[v2,2/2] of: dynamic: flush devlinks workqueue before destroying the changeset

  From: Nuno Sa <nuno.sa@analog.com>

Device links will drop their supplier + consumer refcounts
asynchronously. That means that the refcount of the of_node attached to
these devices will also be dropped asynchronously and so we cannot
guarantee the DT overlay assumption that the of_node refcount must be 1 in
__of_changeset_entry_destroy().

Given the above, call the new fwnode_links_flush_queue() helper to flush
the devlink workqueue so we can be sure that all links are dropped before
doing the proper checks.

Signed-off-by: Nuno Sa <nuno.sa@analog.com>
---
 drivers/of/dynamic.c | 8 ++++++++
 1 file changed, 8 insertions(+)
  

On Mon, Feb 05, 2024 at 01:09:33PM +0100, Nuno Sa via B4 Relay wrote:
> From: Nuno Sa <nuno.sa@analog.com>
> 
> Device links will drop their supplier + consumer refcounts
> asynchronously. That means that the refcount of the of_node attached to
> these devices will also be dropped asynchronously and so we cannot
> guarantee the DT overlay assumption that the of_node refcount must be 1 in
> __of_changeset_entry_destroy().
> 
> Given the above, call the new fwnode_links_flush_queue() helper to flush
> the devlink workqueue so we can be sure that all links are dropped before
> doing the proper checks.

Have you seen my comments against v1?

> +++ b/drivers/of/dynamic.c
> @@ -14,6 +14,7 @@
>  #include <linux/slab.h>
>  #include <linux/string.h>
>  #include <linux/proc_fs.h>
> +#include <linux/fwnode.h>

Try to squeeze this to make it ordered (with given context it may go before
linux/s* ones, but maybe you may find a better spot).

..

> +	/*
> +	 * device links drop their device references (and hence their of_node

Device links...

> +	 * references) asynchronously on a dedicated workqueue. Hence we need
> +	 * to flush it to make sure everything is done before doing the below
> +	 * checks.
> +	 */
  

> -----Original Message-----
> From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Sent: Monday, February 5, 2024 1:36 PM
> To: Sa, Nuno <Nuno.Sa@analog.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>; Rafael J. Wysocki
> <rafael@kernel.org>; Frank Rowand <frowand.list@gmail.com>; Rob Herring
> <robh+dt@kernel.org>; Daniel Scally <djrscally@gmail.com>; Heikki Krogerus
> <heikki.krogerus@linux.intel.com>; Sakari Ailus <sakari.ailus@linux.intelcom>;
> Len Brown <lenb@kernel.org>; linux-acpi@vger.kernel.org;
> devicetree@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH v2 2/2] of: dynamic: flush devlinks workqueue before
> destroying the changeset
> 
> [External]
> 
> On Mon, Feb 05, 2024 at 01:09:33PM +0100, Nuno Sa via B4 Relay wrote:
> > From: Nuno Sa <nuno.sa@analog.com>
> >
> > Device links will drop their supplier + consumer refcounts
> > asynchronously. That means that the refcount of the of_node attached to
> > these devices will also be dropped asynchronously and so we cannot
> > guarantee the DT overlay assumption that the of_node refcount must be 1 in
> > __of_changeset_entry_destroy().
> >
> > Given the above, call the new fwnode_links_flush_queue() helper to flush
> > the devlink workqueue so we can be sure that all links are dropped before
> > doing the proper checks.
> 
> Have you seen my comments against v1?

Hmm, not really. lei is not fetching any email (even this one - that's why I'm using my work email + awesome
email client to reply).
And looking directly in lore... I'm also not seeing any reply from you. Maybe there's an issue.

- Nuno Sá
  

On Mon, 2024-02-05 at 13:09 +0100, Nuno Sa wrote:
> Device links will drop their supplier + consumer refcounts
> asynchronously. That means that the refcount of the of_node attached to
> these devices will also be dropped asynchronously and so we cannot
> guarantee the DT overlay assumption that the of_node refcount must be 1 in
> __of_changeset_entry_destroy().
> 
> Given the above, call the new fwnode_links_flush_queue() helper to flush
> the devlink workqueue so we can be sure that all links are dropped before
> doing the proper checks.
> 
> Signed-off-by: Nuno Sa <nuno.sa@analog.com>
> ---
>  drivers/of/dynamic.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
> index 3bf27052832f..b7153c72c9c9 100644
> --- a/drivers/of/dynamic.c
> +++ b/drivers/of/dynamic.c
> @@ -14,6 +14,7 @@
>  #include <linux/slab.h>
>  #include <linux/string.h>
>  #include <linux/proc_fs.h>
> +#include <linux/fwnode.h>
>  
>  #include "of_private.h"
>  
> @@ -518,6 +519,13 @@ EXPORT_SYMBOL(of_changeset_create_node);
>  
>  static void __of_changeset_entry_destroy(struct of_changeset_entry *ce)
>  {
> +	/*
> +	 * device links drop their device references (and hence their of_node
> +	 * references) asynchronously on a dedicated workqueue. Hence we need
> +	 * to flush it to make sure everything is done before doing the below
> +	 * checks.
> +	 */
> +	fwnode_links_flush_queue();
>  	if (ce->action == OF_RECONFIG_ATTACH_NODE &&
>  	    of_node_check_flag(ce->np, OF_OVERLAY)) {
>  		if (kref_read(&ce->np->kobj.kref) > 1) {
> 

Hi Rob and Frank,

Any way you could take a look at this and see if you're ok with the change in the
overlay code? 

On the devlink side , we already got the ok from Rafael.

Thanks!
- Nuno Sá
  

On Mon, Feb 12, 2024 at 01:10:27PM +0100, Nuno Sá wrote:
> On Mon, 2024-02-05 at 13:09 +0100, Nuno Sa wrote:
> > Device links will drop their supplier + consumer refcounts
> > asynchronously. That means that the refcount of the of_node attached to
> > these devices will also be dropped asynchronously and so we cannot
> > guarantee the DT overlay assumption that the of_node refcount must be 1 in
> > __of_changeset_entry_destroy().
> > 
> > Given the above, call the new fwnode_links_flush_queue() helper to flush
> > the devlink workqueue so we can be sure that all links are dropped before
> > doing the proper checks.
> > 
> > Signed-off-by: Nuno Sa <nuno.sa@analog.com>
> > ---
> >  drivers/of/dynamic.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> > 
> > diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
> > index 3bf27052832f..b7153c72c9c9 100644
> > --- a/drivers/of/dynamic.c
> > +++ b/drivers/of/dynamic.c
> > @@ -14,6 +14,7 @@
> >  #include <linux/slab.h>
> >  #include <linux/string.h>
> >  #include <linux/proc_fs.h>
> > +#include <linux/fwnode.h>
> >  
> >  #include "of_private.h"
> >  
> > @@ -518,6 +519,13 @@ EXPORT_SYMBOL(of_changeset_create_node);
> >  
> >  static void __of_changeset_entry_destroy(struct of_changeset_entry *ce)
> >  {
> > +	/*
> > +	 * device links drop their device references (and hence their of_node
> > +	 * references) asynchronously on a dedicated workqueue. Hence we need
> > +	 * to flush it to make sure everything is done before doing the below
> > +	 * checks.
> > +	 */
> > +	fwnode_links_flush_queue();
> >  	if (ce->action == OF_RECONFIG_ATTACH_NODE &&
> >  	    of_node_check_flag(ce->np, OF_OVERLAY)) {
> >  		if (kref_read(&ce->np->kobj.kref) > 1) {
> > 
> 
> Hi Rob and Frank,
> 
> Any way you could take a look at this and see if you're ok with the change in the
> overlay code? 
> 
> On the devlink side , we already got the ok from Rafael.

Didn't Saravana say he was going to look at this? As of yesterday, he's 
also a DT maintainer so deferring to him.

Rob
  

On Tue, 2024-02-13 at 08:51 -0600, Rob Herring wrote:
> On Mon, Feb 12, 2024 at 01:10:27PM +0100, Nuno Sá wrote:
> > On Mon, 2024-02-05 at 13:09 +0100, Nuno Sa wrote:
> > > Device links will drop their supplier + consumer refcounts
> > > asynchronously. That means that the refcount of the of_node attached to
> > > these devices will also be dropped asynchronously and so we cannot
> > > guarantee the DT overlay assumption that the of_node refcount must be 1 in
> > > __of_changeset_entry_destroy().
> > > 
> > > Given the above, call the new fwnode_links_flush_queue() helper to flush
> > > the devlink workqueue so we can be sure that all links are dropped before
> > > doing the proper checks.
> > > 
> > > Signed-off-by: Nuno Sa <nuno.sa@analog.com>
> > > ---
> > >  drivers/of/dynamic.c | 8 ++++++++
> > >  1 file changed, 8 insertions(+)
> > > 
> > > diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
> > > index 3bf27052832f..b7153c72c9c9 100644
> > > --- a/drivers/of/dynamic.c
> > > +++ b/drivers/of/dynamic.c
> > > @@ -14,6 +14,7 @@
> > >  #include <linux/slab.h>
> > >  #include <linux/string.h>
> > >  #include <linux/proc_fs.h>
> > > +#include <linux/fwnode.h>
> > >  
> > >  #include "of_private.h"
> > >  
> > > @@ -518,6 +519,13 @@ EXPORT_SYMBOL(of_changeset_create_node);
> > >  
> > >  static void __of_changeset_entry_destroy(struct of_changeset_entry *ce)
> > >  {
> > > +	/*
> > > +	 * device links drop their device references (and hence their
> > > of_node
> > > +	 * references) asynchronously on a dedicated workqueue. Hence we
> > > need
> > > +	 * to flush it to make sure everything is done before doing the
> > > below
> > > +	 * checks.
> > > +	 */
> > > +	fwnode_links_flush_queue();
> > >  	if (ce->action == OF_RECONFIG_ATTACH_NODE &&
> > >  	    of_node_check_flag(ce->np, OF_OVERLAY)) {
> > >  		if (kref_read(&ce->np->kobj.kref) > 1) {
> > > 
> > 
> > Hi Rob and Frank,
> > 
> > Any way you could take a look at this and see if you're ok with the change
> > in the
> > overlay code? 
> > 
> > On the devlink side , we already got the ok from Rafael.
> 
> Didn't Saravana say he was going to look at this? As of yesterday, he's 
> also a DT maintainer so deferring to him.
> 

Yeah, I did asked him but I guess he never had the time for it... Saravana,
could you please give some feedback on this? I think the most sensible part is
on the devlink side but I assume this is not going to be merged without an ack
from a DT maintainer...

- Nuno Sá
  

On Tue, Feb 13, 2024 at 6:57 AM Nuno Sá <noname.nuno@gmail.com> wrote:
>
> On Tue, 2024-02-13 at 08:51 -0600, Rob Herring wrote:
> > On Mon, Feb 12, 2024 at 01:10:27PM +0100, Nuno Sá wrote:
> > > On Mon, 2024-02-05 at 13:09 +0100, Nuno Sa wrote:
> > > > Device links will drop their supplier + consumer refcounts
> > > > asynchronously. That means that the refcount of the of_node attached to
> > > > these devices will also be dropped asynchronously and so we cannot
> > > > guarantee the DT overlay assumption that the of_node refcount must be 1 in
> > > > __of_changeset_entry_destroy().
> > > >
> > > > Given the above, call the new fwnode_links_flush_queue() helper to flush
> > > > the devlink workqueue so we can be sure that all links are dropped before
> > > > doing the proper checks.
> > > >
> > > > Signed-off-by: Nuno Sa <nuno.sa@analog.com>
> > > > ---
> > > >  drivers/of/dynamic.c | 8 ++++++++
> > > >  1 file changed, 8 insertions(+)
> > > >
> > > > diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
> > > > index 3bf27052832f..b7153c72c9c9 100644
> > > > --- a/drivers/of/dynamic.c
> > > > +++ b/drivers/of/dynamic.c
> > > > @@ -14,6 +14,7 @@
> > > >  #include <linux/slab.h>
> > > >  #include <linux/string.h>
> > > >  #include <linux/proc_fs.h>
> > > > +#include <linux/fwnode.h>
> > > >
> > > >  #include "of_private.h"
> > > >
> > > > @@ -518,6 +519,13 @@ EXPORT_SYMBOL(of_changeset_create_node);
> > > >
> > > >  static void __of_changeset_entry_destroy(struct of_changeset_entry *ce)
> > > >  {
> > > > + /*
> > > > +  * device links drop their device references (and hence their
> > > > of_node
> > > > +  * references) asynchronously on a dedicated workqueue. Hence we
> > > > need
> > > > +  * to flush it to make sure everything is done before doing the
> > > > below
> > > > +  * checks.
> > > > +  */
> > > > + fwnode_links_flush_queue();
> > > >   if (ce->action == OF_RECONFIG_ATTACH_NODE &&
> > > >       of_node_check_flag(ce->np, OF_OVERLAY)) {
> > > >           if (kref_read(&ce->np->kobj.kref) > 1) {
> > > >
> > >
> > > Hi Rob and Frank,
> > >
> > > Any way you could take a look at this and see if you're ok with the change
> > > in the
> > > overlay code?
> > >
> > > On the devlink side , we already got the ok from Rafael.
> >
> > Didn't Saravana say he was going to look at this? As of yesterday, he's
> > also a DT maintainer so deferring to him.
> >
>
> Yeah, I did asked him but I guess he never had the time for it... Saravana,
> could you please give some feedback on this? I think the most sensible part is
> on the devlink side but I assume this is not going to be merged without an ack
> from a DT maintainer...

Sorry for the delay Nuno. I'll get to this. I promise. This week is a bit busy.

-Saravana
  

On Tue, 2024-02-13 at 19:44 -0800, Saravana Kannan wrote:
> On Tue, Feb 13, 2024 at 6:57 AM Nuno Sá <noname.nuno@gmail.com> wrote:
> > 
> > On Tue, 2024-02-13 at 08:51 -0600, Rob Herring wrote:
> > > On Mon, Feb 12, 2024 at 01:10:27PM +0100, Nuno Sá wrote:
> > > > On Mon, 2024-02-05 at 13:09 +0100, Nuno Sa wrote:
> > > > > Device links will drop their supplier + consumer refcounts
> > > > > asynchronously. That means that the refcount of the of_node attached
> > > > > to
> > > > > these devices will also be dropped asynchronously and so we cannot
> > > > > guarantee the DT overlay assumption that the of_node refcount must be
> > > > > 1 in
> > > > > __of_changeset_entry_destroy().
> > > > > 
> > > > > Given the above, call the new fwnode_links_flush_queue() helper to
> > > > > flush
> > > > > the devlink workqueue so we can be sure that all links are dropped
> > > > > before
> > > > > doing the proper checks.
> > > > > 
> > > > > Signed-off-by: Nuno Sa <nuno.sa@analog.com>
> > > > > ---
> > > > >  drivers/of/dynamic.c | 8 ++++++++
> > > > >  1 file changed, 8 insertions(+)
> > > > > 
> > > > > diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
> > > > > index 3bf27052832f..b7153c72c9c9 100644
> > > > > --- a/drivers/of/dynamic.c
> > > > > +++ b/drivers/of/dynamic.c
> > > > > @@ -14,6 +14,7 @@
> > > > >  #include <linux/slab.h>
> > > > >  #include <linux/string.h>
> > > > >  #include <linux/proc_fs.h>
> > > > > +#include <linux/fwnode.h>
> > > > > 
> > > > >  #include "of_private.h"
> > > > > 
> > > > > @@ -518,6 +519,13 @@ EXPORT_SYMBOL(of_changeset_create_node);
> > > > > 
> > > > >  static void __of_changeset_entry_destroy(struct of_changeset_entry
> > > > > *ce)
> > > > >  {
> > > > > + /*
> > > > > +  * device links drop their device references (and hence their
> > > > > of_node
> > > > > +  * references) asynchronously on a dedicated workqueue. Hence we
> > > > > need
> > > > > +  * to flush it to make sure everything is done before doing the
> > > > > below
> > > > > +  * checks.
> > > > > +  */
> > > > > + fwnode_links_flush_queue();
> > > > >   if (ce->action == OF_RECONFIG_ATTACH_NODE &&
> > > > >       of_node_check_flag(ce->np, OF_OVERLAY)) {
> > > > >           if (kref_read(&ce->np->kobj.kref) > 1) {
> > > > > 
> > > > 
> > > > Hi Rob and Frank,
> > > > 
> > > > Any way you could take a look at this and see if you're ok with the
> > > > change
> > > > in the
> > > > overlay code?
> > > > 
> > > > On the devlink side , we already got the ok from Rafael.
> > > 
> > > Didn't Saravana say he was going to look at this? As of yesterday, he's
> > > also a DT maintainer so deferring to him.
> > > 
> > 
> > Yeah, I did asked him but I guess he never had the time for it... Saravana,
> > could you please give some feedback on this? I think the most sensible part
> > is
> > on the devlink side but I assume this is not going to be merged without an
> > ack
> > from a DT maintainer...
> 
> Sorry for the delay Nuno. I'll get to this. I promise. This week is a bit
> busy.
> 

No worries. Just making sure it's not forgotten :)

- Nuno Sá