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

Greg Kroah-Hartman
2024-09-24T09:24:00Z

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@gmail.com>
> > Signed-off-by: David Jeffery <djeffery@redhat.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