linux-kernel - Re: [PATCH 0/2] Synchronize DT overlay removal with devlink removals

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Message-ID: <20231206171540.GA2697853-robh@kernel.org>
Date:   Wed, 6 Dec 2023 11:15:40 -0600
From:   Rob Herring <robh@...nel.org>
To:     Herve Codina <herve.codina@...tlin.com>,
        Saravana Kannan <saravanak@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...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>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 0/2] Synchronize DT overlay removal with devlink removals

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
>