Re: [PATCH v4 2/2] of: dynamic: Synchronize of_changeset_destroy() with the devlink removals

[Luca Ceresoli]

On Wed,  6 Mar 2024 09:50:03 +0100
Herve Codina <herve.codina@xxxxxxxxxxx> wrote:

> In the following sequence:
>   1) of_platform_depopulate()
>   2) of_overlay_remove()
> 
> During the step 1, devices are destroyed and devlinks are removed.
> During the step 2, OF nodes are destroyed but
> __of_changeset_entry_destroy() can raise warnings related to missing
> of_node_put():
>   ERROR: memory leak, expected refcount 1 instead of 2 ...
> 
> Indeed, during the devlink removals performed at step 1, the removal
> itself releasing the device (and the attached of_node) is done by a job
> queued in a workqueue and so, it is done asynchronously with respect to
> function calls.
> When the warning is present, of_node_put() will be called but wrongly
> too late from the workqueue job.
> 
> In order to be sure that any ongoing devlink removals are done before
> the of_node destruction, synchronize the of_changeset_destroy() with the
> devlink removals.
> 
> Fixes: 80dd33cf72d1 ("drivers: base: Fix device link removal")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Herve Codina <herve.codina@xxxxxxxxxxx>
> ---
>  drivers/of/dynamic.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
> index 3bf27052832f..169e2a9ae22f 100644
> --- a/drivers/of/dynamic.c
> +++ b/drivers/of/dynamic.c
> @@ -9,6 +9,7 @@
>  
>  #define pr_fmt(fmt)	"OF: " fmt
>  
> +#include <linux/device.h>
>  #include <linux/of.h>
>  #include <linux/spinlock.h>
>  #include <linux/slab.h>
> @@ -667,6 +668,12 @@ void of_changeset_destroy(struct of_changeset *ocs)
>  {
>  	struct of_changeset_entry *ce, *cen;
>  
> +	/*
> +	 * Wait for any ongoing device link removals before destroying some of
> +	 * nodes.
> +	 */
> +	device_link_wait_removal();

Tested-by: Luca Ceresoli <luca.ceresoli@xxxxxxxxxxx>

And no problem appeared in my tests due to the removed unlock/lock
around device_link_wait_removal().

Luca

-- 
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com