The real solution would be

1. mknod $$.lock
2. open $$.lock,"rw"
3. (hard)link $$.lock nach reallock

Now two possible outcomes:

• Can link:
  1. (re)open reallock,">"
  2. (if error begin anew)
  3. close $$.lock
  4. unlink $$.lock
  5. You Can Work Now
• Can't link:
  1. open reallock,"rw"
  2. reopen reallock,"<"
  3. close reallock(rw)
  4. read from reallock(<)
  5. on eof unlink reallock
  6. close reallock(<)
  7. begin anew