flock: Decribe limitations of flock: deadlock, NFS, CIFS

The flock(1) does not refer to limitations of flock(2). Provide an
documentation entry point for solving of problems with flock on NFS
and CIFS and mention risk of deadlock.

Signed-off-by: Stanislav Brabec <sbrabec@suse.cz>
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/sys-utils/flock.1.adoc b/sys-utils/flock.1.adoc
index c645a60f6d2ce09e82639aedc8beef1fc50f0de1..d5b4f10aa90da0851eec7ce7d986a39ca1c5d8a1 100644 (file)
--- a/sys-utils/flock.1.adoc
+++ b/sys-utils/flock.1.adoc
@@ -91,6 +91,12 @@ The command uses <sysexits.h> exit status values for everything, except when usi
 
 When using the _command_ variant, and executing the child worked, then the exit status is that of the child command.
 
+== NOTES
+
+*flock* does not detect deadlock. See *flock*(2) for details.
+
+Some file systems (e. g. NFS and CIFS) have a limited implementation of *flock*(2) and flock may always fail. For details see *flock*(2), *nfs*(5) and *mount.cifs*(8). Depending on mount options, flock can always fail there.
+
 == EXAMPLES
 
 Note that "shell> " in examples is a command line prompt.