[unix(4) cleanup 2/8] Improve unix socket refcounting.

[markj]

Summary

- Use refcount_init().
- Define an INVARIANTS-only zone destructor to assert that various
bits of PCB state aren't dangling.
- Annotate unp_pcb_rele() with __result_use_check.

[kevans]

We have some other callers doing unp_pcb_rele(...) == 0 that we should probably eventually clean up to match, but I don't suppose that needs to be done here.

[markj]

In D26295#584935, @kevans wrote:

We have some other callers doing unp_pcb_rele(...) == 0 that we should probably eventually clean up to match, but I don't suppose that needs to be done here.

After the full patchset is applied those are all gone, i.e., we use consistent style.

[kevans]

In D26295#584938, @markj wrote:

In D26295#584935, @kevans wrote:

We have some other callers doing unp_pcb_rele(...) == 0 that we should probably eventually clean up to match, but I don't suppose that needs to be done here.

After the full patchset is applied those are all gone, i.e., we use consistent style.

Yeah, my bad. Just started a good, hard look at D26297 and discovered it to take care of most (or all?) of them.

[kib]

sys/kern/uipc_usrreq.c

319 ↗

(On Diff #76541)

I wonder if this function should be moved to refcount.h, I think we already have more than two instances of such code.