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Message-ID: <ca0e141e624edb4f9977ea9f805f74645654bca7.camel@gmail.com>
Date: Tue, 05 Mar 2024 08:17:38 +0100
From: Nuno Sá <noname.nuno@...il.com>
To: Saravana Kannan <saravanak@...gle.com>, Rob Herring <robh@...nel.org>
Cc: Herve Codina <herve.codina@...tlin.com>, Greg Kroah-Hartman
<gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>,
Frank Rowand <frowand.list@...il.com>, Lizhi Hou <lizhi.hou@....com>, Max
Zhen <max.zhen@....com>, Sonal Santan <sonal.santan@....com>, Stefano
Stabellini <stefano.stabellini@...inx.com>, Jonathan Cameron
<Jonathan.Cameron@...wei.com>, linux-kernel@...r.kernel.org,
devicetree@...r.kernel.org, Allan Nielsen <allan.nielsen@...rochip.com>,
Horatiu Vultur <horatiu.vultur@...rochip.com>, Steen Hegelund
<steen.hegelund@...rochip.com>, Luca Ceresoli <luca.ceresoli@...tlin.com>,
Nuno Sa <nuno.sa@...log.com>, Thomas Petazzoni
<thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v3 0/2] Synchronize DT overlay removal with devlink
removals
On Mon, 2024-03-04 at 22:17 -0800, Saravana Kannan wrote:
> On Mon, Mar 4, 2024 at 7:02 AM Rob Herring <robh@...nel.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
> > >
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