From: "Michal Koutný" <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()
Date: Mon, 6 Dec 2021 16:43:01 +0100 [thread overview]
Message-ID: <20211206154301.GD45344@blackbody.suse.cz> (raw)
In-Reply-To: <c8a16fe9-4ad2-682d-0d34-1049dc217d62@huawei.com>
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On Sat, Dec 04, 2021 at 04:03:53PM +0800, "yukuai (C)" <yukuai3@huawei.com> wrote:
> I was thinking that if there are active blkgs, holding queue_lock will
> ensure blkcg won't be freed.
My take is that the function traverses the whole blkcg tree (from global
root) and nothing prevents concurrent blkcg_css_free() in a possibly
unrelated branch (or queue).
> By the way, does spin_lock can guarantee this since it disables preempt
> like what rcu_read_lock() does?
Yes (but don't quoRTe me on that :-).
(It even isn't issue with a non-preemptible kernel neither but the code
IMO should be generic to allow for different configs -- or as I
mentioned initially, make a comment why the tree traversal is not
affected by concurrent frees.)
Thanks,
Michal
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prev parent reply other threads:[~2021-12-06 16:00 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-02 13:04 [PATCH v4 0/2] cancel all throttled bios in del_gendisk() Yu Kuai
2021-12-02 13:04 ` [PATCH v4 1/2] blk-throtl: move WARN_ON_ONCE() from throtl_rb_first() to it's caller Yu Kuai
2021-12-02 13:04 ` [PATCH v4 2/2] block: cancel all throttled bios in del_gendisk() Yu Kuai
2021-12-02 14:48 ` Michal Koutný
2021-12-03 7:50 ` yukuai (C)
2021-12-03 10:27 ` Michal Koutný
2021-12-04 8:03 ` yukuai (C)
2021-12-06 15:43 ` Michal Koutný [this message]
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