ivy-code.txt

This is a copy of the code in Section 3.1 of Li and Hudak's Memory
Coherence in Shared Virtual Memory Systems (1986), somewhat simplified
and clarified. We've deleted 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 [RQ]
  wait for someone to send me p's content [RD]
  ptable[p].access = read
  send confirmation to manager [RC]
  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 [RD]
  unlock(ptable[p].lock)

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

WriteFaultHandler(PageNumber p):
  lock(ptable[p].lock)
  ask manager for write access to p [WQ]
  wait for someone to send me p's content [WD]
  ptable[p].access = write
  send confirmation to manager [WC]
  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 [WD]
    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 [IV]
    wait for all invalidate confirmations [IC]
    info[p].copy_set = empty
    ask info[p].owner to send copy of p to request_node [WF]
    info[p].owner = request_node
    wait for confirmation from request_node [WC]
    unlock(info[p].lock)

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