linux-kernel - Re: [PATCH v3] rapidio/tsi721: Replace flush_scheduled_work() with flush

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Message-ID: <d039cbbd-4aa7-58bf-b93d-be23443c52b6@I-love.SAKURA.ne.jp>
Date:   Mon, 26 Sep 2022 19:28:37 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     Alan Stern <stern@...land.harvard.edu>, Tejun Heo <tj@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Matt Porter <mporter@...nel.crashing.org>,
        Alexandre Bounine <alex.bou9@...il.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3] rapidio/tsi721: Replace flush_scheduled_work() with
 flush_work().

On 2022/09/26 2:27, Andrew Morton wrote:
> On Sat, 24 Sep 2022 14:11:25 +0900 Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp> wrote:
> 
>> Like commit c4f135d643823a86 ("workqueue: Wrap flush_workqueue() using a
>> macro") says, flush_scheduled_work() is dangerous and will be forbidden.
>> We are on the way for removing all flush_scheduled_work() callers from
>> the kernel, and this patch is for removing flush_scheduled_work() call
>>  from tsi721 driver.
>>
>> Since "struct tsi721_device" is per a device struct, I assume that
>> tsi721_remove() needs to wait for only two works associated with that
>> device. Therefore, wait for only these works using flush_work().
>>
>> --- a/drivers/rapidio/devices/tsi721.c
>> +++ b/drivers/rapidio/devices/tsi721.c
>> @@ -2941,7 +2941,8 @@ static void tsi721_remove(struct pci_dev *pdev)
>>  
>>  	tsi721_disable_ints(priv);
>>  	tsi721_free_irq(priv);
>> -	flush_scheduled_work();
>> +	flush_work(&priv->idb_work);
>> +	flush_work(&priv->pw_work);
>>  	rio_unregister_mport(&priv->mport);
> 
> Why not use cancel_work[_sync](), as the flush_scheduled_work() comment
> recommends?
> 

Alan Stern suggested to use cancel_work_sync() in
commit eef6a7d5c2f38ada ("workqueue: warn about flush_scheduled_work()")
and Tejun Heo suggested to use flush_work() in
https://lkml.kernel.org/r/YjivtdkpY+reW0Gt@slm.duckdns.org .

Is there some reason to prefer one over the other?
I think that user-visible results between flush_work() and cancel_work_sync()
are the same because both wait until work completes.