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Date: Thu, 11 Apr 2024 15:23:19 +0200
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Saravana Kannan <saravanak@google.com>
Cc: Rob Herring <robh@kernel.org>, Herve Codina <herve.codina@bootlin.com>,
	"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>
Subject: Re: [PATCH v5 0/2] Synchronize DT overlay removal with devlink
 removals
Message-ID: <2024041111-unsaid-shrine-63f8@gregkh>
References: <20240307111036.225007-1-herve.codina@bootlin.com>
 <20240308200548.GA1189199-robh@kernel.org>
 <CAGETcx8ReCH2z64_PGhmbqdH_ge3B_xOqTOP-yanRf3T8TkzLg@mail.gmail.com>
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On Fri, Mar 08, 2024 at 02:29:28PM -0800, Saravana Kannan wrote:
> On Fri, Mar 8, 2024 at 12:05 PM 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 the
> > > 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 == 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.codina@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-v2-2-5344f8c79d57@analog.com/
> > >
> > > Best regards,
> > > Hervé
> > >
> > > 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>

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>