Re: [PATCH] mm/slub: fix a deadlock in shuffle_freelist()

[Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>]

On 2019-09-13 12:27:44 [-0400], Qian Cai wrote:
…
> Chain exists of:
>   random_write_wait.lock --> &rq->lock --> batched_entropy_u32.lock
> 
>  Possible unsafe locking scenario:
> 
>        CPU0                    CPU1
>        ----                    ----
>   lock(batched_entropy_u32.lock);
>                                lock(&rq->lock);
>                                lock(batched_entropy_u32.lock);
>   lock(random_write_wait.lock);

would this deadlock still occur if lockdep knew that
batched_entropy_u32.lock on CPU0 could be acquired at the same time
as CPU1 acquired its batched_entropy_u32.lock?

Sebastian