linux-kernel - Re: [PATCH v4 2/2] block: cancel all throttled bios in del

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Message-ID: <20211203102739.GB64349@blackbody.suse.cz>
Date:   Fri, 3 Dec 2021 11:27:39 +0100
From:   Michal Koutný <mkoutny@...e.com>
To:     "yukuai (C)" <yukuai3@...wei.com>
Cc:     hch@...radead.org, tj@...nel.org, axboe@...nel.dk,
        cgroups@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, yi.zhang@...wei.com
Subject: Re: [PATCH v4 2/2] block: cancel all throttled bios in del_gendisk()

On Fri, Dec 03, 2021 at 03:50:01PM +0800, "yukuai (C)" <yukuai3@...wei.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()).

[Actually, I think you should see a warning in your situation if you
enable CONFIG_PROVE_RCU.]

HTH,
Michal

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