A simplified counters example with a deadlock issue. The SQL is here https://gist.github.com/drsnyder/8222047.

counters.py

import os                                                                                                                                                                                                                                     
import random
import time
import psycopg2

COUNTERS = 5 
THREADS = 10
ITERATIONS = 500 

def increment():
  outf = open('synctest.out.%d' % os.getpid(), 'w')
  conn = psycopg2.connect(database="test")
  cur = conn.cursor()
  for i in range(0,ITERATIONS):
    time.sleep(random.random())
    start = time.time()
    cur.execute("SELECT increment_count(0, %s, 1)", [random.randint(1,COUNTERS)])
    conn.commit()
    outf.write("%f\n" % (time.time() - start))
  conn.close()
  outf.close()

def update(n):
  outf = open('synctest.update', 'w')
  conn = psycopg2.connect(database="test")
  cur = conn.cursor()
  for i in range(0,n):
    time.sleep(random.random())
    start = time.time()
    cur.execute("SELECT update_primary_a_count(0)")
    conn.commit()
    outf.write("%f\n" % (time.time() - start))
  conn.close()

pids = []
for i in range(THREADS):
  pid = os.fork()
  if pid != 0:
    print 'Process %d spawned' % pid 
    pids.append(pid)
  else:
    print 'Starting child %d' % os.getpid()
    increment()
    print 'Exiting child %d' % os.getpid()
    os._exit(0)

update(ITERATIONS)
for pid in pids:
  print "waiting on %d" % pid 
  os.waitpid(pid, 0)

# cleanup
update(1)