linux-kernel - Re: [PATCH v8 3/4] driver core: shut down devices asynchronously

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Message-ID: <2024092440-embattled-magical-64bc@gregkh>
Date: Tue, 24 Sep 2024 11:23:54 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Andrey Skvortsov <andrej.skvortzov@...il.com>,
	Stuart Hayes <stuart.w.hayes@...il.com>,
	linux-kernel@...r.kernel.org,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	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>,
	Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>,
	linux-nvme@...ts.infradead.org
Subject: Re: [PATCH v8 3/4] driver core: shut down devices asynchronously

On Mon, Sep 23, 2024 at 11:50:39PM +0300, Andrey Skvortsov wrote:
> Hi Stuart,
> 
> On 24-08-22 15:28, Stuart Hayes wrote:
> > Add code to allow asynchronous shutdown of devices, ensuring that each
> > device is shut down before its parents & suppliers.
> > 
> > Only devices with drivers that have async_shutdown_enable enabled will be
> > shut down asynchronously.
> > 
> > This can dramatically reduce system shutdown/reboot time on systems that
> > have multiple devices that take many seconds to shut down (like certain
> > NVMe drives). On one system tested, the shutdown time went from 11 minutes
> > without this patch to 55 seconds with the patch.
> > 
> > Signed-off-by: Stuart Hayes <stuart.w.hayes@...il.com>
> > Signed-off-by: David Jeffery <djeffery@...hat.com>
> > ---
> >  drivers/base/base.h           |  4 +++
> >  drivers/base/core.c           | 54 ++++++++++++++++++++++++++++++++++-
> >  include/linux/device/driver.h |  2 ++
> >  3 files changed, 59 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/base/base.h b/drivers/base/base.h
> > index 0b53593372d7..aa5a2bd3f2b8 100644
> > --- a/drivers/base/base.h
> > +++ b/drivers/base/base.h
> > @@ -10,6 +10,7 @@
> >   * shared outside of the drivers/base/ directory.
> 
> This change landed in linux-next and I have problem with shutdown on
> ARM Allwinner A64 device. Device usually hangs at shutdown.
> git bisect pointed to "driver core: shut down devices asynchronously"
> as a first bad commit.
> 
> I've tried to debug the problem and this is what I see:
> 
> 1) device 'mmc_host mmc0' processed in device_shutdown. For this device
> async_schedule_domain is called (cookie 264, for example).
> 
> 2) after that 'mmcblk mmc0:aaaa' is processed. For this device
> async_schedule_domain is called (cookie 296, for example).
> 
> 3) 'mmc_host mmc0' is parent of 'mmcblk mmc0:aaaa' and
> parent->p->shutdown_after is updated from 263 to 296.
> 
> 4) After sometime shutdown_one_device_async is called for 264
> (mmc_host mmc0), but dev->p->shutdown_after was updated to 296 and the
> code calls first async_synchronize_cookie_domain for 297.
> 
> 264 can't finish, because it waits for 297. shutdown process can't continue.
> 
> The problem is always with a MMC host controller.

If you take the patch here:
	https://lore.kernel.org/r/20240919043143.1194950-1-stuart.w.hayes@gmail.com
does it solve the problem?

thanks,

greg k-h