mbox series

[v2,0/2] Synchronize DT overlay removal with devlink removals

Message ID 20240229083953.607569-1-herve.codina@bootlin.com
Headers
Series Synchronize DT overlay removal with devlink removals |

Message

Herve Codina Feb. 29, 2024, 8:39 a.m. UTC 
  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/20231130174126.688486-1-herve.codina@bootlin.com/
this v2 series mainly:
- Renames the workqueue used.
- Calls device_link_wait_removal() a bit later to handle 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 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   |  9 ++++++++-
 include/linux/device.h |  1 +
 3 files changed, 32 insertions(+), 4 deletions(-)

Comments

Herve Codina Feb. 29, 2024, 10:55 a.m. UTC | #1 
Hi All,

I did a mistake in this series.
As noted by Nuno, the device.h include is missing in patch 2 and so
the patch 2 doesn't compile :(

A v3 is already sent fixing my missing device.h mistake.
  https://lore.kernel.org/all/20240229105204.720717-1-herve.codina@bootlin.com/

Sorry for this error.
Best regards,
Hervé

On Thu, 29 Feb 2024 09:39:40 +0100
Herve Codina <herve.codina@bootlin.com> 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/20231130174126.688486-1-herve.codina@bootlin.com/
> this v2 series mainly:
> - Renames the workqueue used.
> - Calls device_link_wait_removal() a bit later to handle 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 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   |  9 ++++++++-
>  include/linux/device.h |  1 +
>  3 files changed, 32 insertions(+), 4 deletions(-)
>