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

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Date: Wed, 29 May 2024 08:06:00 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: stuart hayes <stuart.w.hayes@...il.com>
Cc: Christoph Hellwig <hch@....de>, linux-kernel@...r.kernel.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 Tue, May 28, 2024 at 10:35:27PM -0500, stuart hayes wrote:
> 
> 
> 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.

Opt-in is the requirement here, that's all I asked for.  The "on" can
probably be removed, and by doing that, you can make this option simpler
as well.

thanks,

greg k-h