On Fri, May 16, 2025 at 12:48:56PM +0200, Jan Kara wrote: > Hi! > > On Thu 15-05-25 23:33:22, Alejandro Colomar wrote: > > I'm updating the manual pages for POSIX.1-2024, and have some doubts > > about close(2). The manual page for close(2) says (conforming to > > POSIX.1-2008): > > > > The EINTR error is a somewhat special case. Regarding the EINTR > > error, POSIX.1‐2008 says: > > > > If close() is interrupted by a signal that is to be > > caught, it shall return -1 with errno set to EINTR and > > the state of fildes is unspecified. > > > > This permits the behavior that occurs on Linux and many other > > implementations, where, as with other errors that may be re‐ > > ported by close(), the file descriptor is guaranteed to be > > closed. However, it also permits another possibility: that the > > implementation returns an EINTR error and keeps the file de‐ > > scriptor open. (According to its documentation, HP‐UX’s close() > > does this.) The caller must then once more use close() to close > > the file descriptor, to avoid file descriptor leaks. This di‐ > > vergence in implementation behaviors provides a difficult hurdle > > for portable applications, since on many implementations, > > close() must not be called again after an EINTR error, and on at > > least one, close() must be called again. There are plans to ad‐ > > dress this conundrum for the next major release of the POSIX.1 > > standard. > > > > TL;DR: close(2) with EINTR is allowed to either leave the fd open or > > closed, and Linux leaves it closed, while others (HP-UX only?) leaves it > > open. > > > > Now, POSIX.1-2024 says: > > > > If close() is interrupted by a signal that is to be caught, then > > it is unspecified whether it returns -1 with errno set to > > [EINTR] and fildes remaining open, or returns -1 with errno set > > to [EINPROGRESS] and fildes being closed, or returns 0 to > > indicate successful completion; [...] > > > > <https://pubs.opengroup.org/onlinepubs/9799919799/functions/close.html> > > > > Which seems to bless HP-UX and screw all the others, requiring them to > > report EINPROGRESS. > > > > Was there any discussion about what to do in the Linux kernel? > > I'm not aware of any discussions but indeed we are returning EINTR while > closing the fd. Frankly, changing the error code we return in that case is > really asking for userspace regressions so I'm of the opinion we just > ignore the standard as in my opinion it goes against a long established > reality. Ignore. We've long since stopped designing apis with input from that standard in mind. And I think that was a very wise decision.
