Re: ci_mtx_count issue on NetBSD/Milkymist

[Mindaugas Rasiukevicius <rmind%netbsd.org@localhost>]

Yann Sionneau <yann.sionneau%gmail.com@localhost> wrote:
> I've tried to understand how ci_mtx_count is supposed to be managed my 
> MD code, so far I failed to understand.
> It seems some arch use spin_mutex and inc/dec ci_mtx_count upon 
> spin_mutex_enter/exit.
> Some other archs do it in softint handling.
> 
> Could someone give my some clue (or documentation) about the intended 
> behaviour of curcpu()->ci_mtx_count please?

It is a reference count on the IPL raised by spin-mutexes.  The IPL should
be lowered (straight to IPL_NONE) on a last reference.  Notice that this is
a negative counter - mutex_spin_enter() decrements, while mutex_spin_exit()
incremenets.  Not the other way round.

-- 
Mindaugas