linux-kernel - [PATCH v4 1/4] devres: Make locking straight forward in release

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Date:   Mon, 17 May 2021 15:29:43 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>
Subject: [PATCH v4 1/4] devres: Make locking straight forward in release_nodes()

It seems for the sake of saving stack memory of couple of pointers,
the locking in release_nodes() callers becomes interesting.

Replace this logic with a straight forward locking and unlocking scheme.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
v4: rebased on top of v5.13-rc2
 drivers/base/devres.c | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/drivers/base/devres.c b/drivers/base/devres.c
index 8746f2212781..7970217191e0 100644
--- a/drivers/base/devres.c
+++ b/drivers/base/devres.c
@@ -503,28 +503,18 @@ static int remove_nodes(struct device *dev,
 	return cnt;
 }
 
-static int release_nodes(struct device *dev, struct list_head *first,
-			 struct list_head *end, unsigned long flags)
-	__releases(&dev->devres_lock)
+static void release_nodes(struct device *dev, struct list_head *todo)
 {
-	LIST_HEAD(todo);
-	int cnt;
 	struct devres *dr, *tmp;
 
-	cnt = remove_nodes(dev, first, end, &todo);
-
-	spin_unlock_irqrestore(&dev->devres_lock, flags);
-
 	/* Release.  Note that both devres and devres_group are
 	 * handled as devres in the following loop.  This is safe.
 	 */
-	list_for_each_entry_safe_reverse(dr, tmp, &todo, node.entry) {
+	list_for_each_entry_safe_reverse(dr, tmp, todo, node.entry) {
 		devres_log(dev, &dr->node, "REL");
 		dr->node.release(dev, dr->data);
 		kfree(dr);
 	}
-
-	return cnt;
 }
 
 /**
@@ -537,13 +527,19 @@ static int release_nodes(struct device *dev, struct list_head *first,
 int devres_release_all(struct device *dev)
 {
 	unsigned long flags;
+	LIST_HEAD(todo);
+	int cnt;
 
 	/* Looks like an uninitialized device structure */
 	if (WARN_ON(dev->devres_head.next == NULL))
 		return -ENODEV;
+
 	spin_lock_irqsave(&dev->devres_lock, flags);
-	return release_nodes(dev, dev->devres_head.next, &dev->devres_head,
-			     flags);
+	cnt = remove_nodes(dev, dev->devres_head.next, &dev->devres_head, &todo);
+	spin_unlock_irqrestore(&dev->devres_lock, flags);
+
+	release_nodes(dev, &todo);
+	return cnt;
 }
 
 /**
@@ -679,6 +675,7 @@ int devres_release_group(struct device *dev, void *id)
 {
 	struct devres_group *grp;
 	unsigned long flags;
+	LIST_HEAD(todo);
 	int cnt = 0;
 
 	spin_lock_irqsave(&dev->devres_lock, flags);
@@ -691,7 +688,10 @@ int devres_release_group(struct device *dev, void *id)
 		if (!list_empty(&grp->node[1].entry))
 			end = grp->node[1].entry.next;
 
-		cnt = release_nodes(dev, first, end, flags);
+		cnt = remove_nodes(dev, first, end, &todo);
+		spin_unlock_irqrestore(&dev->devres_lock, flags);
+
+		release_nodes(dev, &todo);
 	} else {
 		WARN_ON(1);
 		spin_unlock_irqrestore(&dev->devres_lock, flags);
-- 
2.30.2