Re: [PATCH v3 0/2] Synchronize DT overlay removal with devlink removals

Rob Herring
2024-03-04T15:02:52Z

On Thu, Feb 29, 2024 at 11:52:01AM +0100, Herve Codina wrote:
> Hi,

Please CC Saravana on this.

>
> 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/20231130174126.688486-1-herve.codina@bootlin.com/
> this v3 series:
> - add the missing device.h
>
> 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 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: overlay: Synchronize of_overlay_remove() with the devlink removals
>
> drivers/base/core.c | 26 +++++++++++++++++++++++---
> drivers/of/overlay.c | 10 +++++++++-
> include/linux/device.h | 1 +
> 3 files changed, 33 insertions(+), 4 deletions(-)
>
> --
> 2.43.0
>