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

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Message-ID: <20240229111430.54bdb6b1@bootlin.com>
Date: Thu, 29 Feb 2024 11:14:30 +0100
From: Herve Codina <herve.codina@...tlin.com>
To: Nuno Sá <noname.nuno@...il.com>
Cc: Greg Kroah-Hartman  <gregkh@...uxfoundation.org>, "Rafael J. Wysocki"
 <rafael@...nel.org>, Rob Herring <robh+dt@...nel.org>, Frank Rowand
 <frowand.list@...il.com>, 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, 29 Feb 2024 10:50:21 +0100
Nuno Sá <noname.nuno@...il.com> wrote:

> 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 :)
> 

Damned. I missed device.h in this patch.
Without this one, the patch do not compile :(

A fixup commit I missed to squash before sending.

A v3 is planned to add this device.h.

Nuno, do you prefer I wait few days before sending this v3 waiting for more replies
or I send it right now and you re-do your comment on the v3 ?

I would really prefer to send it now :)

Sorry about my mistake.
Best regards,
Hervé

-- 
Hervé Codina, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com