linux-kernel - Re: [v2] workqueue: Fix double kfree for rescuer

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Message-ID: <e002d552-b161-0cc3-88ea-daee541ee6f4@windriver.com>
Date:   Tue, 26 May 2020 10:05:44 +0800
From:   qzhang2 <qiang.zhang@...driver.com>
To:     Markus Elfring <Markus.Elfring@....de>, Tejun Heo <tj@...nel.org>,
        Lai Jiangshan <jiangshanlai@...il.com>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [v2] workqueue: Fix double kfree for rescuer

Thanks for your advice.
The rescuer null pointer is intentionally passed by a data structure?
and also I read the code of workqueue again, when destroy_workqueue is
called, after "wq->rescuer = NULL" was executed, The scenario described 
below does not happen

"if non-null pointers (according to valid rescuer objects) are 
occasionally passed by the corresponding data structure member
for the callback function "rcu_free_wq"."


On 5/25/20 6:40 PM, Markus Elfring wrote:
>> I see, kfree does nothing with null pointers and direct return.
>> but again kfree is not a good suggestion.
> 
> I have got the impression that the implementation detail is important here
> if non-null pointers (according to valid rescuer objects) are occasionally
> passed by the corresponding data structure member for the callback
> function “rcu_free_wq”.
> Can another clarification attempt reduce unwanted confusion for this patch review?
> 
> Regards,
> Markus
>