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The manpage for flock(2) states:

flock()  does  not lock files over NFS.  Use fcntl(2) instead: that does  work   over NFS, given a sufficiently recent version of Linux and a server which supports locking.

But as far as I can tell, from a programmer's point of view, flock() does work over NFS. The shell command "flock a.a bash" experimentlaly locks a file on an NFS mounted volume, while in e.g. linux-2.6.18-274.3.1.el5.x86_64/fs/nfs/file.c
there is a comment
"We're simulating flock() locks using posix locks on the server"

suggesting to me that flock() works on NFS in RHEL5 and RHEL6.

Adding steved.

Hi, Steve,

any progress?

Jan

Upstream e449654fdb3f19aafc569df47d12bffdf6276236 probably addresss this bug, I think. That change will go out with the next release.

(In reply to Michael Kerrisk from comment #3)
> Upstream e449654fdb3f19aafc569df47d12bffdf6276236 probably addresss this
> bug, I think. That change will go out with the next release.

What git tree is that commit relative to?

man-pages Git
https://www.kernel.org/doc/man-pages/download.html

Created attachment 909193 [details]
The upstream patch

Created attachment 909385 [details]
flock.2 NFS flock for MPO

Thank you very much guys

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHBA-2014-1382.html