linux-kernel - Re: [PATCH v6 3/4] driver core: shut down devices asynchronously

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Date: Tue, 28 May 2024 22:35:27 -0500
From: stuart hayes <stuart.w.hayes@...il.com>
To: Christoph Hellwig <hch@....de>
Cc: linux-kernel@...r.kernel.org,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "Rafael J . Wysocki" <rafael@...nel.org>,
 Tanjore Suresh <tansuresh@...gle.com>,
 Martin Belanger <Martin.Belanger@...l.com>,
 Oliver O'Halloran <oohall@...il.com>, Daniel Wagner <dwagner@...e.de>,
 Keith Busch <kbusch@...nel.org>, Lukas Wunner <lukas@...ner.de>,
 David Jeffery <djeffery@...hat.com>, Jeremy Allison <jallison@....com>,
 Jens Axboe <axboe@...com>, Sagi Grimberg <sagi@...mberg.me>,
 linux-nvme@...ts.infradead.org
Subject: Re: [PATCH v6 3/4] driver core: shut down devices asynchronously

On 5/28/2024 1:31 AM, Christoph Hellwig wrote:
> On Thu, May 16, 2024 at 10:49:19AM -0500, Stuart Hayes wrote:
>> Add /sys/kernel/async_shutdown to allow user control of this feature:
>>
>>    safe: shut down all devices synchronously, unless driver prefers async
>> 	shutdown (driver opt-in) (default)
>>    on:	shut down all devices asynchronously, unless disabled by the driver
>> 	(driver opt-out)
>>    off:	shut down all devices synchronously
> 
> The on option seems very odd.  IMHO safe is the only really sensible
> option, and maybe we have to support off as a bandaid due to userspace
> behavior dependent on synchronous shutdown, but I'd rather try even
> without that first.
> 

I added the option because of comments from Greg K-H on the v4 submission
of this patch--see

https://lore.kernel.org/lkml/2023102151-rejoicing-studio-6126@gregkh/T/#m5d0459480bc0fda4563040cab2036839bcbb79a8).

I thought it would be nice to have the option for testing, even if it gets
removed later, but I'll certainly remove it now if necessary.