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From: Vincenzo Mezzela <vincenzo.mezzela@gmail.com>
To: sudeep.holla@arm.com
Cc: gregkh@linuxfoundation.org,
	javier.carrasco.cruz@gmail.com,
	julia.lawall@inria.fr,
	linux-kernel@vger.kernel.org,
	rafael@kernel.org,
	skhan@linuxfoundation.org,
	vincenzo.mezzela@gmail.com
Subject: [PATCH v2] drivers: use __free attribute instead of of_node_put()
Date: Mon, 22 Apr 2024 15:09:31 +0200
Message-Id: <20240422130931.176635-1-vincenzo.mezzela@gmail.com>
In-Reply-To: <20240419140106.3mkayxriqjt2cz5i@bogus>
References: <20240419140106.3mkayxriqjt2cz5i@bogus>
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MIME-Version: 1.0
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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>
---
changes in v2:
    - check loop exit condition within the loop
    - add cleanup.h header

 drivers/base/arch_topology.c | 150 +++++++++++++++++------------------
 1 file changed, 73 insertions(+), 77 deletions(-)

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 024b78a0cfc1..c9c4af55953e 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -20,6 +20,7 @@
 #include <linux/rcupdate.h>
 #include <linux/sched.h>
 #include <linux/units.h>
+#include <linux/cleanup.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/thermal_pressure.h>
@@ -513,10 +514,10 @@ 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 +528,6 @@ 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;
 }
 
@@ -538,28 +538,27 @@ 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 {
+	for(;;) {
 		snprintf(name, sizeof(name), "thread%d", i);
-		t = of_get_child_by_name(core, name);
-		if (t) {
-			leaf = false;
-			cpu = get_cpu_for_node(t);
-			if (cpu >= 0) {
-				cpu_topology[cpu].package_id = package_id;
-				cpu_topology[cpu].cluster_id = cluster_id;
-				cpu_topology[cpu].core_id = core_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);
+		struct device_node *t __free(device_node) =
+			of_get_child_by_name(core, name);
+		if (!t)
+			break;
+
+		leaf = false;
+		cpu = get_cpu_for_node(t);
+		if (cpu >= 0) {
+			cpu_topology[cpu].package_id = package_id;
+			cpu_topology[cpu].cluster_id = cluster_id;
+			cpu_topology[cpu].core_id = core_id;
+			cpu_topology[cpu].thread_id = i;
+		} else if (cpu != -ENODEV) {
+			pr_err("%pOF: Can't get CPU for thread\n", t);
+			return -EINVAL;
 		}
 		i++;
-	} while (t);
+	}
 
 	cpu = get_cpu_for_node(core);
 	if (cpu >= 0) {
@@ -586,7 +585,6 @@ 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;
 
@@ -596,51 +594,51 @@ static int __init parse_cluster(struct device_node *cluster, int package_id,
 	 * scheduler with a flat list of them.
 	 */
 	i = 0;
-	do {
+	for(;;) {
 		snprintf(name, sizeof(name), "cluster%d", i);
-		c = 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;
-		}
+		struct device_node *c __free(device_node) =
+			of_get_child_by_name(cluster, name);
+		if (!c)
+			break;
+
+		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");
+		if (ret != 0)
+			return ret;
 		i++;
-	} while (c);
+	}
 
 	/* Now check for cores */
 	i = 0;
-	do {
+	for(;;) {
 		snprintf(name, sizeof(name), "core%d", i);
-		c = 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;
-			}
+		struct device_node *c __free(device_node) =
+			of_get_child_by_name(cluster, name);
+		if (!c)
+			break;
 
-			if (leaf) {
-				ret = parse_core(c, package_id, cluster_id,
-						 core_id++);
-			} else {
-				pr_err("%pOF: Non-leaf cluster with core %s\n",
-				       cluster, name);
-				ret = -EINVAL;
-			}
+		has_cores = true;
 
-			of_node_put(c);
-			if (ret != 0)
-				return ret;
+		if (depth == 0) {
+			pr_err("%pOF: cpu-map children should be clusters\n", c);
+			return -EINVAL;
+		}
+
+		if (leaf) {
+			ret = parse_core(c, package_id, cluster_id, core_id++);
+		} else {
+			pr_err("%pOF: Non-leaf cluster with core %s\n",
+					cluster, name);
+			ret = -EINVAL;
 		}
+
+		if (ret != 0)
+			return ret;
+
 		i++;
-	} while (c);
+	}
 
 	if (leaf && !has_cores)
 		pr_warn("%pOF: empty cluster\n", cluster);
@@ -651,22 +649,23 @@ 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 {
+	for(;;) {
 		snprintf(name, sizeof(name), "socket%d", package_id);
-		c = 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;
-		}
+		struct device_node *c __free(device_node) =
+			of_get_child_by_name(socket, name);
+		if (!c)
+			break;
+
+		has_socket = true;
+		ret = parse_cluster(c, package_id, -1, 0);
+		if (ret != 0)
+			return ret;
+
 		package_id++;
-	} while (c);
+	}
 
 	if (!has_socket)
 		ret = parse_cluster(socket, 0, -1, 0);
@@ -676,11 +675,11 @@ 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 +689,14 @@ 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(device_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 +710,6 @@ 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