I do not understand this block. LOCK_PROFILING does not depend on KDTRACE_HOOK. While your patch puts LOCK_PROFILING control inside KDTRACE_HOOK block.

I think I misunderstood the intent behind doing_lockprof. It's to allow lock profiling to be enabled either unconditionally (with LOCK_PROFILING) or conditionally. (if KDTRACE_HOOKS and LOCKSTAT_PROFILE_ENABLED() returns true).

So the correct thing here would be:

#if defined(KDTRACE_HOOKS)
	uintptr_t state = 0;
#endif
#if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
	int doing_lockprof = 0;
#endif

(And then not have this #ifdef LOCK_PROFILING here, of course)

Yes, this sounds more correct.

Merge this block of ifdef with the previous one?

Remove the assignment?

Same?

Same, merge?

This line can be removed, the same assignment is happen right after the block.

Same

I don't see how this assignment can be removed. Without we'd always have state = 0.

It’ll be set if doing_lockprof == 1, which is the only case we actually use it.
Either because LOCKSTAT_PROFILE_ENABLED or LOCK_PROFILING.