linux-kernel - Re: [PATCH] block, bfq: switch 'bfqg->ref' to use atomic refcount apis

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Message-Id: <167384123010.165459.4491550988140898321.b4-ty@kernel.dk>
Date:   Sun, 15 Jan 2023 20:53:50 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     jack@...e.cz, paolo.valente@...aro.org, tj@...nel.org,
        josef@...icpanda.com, Yu Kuai <yukuai1@...weicloud.com>
Cc:     linux-block@...r.kernel.org, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, yukuai3@...wei.com,
        yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH] block, bfq: switch 'bfqg->ref' to use atomic refcount
 apis


On Tue, 03 Jan 2023 16:47:55 +0800, Yu Kuai wrote:
> The updating of 'bfqg->ref' should be protected by 'bfqd->lock', however,
> during code review, we found that bfq_pd_free() update 'bfqg->ref'
> without holding the lock, which is problematic:
> 
> 1) bfq_pd_free() triggered by removing cgroup is called asynchronously;
> 2) bfqq will grab bfqg reference, and exit bfqq will drop the reference,
> which can concurrent with 1).
> 
> [...]

Applied, thanks!

[1/1] block, bfq: switch 'bfqg->ref' to use atomic refcount apis
      commit: 216f764716f34fe68cedc7296ae2043a7727e640

Best regards,
-- 
Jens Axboe