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SubjectRe: [PATCH] cpu-topology: Skip the exist but not possible cpu nodes
On Thu, Jan 02, 2020 at 11:24:49AM +0800, Zeng Tao wrote:
> When CONFIG_NR_CPUS is smaller than the cpu nodes defined in the device
> tree, the cpu node parsing will fail. And this is not reasonable for a
> legal device tree configs.
> In this patch, skip such cpu nodes rather than return an error.
>
> Signed-off-by: Zeng Tao <prime.zeng@hisilicon.com>
> ---
> drivers/base/arch_topology.c | 35 ++++++++++++++++++++++++++---------
> 1 file changed, 26 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index 5fe44b3..4cddfeb 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -250,20 +250,34 @@ core_initcall(free_raw_capacity);
> #if defined(CONFIG_ARM64) || defined(CONFIG_RISCV)
> static int __init get_cpu_for_node(struct device_node *node)
> {
> - struct device_node *cpu_node;
> + struct device_node *cpu_node, *t;
> int cpu;
> + bool found = false;
>
> cpu_node = of_parse_phandle(node, "cpu", 0);
> if (!cpu_node)
> - return -1;
> + return -EINVAL;
> +
> + for_each_of_cpu_node(t)
> + if (t == cpu_node) {
> + found = true;
> + break;
> + }
> +
> + if (!found) {
> + pr_crit("Unable to find CPU node for %pOF\n", cpu_node);
> + return -EINVAL;
> + }
>

The whole extra logic added above sounds redundant, details below...

> cpu = of_cpu_node_to_id(cpu_node);
> if (cpu >= 0)
> topology_parse_cpu_capacity(cpu_node, cpu);
> - else
> - pr_crit("Unable to find CPU node for %pOF\n", cpu_node);
> + else {
> + pr_warn("CPU node for %pOF exist but the possible cpu range is :%*pbl\n",
> + cpu_node, cpumask_pr_args(cpu_possible_mask));
> + cpu = -ENODEV;

.. of_cpu_node_to_id returns -ENODEV anyways so above assignment is also
redundant. All you achieved is explicit error message. I think we should
be fine combining them. Just extend existing error log with both message.

> + }
>
> - of_node_put(cpu_node);
> return cpu;
> }
>
> @@ -287,10 +301,13 @@ static int __init parse_core(struct device_node *core, int package_id,
> cpu_topology[cpu].core_id = core_id;
> cpu_topology[cpu].thread_id = i;
> } else {
> - pr_err("%pOF: Can't get CPU for thread\n",
> - t);
> + if (cpu != -ENODEV)
> + pr_err("%pOF: Can't get CPU for thread\n",
> + t);
> + else
> + cpu = 0;

I would rather use another variable instead of reusing 'cpu'

> of_node_put(t);
> - return -EINVAL;
> + return cpu;

Shouldn't we continue here if cpu == -ENODEV instead of returning 0 ?

> }
> of_node_put(t);
> }
> @@ -307,7 +324,7 @@ static int __init parse_core(struct device_node *core, int package_id,
>
> cpu_topology[cpu].package_id = package_id;
> cpu_topology[cpu].core_id = core_id;
> - } else if (leaf) {
> + } else if (leaf && cpu != -ENODEV) {

I am still not sure on the approach, it is based on -ENODEV as valid
error and allow to continue. It may be fine, I just need to make sure.

--
Regards,
Sudeep

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