how to programmatically make a function opened by exactly one process?

I have a device driver and I want it to be opened by only one process exactly. What structures do I have to use to actually set this property? Freebsd OS, C language, Kernel Device drivers Any tips on it?

Solution

You could track this inside your device driver; and reject the open. I.e. do some book keeping (is_open=true on open, is_open=false on close/loss).

Or you could simply use the normal locking semantics of open() itself - if needed in conjunction with exclusive mode and/or fcntl/flock.

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