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

[Rob Herring <robh@kernel.org>]

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