flock(3)-based locks.

Wins:

• Locks do not survive crashes of either the system or the application.

• Waiting for a lock is handled by the kernel and doesn't require polling

• Potentially compatible with NFS or other shared filesystem if you trust their lockd (or equivalent) implemenation. Note that this is a big if!

• No false positives on stale locks

Loses:

• Leaves lockfiles around, since unlink would cause a race.

do_acquire ( self,  waitflag=False )

do_release ( self )