Date:   Fri, 3 Dec 2021 11:27:39 +0100
From:   Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
To:     "yukuai (C)" <yukuai3@huawei.com>
Cc:     hch@infradead.org, tj@kernel.org, axboe@kernel.dk,
        cgroups@vger.kernel.org, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, yi.zhang@huawei.com
Subject: Re: [PATCH v4 2/2] block: cancel all throttled bios in del_gendisk()
Message-ID: <20211203102739.GB64349@blackbody.suse.cz>
References: <20211202130440.1943847-1-yukuai3@huawei.com>
 <20211202130440.1943847-3-yukuai3@huawei.com>
 <20211202144818.GB16798@blackbody.suse.cz>
 <95825098-a532-a0e4-9ed0-0b5f2a0e5f04@huawei.com>
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On Fri, Dec 03, 2021 at 03:50:01PM +0800, "yukuai (C)" <yukuai3@huawei.com>=
 wrote:
> blkg_destroy() is protected by the queue_lock=EF=BC=8Cso I think queue_lo=
ck 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=3Dthrotl_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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