more on locks

Henry J. Cobb hcobb at fly2.berkeley.edu
Fri Sep 24 14:18:39 EST 1993


	Thanks, OK I won't mess with the policy of global database locking.

	But unless there is something else I've overlooked, I'll add a
section to filopen() (protected by a #ifndef NO_ATOMIC_CREATION (I hope
that nothing is really that broken)).

	I'll check for spec == "atomic" and do an open() with O_WRONLY |
O_CREAT | O_EXCL followed by an fdopen() for lockfile itself.

	Then I'll change the ...WriteLock functions to atomically create
the lockfile, or remove it, etc.

	Also I'd like to set a special protocol in the client/server setup
to request a break of the lock.

	All of the OS'es I am aware of have some procedure for atomic file
creation, and I know of no other IPC which is common to all of them.  If
this is a problem under say VMS or MVS or Novell or Appleshare, etc.,
please let me know.
--
	Henry J. Cobb	hcobb at fly2.berkeley.edu	SFB Tyrant




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