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

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Message-ID: <20240819171954.0000600d@Huawei.com>
Date: Mon, 19 Aug 2024 17:19:54 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
CC: Ulf Hansson <ulf.hansson@...aro.org>, "Rafael J. Wysocki"
	<rafael@...nel.org>, Daniel Lezcano <daniel.lezcano@...aro.org>, Anup Patel
	<anup@...infault.org>, Paul Walmsley <paul.walmsley@...ive.com>, "Palmer
 Dabbelt" <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
	<linux-pm@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH 2/4] cpuidle: riscv-sbi: Use scoped device node handling
 to simplify error paths

On Mon, 19 Aug 2024 17:13:13 +0100
Jonathan Cameron <Jonathan.Cameron@...wei.com> wrote:

> On Fri, 16 Aug 2024 17:09:29 +0200
> Krzysztof Kozlowski <krzysztof.kozlowski@...aro.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@...aro.org>  
> The original code looks suspect. See below.

Whilst here...  Why not do similar for state_node to avoid
the delayed return check.
Existing code
	{
		state_node = of_get_cpu_state_node(cpu_node, i - 1);
		if (!state_node)
			break;

		ret = sbi_dt_parse_state_node(state_node, &states[i]);
		of_node_put(state_node);

		if (ret)
			//another bug here on holding cpu_node btw.
			return ret;
		pr_debug("sbi-state %#x index %d\n", states[i], i);
	}
//I think only path to this is is early break above.
	if (i != state_count) {
		ret = -ENODEV;
		goto fail;
	}
Can be something like

	{
		struct device_node *state_node __free(device_node) =
			= of_get-cpu_State_nod(cpu_node, i - 1);
	
		if (!state_node)
			return -ENODEV;

		ret = sbi_dt_parse_state_node(state_node, &states[i]);
		if (ret)
			return ret;

		pr_debug("sbi-state %#x index %d\n", states[i], i);
	}
		

> 
> > ---
> >  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)  
>