linux-kernel - Re: [PATCH 1/2] ARM: cpuidle: refine failure handling in init flow

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Date:   Mon, 9 Oct 2017 14:04:40 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Leo Yan <leo.yan@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Stefan Wahren <stefan.wahren@...e.com>
Subject: Re: [PATCH 1/2] ARM: cpuidle: refine failure handling in init flow

On 04/09/2017 08:52, Leo Yan wrote:
> After applied Stefan Wahren patch ("ARM: cpuidle: Avoid memleak if init
> fail") there have no memleak issue, but the code is not consistent to
> handle initialization failure between driver registration and device
> registration. And when device registration fails, it misses to
> unregister the driver.
> 
> So this patch is to refine failure handling in init flow, it adds two
> 'goto' tags: when register device fails, it goto 'init_dev_fail' tag and
> free 'dev' structure and unregister driver; when register driver fails,
> it goto 'init_drv_fail' tag and free 'drv' structure.
> 
> Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
> Cc: Stefan Wahren <stefan.wahren@...e.com>
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---
>  drivers/cpuidle/cpuidle-arm.c | 25 ++++++++++++++++---------
>  1 file changed, 16 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/cpuidle/cpuidle-arm.c b/drivers/cpuidle/cpuidle-arm.c
> index 52a7505..f419f6a 100644
> --- a/drivers/cpuidle/cpuidle-arm.c
> +++ b/drivers/cpuidle/cpuidle-arm.c
> @@ -86,10 +86,13 @@ static int __init arm_idle_init(void)
>  
>  	for_each_possible_cpu(cpu) {
>  
> +		drv = NULL;

     ^^^^^

This initialization is not needed.


> +		dev = NULL;
> +
>  		drv = kmemdup(&arm_idle_driver, sizeof(*drv), GFP_KERNEL);
>  		if (!drv) {
>  			ret = -ENOMEM;
> -			goto out_fail;
> +			goto init_drv_fail;

Here we can jump directly to out_fail, no ?


>  		}
>  
>  		drv->cpumask = (struct cpumask *)cpumask_of(cpu);
> @@ -104,13 +107,13 @@ static int __init arm_idle_init(void)
>  		ret = dt_init_idle_driver(drv, arm_idle_state_match, 1);
>  		if (ret <= 0) {
>  			ret = ret ? : -ENODEV;
> -			goto init_fail;
> +			goto init_drv_fail;

	goto out_kfree_drv;

>  		}
>  
>  		ret = cpuidle_register_driver(drv);
>  		if (ret) {
>  			pr_err("Failed to register cpuidle driver\n");
> -			goto init_fail;
> +			goto init_drv_fail;

	goto out_unregister_drv;


etc ...

>  	return 0;
> -init_fail:
> +
> +init_dev_fail:
> +	kfree(dev);
> +	cpuidle_unregister_driver(drv);
> +
> +init_drv_fail:
>  	kfree(drv);
> -out_fail:
> +

So, the code should end up with:

out_kfree_dev:
	kfree(dev);
out_unregister_drv:
	cpuidle_unregister_drv(drv);
out_kfree_drv:
	kfree(drv);

>  	while (--cpu >= 0) {
>  		dev = per_cpu(cpuidle_devices, cpu);
>  		cpuidle_unregister_device(dev);
> 

Perhaps it could nicer to create a function with the rollback embedded:

	for_each_possible_cpu(cpu) {
		ret = arm_idle_init_cpu(cpu)
		if (ret)
			goto out_fail;
	}

	return 0;

out_fail:

	while (--cpu >= 0) {
		cpuidle_unregister_device(per_cpu(cpuidle_devices,cpu));
		cpuidle_unregister_driver(cpuidle_get_cpu_driver(dev));
		kfree(dev);
		kfree(drv);
	}

	return ret;

And arm_idle_init_cpu(int cpu) does what is currently in the loop content.

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