Bug 184223

Description of problem:

Cooperative file locks using the fcntl() system call do
not seem to work on NFS mounted drives in rhel4u2.  The
python script appended to this message demonstrates the
problem.

The script forks off 70 child processes.  Each child attempts
to obtain a lock on a file.  When the lock is granted the child
simply writes a message to the file, releases the lock and exits.
On a working system, this all occurs very quickly.  On rhel4,
child processes are left hanging around and locks are not granted
for a long time.  It takes between 4 and 20 minutes for the child
processes all to access the file and exit.

How reproducible:
Use the following script:

#!/usr/bin/python

import os, sys, time, fcntl

FNAME = "test.txt"

NFORKS = 70

def dochild():
    fp = open(FNAME, 'a+b')
    fcntl.lockf(fp.fileno(), fcntl.LOCK_EX)
    fp.write("Hello from: " + str(os.getpid()) + '\n')
    fcntl.lockf(fp.fileno(), fcntl.LOCK_UN)
    fp.close()

for x in xrange(NFORKS):
    pid = os.fork()
    if pid == 0: # Child
        dochild()
        sys.exit(0)



Steps to Reproduce:
1. mount nfs filesystem
2. run python script
3.
  
Actual results:
Take several minutes to complete

Expected results:
Should take seconds to complete

Additional info: