linux-kernel - Re: [PATCH 1/6] drivers: base: devres: Allow to release group on device release

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Message-ID: <2025022007-judiciary-broadly-a1f8@gregkh>
Date: Thu, 20 Feb 2025 13:24:20 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Lucas De Marchi <lucas.demarchi@...el.com>
Cc: linux-kernel@...r.kernel.org, Rodrigo Vivi <rodrigo.vivi@...el.com>,
	dri-devel@...ts.freedesktop.org, Danilo Krummrich <dakr@...nel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH 1/6] drivers: base: devres: Allow to release group on
 device release

On Wed, Feb 12, 2025 at 12:05:37PM -0800, Lucas De Marchi wrote:
> When releasing a device, if the release action causes a group to be
> released, a warning is emitted because it can't find the group. This
> happens because devres_release_all() moves the entire list to a todo
> list and also move the group markers. Considering r* normal resource
> nodes and g1 a group resource node:
> 
> 		    g1 -----------.
> 		    v		  v
> 	r1 -> r2 -> g1[0] -> r3-> g[1] -> r4
> 
> After devres_release_all(), dev->devres_head becomes empty and the todo
> list it iterates on becomes:
> 
> 			       g1
> 			       v
> 	r1 -> r2 -> r3-> r4 -> g1[0]
> 
> When a call to component_del() is made and takes down the aggregate
> device, a warning like this happen:
> 
> 	RIP: 0010:devres_release_group+0x362/0x530
> 	...
> 	Call Trace:
> 	 <TASK>
> 	 component_unbind+0x156/0x380
> 	 component_unbind_all+0x1d0/0x270
> 	 mei_component_master_unbind+0x28/0x80 [mei_hdcp]
> 	 take_down_aggregate_device+0xc1/0x160
> 	 component_del+0x1c6/0x3e0
> 	 intel_hdcp_component_fini+0xf1/0x170 [xe]
> 	 xe_display_fini+0x1e/0x40 [xe]
> 
> Because the devres group corresponding to the hdcp component cannot be
> found. Just ignore this corner case: if the dev->devres_head is empty
> and the caller is trying to remove a group, it's likely in the process
> of device cleanup so just ignore it instead of warning.
> 
> Signed-off-by: Lucas De Marchi <lucas.demarchi@...el.com>
> ---

Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>