Re: [PATCH] Fix boot problem in situations where the boot CPU is running on a memoryless node

Pekka J Enberg
2008-01-23T14:18:37Z

Hi Mel,

On Wed, 23 Jan 2008, Mel Gorman wrote:
> diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.24-rc8-005-revert-memoryless-slab/mm/slab.c linux-2.6.24-rc8-010_handle_missing_l3/mm/slab.c
> --- linux-2.6.24-rc8-005-revert-memoryless-slab/mm/slab.c 2008-01-22 17:46:32.000000000 +0000
> +++ linux-2.6.24-rc8-010_handle_missing_l3/mm/slab.c 2008-01-22 18:42:53.000000000 +0000
> @@ -2775,6 +2775,11 @@ static int cache_grow(struct kmem_cache
> /* Take the l3 list lock to change the colour_next on this node */
> check_irq_off();
> l3 = cachep->nodelists[nodeid];
> + if (!l3) {
> + nodeid = numa_node_id();
> + l3 = cachep->nodelists[nodeid];
> + }
> + BUG_ON(!l3);
> spin_lock(&l3->list_lock);
>
> /* Get colour for the slab, and cal the next value. */
> @@ -3317,6 +3322,10 @@ static void *____cache_alloc_node(struct
> int x;
>
> l3 = cachep->nodelists[nodeid];
> + if (!l3) {
> + nodeid = numa_node_id();
> + l3 = cachep->nodelists[nodeid];
> + }

What guarantees that current node ->nodelists is never NULL?

I still think Christoph's kmem_getpages() patch is correct (to fix
cache_grow() oops) but I overlooked the fact that none the callers of
____cache_alloc_node() deal with bootstrapping (with the exception of
__cache_alloc_node() that even has a comment about it).

But what I am really wondering about is, why wasn't the
N_NORMAL_MEMORY revert enough? I assume this used to work before so what
more do we need to revert for 2.6.24?

Pekka