[PATCH][RESEND 2] component: enhance handling of devres group for master

[PATCH][RESEND 2] component: enhance handling of devres group for master

[bgoswami]

From: Banajit Goswami <bgoswami@codeaurora.org>

The devres group opened for a master is left open-ended (without
devres_group_close) even after bind() is complete. Similarly, while
releasing the devres resources for master, the most recently opened
devres group is selected, and released without identifying the
targeted group. As the devres group opened before master bind was
never closed, there may have unintended consequences of releasing
devres resources that were allocated after master bind() function
was complete.

Change adds a devres_group_close() after bind() call to master, to
encapsulate the resources allocated during bind, and then use a
group ID to specifically identify the group in release, so that
during master unbind, only the resources that are part of that
specific devres group, are released.

Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>
---
 drivers/base/component.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/base/component.c b/drivers/base/component.c
index 89b032f..f9ce937 100644
--- a/drivers/base/component.c
+++ b/drivers/base/component.c
@@ -155,17 +155,19 @@ static int try_to_bring_up_master(struct master *master,
 		return 0;
 	}
 
-	if (!devres_open_group(master->dev, NULL, GFP_KERNEL))
+	if (!devres_open_group(master->dev, master, GFP_KERNEL))
 		return -ENOMEM;
 
 	/* Found all components */
 	ret = master->ops->bind(master->dev);
 	if (ret < 0) {
-		devres_release_group(master->dev, NULL);
+		devres_release_group(master->dev, master);
 		dev_info(master->dev, "master bind failed: %d\n", ret);
 		return ret;
 	}
 
+	devres_close_group(master->dev, master);
+
 	master->bound = true;
 	return 1;
 }
@@ -190,7 +192,7 @@ static void take_down_master(struct master *master)
 {
 	if (master->bound) {
 		master->ops->unbind(master->dev);
-		devres_release_group(master->dev, NULL);
+		devres_release_group(master->dev, master);
 		master->bound = false;
 	}
 }
-- 
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a Linux Foundation Collaborative Project

Re: [PATCH][RESEND 2] component: enhance handling of devres group for master

[Russell King - ARM Linux]

On Wed, Jul 25, 2018 at 11:06:28PM -0700, bgoswami@codeaurora.org wrote:
> From: Banajit Goswami <bgoswami@codeaurora.org>
> 
> The devres group opened for a master is left open-ended (without
> devres_group_close) even after bind() is complete. Similarly, while
> releasing the devres resources for master, the most recently opened
> devres group is selected, and released without identifying the
> targeted group. As the devres group opened before master bind was
> never closed, there may have unintended consequences of releasing
> devres resources that were allocated after master bind() function
> was complete.

... as intended, because this layers on top of the driver model.
You are aware that the driver model leaves its implicit group open
as well?

I think you need to explain why you need this - what is the problem
scenario that you are encountering.

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