This is a copy of the code in Section 3.1 of Li and Hudak's Memory
Coherence in Shared Virtual Memory Systems (1986), with some bugs
fixed. We've stripped out the code for the case in which the manager
takes faults -- in this version, the manager does not run application
code. Messages are delivered reliably. There are no failures.

ReadFaultHandler(PageNumber p):
  lock(ptable[p].lock)
  ask manager for read access to p
  wait for someone to send me p's content
  ptable[p].access = read
  send confirmation to manager
  unlock(ptable[p].lock)

ReadServer(PageNumber p, MachineID request_node):
  lock(ptable[p].lock)
  if I am owner of p:
    ptable[p].access = read
    send copy of p to request_node
  unlock(ptable[p].lock)

  if I am manager:
    lock(info[p].lock)
    info[p].copy_set |= request_node
    ask info[p].ownder to send copy of p to request_node
    wait for confirmation from request_node
    unlock(info[p].lock)

WriteFaultHandler(PageNumber p):
  lock(ptable[p].lock)
  ask manager for write access to p
  wait for someone to send me p's content
  ptable[p].access = write
  send confirmation to manager
  unlock(ptable[p].lock)

WriteServer(PageNumber p, MachineID request_node):
  lock(ptable[p].lock)
  if I am owner of p:
    send copy of p to request_node
    ptable[p].access = nil
  unlock(ptable[p].lock)

  if I am manager:
    lock(info[p].lock)
    send invalidate to each node in info[p].copy_set
    wait for all invalidate confirmations
    info[p].copy_set = empty
    ask info[p].owner to send copy of p to request_node
    info[p].owner = request_node
    wait for confirmation from request_node
    unlock(info[p].lock)

InvalidateServer(PageNumber p):
  # no lock...
  ptable[p].access = nil
  send confirmation to manager