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References: <20240307111036.225007-1-herve.codina@bootlin.com> <20240308200548.GA1189199-robh@kernel.org>
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From: Saravana Kannan <saravanak@google.com>
Date: Fri, 8 Mar 2024 14:29:28 -0800
Message-ID: <CAGETcx8ReCH2z64_PGhmbqdH_ge3B_xOqTOP-yanRf3T8TkzLg@mail.gmail.com>
Subject: Re: [PATCH v5 0/2] Synchronize DT overlay removal with devlink removals
To: Rob Herring <robh@kernel.org>
Cc: Herve Codina <herve.codina@bootlin.com>, 
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>, "Rafael J. Wysocki" <rafael@kernel.org>, 
	Frank Rowand <frowand.list@gmail.com>, Lizhi Hou <lizhi.hou@amd.com>, Max Zhen <max.zhen@amd.com>, 
	Sonal Santan <sonal.santan@amd.com>, Stefano Stabellini <stefano.stabellini@xilinx.com>, 
	Jonathan Cameron <Jonathan.Cameron@huawei.com>, linux-kernel@vger.kernel.org, 
	devicetree@vger.kernel.org, Allan Nielsen <allan.nielsen@microchip.com>, 
	Horatiu Vultur <horatiu.vultur@microchip.com>, 
	Steen Hegelund <steen.hegelund@microchip.com>, Luca Ceresoli <luca.ceresoli@bootlin.com>, 
	Nuno Sa <nuno.sa@analog.com>, Thomas Petazzoni <thomas.petazzoni@bootlin.com>
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On Fri, Mar 8, 2024 at 12:05=E2=80=AFPM Rob Herring <robh@kernel.org> wrote=
:
>
> On Thu, Mar 07, 2024 at 12:09:59PM +0100, Herve Codina wrote:
> > Hi,
> >
> > In the following sequence:
> >   of_platform_depopulate(); /* Remove devices from a DT overlay node */
> >   of_overlay_remove(); /* Remove the DT overlay node itself */
> >
> > Some warnings are raised by __of_changeset_entry_destroy() which  was
> > called from of_overlay_remove():
> >   ERROR: memory leak, expected refcount 1 instead of 2 ...
> >
> > The issue is that, during the device devlink removals triggered from th=
e
> > of_platform_depopulate(), jobs are put in a workqueue.
> > These jobs drop the reference to the devices. When a device is no more
> > referenced (refcount =3D=3D 0), it is released and the reference to its
> > of_node is dropped by a call to of_node_put().
> > These operations are fully correct except that, because of the
> > workqueue, they are done asynchronously with respect to function calls.
> >
> > In the sequence provided, the jobs are run too late, after the call to
> > __of_changeset_entry_destroy() and so a missing of_node_put() call is
> > detected by __of_changeset_entry_destroy().
> >
> > This series fixes this issue introducing device_link_wait_removal() in
> > order to wait for the end of jobs execution (patch 1) and using this
> > function to synchronize the overlay removal with the end of jobs
> > execution (patch 2).
> >
> > Compared to the previous iteration:
> >   https://lore.kernel.org/linux-kernel/20240306085007.169771-1-herve.co=
dina@bootlin.com/
> > this v5 series:
> > - Remove a 'Fixes' tag
> > - Update a comment
> > - Add 'Tested-by' and ''Reviewed-by' tags
> >
> > This series handles cases reported by Luca [1] and Nuno [2].
> >   [1]: https://lore.kernel.org/all/20231220181627.341e8789@booty/
> >   [2]: https://lore.kernel.org/all/20240205-fix-device-links-overlays-v=
2-2-5344f8c79d57@analog.com/
> >
> > Best regards,
> > Herv=C3=A9
> >
> > Changes v4 -> v5
> >   - Patch 1
> >     Remove the 'Fixes' tag
> >     Add 'Tested-by: Luca Ceresoli <luca.ceresoli@bootlin.com>'
> >     Add 'Reviewed-by: Nuno Sa <nuno.sa@analog.com>'
> >
> >   - Patch 2
> >     Update comment as suggested
> >     Add 'Reviewed-by: Saravana Kannan <saravanak@google.com>'
> >     Add 'Tested-by: Luca Ceresoli <luca.ceresoli@bootlin.com>'
> >     Add 'Reviewed-by: Nuno Sa <nuno.sa@analog.com>'
> >
> > Changes v3 -> v4
> >   - Patch 1
> >     Uses flush_workqueue() instead of drain_workqueue().
> >
> >   - Patch 2
> >     Remove unlock/re-lock when calling device_link_wait_removal()
> >     Move device_link_wait_removal() call to of_changeset_destroy()
> >     Update commit log
> >
> > Changes v2 -> v3
> >   - Patch 1
> >     No changes
> >
> >   - Patch 2
> >     Add missing device.h
> >
> > Changes v1 -> v2
> >   - Patch 1
> >     Rename the workqueue to 'device_link_wq'
> >     Add 'Fixes' tag and Cc stable
> >
> >   - Patch 2
> >     Add device.h inclusion.
> >     Call device_link_wait_removal() later in the overlay removal
> >     sequence (i.e. in free_overlay_changeset() function).
> >     Drop of_mutex lock while calling device_link_wait_removal().
> >     Add       'Fixes' tag and Cc stable
> >
> > Herve Codina (2):
> >   driver core: Introduce device_link_wait_removal()
> >   of: dynamic: Synchronize of_changeset_destroy() with the devlink
> >     removals
> >
> >  drivers/base/core.c    | 26 +++++++++++++++++++++++---
> >  drivers/of/dynamic.c   | 12 ++++++++++++
> >  include/linux/device.h |  1 +
> >  3 files changed, 36 insertions(+), 3 deletions(-)
>
> This looks good to me. I can take this given the user is DT. Looking for
> a R-by from Saravana and Ack from Greg. A R-by from Rafael would be
> great too.

Reviewed-by: Saravana Kannan <saravanak@google.com>

-Saravana