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From: Vincenzo Mezzela <vincenzo.mezzela@gmail.com>
To: sudeep.holla@arm.com,
	gregkh@linuxfoundation.org,
	rafael@kernel.org
Cc: linux-kernel@vger.kernel.org,
	julia.lawall@inria.fr,
	javier.carrasco.cruz@gmail.com,
	skhan@linuxfoundation.org,
	Vincenzo Mezzela <vincenzo.mezzela@gmail.com>
Subject: [PATCH] drivers: use __free attribute instead of of_node_put()
Date: Fri, 19 Apr 2024 15:19:56 +0200
Message-Id: <20240419131956.665769-1-vincenzo.mezzela@gmail.com>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

Introduce the __free attribute for scope-based resource management.
Resources allocated with __free are automatically released at the end of
the scope. This enhancement aims to mitigate memory management issues
associated with forgetting to release resources by utilizing __free
instead of of_node_put().

The declaration of the device_node used within the do-while loops is
moved directly within the loop so that the resource is automatically
freed at the end of each iteration.

Suggested-by: Julia Lawall <julia.lawall@inria.fr>
Signed-off-by: Vincenzo Mezzela <vincenzo.mezzela@gmail.com>
---
 drivers/base/arch_topology.c | 41 ++++++++++++++----------------------
 1 file changed, 16 insertions(+), 25 deletions(-)

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 024b78a0cfc1..58eeb8183747 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -513,10 +513,10 @@ core_initcall(free_raw_capacity);
  */
 static int __init get_cpu_for_node(struct device_node *node)
 {
-	struct device_node *cpu_node;
 	int cpu;
 
-	cpu_node = of_parse_phandle(node, "cpu", 0);
+	struct device_node *cpu_node __free(device_node) =
+		of_parse_phandle(node, "cpu", 0);
 	if (!cpu_node)
 		return -1;
 
@@ -527,7 +527,6 @@ static int __init get_cpu_for_node(struct device_node *node)
 		pr_info("CPU node for %pOF exist but the possible cpu range is :%*pbl\n",
 			cpu_node, cpumask_pr_args(cpu_possible_mask));
 
-	of_node_put(cpu_node);
 	return cpu;
 }
 
@@ -538,11 +537,11 @@ static int __init parse_core(struct device_node *core, int package_id,
 	bool leaf = true;
 	int i = 0;
 	int cpu;
-	struct device_node *t;
 
 	do {
 		snprintf(name, sizeof(name), "thread%d", i);
-		t = of_get_child_by_name(core, name);
+		struct device_node *t __free(device_node) =
+			of_get_child_by_name(core, name);
 		if (t) {
 			leaf = false;
 			cpu = get_cpu_for_node(t);
@@ -553,10 +552,8 @@ static int __init parse_core(struct device_node *core, int package_id,
 				cpu_topology[cpu].thread_id = i;
 			} else if (cpu != -ENODEV) {
 				pr_err("%pOF: Can't get CPU for thread\n", t);
-				of_node_put(t);
 				return -EINVAL;
 			}
-			of_node_put(t);
 		}
 		i++;
 	} while (t);
@@ -586,7 +583,6 @@ static int __init parse_cluster(struct device_node *cluster, int package_id,
 	char name[20];
 	bool leaf = true;
 	bool has_cores = false;
-	struct device_node *c;
 	int core_id = 0;
 	int i, ret;
 
@@ -598,13 +594,13 @@ static int __init parse_cluster(struct device_node *cluster, int package_id,
 	i = 0;
 	do {
 		snprintf(name, sizeof(name), "cluster%d", i);
-		c = of_get_child_by_name(cluster, name);
+		struct device_node *c __free(device_node) =
+			of_get_child_by_name(cluster, name);
 		if (c) {
 			leaf = false;
 			ret = parse_cluster(c, package_id, i, depth + 1);
 			if (depth > 0)
 				pr_warn("Topology for clusters of clusters not yet supported\n");
-			of_node_put(c);
 			if (ret != 0)
 				return ret;
 		}
@@ -615,14 +611,14 @@ static int __init parse_cluster(struct device_node *cluster, int package_id,
 	i = 0;
 	do {
 		snprintf(name, sizeof(name), "core%d", i);
-		c = of_get_child_by_name(cluster, name);
+		struct device_node *c __free(device_node) =
+			of_get_child_by_name(cluster, name);
 		if (c) {
 			has_cores = true;
 
 			if (depth == 0) {
 				pr_err("%pOF: cpu-map children should be clusters\n",
 				       c);
-				of_node_put(c);
 				return -EINVAL;
 			}
 
@@ -635,7 +631,6 @@ static int __init parse_cluster(struct device_node *cluster, int package_id,
 				ret = -EINVAL;
 			}
 
-			of_node_put(c);
 			if (ret != 0)
 				return ret;
 		}
@@ -651,17 +646,16 @@ static int __init parse_cluster(struct device_node *cluster, int package_id,
 static int __init parse_socket(struct device_node *socket)
 {
 	char name[20];
-	struct device_node *c;
 	bool has_socket = false;
 	int package_id = 0, ret;
 
 	do {
 		snprintf(name, sizeof(name), "socket%d", package_id);
-		c = of_get_child_by_name(socket, name);
+		struct device_node *c __free(device_node) =
+			of_get_child_by_name(socket, name);
 		if (c) {
 			has_socket = true;
 			ret = parse_cluster(c, package_id, -1, 0);
-			of_node_put(c);
 			if (ret != 0)
 				return ret;
 		}
@@ -676,11 +670,11 @@ static int __init parse_socket(struct device_node *socket)
 
 static int __init parse_dt_topology(void)
 {
-	struct device_node *cn, *map;
 	int ret = 0;
 	int cpu;
 
-	cn = of_find_node_by_path("/cpus");
+	struct device_node *cn __free(device_node) =
+		of_find_node_by_path("/cpus");
 	if (!cn) {
 		pr_err("No CPU information found in DT\n");
 		return 0;
@@ -690,13 +684,14 @@ static int __init parse_dt_topology(void)
 	 * When topology is provided cpu-map is essentially a root
 	 * cluster with restricted subnodes.
 	 */
-	map = of_get_child_by_name(cn, "cpu-map");
+	struct device_node *map __free(devide_node) =
+		of_get_child_by_name(cn, "cpu-map");
 	if (!map)
-		goto out;
+		return ret;
 
 	ret = parse_socket(map);
 	if (ret != 0)
-		goto out_map;
+		return ret;
 
 	topology_normalize_cpu_scale();
 
@@ -710,10 +705,6 @@ static int __init parse_dt_topology(void)
 			break;
 		}
 
-out_map:
-	of_node_put(map);
-out:
-	of_node_put(cn);
 	return ret;
 }
 #endif
-- 
2.34.1