linux-kernel - Re: [PATCH v2 2/2] of: overlay: Synchronize of_overlay

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Message-ID: <c2b830bb4a4cf76dec8783f38b2477120edb1a15.camel@gmail.com>
Date: Thu, 29 Feb 2024 10:50:21 +0100
From: Nuno Sá <noname.nuno@...il.com>
To: Herve Codina <herve.codina@...tlin.com>, Greg Kroah-Hartman
	 <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>, Rob
	Herring <robh+dt@...nel.org>, Frank Rowand <frowand.list@...il.com>
Cc: Lizhi Hou <lizhi.hou@....com>, Max Zhen <max.zhen@....com>, Sonal Santan
 <sonal.santan@....com>, Stefano Stabellini <stefano.stabellini@...inx.com>,
  Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, Allan Nielsen
 <allan.nielsen@...rochip.com>, Horatiu Vultur
 <horatiu.vultur@...rochip.com>, Steen Hegelund
 <steen.hegelund@...rochip.com>, Luca Ceresoli <luca.ceresoli@...tlin.com>,
 Nuno Sa <nuno.sa@...log.com>, Thomas Petazzoni
 <thomas.petazzoni@...tlin.com>,  stable@...r.kernel.org
Subject: Re: [PATCH v2 2/2] of: overlay: Synchronize of_overlay_remove()
 with the devlink removals

On Thu, 2024-02-29 at 09:39 +0100, Herve Codina wrote:
> In the following sequence:
>   1) of_platform_depopulate()
>   2) of_overlay_remove()
> 
> During the step 1, devices are destroyed and devlinks are removed.
> During the step 2, OF nodes are destroyed but
> __of_changeset_entry_destroy() can raise warnings related to missing
> of_node_put():
>   ERROR: memory leak, expected refcount 1 instead of 2 ...
> 
> Indeed, during the devlink removals performed at step 1, the removal
> itself releasing the device (and the attached of_node) is done by a job
> queued in a workqueue and so, it is done asynchronously with respect to
> function calls.
> When the warning is present, of_node_put() will be called but wrongly
> too late from the workqueue job.
> 
> In order to be sure that any ongoing devlink removals are done before
> the of_node destruction, synchronize the of_overlay_remove() with the
> devlink removals.
> 
> Fixes: 80dd33cf72d1 ("drivers: base: Fix device link removal")
> Cc: stable@...r.kernel.org
> Signed-off-by: Herve Codina <herve.codina@...tlin.com>
> ---
>  drivers/of/overlay.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
> index 2ae7e9d24a64..99659ae9fb28 100644
> --- a/drivers/of/overlay.c
> +++ b/drivers/of/overlay.c

In the cover, you mention device.h inclusion but I'm not seeing it? This is
clearly up to the DT maintainers to decide but, IMHO, I would very much prefer
to see fwnode.h included in here rather than directly device.h (so yeah,
renaming the function to fwnode_*). But yeah, I might be biased by own series :)

- Nuno Sá