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

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Message-ID: <20231130174126.688486-3-herve.codina@bootlin.com>
Date:   Thu, 30 Nov 2023 18:41:09 +0100
From:   Herve Codina <herve.codina@...tlin.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>
Cc:     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>,
        Herve Codina <herve.codina@...tlin.com>
Subject: [PATCH 2/2] of: overlay: Synchronize of_overlay_remove() with the devlink removals

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.

Signed-off-by: Herve Codina <herve.codina@...tlin.com>
---
 drivers/of/overlay.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index a9a292d6d59b..5c5f808b163e 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -1202,6 +1202,12 @@ int of_overlay_remove(int *ovcs_id)
 		goto out;
 	}

+	/*
+	 * Wait for any ongoing device link removals before removing some of
+	 * nodes
+	 */
+	device_link_wait_removal();
+
 	mutex_lock(&of_mutex);

 	ovcs = idr_find(&ovcs_idr, *ovcs_id);
-- 
2.42.0