Re: [PATCH v5 0/2] Synchronize DT overlay removal with devlink removals

From: Rob Herring
Date: Fri Mar 08 2024 - 15:06:04 EST


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@xxxxxxxxxxx/
> 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@xxxxxxxxxx/
>
> Best regards,
> Hervé
>
> Changes v4 -> v5
> - Patch 1
> Remove the 'Fixes' tag
> Add 'Tested-by: Luca Ceresoli <luca.ceresoli@xxxxxxxxxxx>'
> Add 'Reviewed-by: Nuno Sa <nuno.sa@xxxxxxxxxx>'
>
> - Patch 2
> Update comment as suggested
> Add 'Reviewed-by: Saravana Kannan <saravanak@xxxxxxxxxx>'
> Add 'Tested-by: Luca Ceresoli <luca.ceresoli@xxxxxxxxxxx>'
> Add 'Reviewed-by: Nuno Sa <nuno.sa@xxxxxxxxxx>'
>
> 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.

Rob