the error code description implies that this would
> return ENXIO, not EWOULDBLOCK.)
Thanks. In open.2, I have added the following text:
EWOULDBLOCK
The O_NONBLOCK flag was specified, and an incom-
patible lease was held on the file (see
fcntl(2)).
> Also, the fcntl(2) page doesn't say whether opening a leased file with
> O_NONBLOCK will actually request the lease to be broken or not.
It explains a sequence of steps, which include the lease being
broken. Those steps occur independently of O_NONBLOCK. The
man page does pretty much imply that IMO. But I do agree that
things could be stated a little more verbosely.
> It appears you *have* to open in blocking mode in order to
> open a leased file at all,
Yes.
> but that's not clear from the description.
Again, I would say that's fairly clear from the man page:
if the open() call returns (i.e., fails) with EWOULDBLOCK,
then clearly the file was not opened. But again, it might
help to add a little more text.
> It wouldn't be so bad to open in blocking mode since a lease is
> guaranteed
> to be broken after a certain timeout. But a naive implementation would
> introduce a security hole since the file might be replaced by surprise
> with a FIFO, which has no open timeout at all.
I do not understand this last piece.
In fcntl.2, I removed the phrase that you referred to that
specified O_NONBLOCK. Later in the description, I added
this new text:
If the lease breaker's blocked open() or truncate() is
interrupted by a signal handler, then the system call
fails with the error EINTR, but the other steps still
occur as described above. If the lease breaker is
killed by a signal while blocked in open() or trun-
cate(), then the other steps still occur as described
above. If the lease breaker specifies the O_NONBLOCK
flag when calling open(), then the call immediately
fails with the error EWOULDBLOCK, but the other steps
still occur as described above.
These changes will appear in man-pages-2.14.
Cheers,
Michael
--
Michael Kerrisk
maintainer of Linux man pages Sections 2, 3, 4, 5, and 7
Want to help with man page maintenance? Grab the latest
tarball at ftp://ftp.win.tue.nl/pub/linux-local/manpages/
and grep the source files for 'FIXME'.
--
To UNSUBSCRIBE, email to [EMAIL PROTECTED]
with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
