linux-kernel - Re: [PATCH] software node: recursively unregister child swnodes

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Date:   Thu, 4 Jun 2020 13:57:01 -0700
From:   Jordan Hand <jorhand@...ux.microsoft.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, linux-next@...r.kernel.org
Subject: Re: [PATCH] software node: recursively unregister child swnodes

On 6/4/20 1:15 PM, Greg Kroah-Hartman wrote:
> On Thu, Jun 04, 2020 at 12:36:23PM -0700, jorhand@...ux.microsoft.com wrote:
>> From: Jordan Hand <jorhand@...ux.microsoft.com>
>>
>> If a child swnode is unregistered after it's parent, it can lead to
>> undefined behavior.
> 
> Crashing the system is not really "undefined" :)

Fair point :)

> 
>> When a swnode is unregistered, recursively free it's children to avoid
>> this condition.
> 
> Are you sure?  Why would you be unregistering a child after it's parent?
> Why not just do not do that?
> 

The main motivation for doing this was to support 
`software_node_unregister_nodes` so that the passed list of nodes does 
not need to be ordered in any particular way.

I suppose another way to do this would be to add a new function 
`fwnode_remove_software_node_recursive` and just call that from 
`software_node_unregister_nodes`.

That said, I suppose just ordering the nodes so that children come 
before parents would also be fine. My thinking was just that accepting 
any node ordering is simpler.

Thanks,
Jordan