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

["Nuno Sá" <noname.nuno@gmail.com>]

On Mon, 2024-03-04 at 22:17 -0800, Saravana Kannan wrote:
> On Mon, Mar 4, 2024 at 7:02 AM Rob Herring <robh@kernel.org> wrote:
> > 
> > On Thu, Feb 29, 2024 at 11:52:01AM +0100, Herve Codina wrote:
> > > Hi,
> > 
> > Please CC Saravana on this.
> 
> Nuno, this is why I was replying to the older series. I didn't even
> get this one.

Arghh, I see... In lot's of replies I was mentioning you :)

- Nuno Sá

> 
> > 
> > > 
> > > 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
> > >