Re: [PATCH 2/4] cpuidle: riscv-sbi: Use scoped device node handling to simplify error paths

From: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: Ulf Hansson <ulf.hansson@linaro.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Anup Patel <anup@brainfault.org>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>, <linux-pm@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>, <linux-riscv@lists.infradead.org>
Subject: Re: [PATCH 2/4] cpuidle: riscv-sbi: Use scoped device node handling to simplify error paths
Date: Mon, 19 Aug 2024 17:13:13 +0100	[thread overview]
Message-ID: <20240819171313.00004677@Huawei.com> (raw)
In-Reply-To: <20240816150931.142208-2-krzysztof.kozlowski@linaro.org>

On Fri, 16 Aug 2024 17:09:29 +0200
Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> wrote:

> Obtain the device node reference with scoped/cleanup.h to reduce error
> handling and make the code a bit simpler.
> 
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
The original code looks suspect. See below.

> ---
>  drivers/cpuidle/cpuidle-riscv-sbi.c | 21 +++++++--------------
>  1 file changed, 7 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/cpuidle/cpuidle-riscv-sbi.c b/drivers/cpuidle/cpuidle-riscv-sbi.c
> index a6e123dfe394..5bb3401220d2 100644
> --- a/drivers/cpuidle/cpuidle-riscv-sbi.c
> +++ b/drivers/cpuidle/cpuidle-riscv-sbi.c
> @@ -8,6 +8,7 @@
>  
>  #define pr_fmt(fmt) "cpuidle-riscv-sbi: " fmt
>  
> +#include <linux/cleanup.h>
>  #include <linux/cpuhotplug.h>
>  #include <linux/cpuidle.h>
>  #include <linux/cpumask.h>
> @@ -236,19 +237,16 @@ static int sbi_cpuidle_dt_init_states(struct device *dev,
>  {
>  	struct sbi_cpuidle_data *data = per_cpu_ptr(&sbi_cpuidle_data, cpu);
>  	struct device_node *state_node;
> -	struct device_node *cpu_node;
>  	u32 *states;
>  	int i, ret;
>  
> -	cpu_node = of_cpu_device_node_get(cpu);
> +	struct device_node *cpu_node __free(device_node) = of_cpu_device_node_get(cpu);
>  	if (!cpu_node)
>  		return -ENODEV;
>  
>  	states = devm_kcalloc(dev, state_count, sizeof(*states), GFP_KERNEL);
> -	if (!states) {
> -		ret = -ENOMEM;
> -		goto fail;
> -	}
> +	if (!states)
> +		return -ENOMEM;
>  
>  	/* Parse SBI specific details from state DT nodes */
>  	for (i = 1; i < state_count; i++) {
> @@ -264,10 +262,8 @@ static int sbi_cpuidle_dt_init_states(struct device *dev,
>  
>  		pr_debug("sbi-state %#x index %d\n", states[i], i);
>  	}
> -	if (i != state_count) {
> -		ret = -ENODEV;
> -		goto fail;
> -	}
> +	if (i != state_count)
> +		return -ENODEV;
>  
>  	/* Initialize optional data, used for the hierarchical topology. */
>  	ret = sbi_dt_cpu_init_topology(drv, data, state_count, cpu);
The handling of error ret from here doesn't free the node.

Bug or something subtle I'm missing?

If it's a bug, then fixes tag.

> @@ -277,10 +273,7 @@ static int sbi_cpuidle_dt_init_states(struct device *dev,
>  	/* Store states in the per-cpu struct. */
>  	data->states = states;
>  
> -fail:
> -	of_node_put(cpu_node);
> -
> -	return ret;
> +	return 0;
>  }
>  
>  static void sbi_cpuidle_deinit_cpu(int cpu)