On Thu, Aug 3, 2017 at 4:11 PM, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> Where is this INIT_LIST_HEAD()?
I think it's this one:
list_del_init(&info->shrinklist);
in shmem_unused_huge_shrink().
> I'm not sure I'm understanding this. AFAICT all the list operations to
> which you refer are synchronized under spin_lock(&sbinfo->shrinklist_lock)?
No, notice how shmem_unused_huge_shrink() does the
list_move(&info->shrinklist, &to_remove);
and
list_move(&info->shrinklist, &list);
to move to (two different) private lists under the shrinklist_lock,
but once it is on that private "list/to_remove" list, it is then
accessed outside the locked region.
Honestly, I don't love this situation, or the patch, but I think the
patch is likely the right thing to do.
Linus
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