linux-kernel - Re: [PATCH v3 46/57] perf: Simplify pmu_dev

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Date:   Mon, 12 Jun 2023 11:44:00 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     torvalds@...ux-foundation.org, keescook@...omium.org,
        gregkh@...uxfoundation.org, pbonzini@...hat.com
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Subject: Re: [PATCH v3 46/57] perf: Simplify pmu_dev_alloc()

On Mon, Jun 12, 2023 at 11:07:59AM +0200, Peter Zijlstra wrote:
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  kernel/events/core.c |   65 ++++++++++++++++++++++++---------------------------
>  1 file changed, 31 insertions(+), 34 deletions(-)
> 
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -11285,49 +11285,46 @@ static void pmu_dev_release(struct devic
>  
>  static int pmu_dev_alloc(struct pmu *pmu)
>  {
> +	int ret;
>  
> +	struct device *dev __free(put_device) =
> +		kzalloc(sizeof(struct device), GFP_KERNEL);
> +	if (!dev)
> +		return -ENOMEM;
>  
> +	dev->groups = pmu->attr_groups;
> +	device_initialize(dev);
>  
> +	dev_set_drvdata(dev, pmu);
> +	dev->bus = &pmu_bus;
> +	dev->release = pmu_dev_release;
>  
> +	ret = dev_set_name(dev, "%s", pmu->name);
>  	if (ret)
> +		return ret;
>  
> +	ret = device_add(dev);
>  	if (ret)
> +		return ret;
>  
> +	struct device *del __free(device_del) = dev;

Greg, I'm not much familiar with the whole device model, but it seems
unfortunate to me that one has to call device_del() explicitly if we
already have a put_device() queued.

Is there a saner way to write this?

>  
> +	/* For PMUs with address filters, throw in an extra attribute: */
> +	if (pmu->nr_addr_filters) {
> +		ret = device_create_file(dev, &dev_attr_nr_addr_filters);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	if (pmu->attr_update) {
> +		ret = sysfs_update_groups(&dev->kobj, pmu->attr_update);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	no_free_ptr(del);
> +	pmu->dev = no_free_ptr(dev);
> +	return 0;
>  }