On Thu, Aug 26, 2010 at 06:43:31PM -0700, Hugh Dickins wrote: > some light., I think you're mistaking the role that RCU plays here. That's exactly correct, I thought it prevented reuse of the slab entry, not only of the whole slab... SLAB_DESTROY_BY_RCU is a lot more tricky to use than I though... However at the light of this, I think page_lock_anon_vma could have returned a freed and reused anon_vma well before the anon-vma changes. The anon_vma could have been freed after the first page_mapped check succeed but before taking the spinlock. I think, it worked fine because the rmap walks are robust enough just not to fall apart on a reused anon_vma while the lock is hold. It become a visible problem now because we were unlocking the wrong lock leading to a deadlock. But I guess it wasn't too intentional to return a reused anon_vma out of page_lock_anon_vma. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>