Messages in this thread | | | Subject | Re: [PATCH v4 2/2] block: cancel all throttled bios in del_gendisk() | From | "yukuai (C)" <> | Date | Sat, 4 Dec 2021 16:03:53 +0800 |
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在 2021/12/03 18:27, Michal Koutný 写道: > On Fri, Dec 03, 2021 at 03:50:01PM +0800, "yukuai (C)" <yukuai3@huawei.com> 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-> css_free_rwork_fn.
By the way, does spin_lock can guarantee this since it disables preempt like what rcu_read_lock() does?
Thanks, Kuai
> > [Actually, I think you should see a warning in your situation if you > enable CONFIG_PROVE_RCU.] > > HTH, > Michal >
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