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From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Dan Scally <djrscally@gmail.com>
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>,
	linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
	linux.walleij@linaro.org,
	prabhakar.mahadev-lad.rj@bp.renesas.com,
	heikki.krogerus@linux.intel.com, dmitry.torokhov@gmail.com,
	laurent.pinchart+renesas@ideasonboard.com,
	kieran.bingham+renesas@ideasonboard.com,
	jacopo+renesas@jmondi.org, robh@kernel.org, davem@davemloft.net,
	linux@rasmusvillemoes.dk, sergey.senozhatsky@gmail.com,
	rostedt@goodmis.org, pmladek@suse.com, mchehab@kernel.org,
	tian.shu.qiu@intel.com, bingbu.cao@intel.com, yong.zhi@intel.com,
	rafael@kernel.org, gregkh@linuxfoundation.org, kitakar@gmail.com,
	dan.carpenter@oracle.org
Subject: Re: [RFC PATCH v3 1/9] software_node: Add helper function to unregister arrays of software_nodes ordered parent to child
Date: Wed, 21 Oct 2020 12:40:09 +0300	[thread overview]
Message-ID: <20201021094009.GN4077@smile.fi.intel.com> (raw)
In-Reply-To: <b6909e37-cd8f-2c1a-126c-40e34ba2a560@gmail.com>

On Tue, Oct 20, 2020 at 11:52:56PM +0100, Dan Scally wrote:
> On 20/10/2020 11:05, Sakari Ailus wrote:
> > On Mon, Oct 19, 2020 at 11:58:55PM +0100, Daniel Scally wrote:
> >> Software nodes that are children of another software node should be
> >> unregistered before their parent. To allow easy unregistering of an array
> >> of software_nodes ordered parent to child, add a helper function to loop
> >> over and unregister nodes in such an array in reverse order.

...

> >> + * software_node_unregister_nodes_reverse - Unregister an array of software
> >> + * nodes in reverse order.
> >> + * @nodes: Array of software nodes to be unregistered.
> >> + *
> >> + * NOTE: The same warning applies as with software_node_unregister_nodes.
> >> + * Unless you are _sure_ that the array of nodes is ordered parent to child
> >> + * it is wiser to remove them individually in the correct order.
> > Could the default order in software_node_unregister_nodes() be reversed
> > instead? There are no users so this should be easy to change.
> >
> > Doing this only one way may require enforcing the registration order in
> > software_node_register_nodes(), but the end result would be safer.
> >
> > What do you think?
> 
> Yeah fine by me. We can just use software_node_to_swnode(node->parent)
> within software_node_unregister_nodes() to check that children come
> after their parents have already been processed. I'll add a patch to do
> that in the next version of this series, and another changing the
> ordering of software_node_unregister_node_group() as Andy suggests for
> consistency.

I remember it was a big discussion between Rafael, Heikki and Greg KH about
child-parent release in kobjects. That ended up with few patches to device
object handling along with one that reversed the order of swnode unregistering
in test_printf.c. So here is the question who is maintaining the order: a kref
(via kobject) or a caller?

-- 
With Best Regards,
Andy Shevchenko



  reply	other threads:[~2020-10-21  9:39 UTC|newest]

Thread overview: 82+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-19 22:58 [RFC PATCH v3 0/9] Add functionality to ipu3-cio2 driver allowing software_node connections to sensors on platforms designed for Windows Daniel Scally
2020-10-19 22:58 ` [RFC PATCH v3 1/9] software_node: Add helper function to unregister arrays of software_nodes ordered parent to child Daniel Scally
2020-10-20  9:22   ` Andy Shevchenko
2020-10-20 10:05   ` Sakari Ailus
2020-10-20 11:01     ` Andy Shevchenko
2020-10-20 11:02       ` Andy Shevchenko
2020-10-20 11:04       ` Heikki Krogerus
2020-10-20 22:52     ` Dan Scally
2020-10-21  9:40       ` Andy Shevchenko [this message]
2020-10-21  9:54         ` Dan Scally
2020-10-19 22:58 ` [RFC PATCH v3 2/9] lib/test_printf.c: Use helper function to unwind array of software_nodes Daniel Scally
2020-10-20  7:23   ` Petr Mladek
2020-10-20  9:20   ` Andy Shevchenko
2020-10-19 22:58 ` [RFC PATCH v3 3/9] software_node: Fix failure to hold refcount in software_node_get_next_child Daniel Scally
2020-10-20 12:44   ` Rafael J. Wysocki
2020-10-20 13:31   ` Sakari Ailus
2020-10-20 23:25     ` Dan Scally
2020-10-21  9:33       ` Andy Shevchenko
2020-10-21  9:37         ` Sakari Ailus
2020-10-21  9:56         ` Dan Scally
2020-10-19 22:58 ` [RFC PATCH v3 4/9] software_node: Add support for fwnode_graph*() family of functions Daniel Scally
2020-10-20  9:17   ` Andy Shevchenko
2020-10-20 12:35   ` Sakari Ailus
2020-10-20 13:32     ` Sakari Ailus
2020-10-19 22:58 ` [RFC PATCH v3 5/9] ipu3-cio2: Add T: entry to MAINTAINERS Daniel Scally
2020-10-20  9:16   ` Andy Shevchenko
2020-10-24  0:28   ` Laurent Pinchart
2020-10-19 22:59 ` [RFC PATCH v3 6/9] ipu3-cio2: Rename ipu3-cio2.c to allow module to be built from multiple sources files retaining ipu3-cio2 name Daniel Scally
2020-10-20  9:15   ` Andy Shevchenko
2020-10-20 20:41     ` Dan Scally
2020-10-24  0:34   ` Laurent Pinchart
2020-10-19 22:59 ` [RFC PATCH v3 7/9] ipu3-cio2: Check if pci_dev->dev's fwnode is a software_node in cio2_parse_firmware() and set FWNODE_GRAPH_DEVICE_DISABLED if so Daniel Scally
2020-10-20  9:19   ` Andy Shevchenko
2020-10-20 12:06     ` Sakari Ailus
2020-10-20 19:56       ` Dan Scally
2020-10-20 22:49         ` Sakari Ailus
2020-10-20 22:55           ` Dan Scally
2020-10-24  0:39           ` Laurent Pinchart
2020-10-24 14:29             ` Sakari Ailus
2020-10-24 16:33               ` Dan Scally
2020-10-24 16:55                 ` Laurent Pinchart
2020-10-19 22:59 ` [RFC PATCH v3 8/9] media: v4l2-core: v4l2-async: Check possible match in match_fwnode based on sd->fwnode->secondary Daniel Scally
2020-10-19 22:59 ` [RFC PATCH v3 9/9] ipu3-cio2: Add functionality allowing software_node connections to sensors on platforms designed for Windows Daniel Scally
2020-10-20  9:41   ` Andy Shevchenko
2020-10-21 22:05     ` Daniel Scally
2020-10-22 13:40       ` Andy Shevchenko
2020-10-23 10:06         ` Dan Scally
2020-10-24  1:24   ` Laurent Pinchart
2020-10-24  8:50     ` Dan Scally
2020-10-24  9:37       ` Laurent Pinchart
2020-10-24 22:28         ` Daniel Scally
2020-10-24 22:36           ` Laurent Pinchart
2020-10-24 22:50             ` Daniel Scally
2020-10-26  8:20             ` Dan Scally
2020-10-26 16:05               ` Andy Shevchenko
2020-10-29 20:17                 ` Laurent Pinchart
2020-10-29 22:36                   ` Dan Scally
2020-10-26 16:10         ` Andy Shevchenko
2020-10-29 20:19           ` Laurent Pinchart
2020-10-29 20:26             ` Andy Shevchenko
2020-10-29 21:29               ` Laurent Pinchart
2020-10-29 22:22                 ` Andy Shevchenko
2020-10-29 22:51                   ` Laurent Pinchart
2020-11-13 10:02                     ` Dan Scally
2020-11-13 16:22                       ` Laurent Pinchart
2020-11-13 19:45                         ` Andy Shevchenko
2020-11-15  8:45                           ` Daniel Scally
2020-11-16  8:53                           ` Laurent Pinchart
2020-11-16 13:57                             ` Andy Shevchenko
2020-11-16 14:10                               ` Laurent Pinchart
2020-11-16 14:15                                 ` Dan Scally
2020-11-16 16:16                                   ` Andy Shevchenko
2020-11-17 12:01                                     ` Dan Scally
2020-11-17 16:42                                       ` Andy Shevchenko
2020-11-17 22:59                                         ` Dan Scally
2020-10-24 15:11     ` Sakari Ailus
2020-10-24 15:14   ` Sakari Ailus
2020-10-24 20:28     ` Dan Scally
2020-10-25 11:18       ` Sakari Ailus
2020-10-20  9:24 ` [RFC PATCH v3 0/9] Add functionality to ipu3-cio2 driver " Andy Shevchenko
2020-10-20 13:38 ` Rafael J. Wysocki
2020-10-21 20:59   ` Daniel Scally

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