Re: [PATCH v5 0/2] Synchronize DT overlay removal with devlink removals
From: Rob Herring
Date: Wed Mar 20 2024 - 10:42:03 EST
On Fri, Mar 08, 2024 at 02:05:48PM -0600, Rob Herring wrote:
> 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.
You may want to resend this as Greg may have seen the discussion and
moved on.
Rob