linux-kernel - Re: [PATCH v10 2/5] driver core: don't always lock parent in shutdown

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Message-ID: <2025070157-undaunted-curler-bda3@gregkh>
Date: Tue, 1 Jul 2025 10:50:28 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Stuart Hayes <stuart.w.hayes@...il.com>
Cc: 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,
	Nathan Chancellor <nathan@...nel.org>,
	Jan Kiszka <jan.kiszka@...mens.com>,
	Bert Karwatzki <spasswolf@....de>
Subject: Re: [PATCH v10 2/5] driver core: don't always lock parent in shutdown

On Wed, Jun 25, 2025 at 03:18:50PM -0500, Stuart Hayes wrote:
> Don't lock a parent device unless it is needed in device_shutdown. This
> is in preparation for making device shutdown asynchronous, when it will
> be needed to allow children of a common parent to shut down
> simultaneously.
> 
> Signed-off-by: Stuart Hayes <stuart.w.hayes@...il.com>
> Signed-off-by: David Jeffery <djeffery@...hat.com>
> ---
>  drivers/base/core.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index cbc0099d8ef2..58c772785606 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -4823,7 +4823,7 @@ void device_shutdown(void)
>  		spin_unlock(&devices_kset->list_lock);
>  
>  		/* hold lock to avoid race with probe/release */
> -		if (parent)
> +		if (parent && dev->bus && dev->bus->need_parent_lock)
>  			device_lock(parent);

What about parents for a device that is not on a bus?  Don't they need
to be properly locked?


>  		device_lock(dev);
>  
> @@ -4847,7 +4847,7 @@ void device_shutdown(void)
>  		}
>  
>  		device_unlock(dev);
> -		if (parent)
> +		if (parent && dev->bus && dev->bus->need_parent_lock)
>  			device_unlock(parent);

Same here.

thanks,

greg k-h