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

Jonathan Cameron
2024-08-19T16:19:59Z

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

> 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.

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)
>