Re: [PATCH] mm/page_alloc: Add a reason for reserved pages in has_unmovable_pages()

[Qian Cai]

> On Oct 5, 2019, at 5:22 PM, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> 
> Apparently some console drivers can do memory allocation on the printk()
> path.
> 
> This behavior is daft, IMO.  Have we identified which ones and looked
> into fixing them?

Not necessary that simple. It is more of 2+ CPUs required to trigger the deadlock. Please see my v2 patch I sent which has all the information. Especially, the thread link included there which contains a few lockdep splat traces and the s390 one in the patch description.