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Date: Fri, 19 Apr 2024 15:01:06 +0100
From: Sudeep Holla <sudeep.holla@....com>
To: Vincenzo Mezzela <vincenzo.mezzela@...il.com>
Cc: gregkh@...uxfoundation.org, rafael@...nel.org,
Sudeep Holla <sudeep.holla@....com>, linux-kernel@...r.kernel.org,
julia.lawall@...ia.fr, javier.carrasco.cruz@...il.com,
skhan@...uxfoundation.org
Subject: Re: [PATCH] drivers: use __free attribute instead of of_node_put()
On Fri, Apr 19, 2024 at 03:19:56PM +0200, Vincenzo Mezzela wrote:
> 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@...ia.fr>
> Signed-off-by: Vincenzo Mezzela <vincenzo.mezzela@...il.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) =
Missing include <linux/cleanup.h> for this ?
> + 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);
OK you moved 't' inside the loop and this must be taken care, but...
> }
> i++;
> } while (t);
...now, will it even compile if 't' is not in scope ? I think you might get
compilation here. If not, I still don't understand what is the value of
't' being checked there.
> @@ -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;
> }
Same thing applies to these while(c) loop. I don't understand how this
could work even if it is compiling fine which I doubt.
> @@ -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) =
If not above ones, this must fail to compile. Perhaps s/devide_node/device_node/ ?
I now doubt if this patch is compile tested ?
--
Regards,
Sudeep
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