linux-kernel - Re: 回复: [PATCH v5] workqueue: Remove unnecessary kfree() call in rcu_free

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Message-ID: <20200528140357.GL83516@mtj.thefacebook.com>
Date:   Thu, 28 May 2020 10:03:57 -0400
From:   Tejun Heo <tj@...nel.org>
To:     Lai Jiangshan <jiangshanlai@...il.com>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        "Zhang, Qiang" <Qiang.Zhang@...driver.com>,
        Markus Elfring <markus.elfring@....de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>
Subject: Re: 回复: [PATCH v5] workqueue:
 Remove unnecessary kfree() call in rcu_free_wq()

Hello,

On Thu, May 28, 2020 at 09:27:03PM +0800, Lai Jiangshan wrote:
> wq owns the ultimate or permanent references to itself by
> owning references to wq->numa_pwq_tbl[node], wq->dfl_pwq.
> The pwq's references keep the pwq in wq->pwqs.

Yeah, regardless of who puts a wq the last time, the base reference is put
by destroy_workqueue() and thus it's guaranteed that a wq can't be rcu freed
without going through destroy_workqueue(). lol I'm undoing the revert.

Thanks.

-- 
tejun