linux-kernel - Re: [PATCH 2/7] coresight: perf: Add "sinks" group to PMU directory

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Date:   Wed, 16 Jan 2019 16:39:48 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:     acme@...nel.org, peterz@...radead.org, mingo@...hat.com,
        tglx@...utronix.de, alexander.shishkin@...ux.intel.com,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        will.deacon@....com, mark.rutland@....com, jolsa@...hat.com,
        namhyung@...nel.org, adrian.hunter@...el.com, ast@...nel.org,
        hpa@...or.com, suzuki.poulose@....com, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/7] coresight: perf: Add "sinks" group to PMU directory

On Tue, Jan 15, 2019 at 04:07:37PM -0700, Mathieu Poirier wrote:
> Add a "sinks" directory entry so that users can see all the sinks
> available in the system in a single place.  Individual sink are added
> as they are registered with the coresight bus.
> 
> Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> ---
>  .../hwtracing/coresight/coresight-etm-perf.c  | 43 +++++++++++++++++++
>  .../hwtracing/coresight/coresight-etm-perf.h  |  1 +
>  drivers/hwtracing/coresight/coresight.c       | 17 ++++++++
>  3 files changed, 61 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
> index f21eb28b6782..292bd409a68c 100644
> --- a/drivers/hwtracing/coresight/coresight-etm-perf.c
> +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
> @@ -14,6 +14,7 @@
>  #include <linux/perf_event.h>
>  #include <linux/percpu-defs.h>
>  #include <linux/slab.h>
> +#include <linux/stringhash.h>
>  #include <linux/types.h>
>  #include <linux/workqueue.h>
>  
> @@ -43,8 +44,18 @@ static const struct attribute_group etm_pmu_format_group = {
>  	.attrs  = etm_config_formats_attr,
>  };
>  
> +static struct attribute *etm_config_sinks_attr[] = {
> +	NULL,
> +};
> +
> +static const struct attribute_group etm_pmu_sinks_group = {
> +	.name   = "sinks",
> +	.attrs  = etm_config_sinks_attr,
> +};
> +
>  static const struct attribute_group *etm_pmu_attr_groups[] = {
>  	&etm_pmu_format_group,
> +	&etm_pmu_sinks_group,
>  	NULL,
>  };
>  
> @@ -479,6 +490,38 @@ int etm_perf_symlink(struct coresight_device *csdev, bool link)
>  	return 0;
>  }
>  
> +static ssize_t etm_perf_sink_name_show(struct device *dev,
> +				       struct device_attribute *dattr,
> +				       char *buf)
> +{
> +	/* See function coresight_sink_by_id() to know where this is used */
> +	u32 hash = hashlen_hash(hashlen_string(NULL, dattr->attr.name));
> +
> +	return scnprintf(buf, PAGE_SIZE, "%x\n", hash);
> +}
> +
> +int etm_perf_symlink_sink(struct coresight_device *csdev)
> +{
> +	struct device *pmu_dev = etm_pmu.dev;
> +	struct device *pdev = csdev->dev.parent;
> +	struct device_attribute *dev_attr;
> +
> +	if (csdev->type != CORESIGHT_DEV_TYPE_SINK &&
> +	    csdev->type != CORESIGHT_DEV_TYPE_LINKSINK)
> +		return -EINVAL;
> +
> +	if (!etm_perf_up)
> +		return -EPROBE_DEFER;
> +
> +	dev_attr = kzalloc(sizeof(*dev_attr), GFP_KERNEL);
> +	dev_attr->attr.name = kstrdup(dev_name(pdev), GFP_KERNEL);
> +	dev_attr->attr.mode = 0444;
> +	dev_attr->show = etm_perf_sink_name_show;
> +
> +	return sysfs_add_file_to_group(&pmu_dev->kobj,
> +				       &dev_attr->attr, "sinks");

What is so odd about this call that you needed me to review this?

And what happens if this call fails, do you leak memory?

thanks,

greg k-h