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Date: Wed, 6 Dec 2023 11:15:40 -0600
From: Rob Herring <robh@kernel.org>
To: Herve Codina <herve.codina@bootlin.com>, Saravana Kannan <saravanak@google.com>
Cc: 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>, Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Subject: Re: [PATCH 0/2] Synchronize DT overlay removal with devlink removals
Message-ID: <20231206171540.GA2697853-robh@kernel.org>
References: <20231130174126.688486-1-herve.codina@bootlin.com>
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In-Reply-To: <20231130174126.688486-1-herve.codina@bootlin.com>

On Thu, Nov 30, 2023 at 06:41:07PM +0100, Herve Codina wrote:
> Hi,

+Saravana for comment

Looks okay to me though.

> 
> 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).
> 
> Best regards,
> Hervé
> 
> Herve Codina (2):
>   driver core: Introduce device_link_wait_removal()
>   of: overlay: Synchronize of_overlay_remove() with the devlink removals
> 
>  drivers/base/core.c    | 26 +++++++++++++++++++++++---
>  drivers/of/overlay.c   |  6 ++++++
>  include/linux/device.h |  1 +
>  3 files changed, 30 insertions(+), 3 deletions(-)
> 
> -- 
> 2.42.0
>