linux-kernel - Re: [PATCH] workqueue: make manage_workers() and pool destruction exclusive

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Message-ID: <20180319152746.GN2943022@devbig577.frc2.facebook.com>
Date:   Mon, 19 Mar 2018 08:27:46 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Lai Jiangshan <jiangshanlai@...il.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] workqueue: make manage_workers() and pool destruction
 exclusive

On Mon, Mar 19, 2018 at 03:35:07PM +0800, Lai Jiangshan wrote:
> The original code allows destroying the pool when the pool
> is still active in manage_workers(). A synchronization
> mechanism between manage_workers() and pool destruction
> was added for protection.
> 
> This patch simply makes manage_workers() and pool destruction
> exclusive by getting an indirect refcount of the pool in
> manage_workers(). "indirect" means it gets a refcount of
> the first involved pwq which holds a refcount of the pool.
> This refcount can prevent the pool from being destroyed.
> 
> The original synchronization mechanism (wq_manager_wait)
> is also removed.

Hmm... idk, this is more indirect and subtle than the existing code
and it's not like the existing code was overly complicated.

Thanks.

-- 
tejun