Trouble with l4rm_region_cache slab

[Marc CHALAND]

After more investigation, I've found that slab_alloc and slab_free on
l4rm_region_cache are not all into a critical section (for example:
l4rm_attach may be called by several threads). At first, I though
region_list_lock aimed at that, but in fact, this is not the case.

My first idea is to put slab_alloc between l4rm_lock_region_list and
l4rm_unlock_region_list into l4rm_region_desc_alloc. Same for
slab_free. But I'm not sure this is a good idea. What is your opinion
?

Regards
Marc