At first: there are two different style of file locking:

   1. POSIX-style:
   fcntl(2) <https://illumos.org/man/2/fcntl> and lockf(3C)
   <https://illumos.org/man/3C/lockf>
   2. OFD-style:
   flock(3C) <https://illumos.org/man/3c/flock>

And as it is stated in the flock(3C) manual page:

> These locks (...the flock(3C) one...) are currently not supported over
> remote file systems
>
(e.g. nfs(4) <https://illumos.org/man/4/nfs>) which use the Network Lock
> Manager.
>

Bob Friesenhahn <[email protected]> ezt írta (időpont: 2020.
ápr. 18., Szo, 2:05):

> On Sat, 18 Apr 2020, Gergő Doma wrote:
>
> > Hi.
> >
> > autom4te tries to use flock() over NFS but NFS doesn't supports that.
>
> If this is so, why do OpenIndiana oi_151a9, Solaris 10, and Ubuntu
> 18.04 not report a problem?
>

Before Feature #3252: Need a proper flock() implementation
<https://www.illumos.org/issues/3252>, flock() was broken and it
behaved like a POSIX one and for this reason that worked over NFS.

>From the Linux flock(2) <http://man7.org/linux/man-pages/man2/flock.2.html>
manual page,* "NFS details*" subsection:

> Since Linux 2.6.12, NFS clients support *flock*() locks by emulating
> them as fcntl(2) <http://man7.org/linux/man-pages/man2/fcntl.2.html> 
> byte-range locks on the entire file.  This means
> that fcntl(2) <http://man7.org/linux/man-pages/man2/fcntl.2.html> and 
> *flock*() locks *do* interact with one another over
> NFS.  It also means that in order to place an exclusive lock, the
> file must be opened for writing.
>
> Since Linux 2.6.37, the kernel supports a compatibility mode that
> allows *flock*() locks (and also fcntl(2) 
> <http://man7.org/linux/man-pages/man2/fcntl.2.html> byte region locks) to be
> treated as local; see the discussion of the *local_lock* option innfs(5) 
> <http://man7.org/linux/man-pages/man5/nfs.5.html>.
>
>
> Is this an Illumos-specific locking agent issue, or is it a NFS
> general issue?
>
> Neither of them, just Autoconf uses the less portable function.


> I do recall that Illumos re-wrote the NFS locking daemon.
>
>
Bob
> --
> Bob Friesenhahn
> [email protected], http://www.simplesystems.org/users/bfriesen/
> GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
> Public Key,     http://www.simplesystems.org/users/bfriesen/public-key.txt

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