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SubjectRe: [PATCH v4 2/2] block: cancel all throttled bios in del_gendisk()
在 2021/12/03 18:27, Michal Koutný 写道:
> On Fri, Dec 03, 2021 at 03:50:01PM +0800, "yukuai (C)" <> wrote:
>> blkg_destroy() is protected by the queue_lock,so I think queue_lock can
>> protect such concurrent scenario.
> blkg_destroy() is not as destroying :-) as actual free, you should
> synchronize against (the queue_lock ensures this for
> pd_free_fn=throtl_pd_free but you may still trip on blkcg after
> blkcg_css_free()).

Hi, Michal

I was thinking that if there are active blkgs, holding queue_lock will
ensure blkcg won't be freed. However, if there are no active blkgs in
the first place, it seems right rcu_read_lock() can prevent this
iteration concurrent with css_release->css_release_work_fn->

By the way, does spin_lock can guarantee this since it disables preempt
like what rcu_read_lock() does?


> [Actually, I think you should see a warning in your situation if you
> HTH,
> Michal

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