Re: [patch 1/2] fix call to alloc_bootmem after bootmem has been freed

Arnd Bergmann
2006-11-22T09:23:40Z

On Tuesday 21 November 2006 19:26, Andrew Morton wrote:
> slab is a very different thing from vmalloc. One could easily envisage
> situations (now or in the future) in which slab is ready, but vmalloc is
> not (more likely vice versa).
>
> It'd be better to add a new vmalloc_is_available. (Just an int - no need
> for a helper function).

In the time line, we currently have

start_kernel()
...
setup_arch()
init_bootmem() # alloc_bootmem starts working
...
paging_init() # needed for vmalloc
... #
mem_init()
free_all_bootmem() # alloc_bootmem stops working, alloc_pages
# starts working
kmem_cache_init() # kmalloc and vmalloc start working
...
system_state = SYSTEM_RUNNING

The one interesting point here is where you have to transition between
calling alloc_bootmem and calling the regular allocator functions.
Maybe calling it slab_is_available() was not the best choice for a name,
but I don't see a point in having different names for essentially the
same question, "bootmem or not bootmem". The powerpc platform has an
integer variable called 'mem_init_done', which expresses this well
IMHO, but it's currently not portable.

Checking for SYSTEM_RUNNING is obviously the wrong choice, since it is
set at a very late point in bootup, long after bootmem is gone.